Total petroleum hydrocarbons (TPHs) in groundwater of the Ecuadorian Amazon: Implications for human health

Total petroleum hydrocarbons (TPHs) in groundwater of the Ecuadorian Amazon: Implications for human health | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Total petroleum hydrocarbons (TPHs) in groundwater of the Ecuadorian Amazon: Implications for human health Johanna Zambrano-Anchundia, Janner Galarza-Alava, Samantha Jiménez-Oyola, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7466071/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The Ecuadorian Amazon, particularly in the provinces of Sucumbíos and Orellana, has been heavily impacted by oil activity since the 1970s. In this context, this study carried out between March and June 2024 analyzed 161 groundwater samples taken from deep domestic wells in both provinces, with the aim of determining the concentrations of total petroleum hydrocarbons (TPH) and their implication on the health of consumers. The results showed that, in Orellana, TPH concentrations ranged between 0.11 and 7.30 mg/L, while in Sucumbíos they varied between 0.13 and 7.45 mg/L. More than 95% of water samples exceeded the maximum permissible limit of 0.2 mg/L for drinking water, according to the quality criteria established by Ecuadorian regulations. These levels of contamination reflect a significant exposure of local communities to health risks. In particular, the study revealed that the consumption of groundwater with high concentrations of TPH can generate non-cancer and carcinogenic risks greater than the levels recommended by the United States Environmental Protection Agency (USEPA). This situation endangers the health of people, especially children, who are the most vulnerable. The findings of this study highlight the urgency of implementing control measures and risk management strategies to mitigate contamination in areas affected by oil activity and protect the health of communities that depend on groundwater in the Amazon region. Earth and environmental sciences/Environmental sciences Health sciences/Risk factors Groundwater quality drinking water petroleum industry oil pollution human health Figures Figure 1 Figure 2 Figure 3 1. Introduction The Amazon, known as the lung of the planet, is the largest and most biodiverse rainforest in the world, with an area of approximately 7 million km² spanning nine countries in South America [ 1 ], [ 2 ]. This ecosystem plays a fundamental role in global climate control and provides vital resources for native communities and diverse species of flora and fauna. However, the Amazon faces serious threats from anthropogenic activities such as deforestation, mining and, in particular, oil extraction, which have not only caused significant alterations to its ecosystems[ 3 ], [ 4 ], [ 5 ], but have also introduced persistent pollutants that pose risks to the environment and human health[ 6 ], [ 7 ], [ 8 ], [ 9 ], [ 10 ], [ 11 ] Among these pollutants, total petroleum hydrocarbons (TPH) constitute a heterogeneous group of chemical compounds derived from both low and high molecular weight [ 12 ]. TPHs are considered persistent and priority pollutants arising from oil and gas exploration and production[ 13 ], [ 14 ]. Among these compounds, polycyclic aromatic hydrocarbons (PAHs) and asphaltenes have a negative impact on soil, groundwater and ecosystems. PAHs, known for their mutagenic and carcinogenic properties, are classified as priority pollutants by the United States Environmental Protection Agency [ 15 ], [ 16 ], [ 17 ], due to the significant risk they pose to the health of ecosystems and living beings [ 18 ], [ 19 ], [ 20 ], [ 21 ], [ 22 ], [ 23 ], [ 24 ], [ 25 ]. Significant impacts of TPH pollution have been documented globally in various regions. In Iran, oil activities have affected agricultural areas, with PAHs concentrations of up to 45.04 mg/L recorded in surface water during the wet season, in addition to carcinogenic risk levels from exposure to contaminated soils exceeding the safe exposure threshold (CR > 10⁻⁴) [ 26 ]. Similarly, in Nigeria, TPH concentrations in soils between 1480 and 1810 mg/kg have been reported, exceeding the permissible limit for the protection of marine life in up to 16% of the cases evaluated [ 27 ], [ 28 ]. In wetland soils in the same region, PAHs were found in concentrations between 1.9 and 461 mg/kg, posing ecological and health risks [ 29 ], [ 30 ]. In Latin America, where the oil industry plays an important role, cases of contamination by hydrocarbons, heavy metal(loid)s and other pollutants derived from extractive activities have been reported [ 6 ], [ 12 ]. These impacts not only affect ecosystems, but also local communities, especially those that depend on natural resources for their livelihoods, such as indigenous and rural communities [ 31 ]. Water, soil and air pollution remain one of the main environmental concerns in the Amazon region [ 32 ], [ 33 ]. In the northern Peruvian Amazon, oil pollution in soil and sediments has been confirmed as being linked to oil extraction activities, which has favored the bioaccumulation of toxic compounds in the food chain and has affected human health through the consumption of local wildlife: In San José de Saramuro and Trompeteros, significant concentrations of PAHs were reported, of 66,400 mg/L and 2,024,000 mg/L, respectively [ 34 ]. Moreover, Webb and Coomes[ 35 ] analyzed PAH exposure through the consumption of water and benthic fish in communities near oil extraction activities in the Andean Amazon (Ecuador–Peru). They linked PAH contamination to health risks for the local population in this region. Ecuadorian Amazon is a paradigmatic case of the environmental problems associated with oil production. This region has been the epicenter of intense extractive activity that began in the provinces of northeastern Ecuador in the 1970s [ 36 ], where oil and its derivatives are closely linked to both the ancient and modern history of the area. The provinces of Sucumbíos and Orellana are two of the main areas where oil activity is predominant, and the dependence on groundwater is notable, since a large part of the drinking water comes from deep wells. However, during Texaco's operations, approximately 16.8 million gallons of oil were spilled directly into water sources and soil [ 37 ], [ 38 ], which has raised questions about the quality of groundwater in these provinces [ 39 ]. In the current context, oil continues to be a strategic resource for the development of countries [ 40 ], particularly in Latin America, where a large part of the economy depends on the exploitation of raw materials [ 41 ]. In Ecuador, crude oil exports accounted for 29.1% of all exports in 2024 [ 42 ]. However, this economic dependence brings with it significant environmental and social challenges, especially in the Amazon region [ 43 ], [ 44 ], [ 45 ]. Previous studies carried out in the Ecuadorian Amazon have documented the level of impact on various environmental compartments. Corral et al[ 36 ] reported TPH concentrations of up to 847700 mg/kg and PAHs of up to 711100 mg/kg in river sediments collected in the provinces of Orellana and Sucumbíos, reflecting significant environmental deterioration in the areas evaluated. Maurice et al[ 46 ] analyzed the quality of drinking water, reporting high concentrations of potentially toxic elements (PTEs) in various environmental matrices, such as Mn (up to 500 mg/L in water), Ba (133.000 mg/Kg in soils) and Al (over 200 mg/L in water samples), which represents health risk for the inhabitants of local communities. Barraza et al[ 47 ] investigated the content of TEP in surface water and local crops, finding concentrations of Mn between 9.75 ng/m³ and 30.25 ng/m³, and a mean concentration of Ba of 94.60 ng/m³, both elements related to hydrocarbon activities, with Ba being associated with the use of drilling fluids [ 48 ], [ 49 ]. Arellano et al[ 41 ] investigated the effects of oil pollution in the Ecuadorian Amazon rainforest, finding a significant reduction in biodiversity and chlorophyll content in contaminated areas. Brice[ 50 ] identified TPH concentrations between 0.382 mg/L and 0.438 mg/L in surface water samples from Yasuní National Park, while they reported TPH levels in streams in the range of 0.097 and 2.883 mg/L. The sediments also showed high concentrations of TPH, reaching up to 6.980.000 mg/Kg in dry weight [ 51 ]. Studies conducted in the Ecuadorian Amazon have highlighted the magnitude of the environmental impact and the potential health risk for populations exposed to pollutants from oil activities. However, these investigations have focused on the analysis of surface water, soil and sediments, leaving a considerable gap in knowledge about groundwater intended for human consumption, an essential resource for local communities. This gap is particularly worrying, given that these waters can be an important vector of exposure to oil-derived pollutants. In this context, the objectives of the present study are; (a) to evaluate the concentration of TPH in groundwater in the provinces of Sucumbíos and Orellana, analyzing the spatial distribution pattern, and (b) to estimate the health risk to people exposed to TPH through direct consumption of this groundwater. This analysis will make it possible to identify the areas with the highest presence of TPH and provide key information to mitigate the impacts on the health of the communities. 2. Materials and methods 2.1. Study area The study was conducted in the Ecuadorian Amazon region, specifically in the provinces of Sucumbíos and Orellana, located in northeast region of Ecuador (Fig. 1). The selected area encompasses the cantons of La Joya de los Sachas, Francisco de Orellana, Loreto, Shushufindi , and Lago Agrio (Nueva Loja) , covering approximately 39,776.52 km². This region features a tropical humid forest climate, with an average temperature of 24°C and an annual precipitation of 2,997 mm [ 52 ]. According to the most recent census, these provinces have a combined population of 381,180 inhabitants [ 53 ]. 2.2. Sample collection A total of 161 groundwater samples were collected from deep wells (GW-1 to GW-161) between March and June 2024. The sampling sites were selected based on their proximity to areas with reported hydrocarbon spill incidents. The sampled wells were private drilled wells used by the local population for water supply. The depth of the wells ranged from 20 to 30 meters, and the water level ranged from 8 to 12 meters. Groundwater samples were collected through pumping and storage in sterilized amber glass bottles to ensure minimal exposure to light and preserve the integrity of the samples. After labeling, the bottles were placed in insulated boxes and kept under refrigeration. All samples were transported to the laboratory on the same day to prevent alterations that could compromise the reliability of the results. 2.3. Physical-chemical analysis Physical parameters were measured in situ, including pH, Electrical conductivity (EC), total dissolved solids (TDS), and temperature, using a calibrated multiparameter equipment HACH, model HQ40D. TPH were extracted directly from the collection bottles by adding 14 mL of solvent S-316 to 140 mL of sample, maintaining a ratio of 10:1 (sample/solvent). The bottle was sealed and shaken manually for two minutes to facilitate the transfer of compounds from the aqueous phase to the organic phase. Subsequently, phase separation was observed, allowing the hydrocarbon-enriched fraction to be visually identified. The organic phase (14 mL) was extracted using a sterile syringe and filtered with silica gel and filter paper placed in a funnel to remove impurities or suspended solids that could interfere with the analysis. The filtered sample was transferred to a quartz cell previously sterilized with the same solvent and analyzed by infrared absorption spectroscopy using the InfraCal2 equipment (Spectro Scientific, Massachusetts, USA). The reading was taken over a period of four minutes, following a calibration curve set at 7.5 mg/L, which allowed for more accurate quantification of the hydrocarbons present in the samples. 2.4. Data Processing and Statistical Analysis Statistical analysis of the data was performed using R free software [ 54 ], which allowed for the evaluation of trends and statistical significance. A spatial distribution map of pollution was generated to identify areas of significant concern for Amazon residents. The ArcGIS 10.8 Geographic Information System (GIS) software was used for map generation. 2.5. Health risk assessment In the study area, the exposure to TPH can occur through ingestion of groundwater used as a drinking water supply; the water supply is provided through private water wells. Therefore, the human health risk was assessed for residential scenarios where the receptors adults and children are exposed through ingestion of water. The average daily dose (ADD: mg/kg-day) for ingestion was calculated according to the Eq. 1 [ 55 ], [ 56 ]. \(\:{ADD}_{ingestion=\:}\frac{{C}_{gw}\:\times\:EF\:\times\:IR\:\times\:ED}{AT\:\times\:BW}\) Eq. 1 Where: C gw is the TPH-concentration in groundwater (mg/L), EF is the annual exposure frequency (days/year), IR is the ingestion rate of water (L/day), ED is the lifetime exposure duration (years), BW is the body weight (kg), and AT is the averaging time (days). For the calculation of the ADD, the 95th percentile of the exposure parameters were used (Table 1 ). The potential human health risk for noncarcinogenic effects was quantified in terms of Hazard Quotients (HQ), by the ratio of the ADD to the reference dose (RfD). If HQ is above 1, the safe exposure threshold is exceeded, and the systemic effects linked with the exposure can be produced. The carcinogenic risk (CR) was estimated by multiplying the ADD by the slope factor (SF). If CR is above 1.0 x 10 − 5 , the safe exposure limit is exceeded [ 55 ], [ 56 ]. The values of parameters used in this study are presented in Table 1 . In this study, a conservative approach was adopted for selecting toxicity values, which is why the RfD and SF were applied to the TPH – Aromatic (high, low, and medium). In general, aromatic hydrocarbons tend to be more water soluble and mobile than the aliphatic hydrocarbons [ 57 ]. The toxicity values, RfD and SF, ​​were obtained from the Risk Assessment Information System website [ 58 ]. The main challenge in assessing TPH toxicity in human health risk assessments is the complexity of TPH mixtures, which can contain hundreds or thousands of compounds. Even if it were possible to measure the concentration of each compound, toxicity data are not available for each. Key factors to consider when estimating TPH toxicity and interpreting results include: (1) TPH mixtures may contain both hydrocarbons and polar compounds; (2) they may include both natural (e.g., humic acids) and anthropogenic substances unrelated to petroleum; and (3) detected compounds depend on the specific TPH analytical method used [ 59 ]. Although TPH concentrations have limited utility for risk assessment, due to the high uncertainty associated with the complexity of TPH mixtures [ 60 ], [ 61 ], [ 62 ], they serve as an inexpensive tool for preliminarily determining whether contamination poses a risk to residents in affected environments. If TPH concentration suggests significant contamination in drinking water, the next step is to gather additional data to quantitatively assess the human health risk [ 59 ]. This will require determining the concentrations of different oil fractions using more precise analytical methods, as well as considering site-specific exposure parameters. Table 1 Parameters used in the risk assessment Parameter Units Point value p95 EF_ adult and children day/year - 365 IR_ adult L/day - 2.0 IR_ children L/day - 1.7 ED_ adult Year 30 - ED_ children Year 6 - Bw_ adult Kg - 78.73 Bw_ chindren Kg - 36.95 AT_ no cancer Day 365 x ED - AT_ cancer Day 365 x 70 - RfD (TPH- Aromatic High) mg/kg-day 0.0003 - RfD (TPH- Aromatic Low) mg/kg-day 0.004 - RfD (TPH- Aromatic Medium) mg/kg-day 0.001 - SF (TPH-Aromatic High) 1/mg/kg-day 1.0 - SF (TPH-Aromatic Low) 1/mg/kg-day 0.055 - 3. Results 3.1. Physical parameters According to the results of the physical parameters of groundwater measured in situ (Table 2 ), significant variations were observed between the provinces of Orellana and Sucumbíos. The pH showed wide variability, with values ranging from 5.40 to 8.47 in Orellana and from 4.96 to 8.72 in Sucumbíos, reflecting conditions ranging from slightly acidic to moderately alkaline. Electrical conductivity (EC) reached a maximum value of 556 µS/cm in Orellana and 465 µS/cm in Sucumbíos. These results, together with total dissolved solids (TDS) concentrations, suggest variations in mineral content between the groundwater of Orellana and Sucumbíos. Notably, Sucumbíos recorded a maximum TDS concentration of 233 mg/L, compared to 11.78 mg/L in Orellana, with the former also exhibiting the highest standard deviation. Regarding temperature, values were considerably high in both areas, reaching 46.3°C in Sucumbíos and 38.88°C in Orellana, which could be due to local hydrogeological conditions. Table 2 Statistical summary of physical parameters of groundwater in Orellana and Sucumbíos. Province pH TDS (mg/L) EC (µS/cm) T (°C) Orellana Min 5.40 0.80 2.00 19.91 p50 6.65 2.29 183.00 27.72 p95 7.88 9.22 432.50 36.24 Max 8.47 11.78 556.00 38.88 SD 0.53 2.57 123.43 3.65 Sucumbíos Min 4.96 1.00 4.00 22.60 p50 6.71 4.46 89.00 28.31 p95 8.21 8.78 275.60 34.08 Max 8.72 233.00 465.00 46.30 SD 0.80 45.65 90.58 3.41 3.2. Concentration of TPH in groundwater The presence of TPH in groundwater samples is a significant indicator of petroleum contamination. In Orellana, TPH concentrations ranged from 0.11 to 7.30 mg/L, while in Sucumbíos, TPH levels varied between 0.13 and 7.45 mg/L (Table 3 ). In Sucumbíos, 97.62% of the samples exceeded the maximum permissible limit (MPL) for TPH concentration in drinking water, which is set at 0.2 mg/L according to the Quality Criteria for Water Sources for Human and Domestic Consumption, established in Ecuadorian regulations [ 63 ]. The situation is similar in Orellana, with 93.51 % o the samples exceeding the MPL for TPH. The samples with the highest TPH content are found in the northern part of the study area, in the province of Sucumbíos (Fig. 2 ). In terms of depth, the samples analyzed mostly come from wells between 10 and 30 meters deep, which indicates that relatively superficial layers of the subsoil are affected. Table 3 TPH concentration (mg/L) in groundwater samples from the Ecuadorian Amazon. Province n Min p50 p95 Max S.D. Orellana 77 0.11 0.71 2.87 7.30 1.38 Sucumbíos 84 0.13 3.75 7.30 7.45 2.51 There are few studies reporting the presence of TPH in the Ecuadorian Amazon. San Sebastían et al reported TPH values ranging from 0.2 to 2.88 mg/L in rivers near oil wells in northeastern Ecuador[ 64 ]. In addition, L. Corral-García et al reported that TPH concentrations vary from 9.4 to 847.4 mg/kg, with polycyclic aromatic hydrocarbon (PAH) levels varying from 10.15 to 711.1 mg/kg in sediment samples from the Aguarico and Napo rivers [ 65 ]. These studies show that TPH contamination is persistent and poses a risk to both the ecosystem and local communities. A similar trend is observed in other countries, where areas with intensive oil activity have resulted in high levels of TPH in various environmental matrices. Ihunwo et al evaluated the concentration of TPH in surface waters at five sampling stations from Woji Creekm, Nigeria, finding TPH values ​​between 1.01 ± 0.12 and 3.64 ± 1.12 [ 66 ]. Ahiamadu et al informed about TPH contents in surface water ranged from 0.017 to 0.033 µ/L, TPH in groundwater ranged from 0.010 to 11600 µ/L, and TPH in soils ranged from 5364 to 71,283 mg/kg in Nigeria [ 67 ]. Ugochukwu et al reported TPH values ​​between 240 and 62,388 in Nigerian soils, where the regulatory intervention limit for TPH is 5000 mg/kg, meaning that soils with TPH concentrations above this limit are considered to pose significant ecological and health risks [ 68 ]. In Ecuadorian legislation, the MPL for TPH is more restrictive compared to other international regulatory frameworks. For example, the U.S. Environmental Protection Agency (EPA) does not set an overall MPL for drinking water but regulates specific aromatic compounds such as benzene (0.005 ml/L) and toluene (1 mg/L) due to the individual health risks they pose [ 69 ]. For its part, Environment and Climate Change Canada (ECCC) regulates individual compounds such as benzene (0.005 mg/L) in drinking water. As for the World Health Organization, it has not established a specific MPL for TPH in water for any use. In the case of Ecuador, the TULSMA establishes a general limit for TPH in drinking water (0.2 mg/L), and additionally, it sets a maximum concentration of 0.5 mg/L of TPH for the preservation of flora and fauna in freshwater, marine, and estuarine waters. It also establishes a limit of 20 mg/L for discharges into the public sewer system and regulates specific compounds such as benzene (0.01 mg/L) and toluene (1 mg/L) [ 70 ]. 3.3. Risk assessment Table 4 shows the results of non-cancer and cancer risk for adults and children residing in the northern Amazon and potentially exposed to oil pollution. It is evident that in the Ecuadorian Amazon, strongly impacted by oil activities, people who consume groundwater with high TPH contents are exposed to non-cancer and cancer risk levels higher than those recommended by the USEPA, HI > 1 and CR > 1.0 x 10 − 5 , respectively. This exposure can lead to long-term health problems for people, especially children, who are the most vulnerable receptors. His study, the risk assessment was made considering the toxicity factors of TPH - aromatic high, TPH - aromatic low, and TPH - aromatic medium. The results of this preliminary risk assessment are worrying, as the sampled sites exceed the safe exposure limit in more than 95% of the sampled sites (Fig. 3 ). In this regard, this assessment reinforces the need to address the problem of contamination by TPH and other potentially toxic elements in petroleum environments. Considering that TPH concentrations can represent very different compositions and pose varying risks to human health and the environment, the results obtained in this study should be handled with caution. As a general measure of petroleum contamination, the TPH results indicate the presence of petroleum hydrocarbons in the sampled environment. The measured TPH values suggest the relative potential for human exposure and, consequently, the potential for health effects. Assessing the health effects of TPH exposure requires much more detailed information than a single TPH value can provide. In our study, due to the lack of knowledge of the type of compounds present in TPH, in risk assessment only the ingestion route was considered, however, other exposure routes such as dermal contact or inhalation of vapors should be quantified, which can cause a cumulative risk in the human body. Table 4 Results of the preliminary human health risk assessment Risk assessment Orellana Sucumbíos Non-cancer risk (HQ) HQ_adults (Min – Max) S.D. HQ_children (Min – max) S.D. HQ_adults (Min – Max) S.D. HQ_ children (Min – Max) S.D. TPH- Aromatic High (6.18E + 02-9.31E + 00) 1.16E + 02 (1.12E + 03-1.69E + 01) 2.11E + 02 (6.31E + 02-1.10E + 01) 2.13E + 02 (1.14E + 03-1.99E + 01) 3.86E + 02 TPH- Aromatic Low (4.64E + 01-6.99E-01) 8.74E + 00 (8.40E + 01-1.27E + 00) 1.58E + 01 (4.73E + 01-8.26E-01) 1.60E + 01 (8.57E + 01-1.50E + 00) 2.89E + 01 TPH- Aromatic Medium (1.85E + 02-2.79E + 00) 3.49E + 01 (3.36E + 02-5.06E + 00) 6.33E + 01 (1.89E + 02-3.30E + 00) 6.39E + 01 (3.43E + 02-5.98E + 00) 1.16E + 02 Cancer risk (CR) CR_adults (Min –Max) S.D. CR_ children (Min – Max) S.D. CR_adults (Min – Max) S.D. CR_ children (Min – Max) S.D. TPH-Aromatic High (7.95E-02-1.20E-03) 1.50E-02 (2.88E-02 - 4.34E-04) 5.42E-03 (8.11E-02-1.42E-03) 2.74E-02 (2.94E-02-5.13E-04) 9.91E-03 TPH-Aromatic Low (4.37E-03-6.59E-05) 8.24E-04 (1.58E-03-2.39E-05) 2.98E-04 (4.46E-03-7.78E-05) 1.51E-03 (1.62E-03-2.82E-05) 5.45E-04 Min = minimum; Max = maximum; S.D. = standard deviation 4. Discussion Various studies have assessed the human health risks associated with TPH exposure in different regions and through different routes of exposure, revealing varying levels of risk. [ 60 ], evaluated the non-carcinogenic cumulative risk in terms of Hazard Index (HI) for ingestion, skin contact, and inhalation routes due to exposure to TPH (C10-C40) in soils at an oil refinery in China, finding that the HQs of aliphatic hydrocarbon (C10-C12) and aliphatic hydrocarbon (C13-C16) were higher than the acceptable risk level for humans (HI > 1), with HI values ​​of 4.78 and 9.04, respectively. In the other hand, the calculated HIs for aromatic hydrocarbons were lower than the safe threshold. [ 71 ] reported significantly high HQ for exposure to TPH via groundwater ingestion in areas impacted by oil activities in Nigeria. The HQ values reached up to 2.0 x 10 + 3 , indicating a severe risk of non-cancer health effects. Furthermore, the cancer risk (CR) associated with this exposure was calculated at 5.6 x 10⁻¹, which is significantly higher than the target cancer risk of 1.0 x 10⁻⁵, emphasizing the significant potential for carcinogenic effects in these areas. In contrast, [ 61 ] focused on the accidental ingestion of contaminated soil, reporting HI values ranging between 0.001 and 5. These values suggest a varying risk of non-cancer health effects, depending on the degree of exposure. Notably, the study found that some of the reported HI values exceeded the threshold of concern, indicating a potential risk for adverse health outcomes in areas where exposure to contaminated soil is higher. [ 72 ] assessed the HQ for exposure to TPH through the accidental ingestion of surface water and found that for children, HQ values ranged between 2.1 x 10⁻⁵ and 1.9 x 10 − 4 , while for adults, they ranged from 4.6 x 10 − 6 to 4.0 x 10⁻⁵. These relatively low HQ values suggest that the risk for non-cancer health effects is minimal, likely due to low exposure levels and the relatively low concentrations of TPH found in the environment in these specific cases. Lastly, [ 73 ] studied carcinogenic risk from dermal exposure to TPHs. They found that the carcinogenic dermal risk for adults exceeded the acceptable risk limits, highlighting the importance of assessing direct skin contact as a significant exposure route for harmful hydrocarbons. Although the cited studies show different levels of risk associated with exposure to TPH, the general trend indicates that areas with higher concentrations of hydrocarbons, such as those with intensive oil activities, present a much greater risk to human health. The studies emphasize the need for intervention strategies. Exposure to petroleum and its derivatives, whether direct or indirect, causes serious health issues in humans, with effects primarily depending on the nature of the contact [ 62 ]. Exposure to TPH may result in a range of health consequences, which can vary depending on the specific hydrocarbons present in the water, their concentrations, and the type and duration of the exposure [ 60 ]. Exposure to TPH through drinking water can cause gastrointestinal problems like stomach pain, diarrhea, nausea, cramps, and vomiting, with prolonged exposure potentially leading to chronic digestive issues. Additionally, TPH exposure can affect various health systems, causing skin and eye irritation, respiratory and neurological issues, and increased stress. It can also lead to toxicity in genetic, immune, and endocrine systems [ 74 ]. Groundwater contaminated with TPH may contain volatile organic compounds (Benzene, Toluene, Ethylbenzene, Xylene, Naphthaleno, etc.) [ 75 ]. Benzene is one of the most worrying TPH compounds due to its toxic and carcinogenic effects [ 58 ]. EPA has set a maximum limit of 5 ppb of benzene in drinking water and a goal of 0 ppb in water sources like rivers and lakes, as benzene can cause leukemia. It is estimated that regular exposure to 10 ppb of benzene in drinking water or 0.4 ppb in air over a lifetime could increase the risk of one additional cancer case for every 100,000 exposed people [ 76 ]. Chronic exposure to individual BTX components and/or BTX-rich mixtures may lead to hematological effects. Some of the specific hematological impacts resulting from prolonged exposure to these compounds remain uncertain [ 74 ]. However, exposure to BTEX may increase the long-term risk of developing adverse health effects, particularly if concentrations of these compounds are high or if exposure is prolonged [ 77 ]. Additional factors, such as the vulnerability of specific population groups—such as children or pregnant women—can exacerbate this risk [ 55 ]. Regarding long-term effects, continued exposure to groundwater contaminated with TPH may result in severe damage to organs such as the liver, kidneys, and central nervous system. While these effects may not be immediately evident, they will become more apparent over time. Health implications are also influenced by the duration and intensity of exposure, highlighting the importance of promptly addressing water contamination issues. Ongoing monitoring and comprehensive assessments of water quality are crucial to understanding potential risks and mitigating adverse health effects on human populations [ 74 ]. The effects of oil contamination in the Ecuadorian Amazon and its impact on the health of the population have been poorly studied. However, studies by [ 78 ], [ 79 ], [ 80 ] have indicated potential health risks associated with living near oil fields. These studies highlight the urgent need for further research and monitoring of the health consequences of oil contamination in the region. [ 78 ] analyzed cancer cases between 1985 and 1998 in the provinces of Sucumbíos, Orellana, Napo, and Pastaza (where oil extraction occurs) and compared incidence rates with areas without oil exploitation. The results showed a significant increase in the relative risk of various types of cancer, such as stomach, rectal, skin, and kidney cancers in men, and cervical and lymphatic cancers in women, as well as an increase in hematopoietic cancers in children under 10 in the exposed areas. Additionally, [ 79 ] examined childhood leukemia incidence in the Ecuadorian Amazon between 1985 and 2000. The results revealed a significantly higher risk of leukemia in children aged 0 to 4 years and in girls aged 0 to 14 years in areas closer to oil fields. Both studies suggest a potential link between cancer incidence and proximity to oil fields. [ 80 ], based on a study conducted from November 1998 to April 1999, reported that women exposed to TPH contamination in communities near oil fields had a higher likelihood of experiencing spontaneous abortions. The significant presence of TPH in groundwater sources in the Amazon region represents a critical challenge for environmental management and public health. Addressing this issue requires comprehensive strategies aimed at both preventing new contamination sources and mitigating existing impacts on ecosystems and communities [ 23 ], [ 81 ]. Although Ecuador has a relatively strict regulatory framework, its effective implementation in the territory is limited, revealing a significant gap between environmental legislation and compliance. One of the priority actions is the establishment of permanent water quality monitoring systems for both groundwater and surface water. This monitoring should be systematic, georeferenced, and publicly accessible in order to identify critical areas, detect temporal trends, and evaluate pollutant dispersion patterns. The incorporation of technologies such as remote sensors, automatic sampling stations, and digital platforms for real-time data reporting can significantly strengthen risk management and facilitate informed decision-making. Similarly, it is urgent to develop and implement environmental remediation programs in the most affected areas. Depending on the type and level of contamination, the use of techniques such as bioremediation, phytoremediation, or physical-chemical treatments is recommended, accompanied by environmental risk assessments and ecological restoration plans to ensure sustainable ecosystem recovery [ 82 ], [ 83 ]. The prevention of new episodes of pollution requires the strengthening of the regulatory framework and its rigorous enforcement[ 84 ]. This includes updating technical standards for hydrocarbon drilling, transportation, and storage, as well as more frequent and comprehensive inspections by the competent authorities. Operating companies must be subject to the implementation of contingency plans, environmental liability insurance, and cleaner and safer technologies. Finally, the importance of ensuring immediate access to safe sources of water for human consumption in risk areas is highlighted. To this end, the installation of treatment plants, the distribution of bottled water in critical areas, and the promotion of domestic purification systems are proposed. These measures should be coordinated with environmental education and community participation programs that raise awareness of the risks associated with consuming contaminated water and promote a culture of water conservation. Complementarily, it is essential to consolidate participatory environmental governance processes that guarantee transparency in managing environmental liabilities and foster the active involvement of local communities in decision-making. The convergence of national and international scientific evidence underscores the need for integrated risk management strategies that combine technical interventions, effective regulation, and strong social commitment. Reducing the impacts of oil pollution requires a multisectoral, sustained, and participatory approach that unites prevention, remediation, regulation, and environmental justice. 5. Conclusions The data analyzed show a worrying persistence of total petroleum hydrocarbon (TPH) contamination in the Amazonian provinces of Sucumbíos and Orellana, Ecuador. In 97.62% of the samples collected in Sucumbíos and 93.51% of those from Orellana, TPH concentrations exceed the maximum permissible limit of 0.2 mg/L established by Ecuadorian regulations for water intended for human consumption. These results reflect sustained exposure of communities to contaminated sources, posing a considerable risk to public health, particularly in vulnerable populations such as children, who are more susceptible to the chronic toxic effects of hydrocarbons. This concern is supported by the calculated risk values, which exceed acceptable thresholds for both non-carcinogenic and carcinogenic effects. However, the findings should be interpreted with certain limitations in mind. Data coverage remains limited in terms of space and time, which restricts a more accurate characterization of the evolution of the phenomenon and its geographical distribution. In addition, detailed information on the specific chemical composition of the hydrocarbons detected was not available, which is essential for a more rigorous toxicological assessment, particularly with regard to aromatic compounds such as benzene and toluene. The potential cumulative impacts on human health and bioaccumulation processes in local fauna were also not addressed in depth. Therefore, the development of longitudinal studies to establish correlations between chronic exposure to TPH and health conditions in affected populations is recommended. It is also suggested that integrated analyses of water, soil, sediments, and air be incorporated and that participatory approaches that include local knowledge be adopted. This research allowed the identification of areas with the highest TPH concentrations and contributed valuable insights for mitigating health risks in exposed communities. Declarations Funding The authors declare that this study did not receive any targeted funding or financial support from external institutions. Conflict of interest the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence work reported in this paper. All other authors have no conflict of interest. Use of Artificial Intelligence Artificial Intelligence tools were used exclusively to improve the clarity, coherence, and structure of the manuscript, without altering the originality or scientific integrity of the content. Sampling permission statement It is hereby declared that during the groundwater sampling process, the corresponding authorization was obtained from the owners of the private wells. Consequently, all samples were collected with the express consent of the owners of the drilled wells. Data availability The datasets supporting the findings of this study will be made available by the corresponding author upon request from the editors or reviewers. Author Contribution ZA (corresponding author) coordinated the project, led the conceptualization of the study, participated in the discussion of results, and drafted and revised the manuscript.JGÁ assisted in methodological planning and prepared the figures and tables.SJO participated in data collection and processing, performed statistical analysis, and contributed to the discussion and interpretation of results.DM-S collaborated in the preparation of the initial draft of the manuscript and in the organization of the information.MJS supported the interpretation of results and revision of the text.SS provided specialized technical advice and critical review of the manuscript.CM-R contributed to the discussion of results, conclusions, and final revision of the document.All authors read and approved the final version of the manuscript. References J. S. 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Zambrano-Anchundia","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA9ElEQVRIiWNgGAWjYBACxgbmhgNAOoEfzC0A4gMEtTBCtEg2gLgGRGgBaQKRCQYHiNXC3N7YePBHzbY84+Ptzx58MGCQ47uRwPjgBz47eg42HJA4drvY7MwZc8MZBgzGkjcSmA178GmZkdhwwIDtduK2Gzls0jwGDIkbbiSwSeP1CUhLwr/biZvnP38G0lIP1ML+m6CWg223EzdIMJiBtCQYAG1hxqsF6JeDjX23iyXO5ID8ImE488zDZkl8fjFsbz788ce323n87ceBIVZhI893PPngB3whZtiAYLMBsQQDLKZwAnkkNhtelaNgFIyCUTByAQBeKVfd2DMvHQAAAABJRU5ErkJggg==","orcid":"","institution":"Escuela Superior Politécnica del Litoral","correspondingAuthor":true,"prefix":"","firstName":"Johanna","middleName":"","lastName":"Zambrano-Anchundia","suffix":""},{"id":519210249,"identity":"e793b49a-714e-4c6c-95cb-ddad210ffb99","order_by":1,"name":"Janner Galarza-Alava","email":"","orcid":"","institution":"Escuela Superior Politécnica del Litoral","correspondingAuthor":false,"prefix":"","firstName":"Janner","middleName":"","lastName":"Galarza-Alava","suffix":""},{"id":519210250,"identity":"6c3c5400-bbf5-4af3-9498-577f891633f0","order_by":2,"name":"Samantha Jiménez-Oyola","email":"","orcid":"","institution":"Escuela Superior Politécnica del Litoral","correspondingAuthor":false,"prefix":"","firstName":"Samantha","middleName":"","lastName":"Jiménez-Oyola","suffix":""},{"id":519210252,"identity":"4d2603d6-5666-4eca-85b4-513e43a21834","order_by":3,"name":"Demmy Mora-Silva","email":"","orcid":"","institution":"Escuela Superior Politécnica de Chimborazo, Sede Orellana","correspondingAuthor":false,"prefix":"","firstName":"Demmy","middleName":"","lastName":"Mora-Silva","suffix":""},{"id":519210254,"identity":"b753629c-5023-40ba-a1d3-534201fa10a7","order_by":4,"name":"María José Sanchez","email":"","orcid":"","institution":"Escuela Superior Politécnica de Chimborazo, Sede Orellana","correspondingAuthor":false,"prefix":"","firstName":"María","middleName":"José","lastName":"Sanchez","suffix":""},{"id":519210255,"identity":"dcc56d68-9e0a-4717-92ff-72865139705b","order_by":5,"name":"Salvatore Straface","email":"","orcid":"","institution":"University of Calabria","correspondingAuthor":false,"prefix":"","firstName":"Salvatore","middleName":"","lastName":"Straface","suffix":""},{"id":519210256,"identity":"95062a45-941e-4757-83c7-75f050988e3c","order_by":6,"name":"Carlos Mestanza-Ramón","email":"","orcid":"","institution":"Escuela Superior Politécnica de Chimborazo, Sede Orellana","correspondingAuthor":false,"prefix":"","firstName":"Carlos","middleName":"","lastName":"Mestanza-Ramón","suffix":""}],"badges":[],"createdAt":"2025-08-26 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06:39:02","extension":"html","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":190618,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7466071/v1/041f37a1b242b783ee9667d7.html"},{"id":92144069,"identity":"aa18294f-36dd-41e0-a348-611f6a66b0bb","added_by":"auto","created_at":"2025-09-25 06:38:59","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":280561,"visible":true,"origin":"","legend":"\u003cp\u003eStudy area and location of sampling stations\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7466071/v1/9ce801a8764e54c863f242ae.jpg"},{"id":92144079,"identity":"ac092af6-ff25-4147-a367-00005a4c8164","added_by":"auto","created_at":"2025-09-25 06:39:00","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":236232,"visible":true,"origin":"","legend":"\u003cp\u003eSpatial distribution of TPHs in the northern Amazon region of Ecuador\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7466071/v1/6e446c2726fef4250cd2557a.jpg"},{"id":92144522,"identity":"88a70809-4e92-4761-a3de-f79f9be49488","added_by":"auto","created_at":"2025-09-25 06:47:00","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":81944,"visible":true,"origin":"","legend":"\u003cp\u003eOutcomes of non-carcinogenic (HQ) and carcinogenic (CR) risk due to exposure to TPH in the Ecuadorian Amazon\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7466071/v1/97c320414c72e99c5a21e9bd.jpg"},{"id":98623305,"identity":"e0a61e33-7cde-4eae-ac12-9e36e3345385","added_by":"auto","created_at":"2025-12-19 17:05:44","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1549447,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7466071/v1/480d78ec-f0d4-4661-99f0-2fa4aa07a3d3.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Total petroleum hydrocarbons (TPHs) in groundwater of the Ecuadorian Amazon: Implications for human health","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe Amazon, known as the lung of the planet, is the largest and most biodiverse rainforest in the world, with an area of approximately 7\u0026nbsp;million km\u0026sup2; spanning nine countries in South America [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e], [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. This ecosystem plays a fundamental role in global climate control and provides vital resources for native communities and diverse species of flora and fauna. However, the Amazon faces serious threats from anthropogenic activities such as deforestation, mining and, in particular, oil extraction, which have not only caused significant alterations to its ecosystems[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], but have also introduced persistent pollutants that pose risks to the environment and human health[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e], [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eAmong these pollutants, total petroleum hydrocarbons (TPH) constitute a heterogeneous group of chemical compounds derived from both low and high molecular weight [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. TPHs are considered persistent and priority pollutants arising from oil and gas exploration and production[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Among these compounds, polycyclic aromatic hydrocarbons (PAHs) and asphaltenes have a negative impact on soil, groundwater and ecosystems. PAHs, known for their mutagenic and carcinogenic properties, are classified as priority pollutants by the United States Environmental Protection Agency [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], due to the significant risk they pose to the health of ecosystems and living beings [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e], [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eSignificant impacts of TPH pollution have been documented globally in various regions. In Iran, oil activities have affected agricultural areas, with PAHs concentrations of up to 45.04 mg/L recorded in surface water during the wet season, in addition to carcinogenic risk levels from exposure to contaminated soils exceeding the safe exposure threshold (CR\u0026thinsp;\u0026gt;\u0026thinsp;10⁻⁴) [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Similarly, in Nigeria, TPH concentrations in soils between 1480 and 1810 mg/kg have been reported, exceeding the permissible limit for the protection of marine life in up to 16% of the cases evaluated [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e], [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. In wetland soils in the same region, PAHs were found in concentrations between 1.9 and 461 mg/kg, posing ecological and health risks [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e], [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIn Latin America, where the oil industry plays an important role, cases of contamination by hydrocarbons, heavy metal(loid)s and other pollutants derived from extractive activities have been reported [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. These impacts not only affect ecosystems, but also local communities, especially those that depend on natural resources for their livelihoods, such as indigenous and rural communities [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eWater, soil and air pollution remain one of the main environmental concerns in the Amazon region [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e], [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. In the northern Peruvian Amazon, oil pollution in soil and sediments has been confirmed as being linked to oil extraction activities, which has favored the bioaccumulation of toxic compounds in the food chain and has affected human health through the consumption of local wildlife: In San Jos\u0026eacute; de Saramuro and Trompeteros, significant concentrations of PAHs were reported, of 66,400 mg/L and 2,024,000 mg/L, respectively [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. Moreover, Webb and Coomes[\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e] analyzed PAH exposure through the consumption of water and benthic fish in communities near oil extraction activities in the Andean Amazon (Ecuador\u0026ndash;Peru). They linked PAH contamination to health risks for the local population in this region. Ecuadorian Amazon is a paradigmatic case of the environmental problems associated with oil production. This region has been the epicenter of intense extractive activity that began in the provinces of northeastern Ecuador in the 1970s [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e], where oil and its derivatives are closely linked to both the ancient and modern history of the area. The provinces of Sucumb\u0026iacute;os and Orellana are two of the main areas where oil activity is predominant, and the dependence on groundwater is notable, since a large part of the drinking water comes from deep wells. However, during Texaco's operations, approximately 16.8\u0026nbsp;million gallons of oil were spilled directly into water sources and soil [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e], [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e], which has raised questions about the quality of groundwater in these provinces [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIn the current context, oil continues to be a strategic resource for the development of countries [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e], particularly in Latin America, where a large part of the economy depends on the exploitation of raw materials [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. In Ecuador, crude oil exports accounted for 29.1% of all exports in 2024 [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. However, this economic dependence brings with it significant environmental and social challenges, especially in the Amazon region [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e], [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e], [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e].\u003c/p\u003e\u003cp\u003ePrevious studies carried out in the Ecuadorian Amazon have documented the level of impact on various environmental compartments. Corral et al[\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e] reported TPH concentrations of up to 847700 mg/kg and PAHs of up to 711100 mg/kg in river sediments collected in the provinces of Orellana and Sucumb\u0026iacute;os, reflecting significant environmental deterioration in the areas evaluated. Maurice et al[\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e] analyzed the quality of drinking water, reporting high concentrations of potentially toxic elements (PTEs) in various environmental matrices, such as Mn (up to 500 mg/L in water), Ba (133.000 mg/Kg in soils) and Al (over 200 mg/L in water samples), which represents health risk for the inhabitants of local communities. Barraza et al[\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e] investigated the content of TEP in surface water and local crops, finding concentrations of Mn between 9.75 ng/m\u0026sup3; and 30.25 ng/m\u0026sup3;, and a mean concentration of Ba of 94.60 ng/m\u0026sup3;, both elements related to hydrocarbon activities, with Ba being associated with the use of drilling fluids [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e], [\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e]. Arellano et al[\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e] investigated the effects of oil pollution in the Ecuadorian Amazon rainforest, finding a significant reduction in biodiversity and chlorophyll content in contaminated areas. Brice[\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e] identified TPH concentrations between 0.382 mg/L and 0.438 mg/L in surface water samples from Yasun\u0026iacute; National Park, while they reported TPH levels in streams in the range of 0.097 and 2.883 mg/L. The sediments also showed high concentrations of TPH, reaching up to 6.980.000 mg/Kg in dry weight [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eStudies conducted in the Ecuadorian Amazon have highlighted the magnitude of the environmental impact and the potential health risk for populations exposed to pollutants from oil activities. However, these investigations have focused on the analysis of surface water, soil and sediments, leaving a considerable gap in knowledge about groundwater intended for human consumption, an essential resource for local communities. This gap is particularly worrying, given that these waters can be an important vector of exposure to oil-derived pollutants. In this context, the objectives of the present study are; (a) to evaluate the concentration of TPH in groundwater in the provinces of Sucumb\u0026iacute;os and Orellana, analyzing the spatial distribution pattern, and (b) to estimate the health risk to people exposed to TPH through direct consumption of this groundwater. This analysis will make it possible to identify the areas with the highest presence of TPH and provide key information to mitigate the impacts on the health of the communities.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Study area\u003c/h2\u003e\u003cp\u003eThe study was conducted in the Ecuadorian Amazon region, specifically in the provinces of Sucumb\u0026iacute;os and Orellana, located in northeast region of Ecuador (Fig.\u0026nbsp;1). The selected area encompasses the cantons of \u003cem\u003eLa Joya de los Sachas, Francisco de Orellana, Loreto, Shushufindi\u003c/em\u003e, and \u003cem\u003eLago Agrio (Nueva Loja)\u003c/em\u003e, covering approximately 39,776.52 km\u0026sup2;. This region features a tropical humid forest climate, with an average temperature of 24\u0026deg;C and an annual precipitation of 2,997 mm [\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e]. According to the most recent census, these provinces have a combined population of 381,180 inhabitants [\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Sample collection\u003c/h2\u003e\u003cp\u003eA total of 161 groundwater samples were collected from deep wells (GW-1 to GW-161) between March and June 2024. The sampling sites were selected based on their proximity to areas with reported hydrocarbon spill incidents. The sampled wells were private drilled wells used by the local population for water supply. The depth of the wells ranged from 20 to 30 meters, and the water level ranged from 8 to 12 meters.\u003c/p\u003e\u003cp\u003eGroundwater samples were collected through pumping and storage in sterilized amber glass bottles to ensure minimal exposure to light and preserve the integrity of the samples. After labeling, the bottles were placed in insulated boxes and kept under refrigeration. All samples were transported to the laboratory on the same day to prevent alterations that could compromise the reliability of the results.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Physical-chemical analysis\u003c/h2\u003e\u003cp\u003ePhysical parameters were measured in situ, including pH, Electrical conductivity (EC), total dissolved solids (TDS), and temperature, using a calibrated multiparameter equipment HACH, model HQ40D.\u003c/p\u003e\u003cp\u003eTPH were extracted directly from the collection bottles by adding 14 mL of solvent S-316 to 140 mL of sample, maintaining a ratio of 10:1 (sample/solvent). The bottle was sealed and shaken manually for two minutes to facilitate the transfer of compounds from the aqueous phase to the organic phase. Subsequently, phase separation was observed, allowing the hydrocarbon-enriched fraction to be visually identified.\u003c/p\u003e\u003cp\u003eThe organic phase (14 mL) was extracted using a sterile syringe and filtered with silica gel and filter paper placed in a funnel to remove impurities or suspended solids that could interfere with the analysis. The filtered sample was transferred to a quartz cell previously sterilized with the same solvent and analyzed by infrared absorption spectroscopy using the InfraCal2 equipment (Spectro Scientific, Massachusetts, USA). The reading was taken over a period of four minutes, following a calibration curve set at 7.5 mg/L, which allowed for more accurate quantification of the hydrocarbons present in the samples.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Data Processing and Statistical Analysis\u003c/h2\u003e\u003cp\u003eStatistical analysis of the data was performed using R free software [\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e], which allowed for the evaluation of trends and statistical significance. A spatial distribution map of pollution was generated to identify areas of significant concern for Amazon residents. The ArcGIS 10.8 Geographic Information System (GIS) software was used for map generation.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.5. Health risk assessment\u003c/h2\u003e\u003cp\u003eIn the study area, the exposure to TPH can occur through ingestion of groundwater used as a drinking water supply; the water supply is provided through private water wells. Therefore, the human health risk was assessed for residential scenarios where the receptors adults and children are exposed through ingestion of water. The average daily dose (ADD: mg/kg-day) for ingestion was calculated according to the Eq.\u0026nbsp;1 [\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e], [\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{ADD}_{ingestion=\\:}\\frac{{C}_{gw}\\:\\times\\:EF\\:\\times\\:IR\\:\\times\\:ED}{AT\\:\\times\\:BW}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eEq.\u0026nbsp;1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eWhere: C\u003csub\u003egw\u003c/sub\u003e is the TPH-concentration in groundwater (mg/L), EF is the annual exposure frequency (days/year), IR is the ingestion rate of water (L/day), ED is the lifetime exposure duration (years), BW is the body weight (kg), and AT is the averaging time (days). For the calculation of the ADD, the 95th percentile of the exposure parameters were used (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe potential human health risk for noncarcinogenic effects was quantified in terms of Hazard Quotients (HQ), by the ratio of the ADD to the reference dose (RfD). If HQ is above 1, the safe exposure threshold is exceeded, and the systemic effects linked with the exposure can be produced. The carcinogenic risk (CR) was estimated by multiplying the ADD by the slope factor (SF). If CR is above 1.0 x 10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e, the safe exposure limit is exceeded [\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e], [\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e]. The values of parameters used in this study are presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. In this study, a conservative approach was adopted for selecting toxicity values, which is why the RfD and SF were applied to the TPH \u0026ndash; Aromatic (high, low, and medium). In general, aromatic hydrocarbons tend to be more water soluble and mobile than the aliphatic hydrocarbons [\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e]. The toxicity values, RfD and SF, ​​were obtained from the Risk Assessment Information System website [\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe main challenge in assessing TPH toxicity in human health risk assessments is the complexity of TPH mixtures, which can contain hundreds or thousands of compounds. Even if it were possible to measure the concentration of each compound, toxicity data are not available for each. Key factors to consider when estimating TPH toxicity and interpreting results include: (1) TPH mixtures may contain both hydrocarbons and polar compounds; (2) they may include both natural (e.g., humic acids) and anthropogenic substances unrelated to petroleum; and (3) detected compounds depend on the specific TPH analytical method used [\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e]. Although TPH concentrations have limited utility for risk assessment, due to the high uncertainty associated with the complexity of TPH mixtures [\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e], [\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e], [\u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e], they serve as an inexpensive tool for preliminarily determining whether contamination poses a risk to residents in affected environments. If TPH concentration suggests significant contamination in drinking water, the next step is to gather additional data to quantitatively assess the human health risk [\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e]. This will require determining the concentrations of different oil fractions using more precise analytical methods, as well as considering site-specific exposure parameters.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eParameters used in the risk assessment\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eParameter\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eUnits\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePoint value\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003ep95\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eEF_\u003csub\u003eadult and children\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eday/year\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e365\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIR_\u003csub\u003eadult\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eL/day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIR_\u003csub\u003echildren\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eL/day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.7\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eED_\u003csub\u003eadult\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eYear\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eED_\u003csub\u003echildren\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eYear\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBw_\u003csub\u003eadult\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eKg\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e78.73\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBw_ \u003csub\u003echindren\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eKg\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e36.95\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAT_\u003csub\u003eno cancer\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDay\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e365 x ED\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAT_\u003csub\u003ecancer\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDay\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e365 x 70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRfD \u003csub\u003e(TPH- Aromatic High)\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003emg/kg-day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.0003\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRfD \u003csub\u003e(TPH- Aromatic Low)\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003emg/kg-day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.004\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRfD \u003csub\u003e(TPH- Aromatic Medium)\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003emg/kg-day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSF \u003csub\u003e(TPH-Aromatic High)\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1/mg/kg-day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSF \u003csub\u003e(TPH-Aromatic Low)\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1/mg/kg-day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.055\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.1. Physical parameters\u003c/h2\u003e\u003cp\u003eAccording to the results of the physical parameters of groundwater measured in situ (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), significant variations were observed between the provinces of Orellana and Sucumb\u0026iacute;os. The pH showed wide variability, with values ranging from 5.40 to 8.47 in Orellana and from 4.96 to 8.72 in Sucumb\u0026iacute;os, reflecting conditions ranging from slightly acidic to moderately alkaline. Electrical conductivity (EC) reached a maximum value of 556 \u0026micro;S/cm in Orellana and 465 \u0026micro;S/cm in Sucumb\u0026iacute;os. These results, together with total dissolved solids (TDS) concentrations, suggest variations in mineral content between the groundwater of Orellana and Sucumb\u0026iacute;os. Notably, Sucumb\u0026iacute;os recorded a maximum TDS concentration of 233 mg/L, compared to 11.78 mg/L in Orellana, with the former also exhibiting the highest standard deviation. Regarding temperature, values were considerably high in both areas, reaching 46.3\u0026deg;C in Sucumb\u0026iacute;os and 38.88\u0026deg;C in Orellana, which could be due to local hydrogeological conditions.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eStatistical summary of physical parameters of groundwater in Orellana and Sucumb\u0026iacute;os.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eProvince\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003epH\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eTDS (mg/L)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eEC (\u0026micro;S/cm)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eT (\u0026deg;C)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eOrellana\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eMin\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e5.40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e2.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e19.91\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003ep50\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e6.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e183.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e27.72\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003ep95\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e7.88\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e9.22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e432.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e36.24\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eMax\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e8.47\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e11.78\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e556.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e38.88\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eSD\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.53\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.57\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e123.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e3.65\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eSucumb\u0026iacute;os\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eMin\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.96\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e4.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e22.60\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003ep50\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e6.71\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e4.46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e89.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e28.31\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003ep95\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e8.21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e8.78\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e275.60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e34.08\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eMax\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e8.72\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e233.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e465.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e46.30\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eSD\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e45.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e90.58\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e3.41\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Concentration of TPH in groundwater\u003c/h2\u003e\u003cp\u003eThe presence of TPH in groundwater samples is a significant indicator of petroleum contamination. In Orellana, TPH concentrations ranged from 0.11 to 7.30 mg/L, while in Sucumb\u0026iacute;os, TPH levels varied between 0.13 and 7.45 mg/L (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). In Sucumb\u0026iacute;os, 97.62% of the samples exceeded the maximum permissible limit (MPL) for TPH concentration in drinking water, which is set at 0.2 mg/L according to the Quality Criteria for Water Sources for Human and Domestic Consumption, established in Ecuadorian regulations [\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e]. The situation is similar in Orellana, with 93.51 % o the samples exceeding the MPL for TPH. The samples with the highest TPH content are found in the northern part of the study area, in the province of Sucumb\u0026iacute;os (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2\u003c/span\u003e). In terms of depth, the samples analyzed mostly come from wells between 10 and 30 meters deep, which indicates that relatively superficial layers of the subsoil are affected.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eTPH concentration (mg/L) in groundwater samples from the Ecuadorian Amazon.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"7\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eProvince\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003en\u003c/em\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMin\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003ep50\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003ep95\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eMax\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eS.D.\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOrellana\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e77\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.71\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e2.87\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e7.30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e1.38\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSucumb\u0026iacute;os\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e84\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e3.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e7.30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e7.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e2.51\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThere are few studies reporting the presence of TPH in the Ecuadorian Amazon. San Sebast\u0026iacute;an et al reported TPH values ranging from 0.2 to 2.88 mg/L in rivers near oil wells in northeastern Ecuador[\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e]. In addition, L. Corral-Garc\u0026iacute;a et al reported that TPH concentrations vary from 9.4 to 847.4 mg/kg, with polycyclic aromatic hydrocarbon (PAH) levels varying from 10.15 to 711.1 mg/kg in sediment samples from the \u003cem\u003eAguarico\u003c/em\u003e and \u003cem\u003eNapo\u003c/em\u003e rivers [\u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e65\u003c/span\u003e]. These studies show that TPH contamination is persistent and poses a risk to both the ecosystem and local communities. A similar trend is observed in other countries, where areas with intensive oil activity have resulted in high levels of TPH in various environmental matrices. Ihunwo et al evaluated the concentration of TPH in surface waters at five sampling stations from Woji Creekm, Nigeria, finding TPH values ​​between 1.01\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12 and 3.64\u0026thinsp;\u0026plusmn;\u0026thinsp;1.12 [\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e]. Ahiamadu et al informed about TPH contents in surface water ranged from 0.017 to 0.033 \u0026micro;/L, TPH in groundwater ranged from 0.010 to 11600 \u0026micro;/L, and TPH in soils ranged from 5364 to 71,283 mg/kg in Nigeria [\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e]. Ugochukwu et al reported TPH values ​​between 240 and 62,388 in Nigerian soils, where the regulatory intervention limit for TPH is 5000 mg/kg, meaning that soils with TPH concentrations above this limit are considered to pose significant ecological and health risks [\u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e68\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIn Ecuadorian legislation, the MPL for TPH is more restrictive compared to other international regulatory frameworks. For example, the U.S. Environmental Protection Agency (EPA) does not set an overall MPL for drinking water but regulates specific aromatic compounds such as benzene (0.005 ml/L) and toluene (1 mg/L) due to the individual health risks they pose [\u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e69\u003c/span\u003e]. For its part, Environment and Climate Change Canada (ECCC) regulates individual compounds such as benzene (0.005 mg/L) in drinking water. As for the World Health Organization, it has not established a specific MPL for TPH in water for any use. In the case of Ecuador, the TULSMA establishes a general limit for TPH in drinking water (0.2 mg/L), and additionally, it sets a maximum concentration of 0.5 mg/L of TPH for the preservation of flora and fauna in freshwater, marine, and estuarine waters. It also establishes a limit of 20 mg/L for discharges into the public sewer system and regulates specific compounds such as benzene (0.01 mg/L) and toluene (1 mg/L) [\u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e70\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e3.3. Risk assessment\u003c/h2\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows the results of non-cancer and cancer risk for adults and children residing in the northern Amazon and potentially exposed to oil pollution. It is evident that in the Ecuadorian Amazon, strongly impacted by oil activities, people who consume groundwater with high TPH contents are exposed to non-cancer and cancer risk levels higher than those recommended by the USEPA, HI\u0026thinsp;\u0026gt;\u0026thinsp;1 and CR\u0026thinsp;\u0026gt;\u0026thinsp;1.0 x 10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e, respectively. This exposure can lead to long-term health problems for people, especially children, who are the most vulnerable receptors. His study, the risk assessment was made considering the toxicity factors of TPH - aromatic high, TPH - aromatic low, and TPH - aromatic medium. The results of this preliminary risk assessment are worrying, as the sampled sites exceed the safe exposure limit in more than 95% of the sampled sites (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e). In this regard, this assessment reinforces the need to address the problem of contamination by TPH and other potentially toxic elements in petroleum environments. Considering that TPH concentrations can represent very different compositions and pose varying risks to human health and the environment, the results obtained in this study should be handled with caution. As a general measure of petroleum contamination, the TPH results indicate the presence of petroleum hydrocarbons in the sampled environment. The measured TPH values suggest the relative potential for human exposure and, consequently, the potential for health effects. Assessing the health effects of TPH exposure requires much more detailed information than a single TPH value can provide. In our study, due to the lack of knowledge of the type of compounds present in TPH, in risk assessment only the ingestion route was considered, however, other exposure routes such as dermal contact or inhalation of vapors should be quantified, which can cause a cumulative risk in the human body.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eResults of the \u003cb\u003epreliminary\u003c/b\u003e human health risk assessment\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRisk assessment\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003eOrellana\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003eSucumb\u0026iacute;os\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNon-cancer risk (HQ)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eHQ_adults\u003c/p\u003e\u003cp\u003e(Min \u0026ndash; Max)\u003c/p\u003e\u003cp\u003eS.D.\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eHQ_children\u003c/p\u003e\u003cp\u003e(Min \u0026ndash; max)\u003c/p\u003e\u003cp\u003eS.D.\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eHQ_adults\u003c/p\u003e\u003cp\u003e(Min \u0026ndash; Max)\u003c/p\u003e\u003cp\u003eS.D.\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eHQ_ children\u003c/p\u003e\u003cp\u003e(Min \u0026ndash; Max)\u003c/p\u003e\u003cp\u003eS.D.\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTPH- Aromatic High\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(6.18E\u0026thinsp;+\u0026thinsp;02-9.31E\u0026thinsp;+\u0026thinsp;00)\u003c/p\u003e\u003cp\u003e1.16E\u0026thinsp;+\u0026thinsp;02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e(1.12E\u0026thinsp;+\u0026thinsp;03-1.69E\u0026thinsp;+\u0026thinsp;01)\u003c/p\u003e\u003cp\u003e2.11E\u0026thinsp;+\u0026thinsp;02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e(6.31E\u0026thinsp;+\u0026thinsp;02-1.10E\u0026thinsp;+\u0026thinsp;01)\u003c/p\u003e\u003cp\u003e2.13E\u0026thinsp;+\u0026thinsp;02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e(1.14E\u0026thinsp;+\u0026thinsp;03-1.99E\u0026thinsp;+\u0026thinsp;01)\u003c/p\u003e\u003cp\u003e3.86E\u0026thinsp;+\u0026thinsp;02\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTPH- Aromatic Low\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(4.64E\u0026thinsp;+\u0026thinsp;01-6.99E-01)\u003c/p\u003e\u003cp\u003e8.74E\u0026thinsp;+\u0026thinsp;00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e(8.40E\u0026thinsp;+\u0026thinsp;01-1.27E\u0026thinsp;+\u0026thinsp;00)\u003c/p\u003e\u003cp\u003e1.58E\u0026thinsp;+\u0026thinsp;01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e(4.73E\u0026thinsp;+\u0026thinsp;01-8.26E-01)\u003c/p\u003e\u003cp\u003e1.60E\u0026thinsp;+\u0026thinsp;01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e(8.57E\u0026thinsp;+\u0026thinsp;01-1.50E\u0026thinsp;+\u0026thinsp;00)\u003c/p\u003e\u003cp\u003e2.89E\u0026thinsp;+\u0026thinsp;01\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTPH- Aromatic Medium\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(1.85E\u0026thinsp;+\u0026thinsp;02-2.79E\u0026thinsp;+\u0026thinsp;00)\u003c/p\u003e\u003cp\u003e3.49E\u0026thinsp;+\u0026thinsp;01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e(3.36E\u0026thinsp;+\u0026thinsp;02-5.06E\u0026thinsp;+\u0026thinsp;00)\u003c/p\u003e\u003cp\u003e6.33E\u0026thinsp;+\u0026thinsp;01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e(1.89E\u0026thinsp;+\u0026thinsp;02-3.30E\u0026thinsp;+\u0026thinsp;00)\u003c/p\u003e\u003cp\u003e6.39E\u0026thinsp;+\u0026thinsp;01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e(3.43E\u0026thinsp;+\u0026thinsp;02-5.98E\u0026thinsp;+\u0026thinsp;00)\u003c/p\u003e\u003cp\u003e1.16E\u0026thinsp;+\u0026thinsp;02\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCancer risk (CR)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eCR_adults\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003e(Min \u0026ndash;Max)\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eS.D.\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003eCR_ children\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003e(Min \u0026ndash; Max)\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eS.D.\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eCR_adults\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003e(Min \u0026ndash; Max)\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eS.D.\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u003cb\u003eCR_ children\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003e(Min \u0026ndash; Max)\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eS.D.\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTPH-Aromatic High\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(7.95E-02-1.20E-03)\u003c/p\u003e\u003cp\u003e1.50E-02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e(2.88E-02\u003cb\u003e-\u003c/b\u003e4.34E-04)\u003c/p\u003e\u003cp\u003e5.42E-03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e(8.11E-02-1.42E-03)\u003c/p\u003e\u003cp\u003e2.74E-02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e(2.94E-02-5.13E-04)\u003c/p\u003e\u003cp\u003e9.91E-03\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTPH-Aromatic Low\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(4.37E-03-6.59E-05)\u003c/p\u003e\u003cp\u003e8.24E-04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e(1.58E-03-2.39E-05)\u003c/p\u003e\u003cp\u003e2.98E-04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e(4.46E-03-7.78E-05)\u003c/p\u003e\u003cp\u003e1.51E-03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e(1.62E-03-2.82E-05)\u003c/p\u003e\u003cp\u003e5.45E-04\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"6\"\u003e\u003cem\u003eMin\u0026thinsp;=\u0026thinsp;minimum; Max\u0026thinsp;=\u0026thinsp;maximum; S.D. = standard deviation\u003c/em\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eVarious studies have assessed the human health risks associated with TPH exposure in different regions and through different routes of exposure, revealing varying levels of risk. [\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e], evaluated the non-carcinogenic cumulative risk in terms of Hazard Index (HI) for ingestion, skin contact, and inhalation routes due to exposure to TPH (C10-C40) in soils at an oil refinery in China, finding that the HQs of aliphatic hydrocarbon (C10-C12) and aliphatic hydrocarbon (C13-C16) were higher than the acceptable risk level for humans (HI\u0026thinsp;\u0026gt;\u0026thinsp;1), with HI values ​​of 4.78 and 9.04, respectively. In the other hand, the calculated HIs for aromatic hydrocarbons were lower than the safe threshold. [\u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e71\u003c/span\u003e] reported significantly high HQ for exposure to TPH via groundwater ingestion in areas impacted by oil activities in Nigeria. The HQ values reached up to 2.0 x 10\u003csup\u003e+\u0026thinsp;3\u003c/sup\u003e, indicating a severe risk of non-cancer health effects. Furthermore, the cancer risk (CR) associated with this exposure was calculated at 5.6 x 10⁻\u0026sup1;, which is significantly higher than the target cancer risk of 1.0 x 10⁻⁵, emphasizing the significant potential for carcinogenic effects in these areas. In contrast, [\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e] focused on the accidental ingestion of contaminated soil, reporting HI values ranging between 0.001 and 5. These values suggest a varying risk of non-cancer health effects, depending on the degree of exposure. Notably, the study found that some of the reported HI values exceeded the threshold of concern, indicating a potential risk for adverse health outcomes in areas where exposure to contaminated soil is higher. [\u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e72\u003c/span\u003e] assessed the HQ for exposure to TPH through the accidental ingestion of surface water and found that for children, HQ values ranged between 2.1 x 10⁻⁵ and 1.9 x 10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e, while for adults, they ranged from 4.6 x 10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e to 4.0 x 10⁻⁵. These relatively low HQ values suggest that the risk for non-cancer health effects is minimal, likely due to low exposure levels and the relatively low concentrations of TPH found in the environment in these specific cases. Lastly, [\u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e73\u003c/span\u003e] studied carcinogenic risk from dermal exposure to TPHs. They found that the carcinogenic dermal risk for adults exceeded the acceptable risk limits, highlighting the importance of assessing direct skin contact as a significant exposure route for harmful hydrocarbons. Although the cited studies show different levels of risk associated with exposure to TPH, the general trend indicates that areas with higher concentrations of hydrocarbons, such as those with intensive oil activities, present a much greater risk to human health. The studies emphasize the need for intervention strategies.\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eExposure to petroleum and its derivatives, whether direct or indirect, causes serious health issues in humans, with effects primarily depending on the nature of the contact [\u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e]. Exposure to TPH may result in a range of health consequences, which can vary depending on the specific hydrocarbons present in the water, their concentrations, and the type and duration of the exposure [\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e]. Exposure to TPH through drinking water can cause gastrointestinal problems like stomach pain, diarrhea, nausea, cramps, and vomiting, with prolonged exposure potentially leading to chronic digestive issues. Additionally, TPH exposure can affect various health systems, causing skin and eye irritation, respiratory and neurological issues, and increased stress. It can also lead to toxicity in genetic, immune, and endocrine systems [\u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e74\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eGroundwater contaminated with TPH may contain volatile organic compounds (Benzene, Toluene, Ethylbenzene, Xylene, Naphthaleno, etc.) [\u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e75\u003c/span\u003e]. Benzene is one of the most worrying TPH compounds due to its toxic and carcinogenic effects [\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e]. EPA has set a maximum limit of 5 ppb of benzene in drinking water and a goal of 0 ppb in water sources like rivers and lakes, as benzene can cause leukemia. It is estimated that regular exposure to 10 ppb of benzene in drinking water or 0.4 ppb in air over a lifetime could increase the risk of one additional cancer case for every 100,000 exposed people [\u003cspan citationid=\"CR76\" class=\"CitationRef\"\u003e76\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eChronic exposure to individual BTX components and/or BTX-rich mixtures may lead to hematological effects. Some of the specific hematological impacts resulting from prolonged exposure to these compounds remain uncertain [\u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e74\u003c/span\u003e]. However, exposure to BTEX may increase the long-term risk of developing adverse health effects, particularly if concentrations of these compounds are high or if exposure is prolonged [\u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e77\u003c/span\u003e]. Additional factors, such as the vulnerability of specific population groups\u0026mdash;such as children or pregnant women\u0026mdash;can exacerbate this risk [\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e]. Regarding long-term effects, continued exposure to groundwater contaminated with TPH may result in severe damage to organs such as the liver, kidneys, and central nervous system. While these effects may not be immediately evident, they will become more apparent over time. Health implications are also influenced by the duration and intensity of exposure, highlighting the importance of promptly addressing water contamination issues. Ongoing monitoring and comprehensive assessments of water quality are crucial to understanding potential risks and mitigating adverse health effects on human populations [\u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e74\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe effects of oil contamination in the Ecuadorian Amazon and its impact on the health of the population have been poorly studied. However, studies by [\u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e78\u003c/span\u003e], [\u003cspan citationid=\"CR79\" class=\"CitationRef\"\u003e79\u003c/span\u003e], [\u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e80\u003c/span\u003e] have indicated potential health risks associated with living near oil fields. These studies highlight the urgent need for further research and monitoring of the health consequences of oil contamination in the region. [\u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e78\u003c/span\u003e] analyzed cancer cases between 1985 and 1998 in the provinces of Sucumb\u0026iacute;os, Orellana, Napo, and Pastaza (where oil extraction occurs) and compared incidence rates with areas without oil exploitation. The results showed a significant increase in the relative risk of various types of cancer, such as stomach, rectal, skin, and kidney cancers in men, and cervical and lymphatic cancers in women, as well as an increase in hematopoietic cancers in children under 10 in the exposed areas. Additionally, [\u003cspan citationid=\"CR79\" class=\"CitationRef\"\u003e79\u003c/span\u003e] examined childhood leukemia incidence in the Ecuadorian Amazon between 1985 and 2000. The results revealed a significantly higher risk of leukemia in children aged 0 to 4 years and in girls aged 0 to 14 years in areas closer to oil fields. Both studies suggest a potential link between cancer incidence and proximity to oil fields. [\u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e80\u003c/span\u003e], based on a study conducted from November 1998 to April 1999, reported that women exposed to TPH contamination in communities near oil fields had a higher likelihood of experiencing spontaneous abortions.\u003c/p\u003e\u003cp\u003eThe significant presence of TPH in groundwater sources in the Amazon region represents a critical challenge for environmental management and public health. Addressing this issue requires comprehensive strategies aimed at both preventing new contamination sources and mitigating existing impacts on ecosystems and communities [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], [\u003cspan citationid=\"CR81\" class=\"CitationRef\"\u003e81\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAlthough Ecuador has a relatively strict regulatory framework, its effective implementation in the territory is limited, revealing a significant gap between environmental legislation and compliance. One of the priority actions is the establishment of permanent water quality monitoring systems for both groundwater and surface water. This monitoring should be systematic, georeferenced, and publicly accessible in order to identify critical areas, detect temporal trends, and evaluate pollutant dispersion patterns. The incorporation of technologies such as remote sensors, automatic sampling stations, and digital platforms for real-time data reporting can significantly strengthen risk management and facilitate informed decision-making.\u003c/p\u003e\u003cp\u003eSimilarly, it is urgent to develop and implement environmental remediation programs in the most affected areas. Depending on the type and level of contamination, the use of techniques such as bioremediation, phytoremediation, or physical-chemical treatments is recommended, accompanied by environmental risk assessments and ecological restoration plans to ensure sustainable ecosystem recovery [\u003cspan citationid=\"CR82\" class=\"CitationRef\"\u003e82\u003c/span\u003e], [\u003cspan citationid=\"CR83\" class=\"CitationRef\"\u003e83\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe prevention of new episodes of pollution requires the strengthening of the regulatory framework and its rigorous enforcement[\u003cspan citationid=\"CR84\" class=\"CitationRef\"\u003e84\u003c/span\u003e]. This includes updating technical standards for hydrocarbon drilling, transportation, and storage, as well as more frequent and comprehensive inspections by the competent authorities. Operating companies must be subject to the implementation of contingency plans, environmental liability insurance, and cleaner and safer technologies.\u003c/p\u003e\u003cp\u003eFinally, the importance of ensuring immediate access to safe sources of water for human consumption in risk areas is highlighted. To this end, the installation of treatment plants, the distribution of bottled water in critical areas, and the promotion of domestic purification systems are proposed. These measures should be coordinated with environmental education and community participation programs that raise awareness of the risks associated with consuming contaminated water and promote a culture of water conservation.\u003c/p\u003e\u003cp\u003eComplementarily, it is essential to consolidate participatory environmental governance processes that guarantee transparency in managing environmental liabilities and foster the active involvement of local communities in decision-making. The convergence of national and international scientific evidence underscores the need for integrated risk management strategies that combine technical interventions, effective regulation, and strong social commitment. Reducing the impacts of oil pollution requires a multisectoral, sustained, and participatory approach that unites prevention, remediation, regulation, and environmental justice.\u003c/p\u003e"},{"header":"5. Conclusions","content":"\u003cp\u003eThe data analyzed show a worrying persistence of total petroleum hydrocarbon (TPH) contamination in the Amazonian provinces of Sucumb\u0026iacute;os and Orellana, Ecuador. In 97.62% of the samples collected in Sucumb\u0026iacute;os and 93.51% of those from Orellana, TPH concentrations exceed the maximum permissible limit of 0.2 mg/L established by Ecuadorian regulations for water intended for human consumption. These results reflect sustained exposure of communities to contaminated sources, posing a considerable risk to public health, particularly in vulnerable populations such as children, who are more susceptible to the chronic toxic effects of hydrocarbons. This concern is supported by the calculated risk values, which exceed acceptable thresholds for both non-carcinogenic and carcinogenic effects. However, the findings should be interpreted with certain limitations in mind. Data coverage remains limited in terms of space and time, which restricts a more accurate characterization of the evolution of the phenomenon and its geographical distribution. In addition, detailed information on the specific chemical composition of the hydrocarbons detected was not available, which is essential for a more rigorous toxicological assessment, particularly with regard to aromatic compounds such as benzene and toluene. The potential cumulative impacts on human health and bioaccumulation processes in local fauna were also not addressed in depth. Therefore, the development of longitudinal studies to establish correlations between chronic exposure to TPH and health conditions in affected populations is recommended. It is also suggested that integrated analyses of water, soil, sediments, and air be incorporated and that participatory approaches that include local knowledge be adopted. This research allowed the identification of areas with the highest TPH concentrations and contributed valuable insights for mitigating health risks in exposed communities.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that this study did not receive any targeted funding or financial\u003c/p\u003e\n\u003cp\u003esupport from external institutions.\u003c/p\u003e\n\u003cp\u003eConflict of interest the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence work reported in this paper. All other authors have no conflict of interest.\u003c/p\u003e\n\u003cp\u003eUse of Artificial Intelligence Artificial Intelligence tools were used exclusively to improve the clarity, coherence, and structure of the manuscript, without altering the originality or scientific integrity of the content.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSampling permission statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIt is hereby declared that during the groundwater sampling process, the corresponding authorization was obtained from the owners of the private wells. Consequently, all samples were collected with the express consent of the owners of the drilled wells.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets supporting the findings of this study will be made available by the corresponding author upon request from the editors or reviewers.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eZA (corresponding author) coordinated the project, led the conceptualization of the study, participated in the discussion of results, and drafted and revised the manuscript.JG\u0026Aacute; assisted in methodological planning and prepared the figures and tables.SJO participated in data collection and processing, performed statistical analysis, and contributed to the discussion and interpretation of results.DM-S collaborated in the preparation of the initial draft of the manuscript and in the organization of the information.MJS supported the interpretation of results and revision of the text.SS provided specialized technical advice and critical review of the manuscript.CM-R contributed to the discussion of results, conclusions, and final revision of the document.All authors read and approved the final version of the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eJ. 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Chira \u003cem\u003eet al.\u003c/em\u003e, \u0026lsquo;Groundwater Contamination by Gas Stations in Two Eastern Amazonian Towns (Northern Brazil)\u0026rsquo;, \u003cem\u003eApplied Sciences\u003c/em\u003e, vol. 14, no. 13, p. 5529, Jun. 2024, doi: 10.3390/app14135529.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Groundwater quality, drinking water, petroleum industry, oil pollution, human health","lastPublishedDoi":"10.21203/rs.3.rs-7466071/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7466071/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe Ecuadorian Amazon, particularly in the provinces of Sucumb\u0026iacute;os and Orellana, has been heavily impacted by oil activity since the 1970s. In this context, this study carried out between March and June 2024 analyzed 161 groundwater samples taken from deep domestic wells in both provinces, with the aim of determining the concentrations of total petroleum hydrocarbons (TPH) and their implication on the health of consumers. The results showed that, in Orellana, TPH concentrations ranged between 0.11 and 7.30 mg/L, while in Sucumb\u0026iacute;os they varied between 0.13 and 7.45 mg/L. More than 95% of water samples exceeded the maximum permissible limit of 0.2 mg/L for drinking water, according to the quality criteria established by Ecuadorian regulations. These levels of contamination reflect a significant exposure of local communities to health risks. In particular, the study revealed that the consumption of groundwater with high concentrations of TPH can generate non-cancer and carcinogenic risks greater than the levels recommended by the United States Environmental Protection Agency (USEPA). This situation endangers the health of people, especially children, who are the most vulnerable. The findings of this study highlight the urgency of implementing control measures and risk management strategies to mitigate contamination in areas affected by oil activity and protect the health of communities that depend on groundwater in the Amazon region.\u003c/p\u003e","manuscriptTitle":"Total petroleum hydrocarbons (TPHs) in groundwater of the Ecuadorian Amazon: Implications for human health","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-25 06:38:50","doi":"10.21203/rs.3.rs-7466071/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"b8f73561-b223-4a16-ab09-e6e4b3f4b9b8","owner":[],"postedDate":"September 25th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":55170115,"name":"Earth and environmental sciences/Environmental sciences"},{"id":55170116,"name":"Health sciences/Risk factors"}],"tags":[],"updatedAt":"2025-12-17T08:25:08+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-25 06:38:50","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7466071","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7466071","identity":"rs-7466071","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}