Assessing the Impact of Shipping on Microplastic Concentration of Filtered Samples

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Brown, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6398226/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 23 Dec, 2025 Read the published version in Microplastics and Nanoplastics → Version 1 posted 11 You are reading this latest preprint version Abstract Background: As microplastics research expands across laboratories worldwide, filtering samples onto inexpensive metal filters and shipping them in metal tins could become the standard practice, replacing the impractical transportation of large water or environmental samples. Despite extensive research on microplastic distribution, there remains a notable absence of standardized methods, including sample transportation, highlighting the need to understand how shipping and packaging methods affect microplastic concentration variability. This study aims to evaluate the influence of different shipping and packaging methods on the recovery rate of microplastic particles that are collected on metal filters. Findings: Water samples spiked with polyethylene spheres were filtered onto 20 µm metal filters. The metal meshes were then placed in metal tins and subjected to six different packaging and shipping methods, ranging from paper boxes and envelopes to insulated hard and foam coolers. Laser Direct Infrared Spectroscopy was employed for the detection and quantification of polyethylene particles. The results revealed significant variation in recovery rates based on the shipping method. The highest recovery rates were observed in samples shipped in insulated hard or foam coolers, with at approximately 91-92% of the microplastics retained, while the lowest recovery was found in samples shipped in a flat rate mailing envelope (10%). Paper boxes with materials that eliminate space for movement inside the box offered moderate protection, with recovery rates of approximately 70%. Conclusions: This study demonstrates that shipping methods can substantially influence the retention of microplastics during transport from field sites to laboratories for analysis. Shipping methods where the packing remains upward such as with a cooler with a handle provided the highest recovery rates. We infer that this is due to the better care in handling from mail/shipping carriers; however, this method cost more. Lowest recover rates occurred when metal tins could freely move within the packaging and the package was allowed to be in any orientation. The findings highlight the importance of packaging choice in minimizing microplastic loss during shipping. Further research is necessary to standardize sample handling protocols and ensure consistent results across various transportation conditions, ultimately improving the reliability of microplastic contamination assessments. Microplastic Polyethylene LDIR Shipping Packaging Recovery Figures Figure 1 Figure 2 Introduction Although research on microplastics (MPs) has increased significantly over the last 20 years (Thompson et al., 2024 ), there remains a significant gap in standardized methods for detecting and quantifying MPs, particularly in diverse environments and under varying conditions. McIlwraith et al., ( 2025 ) highlighted the importance of positive controls which is essential for advancing microplastic research. With growing research interest in microplastics across water and environmental samples (Hale et al., 2020 , Koutnik et al., 2021 ; Mu et al., 2022 ; Piehl et al., 2019), along with an expanding network of laboratories capable of MP analysis, establishing efficient sample shipping methods has become crucial. Rather than transporting bulky water or environmental samples directly, a more practical approach may be filtering the samples onto cost-effective metal filters and transporting them in simple metal containers. This method could become the standard practice for MP analysis, offering a streamlined solution to sample handling and transportation challenges. Additionally, since microplastics research is conducted in various regions, where instrument may not always be available locally, efficient, and reliable sample shipping practices are essential for enabling global collaboration. The handling and shipping process may introduce contamination or lead to microplastic loss, which complicates the accurate assessment of MP levels across different locations. There is a need for studies that investigate the effects of shipping conditions on MP concentration, to ensure reliable testing and comparison of samples transported to laboratories for further analysis. This study specifically investigates the concentration of polyethylene (PE) spheres collected on metal filters subjected to various packaging and shipping methods to assess how transportation conditions affect MP particles concentration. Our hypothesis is that different shipping methods and packaging materials will influence the recovery rate of PE particles. The purpose of this study is to assess the extent of MP contamination introduced and loss of the sample MP during various shipping methods by quantifying PE particles before and after shipment. Materials and Methods Nineteen 1-liter water samples were prepared, each spiked with 2 mg of polyethylene (PE) spheres. The PE spheres used in this experiment were purchased from the Cospheric (CPMS-0.96, Lot # 120907-1-10, Lot Ref #: 2483), with a size range of 10 to 106 µm and a density of 0.96 g/cm 3 . PE particles were selected for testing in this study because they are among the most common plastics found in the environment, widely used in products like packaging and plastic bags (Geyer et al., 2017 ). Additionally, their distinct chemical properties make them easy to detect, ensuring precise and reliable analysis (Hou et al., 2020 ; Prata et al., 2019 ). The samples were filtered through a 20 µm metal filter (Fig. 1A), and the filtered material was stored in a shallow screw-top metal tin (Uline, S-23417), which is designed for durability and versatility (Fig. 1A). With its secure screw-top lid, this tin minimizes contamination from the container during the study while providing easy access to the stored material. One of the nineteen samples was a control sample (non-shipped) to establish a baseline concentration and use for quality control/quality assurance. This control was essential to compare the effect of shipping conditions against a non-shipped sample. To ensure accuracy and assess the detection error of the instrument, all samples were run a second time. This additional analysis allowed for a more reliable measurement by verifying the consistency of results and identifying any potential deviations in the detection process. Eighteen prepared samples were then subjected to six different shipping methods, with three samples for each method, all shipped separately, to ensure triplicate testing and allow for the calculation of standard deviation to assess variability. After shipments were received at Northern Illinois University, the filters and metal containers were washed with 20 mL of microplastic free hydrogen peroxide (H₂O₂). Filtrate was then filtered onto a Polycarbonate (PCTG) Gold-Coated Membrane Filters (Fig. 1B), 0.8 Micron, 40/20 nm Coating, 25 mm (Sterlitech, Aburn, WA) using an all-glass vacuum filter. Filters were analyzed using an Agilent 8700 Laser Direct Infrared Spectroscopy (LDIR) (Santa Clara, CA), a non-destructive technique, as a key analytical tool for the detection and characterization of MPs (Fig. 1B). LDIR is a powerful technique for chemical analysis that combines the precision of laser technology with the sensitivity of infrared spectroscopy (Alwan & Robey, 2022 ; Tian et al., 2022 ; Whiting et al., 2022 ). It offers several advantages, such as high sensitivity for detecting small particles down to 20 µm, faster analysis due to automation, and excellent spatial resolution for locating MPs on surfaces, over traditional methods of MP analysis, making it particularly well-suited for this study. The number of PE particles was recorded for each sample, including those retained in the containers after shipping, to determine the recovery rate of MPs. The recovery rate was calculated by comparing the number of recovered particles to the original number of particles spiked (positive control). This allowed a determination of how shipping conditions affected the loss or contamination of microplastics. Quality Assurance and Quality Control (QA/QC) To ensure the integrity and reliability of the results, several QA/QC measures were implemented throughout the study. These measures were designed to validate and reproduce the findings, ensuring consistency across different shipping and packaging methods. First, the metal tins were used to store filtered samples to minimize external contamination. Each tin was properly labeled, placed in designated boxes, and transported securely to the laboratory. The triplicate shipping was performed to ensure consistency across different shipping conditions and to account for any variability introduced during transport. This approach increased confidence in the study’s findings by reducing the influence of any single shipping event. Personal protective equipment, including 100% cotton laboratory gowns and nitrile gloves, was always worn by the researchers during the experiment and analysis. Sample preparation and filtration were carried out in a laminar flow hood to ensure a controlled environment. All glassware and apparatus were thoroughly cleaned and rinsed with microplastic-free distilled water multiple times to eliminate any potential contamination. A control sample, which was not subjected to shipping, was included to establish a baseline concentration of PE spheres, ensuring accurate comparison with shipped samples. Filters and containers were rigorously cleaned post-shipping with microplastic-free hydrogen peroxide, further reducing the risk of contamination. The sample solution beakers, containing particles with hydrogen peroxide, were covered with aluminum foil until vacuum filtration. The reagent blank was verified to be free of microplastics, acting as a negative control for contamination checks. The use of a polycarbonate gold-coated membrane filter and an Agilent 8700 LDIR instrument for microplastic detection ensured a non-destructive and highly sensitive analytical approach to ensure optimal performance. The filter holder and metal platform were cleaned with cotton using ethanol (96%) before and after analyzing each sample filter in LDIR. Each sample was analyzed in duplicate to assess the consistency and reliability of the measurements. Running samples in duplicate allowed for the identification of any discrepancies in the results, contributing to higher data reliability. A blank control was analyzed after every three samples to monitor potential contamination and verify the accuracy of particle recovery during the analysis. No significant background interference was detected in this study, confirming the reliability of the analytical process. Results and Discussion The results from all six shipping methods exhibited exceptional consistency, with triplicate shipments producing nearly identical recovery rates in each case, as shown in Fig. 2. In Test 1, three samples were shipped via the United States Postal System (USPS) in a small paper cardboard box (Table 1 ) without material to restrict movement of the sample tin, resulting in low recovery. Initial analyses detected 455, 781, and 623 PE particles on the filter, with an additional 23, 40, and 63 particles found in the container, yielding total recoveries of 478, 821, and 686 particles, respectively. The recovery rates were 20%, 35%, and 29%, respectively, when compared to the unshipped positive control sample. A second analysis was conducted to assess detection error relative to the control sample, yielding recovery rates of 18%, 24%, and 27%, which were consistent with the initial findings. The mean recovery rate for Test 1 was 25.5% (± 6.2% standard deviation), representing a moderate level of consistency among the replicates. The substantial loss of PE particles during shipping is evident in this sample, which recorded the second-lowest recovery rate in the study. Results suggest that the use of a small paper box and no material to eliminate movement of the tin provides insufficient protection against external factors such as environmental exposure or mechanical stress during shipment. The small cardboard box may not have adequately cushioned the sample against mechanical agitation, leading to the potential loss of particles during transit. Unlike some of the other test samples, it exhibited a relatively high number of PE particles detected in the container. This may suggest that some particles adhered to the inner walls of the container, potentially due to static or moisture effects, further reducing the number of particles recovered from the filter. However, even with this additional recovery, the overall count remained low. A sample was shipped via FedEx in a small, compact paperboard box (Test 2) with protective material to prevent movement within the container. The initial analysis for this shipment showed a 70% recovery rate, with replicate samples exhibiting recovery rates ranging from 60–70%. A second analysis was conducted, producing recovery rates of 65%, 65%, and 69%, which remained consistent with the initial findings. The low number of particles found in the container (8, 11, and 8 particles) suggests that most PE particles remained on the filter rather than adhering to the container. Across initial and duplicate runs, the recovery rate averaged 68%, with a standard deviation of ± 2.1%, indicating a high level of consistency among replicates. The external factors such as packaging leakage or environmental exposure likely played a larger role in the loss of particles, rather than particles adhering to the container walls. A sample was shipped via USPS in an envelope (Test 3) without protective material to restrict movement of the sample tin. Initial analysis detected 236 PE particles on the filter and 90 particles in the container, resulting in a total recovery of 326 particles (Table 1 ). The recovery rate was 14%, decreasing to 10% upon reanalysis, making it the lowest among all tested shipping methods. Replicate samples showed recovery rates of 22% and 32% (21% and 30% on reanalysis), indicating variability in particle retention. These findings suggest that the envelope provided minimal protection, contributing to substantial particle loss during transit. The thin material may have allowed some particles to escape or become unrecoverable due to inadequate sealing. Additionally, the relatively high number of PE particles found in the metal containers (90, 105, and 187 particles) compared to other shipping methods indicates that a significant portion adhered to the container’s inner walls. Figure 2 highlights a mean recovery rate of 21.5% for Test 3 while the standard deviation of ± 8.6% reflects considerable variability across replicates. The increased loss of particles is likely due to movement, tossing, or vibration during shipping, which caused particles to adhere to the container and become difficult to recover from the filter. These results indicate that envelopes are unsuitable for shipping samples requiring protection against particle loss. The sample shipped via FedEx in an Igloo cooler with an ice pack and material eliminating movement of the sample tin (Test 4) had an initial detection of 2,153 PE particles on the filter and 6 particles in the container, for a total of 2,159 recovered particles. The corresponding recovery rates of triplicates were 92%, 91%, and 94% (92%, 90%, and 92% on reanalysis), which were significantly higher than most other shipping methods in the study. The method demonstrates a relatively strong preservation of the MP particles during shipment, achieving an average recovery rate of 92% with a standard deviation of ± 1.3%, reflecting a high degree of reliability in the results. Results suggests that the insulated packaging provided by the Igloo cooler box was highly effective in preventing particle loss. Although some particles were not recovered, this method demonstrated far better results compared to less insulated shipping methods, such as in an envelope or paper box. The cooler provides thermal insulation, which helps maintain a stable internal environment, protecting the sample from extreme temperature fluctuations during transit. This insulation likely prevented environmental factors such as heat, humidity, or cold from affecting the integrity of the MP sample. The rigid structure of the cooler and the material eliminating movement of the tin offers better protection against mechanical stress, such as jostling or impacts during shipping, contributing to the higher recovery rate by reducing the loss of particles to external forces. A cooler with a handle also likely prevented the cooler from being tossed; we assume that the container was held upright throughout shipping. Only 3–8 particles were observed in the metal containers, suggesting that most of the particles remained on the filter. This indicates that the shipping method prevented significant adherence of particles to the container, minimizing particle loss within the container itself. The sample shipped via FedEx in a foam cooler box, along with ice bags to eliminate movement of the sample tin (Test 5), yielded 2,140 PE particles detected on the filter and 4 particles in the container, for a total of 2,144 recovered particles upon initial analysis. The recovery rate was 92%, with replicate results of 92% and 91% as shown in Fig. 2. Reanalysis produced recovery rates of 90%, 89%, and 90%, confirming the method’s consistency. The average recovery rate for Test 5 was 91% (variability ± 1.3%), indicating a high level of consistency and matching the performance of shipments using an Igloo cooler, making it one of the best-performing methods in this study. The high recovery reveals that the foam cooler, combined with the ice bags, provided effective protection against environmental factors and particle loss during transit. The foam cooler, much like the Igloo cooler, offers thermal insulation, which helps maintain a stable temperature and prevents exposure to extreme heat or cold. The addition of ice bags further enhanced the cooling effect, ensuring the sample remained at a low, stable temperature throughout the shipping process. This minimized any thermal stress that could cause particle loss or degradation. These types of coolers are usually maintained upright and handled with more care than cardboard boxes. Only 4–8 particles were detected in the containers, which is the lowest amount found in the study. This suggests that most of the PE particles remained on the filter and were not lost to adherence within the container, further contributing to the high recovery rate. This emphasizes the importance of using insulated packaging materials for sensitive MP samples. In addition to examining local shipping, this study investigated the impact of international shipping conditions on MP contamination and sample integrity. The Test 6 sample was carried from Northern Illinois University to Cambodia by one of the authors on a commercial airline where it was then shipped back to the United States via DHL; the sample was packaged in a cardboard box with materials used to eliminate shifting of the sample within the box. Test 6, upon initial analysis, detected 1,628 PE particles on the filter and 12 particles in the container, totaling 1,640 recovered particles (Table 1 ). This corresponds to a 70% recovery rate (68% with reanalysis) compared to the control sample. This is the only sample that was not done in triplicate, but the results are consist with the domestically shipped samples in small cardboard box (Test 2) that also had material to eliminate movement of the sample within the box. The Test 6 recovery rate is despite the sample being shipped internationally from Cambodia, with long shipping distances that may introduce additional stressors, such as higher vibrations, changes in temperature and humidity, or extended handling periods. These factors could contribute to the lower recovery rate by affecting the integrity of the packaging or filter system. However, the sample was packed securely to minimize movement and achieved the same recovery rate as the similarly packed cardboard box shipped domestically. While there was loss of particles during each shipment, there was not an introduction of other particles that would indicate outside contamination of the samples. The particle loss is correlated with the way the samples were packed within the shipping containers and the type of shipping container. We are also confident that the shipping materials and packaging is the main driver of recovery rate and not the particular shipper used to transport the packages. Conclusions This study is the first to comprehensively evaluate MP concentrations across different shipping methods. As the interest in MPs in water or environmental sample increases (Cox et al., 2019; Diaz et al., 2023; Vincent et al., 2021; Sangkham et al., 2023) and the number of labs that can analysis MP increases, we need to understand the best methods for shipping samples. The importance of positive controls, QA/QC and standardization in microplastic research is becoming more critical as the number of research projects are done (McIlwraith et al., 2025). Since it might be impractical to ship large quantities of water or other environmental samples, filtering samples onto inexpensive metal filters and shipping in inexpensive metal tins might become the norm for analysis. The study found significant variation in the recovery rates of PE particles across various shipping methods. In comparison to shipments with room for the sample tin to move (Tests 1 and 3), which exhibited recovery rates ranging from 10% to 35%, samples shipped in small cardboard boxes (Tests 2 and 6), with materials to minimize the movement of the metal tins, resulted in mid-range recovery rates of approximately 70%. The mid-range recovery rates were in both the domestically and internationally shipped samples. The addition of material into the boxes to eliminate movement of the sample tins significantly increased the recovery rate. The shipped Igloo cooler (Test 4) and foam cooler box (Test 5), both packed to prevent sample movement, were the top performers, achieving a recovery rate of approximately 92%, with consistent results observed throughout the replicates. This suggests that insulated packaging methods with containers that are more likely to remain upright, regardless of the exact material (hard or foam coolers), provide superior protection for MP samples during shipping. In contrast, shipping methods using paper or envelope packaging with no material to immobilize the sample tin resulted in the lowest recovery rates. While we analyzed samples using LDIR, the shipping and recovery rates could also apply for other analysis methods such as micro Fourier Transform Interferometer (µFTIR) spectroscopy, scanning electron microscope (SEM), Raman spectroscopy, or visual inspection. Future inter-laboratory comparisons of microplastics research across regions could facilitate method harmonization and enhance consistency in MP analysis. Our findings highlight the importance of selecting appropriate packaging materials and packing procedures to minimize MP loss during shipping. Abbreviations DHL: Shipping Company FedEx: Federal Express Corporation LDIR: Laser Direct Infrared Spectroscopy MP: Microplastic MPs: Microplastics PCTG: Polycarbonate PE: Polyethylene SEM: Scanning Electron Microscope µFTIR: micro Fourier Transform Interferometer USPS: United States Postal Service Declarations Availability of data and materials The LDIR export datasets from the current study are available from the corresponding author on reasonable request. Competing interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Funding The authors gratefully acknowledge the support of the National Science Foundation under Grant No. 2320748. Acknowledgements Not applicable Authors' contributions CWO substantially contributed to the conception, acquisition, design of the work, analysis, interpretation of data, and drafted the work or substantively revised it. ML substantially contributed to the conception, design of the work, interpretation of data, and drafted the work or substantively revised it. KEE contributed to the design of the work and interpretation of data. MRMB substantially contributed to the conception, interpretation of data, and drafted the work or substantively revised it. BC contributed to the acquisition, analysis, and interpretation of data. All authors read and approved the final manuscript. References Alwan W, Robey D. Characterization of Microplastics in Environmental Samples by Laser Direct Infrared Imaging; 2022. Cox KD, Covernton GA, Davies HL, Dower JF, Juanes F, Dudas SE. Human Consumption of Microplastics. Environ Sci Technol. 2019;53(12):7068-74. doi.org/10.1021/acs.est.9b01517 Díaz M, Sol D, Laca A, Crisóstomo-Miranda J, Laca A, Carrasco S, et al. Contribution of household dishwashing to microplastic pollution. Environ Sci Pollut Res. 2023. doi.org/10.1007/s11356-023-25433-7 Geyer R, Jambeck JR, Law KL. 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Anal Bioanal Chem. 2022;414(29-30):8353-64. doi.org/10.1007/s00216-022-04371-2 Thompson RC, Jones WC, Boucher J, Pahl S, Raubenheiner K, Koelmans AA. Twenty years of microplastic pollution research—what have we learned? Science. 2024;386(6720). doi/10.1126/science.adl2746 Table Table 1 is available in the Supplementary Files section Additional Declarations No competing interests reported. Supplementary Files SPSSOutput.docx Table1.docx Cite Share Download PDF Status: Published Journal Publication published 23 Dec, 2025 Read the published version in Microplastics and Nanoplastics → Version 1 posted Editorial decision: Revision requested 26 May, 2025 Reviews received at journal 22 May, 2025 Reviews received at journal 20 May, 2025 Reviews received at journal 10 May, 2025 Reviewers agreed at journal 24 Apr, 2025 Reviewers agreed at journal 22 Apr, 2025 Reviewers agreed at journal 22 Apr, 2025 Reviewers invited by journal 22 Apr, 2025 Editor assigned by journal 08 Apr, 2025 Submission checks completed at journal 08 Apr, 2025 First submitted to journal 07 Apr, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6398226","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Short Report","associatedPublications":[],"authors":[{"id":440126446,"identity":"764bc50c-3a37-4f1b-b761-8ca85de3cd4b","order_by":0,"name":"Chit Wityi Oo","email":"","orcid":"","institution":"Northern Illinois University","correspondingAuthor":false,"prefix":"","firstName":"Chit","middleName":"Wityi","lastName":"Oo","suffix":""},{"id":440126447,"identity":"9a9e504b-4ab8-484c-bff7-2fc0e2e61c5a","order_by":1,"name":"Melissa Lenczewski","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAzElEQVRIiWNgGAWjYBACPhhDgpn5AEMCiHWAgBY2hBa2BFK1MPAYQFgEtbD3Hvz4o+KwvWQ7z7cHD9sY5PhuJBDQwnMuWULizOHE2cy82w0S2xiMJQlqkcgxYzBsu50gx8y7TQKoJXEDQS3yb8wYEv/dtpdj5nkG0lJPWIsEjxnDwYbbjLOZedhAWhIMCPslx1iy4dj/xJnNbGYSCeckDGeeeYBfCz/7GcOPP2rS7CXOH34m+aPMRp7vOAFb0IEEacpHwSgYBaNgFGAHAPWqPbxR1uuWAAAAAElFTkSuQmCC","orcid":"","institution":"Northern Illinois University","correspondingAuthor":true,"prefix":"","firstName":"Melissa","middleName":"","lastName":"Lenczewski","suffix":""},{"id":440126448,"identity":"1d310d1f-373b-4ac8-bbf5-f68f896b9bb1","order_by":2,"name":"Khy Eam Eang","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Khy","middleName":"Eam","lastName":"Eang","suffix":""},{"id":440126449,"identity":"f8b30353-adb7-4e1a-95e1-712d40837a9d","order_by":3,"name":"Megan R.M. Brown","email":"","orcid":"","institution":"Northern Illinois University","correspondingAuthor":false,"prefix":"","firstName":"Megan","middleName":"R.M.","lastName":"Brown","suffix":""},{"id":440126450,"identity":"f4bcd25b-59c9-42dc-aa10-49bf88ac8adb","order_by":4,"name":"Boonyarak Chuanchit","email":"","orcid":"","institution":"Northern Illinois University","correspondingAuthor":false,"prefix":"","firstName":"Boonyarak","middleName":"","lastName":"Chuanchit","suffix":""}],"badges":[],"createdAt":"2025-04-08 02:08:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6398226/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6398226/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s43591-025-00147-4","type":"published","date":"2025-12-23T15:57:05+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":80640488,"identity":"e177c806-2499-4c48-97cf-b8c59ddc2cc2","added_by":"auto","created_at":"2025-04-15 13:09:36","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":829577,"visible":true,"origin":"","legend":"\u003cp\u003eSample material examples. A) metal filter and metal tin used to ship samples, B) samples on a gold filter (upper) and LDIR analysis results (lower) showing the PE spheres\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6398226/v1/b47eca3c2a8e3c5e78f40e16.png"},{"id":80641092,"identity":"937b2a8b-be0f-4496-a0c3-7c509fb66199","added_by":"auto","created_at":"2025-04-15 13:17:36","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":24629,"visible":true,"origin":"","legend":"\u003cp\u003eDistribution of recovery rates across different shipping methods\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6398226/v1/770e36cf8fdef1a1035e76c4.png"},{"id":99172221,"identity":"dd940a3f-f83d-4535-ac73-e3bbbdda0927","added_by":"auto","created_at":"2025-12-29 16:03:56","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1461582,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6398226/v1/927bb9d3-caf4-4db0-8dd4-1ba260785322.pdf"},{"id":80640487,"identity":"3bd0e641-728d-453c-b3a0-8295f565cee3","added_by":"auto","created_at":"2025-04-15 13:09:36","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":16678,"visible":true,"origin":"","legend":"","description":"","filename":"SPSSOutput.docx","url":"https://assets-eu.researchsquare.com/files/rs-6398226/v1/807c0f62be6248d4500e57e9.docx"},{"id":80642712,"identity":"49224f47-c16e-46d8-81f7-71c6e9eba750","added_by":"auto","created_at":"2025-04-15 13:33:36","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":1155448,"visible":true,"origin":"","legend":"","description":"","filename":"Table1.docx","url":"https://assets-eu.researchsquare.com/files/rs-6398226/v1/32b7e2a2cde3ceea79c03d13.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Assessing the Impact of Shipping on Microplastic Concentration of Filtered Samples","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAlthough research on microplastics (MPs) has increased significantly over the last 20 years (Thompson et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), there remains a significant gap in standardized methods for detecting and quantifying MPs, particularly in diverse environments and under varying conditions. McIlwraith et al., (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2025\u003c/span\u003e) highlighted the importance of positive controls which is essential for advancing microplastic research. With growing research interest in microplastics across water and environmental samples (Hale et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2020\u003c/span\u003e, Koutnik et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Mu et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Piehl et al., 2019), along with an expanding network of laboratories capable of MP analysis, establishing efficient sample shipping methods has become crucial. Rather than transporting bulky water or environmental samples directly, a more practical approach may be filtering the samples onto cost-effective metal filters and transporting them in simple metal containers. This method could become the standard practice for MP analysis, offering a streamlined solution to sample handling and transportation challenges. Additionally, since microplastics research is conducted in various regions, where instrument may not always be available locally, efficient, and reliable sample shipping practices are essential for enabling global collaboration. The handling and shipping process may introduce contamination or lead to microplastic loss, which complicates the accurate assessment of MP levels across different locations. There is a need for studies that investigate the effects of shipping conditions on MP concentration, to ensure reliable testing and comparison of samples transported to laboratories for further analysis.\u003c/p\u003e \u003cp\u003eThis study specifically investigates the concentration of polyethylene (PE) spheres collected on metal filters subjected to various packaging and shipping methods to assess how transportation conditions affect MP particles concentration. Our hypothesis is that different shipping methods and packaging materials will influence the recovery rate of PE particles. The purpose of this study is to assess the extent of MP contamination introduced and loss of the sample MP during various shipping methods by quantifying PE particles before and after shipment.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cp\u003eNineteen 1-liter water samples were prepared, each spiked with 2 mg of polyethylene (PE) spheres. The PE spheres used in this experiment were purchased from the Cospheric (CPMS-0.96, Lot # 120907-1-10, Lot Ref #: 2483), with a size range of 10 to 106 \u0026micro;m and a density of 0.96 g/cm\u003csup\u003e3\u003c/sup\u003e. PE particles were selected for testing in this study because they are among the most common plastics found in the environment, widely used in products like packaging and plastic bags (Geyer et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Additionally, their distinct chemical properties make them easy to detect, ensuring precise and reliable analysis (Hou et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Prata et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The samples were filtered through a 20 \u0026micro;m metal filter (Fig.\u0026nbsp;1A), and the filtered material was stored in a shallow screw-top metal tin (Uline, S-23417), which is designed for durability and versatility (Fig.\u0026nbsp;1A). With its secure screw-top lid, this tin minimizes contamination from the container during the study while providing easy access to the stored material.\u003c/p\u003e \u003cp\u003eOne of the nineteen samples was a control sample (non-shipped) to establish a baseline concentration and use for quality control/quality assurance. This control was essential to compare the effect of shipping conditions against a non-shipped sample. To ensure accuracy and assess the detection error of the instrument, all samples were run a second time. This additional analysis allowed for a more reliable measurement by verifying the consistency of results and identifying any potential deviations in the detection process.\u003c/p\u003e \u003cp\u003eEighteen prepared samples were then subjected to six different shipping methods, with three samples for each method, all shipped separately, to ensure triplicate testing and allow for the calculation of standard deviation to assess variability. After shipments were received at Northern Illinois University, the filters and metal containers were washed with 20 mL of microplastic free hydrogen peroxide (H₂O₂). Filtrate was then filtered onto a Polycarbonate (PCTG) Gold-Coated Membrane Filters (Fig.\u0026nbsp;1B), 0.8 Micron, 40/20 nm Coating, 25 mm (Sterlitech, Aburn, WA) using an all-glass vacuum filter. Filters were analyzed using an Agilent 8700 Laser Direct Infrared Spectroscopy (LDIR) (Santa Clara, CA), a non-destructive technique, as a key analytical tool for the detection and characterization of MPs (Fig.\u0026nbsp;1B). LDIR is a powerful technique for chemical analysis that combines the precision of laser technology with the sensitivity of infrared spectroscopy (Alwan \u0026amp; Robey, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Tian et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Whiting et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). It offers several advantages, such as high sensitivity for detecting small particles down to 20 \u0026micro;m, faster analysis due to automation, and excellent spatial resolution for locating MPs on surfaces, over traditional methods of MP analysis, making it particularly well-suited for this study. The number of PE particles was recorded for each sample, including those retained in the containers after shipping, to determine the recovery rate of MPs. The recovery rate was calculated by comparing the number of recovered particles to the original number of particles spiked (positive control). This allowed a determination of how shipping conditions affected the loss or contamination of microplastics.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eQuality Assurance and Quality Control (QA/QC)\u003c/h2\u003e \u003cp\u003eTo ensure the integrity and reliability of the results, several QA/QC measures were implemented throughout the study. These measures were designed to validate and reproduce the findings, ensuring consistency across different shipping and packaging methods. First, the metal tins were used to store filtered samples to minimize external contamination. Each tin was properly labeled, placed in designated boxes, and transported securely to the laboratory. The triplicate shipping was performed to ensure consistency across different shipping conditions and to account for any variability introduced during transport. This approach increased confidence in the study\u0026rsquo;s findings by reducing the influence of any single shipping event.\u003c/p\u003e \u003cp\u003ePersonal protective equipment, including 100% cotton laboratory gowns and nitrile gloves, was always worn by the researchers during the experiment and analysis. Sample preparation and filtration were carried out in a laminar flow hood to ensure a controlled environment. All glassware and apparatus were thoroughly cleaned and rinsed with microplastic-free distilled water multiple times to eliminate any potential contamination. A control sample, which was not subjected to shipping, was included to establish a baseline concentration of PE spheres, ensuring accurate comparison with shipped samples. Filters and containers were rigorously cleaned post-shipping with microplastic-free hydrogen peroxide, further reducing the risk of contamination. The sample solution beakers, containing particles with hydrogen peroxide, were covered with aluminum foil until vacuum filtration. The reagent blank was verified to be free of microplastics, acting as a negative control for contamination checks. The use of a polycarbonate gold-coated membrane filter and an Agilent 8700 LDIR instrument for microplastic detection ensured a non-destructive and highly sensitive analytical approach to ensure optimal performance. The filter holder and metal platform were cleaned with cotton using ethanol (96%) before and after analyzing each sample filter in LDIR.\u003c/p\u003e \u003cp\u003eEach sample was analyzed in duplicate to assess the consistency and reliability of the measurements. Running samples in duplicate allowed for the identification of any discrepancies in the results, contributing to higher data reliability. A blank control was analyzed after every three samples to monitor potential contamination and verify the accuracy of particle recovery during the analysis. No significant background interference was detected in this study, confirming the reliability of the analytical process.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results and Discussion","content":"\u003cp\u003eThe results from all six shipping methods exhibited exceptional consistency, with triplicate shipments producing nearly identical recovery rates in each case, as shown in Fig.\u0026nbsp;2. In Test 1, three samples were shipped via the United States Postal System (USPS) in a small paper cardboard box (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) without material to restrict movement of the sample tin, resulting in low recovery. Initial analyses detected 455, 781, and 623 PE particles on the filter, with an additional 23, 40, and 63 particles found in the container, yielding total recoveries of 478, 821, and 686 particles, respectively. The recovery rates were 20%, 35%, and 29%, respectively, when compared to the unshipped positive control sample. A second analysis was conducted to assess detection error relative to the control sample, yielding recovery rates of 18%, 24%, and 27%, which were consistent with the initial findings. The mean recovery rate for Test 1 was 25.5% (\u0026plusmn;\u0026thinsp;6.2% standard deviation), representing a moderate level of consistency among the replicates. The substantial loss of PE particles during shipping is evident in this sample, which recorded the second-lowest recovery rate in the study.\u003c/p\u003e \u003cp\u003eResults suggest that the use of a small paper box and no material to eliminate movement of the tin provides insufficient protection against external factors such as environmental exposure or mechanical stress during shipment. The small cardboard box may not have adequately cushioned the sample against mechanical agitation, leading to the potential loss of particles during transit. Unlike some of the other test samples, it exhibited a relatively high number of PE particles detected in the container. This may suggest that some particles adhered to the inner walls of the container, potentially due to static or moisture effects, further reducing the number of particles recovered from the filter. However, even with this additional recovery, the overall count remained low.\u003c/p\u003e \u003cp\u003eA sample was shipped via FedEx in a small, compact paperboard box (Test 2) with protective material to prevent movement within the container. The initial analysis for this shipment showed a 70% recovery rate, with replicate samples exhibiting recovery rates ranging from 60\u0026ndash;70%. A second analysis was conducted, producing recovery rates of 65%, 65%, and 69%, which remained consistent with the initial findings. The low number of particles found in the container (8, 11, and 8 particles) suggests that most PE particles remained on the filter rather than adhering to the container. Across initial and duplicate runs, the recovery rate averaged 68%, with a standard deviation of \u0026plusmn;\u0026thinsp;2.1%, indicating a high level of consistency among replicates. The external factors such as packaging leakage or environmental exposure likely played a larger role in the loss of particles, rather than particles adhering to the container walls.\u003c/p\u003e \u003cp\u003eA sample was shipped via USPS in an envelope (Test 3) without protective material to restrict movement of the sample tin. Initial analysis detected 236 PE particles on the filter and 90 particles in the container, resulting in a total recovery of 326 particles (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The recovery rate was 14%, decreasing to 10% upon reanalysis, making it the lowest among all tested shipping methods. Replicate samples showed recovery rates of 22% and 32% (21% and 30% on reanalysis), indicating variability in particle retention. These findings suggest that the envelope provided minimal protection, contributing to substantial particle loss during transit. The thin material may have allowed some particles to escape or become unrecoverable due to inadequate sealing. Additionally, the relatively high number of PE particles found in the metal containers (90, 105, and 187 particles) compared to other shipping methods indicates that a significant portion adhered to the container\u0026rsquo;s inner walls. Figure\u0026nbsp;2 highlights a mean recovery rate of 21.5% for Test 3 while the standard deviation of \u0026plusmn;\u0026thinsp;8.6% reflects considerable variability across replicates. The increased loss of particles is likely due to movement, tossing, or vibration during shipping, which caused particles to adhere to the container and become difficult to recover from the filter. These results indicate that envelopes are unsuitable for shipping samples requiring protection against particle loss.\u003c/p\u003e \u003cp\u003eThe sample shipped via FedEx in an Igloo cooler with an ice pack and material eliminating movement of the sample tin (Test 4) had an initial detection of 2,153 PE particles on the filter and 6 particles in the container, for a total of 2,159 recovered particles. The corresponding recovery rates of triplicates were 92%, 91%, and 94% (92%, 90%, and 92% on reanalysis), which were significantly higher than most other shipping methods in the study. The method demonstrates a relatively strong preservation of the MP particles during shipment, achieving an average recovery rate of 92% with a standard deviation of \u0026plusmn;\u0026thinsp;1.3%, reflecting a high degree of reliability in the results.\u003c/p\u003e \u003cp\u003eResults suggests that the insulated packaging provided by the Igloo cooler box was highly effective in preventing particle loss. Although some particles were not recovered, this method demonstrated far better results compared to less insulated shipping methods, such as in an envelope or paper box. The cooler provides thermal insulation, which helps maintain a stable internal environment, protecting the sample from extreme temperature fluctuations during transit. This insulation likely prevented environmental factors such as heat, humidity, or cold from affecting the integrity of the MP sample. The rigid structure of the cooler and the material eliminating movement of the tin offers better protection against mechanical stress, such as jostling or impacts during shipping, contributing to the higher recovery rate by reducing the loss of particles to external forces. A cooler with a handle also likely prevented the cooler from being tossed; we assume that the container was held upright throughout shipping. Only 3\u0026ndash;8 particles were observed in the metal containers, suggesting that most of the particles remained on the filter. This indicates that the shipping method prevented significant adherence of particles to the container, minimizing particle loss within the container itself.\u003c/p\u003e \u003cp\u003eThe sample shipped via FedEx in a foam cooler box, along with ice bags to eliminate movement of the sample tin (Test 5), yielded 2,140 PE particles detected on the filter and 4 particles in the container, for a total of 2,144 recovered particles upon initial analysis. The recovery rate was 92%, with replicate results of 92% and 91% as shown in Fig.\u0026nbsp;2. Reanalysis produced recovery rates of 90%, 89%, and 90%, confirming the method\u0026rsquo;s consistency. The average recovery rate for Test 5 was 91% (variability\u0026thinsp;\u0026plusmn;\u0026thinsp;1.3%), indicating a high level of consistency and matching the performance of shipments using an Igloo cooler, making it one of the best-performing methods in this study. The high recovery reveals that the foam cooler, combined with the ice bags, provided effective protection against environmental factors and particle loss during transit. The foam cooler, much like the Igloo cooler, offers thermal insulation, which helps maintain a stable temperature and prevents exposure to extreme heat or cold. The addition of ice bags further enhanced the cooling effect, ensuring the sample remained at a low, stable temperature throughout the shipping process. This minimized any thermal stress that could cause particle loss or degradation. These types of coolers are usually maintained upright and handled with more care than cardboard boxes. Only 4\u0026ndash;8 particles were detected in the containers, which is the lowest amount found in the study. This suggests that most of the PE particles remained on the filter and were not lost to adherence within the container, further contributing to the high recovery rate. This emphasizes the importance of using insulated packaging materials for sensitive MP samples.\u003c/p\u003e \u003cp\u003eIn addition to examining local shipping, this study investigated the impact of international shipping conditions on MP contamination and sample integrity. The Test 6 sample was carried from Northern Illinois University to Cambodia by one of the authors on a commercial airline where it was then shipped back to the United States via DHL; the sample was packaged in a cardboard box with materials used to eliminate shifting of the sample within the box. Test 6, upon initial analysis, detected 1,628 PE particles on the filter and 12 particles in the container, totaling 1,640 recovered particles (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). This corresponds to a 70% recovery rate (68% with reanalysis) compared to the control sample. This is the only sample that was not done in triplicate, but the results are consist with the domestically shipped samples in small cardboard box (Test 2) that also had material to eliminate movement of the sample within the box.\u003c/p\u003e \u003cp\u003eThe Test 6 recovery rate is despite the sample being shipped internationally from Cambodia, with long shipping distances that may introduce additional stressors, such as higher vibrations, changes in temperature and humidity, or extended handling periods. These factors could contribute to the lower recovery rate by affecting the integrity of the packaging or filter system. However, the sample was packed securely to minimize movement and achieved the same recovery rate as the similarly packed cardboard box shipped domestically.\u003c/p\u003e \u003cp\u003eWhile there was loss of particles during each shipment, there was not an introduction of other particles that would indicate outside contamination of the samples. The particle loss is correlated with the way the samples were packed within the shipping containers and the type of shipping container. We are also confident that the shipping materials and packaging is the main driver of recovery rate and not the particular shipper used to transport the packages.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThis study is the first to comprehensively evaluate MP concentrations across different shipping methods. \u0026nbsp;As the interest in MPs in water or environmental sample increases (Cox et al., 2019; Diaz et al., 2023; Vincent et al., 2021; Sangkham et al., 2023) and the number of labs that can analysis MP increases, we need to understand the best methods for shipping samples. \u0026nbsp;The importance of positive controls, QA/QC and standardization in microplastic research is becoming more critical as the number of research projects are done (McIlwraith et al., 2025). \u0026nbsp;Since it might be impractical to ship large quantities of water or other environmental samples, filtering samples onto inexpensive metal filters and shipping in inexpensive metal tins might become the norm for analysis.\u003c/p\u003e\n\u003cp\u003eThe study found significant variation in the recovery rates of PE particles across various shipping methods. In comparison to shipments with room for the sample tin to move (Tests 1 and 3), which exhibited recovery rates ranging from 10% to 35%, samples shipped in small cardboard boxes (Tests 2 and 6), with materials to minimize the movement of the metal tins, resulted in mid-range recovery rates of approximately 70%. The mid-range recovery rates were in both the domestically and internationally shipped samples. The addition of material into the boxes to eliminate movement of the sample tins significantly increased the recovery rate.\u003c/p\u003e\n\u003cp\u003eThe shipped Igloo cooler (Test 4) and foam cooler box (Test 5), both packed to prevent sample movement, were the top performers, achieving a recovery rate of approximately 92%, with consistent results observed throughout the replicates. This suggests that insulated packaging methods with containers that are more likely to remain upright, regardless of the exact material (hard or foam coolers), provide superior protection for MP samples during shipping. In contrast, shipping methods using paper or envelope packaging with no material to immobilize the sample tin resulted in the lowest recovery rates. While we analyzed samples using LDIR, the shipping and recovery rates could also apply for other analysis methods such as micro Fourier Transform Interferometer (µFTIR) spectroscopy, scanning electron microscope (SEM), Raman spectroscopy, or visual inspection. \u0026nbsp;Future inter-laboratory comparisons of microplastics research across regions could facilitate method harmonization and enhance consistency in MP analysis. Our findings highlight the importance of selecting appropriate packaging materials and packing procedures to minimize MP loss during shipping.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eDHL: Shipping Company\u003c/p\u003e\n\u003cp\u003eFedEx: Federal Express Corporation\u003c/p\u003e\n\u003cp\u003eLDIR: Laser Direct Infrared Spectroscopy\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eMP: Microplastic\u003c/p\u003e\n\u003cp\u003eMPs: Microplastics\u003c/p\u003e\n\u003cp\u003ePCTG: Polycarbonate\u003c/p\u003e\n\u003cp\u003ePE: Polyethylene\u003c/p\u003e\n\u003cp\u003eSEM: Scanning Electron Microscope\u003c/p\u003e\n\u003cp\u003e\u0026micro;FTIR: micro Fourier Transform Interferometer\u003c/p\u003e\n\u003cp\u003eUSPS: United States Postal Service\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe LDIR export datasets from the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors gratefully acknowledge the support of the National Science Foundation under Grant No. 2320748.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors' contributions\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCWO substantially contributed to the conception, acquisition, design of the work, analysis, interpretation of data, and drafted the work or substantively revised it. ML substantially contributed to the conception, design of the work, interpretation of data, and drafted the work or substantively revised it.\u0026nbsp;KEE contributed to the design of the work and interpretation of data.\u003c/p\u003e\n\u003cp\u003eMRMB\u0026nbsp;substantially contributed to the conception, interpretation of data, and drafted the work or substantively revised it. BC contributed to the acquisition, analysis, and interpretation of data. All authors read and approved the final manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAlwan W, Robey D. Characterization of Microplastics in Environmental Samples by Laser Direct Infrared Imaging; 2022.\u003c/li\u003e\n \u003cli\u003eCox KD, Covernton GA, Davies HL, Dower JF, Juanes F, Dudas SE. Human Consumption of Microplastics. Environ Sci Technol. 2019;53(12):7068-74. doi.org/10.1021/acs.est.9b01517\u003c/li\u003e\n \u003cli\u003eD\u0026iacute;az M, Sol D, Laca A, Cris\u0026oacute;stomo-Miranda J, Laca A, Carrasco S, et al. Contribution of household dishwashing to microplastic pollution. Environ Sci Pollut Res. 2023. doi.org/10.1007/s11356-023-25433-7\u003c/li\u003e\n \u003cli\u003eGeyer R, Jambeck JR, Law KL. Production, use, and fate of all plastics ever made. Sci Adv. 2017;3(7):e1700782. doi.org/10.1126/sciadv.1700782\u003c/li\u003e\n \u003cli\u003eHale RC, Seeley ME, La Guardia MJ, Mai L, Zeng EY. A Global Perspective on Microplastics. J Geophys Res Oceans. 2020;125(1). doi.org/10.1029/2018JC014719\u003c/li\u003e\n \u003cli\u003eHou J, Xu X, Lan L, Miao L, Xu Y, You G, et al. Transport behavior of micro polyethylene particles in saturated quartz sand: Impacts of input concentration and physicochemical factors. Environ Pollut. 2020;263:114499. doi.org/10.1016/j.envpol.2020.114499\u003c/li\u003e\n \u003cli\u003eKoutnik VS, Leonard J, Alkidim S, DePrima FJ, Ravi S, Hoek EMV, et al. Distribution of microplastics in soil and freshwater environments: Global analysis and framework for transport modeling. Environ Pollut. 2021;274:116552. doi.org/10.1016/j.envpol.2021.116552\u003c/li\u003e\n \u003cli\u003eKuttykattil A, Raju S, Vanka KS, Bhagwat G, Carbery M, Vincent S G T, Raja S, Palanisami T. Consuming microplastics? Investigation of commercial salts as a source of microplastics (MPs) in diet. 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Ecol Appl. 2021;31(8). doi.org/10.1002/eap.2429\u003c/li\u003e\n \u003cli\u003eWhiting QT, O\u0026apos;Connor KF, Potter PM, Al-Abed SR. A high-throughput, automated technique for microplastics detection, quantification, and characterization in surface waters using laser direct infrared spectroscopy. Anal Bioanal Chem. 2022;414(29-30):8353-64. doi.org/10.1007/s00216-022-04371-2\u003c/li\u003e\n \u003cli\u003eThompson RC, Jones WC, Boucher J, Pahl S, Raubenheiner K, Koelmans AA. Twenty years of microplastic pollution research\u0026mdash;what have we learned? Science. 2024;386(6720). doi/10.1126/science.adl2746\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Table","content":"\u003cp\u003eTable 1 is available in the Supplementary Files section\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"microplastics-and-nanoplastics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"mina","sideBox":"Learn more about [Microplastics and Nanoplastics](http://microplastics.springeropen.com)","snPcode":"43591","submissionUrl":"https://submission.nature.com/new-submission/43591/3","title":"Microplastics and Nanoplastics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Microplastic, Polyethylene, LDIR, Shipping, Packaging, Recovery","lastPublishedDoi":"10.21203/rs.3.rs-6398226/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6398226/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eBackground:\u003c/p\u003e\n\u003cp\u003eAs microplastics research expands across laboratories worldwide, filtering samples onto inexpensive metal filters and shipping them in metal tins could become the standard practice, replacing the impractical transportation of large water or environmental samples. Despite extensive research on microplastic distribution, there remains a notable absence of standardized methods, including sample transportation, highlighting the need to understand how shipping and packaging methods affect microplastic concentration variability. This study aims to evaluate the influence of different shipping and packaging methods on the recovery rate of microplastic particles that are collected on metal filters.\u003c/p\u003e\n\u003cp\u003eFindings:\u003c/p\u003e\n\u003cp\u003eWater samples spiked with polyethylene spheres were filtered onto 20 µm metal filters. The metal meshes were then placed in metal tins and subjected to six different packaging and shipping methods, ranging from paper boxes and envelopes to insulated hard and foam coolers. Laser Direct Infrared Spectroscopy was employed for the detection and quantification of polyethylene particles. The results revealed significant variation in recovery rates based on the shipping method. The highest recovery rates were observed in samples shipped in insulated hard or foam coolers, with at approximately 91-92% of the microplastics retained, while the lowest recovery was found in samples shipped in a flat rate mailing envelope (10%). Paper boxes with materials that eliminate space for movement inside the box offered moderate protection, with recovery rates of approximately 70%.\u003c/p\u003e\n\u003cp\u003eConclusions:\u003c/p\u003e\n\u003cp\u003eThis study demonstrates that shipping methods can substantially influence the retention of microplastics during transport from field sites to laboratories for analysis. Shipping methods where the packing remains upward such as with a cooler with a handle provided the highest recovery rates. We infer that this is due to the better care in handling from mail/shipping carriers; however, this method cost more. Lowest recover rates occurred when metal tins could freely move within the packaging and the package was allowed to be in any orientation. The findings highlight the importance of packaging choice in minimizing microplastic loss during shipping. Further research is necessary to standardize sample handling protocols and ensure consistent results across various transportation conditions, ultimately improving the reliability of microplastic contamination assessments.\u003c/p\u003e","manuscriptTitle":"Assessing the Impact of Shipping on Microplastic Concentration of Filtered Samples","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-15 13:09:31","doi":"10.21203/rs.3.rs-6398226/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-05-26T07:29:17+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-23T01:40:03+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-20T08:19:42+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-10T10:26:01+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"253840195194019039401501330253814885696","date":"2025-04-24T16:47:16+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"215310457627350482127527473688028478744","date":"2025-04-23T00:57:02+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"257792495691606468325463864511839724205","date":"2025-04-22T11:28:06+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-04-22T08:25:36+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-04-08T13:25:30+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-04-08T13:22:33+00:00","index":"","fulltext":""},{"type":"submitted","content":"Microplastics and Nanoplastics","date":"2025-04-08T01:57:48+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"microplastics-and-nanoplastics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"mina","sideBox":"Learn more about [Microplastics and Nanoplastics](http://microplastics.springeropen.com)","snPcode":"43591","submissionUrl":"https://submission.nature.com/new-submission/43591/3","title":"Microplastics and Nanoplastics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"0faa6ab1-5468-421b-9603-dd04c813fca1","owner":[],"postedDate":"April 15th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-12-29T15:59:12+00:00","versionOfRecord":{"articleIdentity":"rs-6398226","link":"https://doi.org/10.1186/s43591-025-00147-4","journal":{"identity":"microplastics-and-nanoplastics","isVorOnly":false,"title":"Microplastics and Nanoplastics"},"publishedOn":"2025-12-23 15:57:05","publishedOnDateReadable":"December 23rd, 2025"},"versionCreatedAt":"2025-04-15 13:09:31","video":"","vorDoi":"10.1186/s43591-025-00147-4","vorDoiUrl":"https://doi.org/10.1186/s43591-025-00147-4","workflowStages":[]},"version":"v1","identity":"rs-6398226","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6398226","identity":"rs-6398226","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}