Microplastics are the breakdown product of various polymers including the deterioration of plastic bottles, containers, and many other consumer products. Due to their size and inherent lack of toxicity, for the past few decades they have been considered relatively harmless to aquatic species and humans.

Studies have shown that microplastics are pervasive in the environment, found in rivers, precipitation, soil, and wildlife. Notably, microplastics have also been detected in the human body, including the lungs (Jenner et al. 2022), digestive system (Fournier et al. 2023), blood (Leslie et al. 2022; Leonard et al. 2024), and reproductive organs (Ragusa et al. 2021; Liu et al. 2022; Codrington et al. 2024). A recent article by the Washington Post suggested that some amount of microplastics may be present in the ambient air due to the release of “fibers” from clothing; “particles” from car tires, plastic packaging, and AstroTurf; as well as “spheres” from cosmetic exfoliating agents (Ducroquet et al. 2024).

The WHO has recently stated that “Based on the limited information we have, microplastics in drinking water don’t appear to pose a health risk at current levels…” (WHO 2019). In fact, the weight of evidence indicates that all current sources of microplastics are generally believed to present no risk, or at least no measurable risk, to humans (Burton 2017; Cox et al. 2019; Backhaus and Wagner 2020; Hwang et al. 2020). Nonetheless, with increasing concentrations in the environment, the growing body of research on microplastics has suggested there are significant concerns.

A July 2024 PubMed search for “microplastics” resulted in 13,765 hits, and 2,532 new publications in 2024 alone. A similar search for “nanoplastics” produced 2,665 hits and 640 publications in 2024 alone. This surge in research highlights the scientific community’s concern about the potential impacts of microplastics, prompting further investigations into their presence, distribution, and effects on human and environmental health.

Although there is no definitive evidence that the presence of these tiny plastic particles have the potential to adversely affect human health, several studies have “linked” or found weak associations between their presence and health issues including cancer, heart disease and other chronic illnesses (Ducroquet et al. 2024). It is difficult, if not impossible, to draw conclusions on disease causation from these studies, due to the presence of a number of confounding factors the authors were unable to account for. 

While some studies in rodents have suggested that high concentrations of microplastics in the blood may result in neurotoxic effects, such results are difficult to extrapolate to humans; especially when potential environmental exposures are hundreds of fold less than what the animals received. (Li et al. 2020; Estrela et al. 2021; Jin et al. 2021; Liu et al. 2022; Shan et al. 2022). A full risk assessment of microplastics would be necessary to draw accurate conclusions on what health hazards, if any, are posed at current or predicted concentrations. 

It has been suggested that microplastics can contain and leach toxic chemicals, depending on the origin of the plastic, and on their own can potentially cause some level of inflammation (Jeong et al. 2016; Kadac-Czapska et al. 2024). Given that cellular irritation could be an important mechanism, the type, size, shape, and, of course, concentration of microplastics almost certainly affect its toxicity. For those not directly excreted from the body, the immune system (macrophages) can engulf microplastics. The ability to then degrade the material is likely dependent on the type of plastic (Hwang et al. 2020; Kuroiwa et al. 2023; Adler et al. 2024).

How Paustenbach & Associates Can Help

Litigation related to microplastics has surged in recent years, with claims against plastics producers under both environmental and consumer protection laws. In a landmark case, Formosa Plastics Corporation was required to pay $50 million to fund environmental remediation projects after being found in violation of its discharge permit by releasing plastic pellets into a water body (plasticpollutioncoalition 2019). 

On the regulatory front, the European Union has proposed measures to curb microplastics pollution, including bans on microplastics in cosmetics and detergents and mandates for companies to cover the costs of removing microplastics from urban wastewater. These regulations aim to significantly reduce human and environmental exposure to microplastics by 2030, supporting the broader zero-pollution action plan (Tsang and Kvedar 2024). In the United States, legislative actions such as the Microbead-Free Waters Act of 2015 have set the stage for further regulatory efforts to address microplastics pollution (NACWA 2024). In 2020, the California State Water Resources Control Board became the first regulatory body to define microplastics in drinking water (Baroni and Henke 2022).

Although these microplastics may very well be fundamentally inert, no different from nuisance dusts, concern over their increasing presence in the environment and the human body persist. Microplastics research is relatively undeveloped. The only way to ensure that regulators, the public, and juries reach sound decisions about the potency of microplastics is to conduct a proper health risk assessment evaluating a diversity of toxicological endpoints across differing doses.

Our organization has offered testimony in more than 800 depositions and 50+ trials over the years where we presented our risk analyses. In the cases for which we were retained, we applied exposure science and the health risk assessment methodology embraced by the National Academies of Science to characterize the possible risks. Over the years, we have conducted more than 1,000 risk assessments. Please contact Michael Stevens for more information regarding our capabilities at mstevens@paustenbachandassociates.com or 708-466-3614.

References

(WHO) WHO. 2019. WHO calls for more research into microplastics and a crackdown on plastic pollution. August 22, 2019. 

Adler MY, Issoual I, Rückert M, Deloch L, Meier C, Tschernig T, et al. 2024. Effect of micro- and nanoplastic particles on human macrophages. Journal of Hazardous Materials. 471: 134253.

Backhaus T, Wagner M. 2020. Microplastics in the Environment: Much Ado about Nothing? A Debate. Global Challenges. 4(6): 1900022.

Baroni M, Henke R. 2022. Microplastics Are in the News, and Manufacturers Are Seeing Lawsuits.  IndustryWeek. 

Burton GA, Jr. 2017. Stressor Exposures Determine Risk: So, Why Do Fellow Scientists Continue To Focus on Superficial Microplastics Risk? Environmental Science & Technology. 51(23): 13515-13516.

Codrington J, Varnum AA, Hildebrandt L, Pröfrock D, Bidhan J, Khodamoradi K, et al. 2024. Detection of microplastics in the human penis. International Journal of Impotence Research. 

Cox KD, Covernton GA, Davies HL, Dower JF, Juanes F, Dudas SE. 2019. Human Consumption of Microplastics. Environmental Science & Technology. 53(12): 7068-7074.

Ducroquet S, Osaka S, Ulmanu M, Eilperin J, Farrell J, Scuiletti J. 2024. The plastics we breathe.  The Washington Post. 

Estrela FN, Guimarães ATB, Araújo A, Silva FG, Luz TMD, Silva AM, et al. 2021. Toxicity of polystyrene nanoplastics and zinc oxide to mice. Chemosphere. 271: 129476.

Fournier E, Leveque M, Ruiz P, Ratel J, Durif C, Chalancon S, et al. 2023. Microplastics: What happens in the human digestive tract? First evidences in adults using in vitro gut models. J Hazard Mater. 442: 130010.

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Jin H, Ma T, Sha X, Liu Z, Zhou Y, Meng X, et al. 2021. Polystyrene microplastics induced male reproductive toxicity in mice. Journal of Hazardous Materials. 401: 123430.

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Kuroiwa M, Yamaguchi S-I, Kato Y, Hori A, Toyoura S, Nakahara M, et al. 2023. Tim4, a macrophage receptor for apoptotic cells, binds polystyrene microplastics via aromatic-aromatic interactions. Science of The Total Environment. 875: 162586.

Leonard VL, Liddle CR, Atherall CA, Chapman E, Watkins M, S DJC, Rotchell JM. 2024. Microplastics in human blood: Polymer types, concentrations and characterisation using μFTIR. Environ Int. 188: 108751.

Leslie HA, van Velzen MJM, Brandsma SH, Vethaak AD, Garcia-Vallejo JJ, Lamoree MH. 2022. Discovery and quantification of plastic particle pollution in human blood. Environ Int. 163: 107199.

Li B, Ding Y, Cheng X, Sheng D, Xu Z, Rong Q, et al. 2020. Polyethylene microplastics affect the distribution of gut microbiota and inflammation development in mice. Chemosphere. 244: 125492.

Liu Z, Zhuan Q, Zhang L, Meng L, Fu X, Hou Y. 2022. Polystyrene microplastics induced female reproductive toxicity in mice. J Hazard Mater. 424(Pt C): 127629.

NACWA NAoCWA. 2024. Senate Addresses Microplastics in Water, NACWA Weighs In. Feb 28, 2024. 

plasticpollutioncoalition. 2019. Formosa Plastics Agrees to Pay $50 Million Settlement for Polluting Texas Waterways. 

Ragusa A, Svelato A, Santacroce C, Catalano P, Notarstefano V, Carnevali O, et al. 2021. Plasticenta: First evidence of microplastics in human placenta. Environ Int. 146: 106274.

Shan S, Zhang Y, Zhao H, Zeng T, Zhao X. 2022. Polystyrene nanoplastics penetrate across the blood-brain barrier and induce activation of microglia in the brain of mice. Chemosphere. 298: 134261.

Tsang L, Kvedar J. 2024. Macro Regulation of Microplastics: New EU Initiatives and Their Global Business Impact.  Ropes & Gray LLP.