Heavy metal levels, potential health risk, and uncertainty analysis in a plant–soil–irrigation system of the Yellow River irrigation area of northern Ningxia (China)

Background: Industrial development results in elevated levels of heavy metals in the local environment, including the air, soil, and water. These heavy metals can contaminate crops in the surrounding area, which may pose severe health risks to local inhabitants. The aims of this study were to determine the levels of heavy metals in plant–soil–irrigation system and the associated human health risk with deterministic and probabilistic approaches. Methods In this study, samples of soil, irrigation water, and maize crops were collected from the Yellow River irrigation area in northern Ningxia, China. Inductively coupled plasma-atomic emission spectrometry(ICP-AES)was applied to determine the heavy metal contents in maize grains, soil samples, and irrigation water. Potential health risks were assessed by deterministic and probabilistic estimation. Results The average concentrations of chromium and lead in maize exceeded the maximum allowable concentrations in food. The average concentrations of metals in the associated soil and irrigation water were both below the safe limits allowed in China. Deterministic estimation indicated a hazard index of 0.0986 for all inhabitants, implying no significant non-carcinogenic risk. The lifetime cancer risk value was 3.261×10−5, lower than the maximum acceptable level of 1×10−4 suggested by USEPA, while above the negligible level of 1×10−6 (USEPA) and 1×10−5 (WHO), with females facing a greater health risk than males. Probabilistic estimation indicated that approximately 0.62% of inhabitants are exposed to non-carcinogenic risk due to maize ingestion, while carcinogenic risk exceeds the maximum acceptable level (1×10−4) for 8.23% and negligible level (1×10−5) for 64.26% of inhabitants. Sensitivity analysis indicated that the concentration of arsenic in maize, the daily intake of maize, and exposure frequency of maize are the primary contributing factors in both non-carcinogenic and carcinogenic risks. Therefore, the content of arsenic in maize is of concern in the study region. Conclusions Based on deterministic and probabilistic risk estimation, there are no obvious non-carcinogenic health risks to inhabitants, while carcinogenic risk from As exposure is higher than the acceptable risk level. Females are at greater risk than males, and inhabitants under 20 years of age have the highest risk among age groups.