Microplastics - The Human Cost

Introduction

In general, microplastic is the term used to refer to pieces of plastic that measure less than 5mm in length.¹ They may be of primary or secondary manufacturing origin and are insoluble in water.²

Like any other pieces of plastic, these microplastics are extremely resilient and can persist in the environment for decades without any significant degradation.³

One of the subdivisions of microplastics are nano plastics which are generally plastic particles smaller than 1 µm. For the sake of this review, microplastics will be understood to include this subdivision of nanoplastics.

Microplastics, in addition to being in waterways, have also been found in the drinking water and in bottles of mineral water in many countries.⁴

Additionally, microplastics have significantly infiltrated and accumulated in both marine and terrestrial food-webs5 - of note, this includes species that are of interest for human consumption, such as oysters and fish.

In addition to ingestion of drinking water and contaminated wildlife, humans may also be exposed to microplastic consumption via the consumption of sea-salt - a staple.⁶

There is an imbalance between the rapid pace at which we produce and consume plastic products and the lack of efficient waste-management systems that are in place to deal with this mass-produced plastic. Instead, it is estimated that plastic waste has risen by 7.11% since 2021.7 While this trend in itself is a worrisome one, another emerging challenge that the world faces is that of microplastics. It is estimated that as of 2024, the United States will have approximately 267,000 tons of microplastics in it’s waterways - a staggering number no doubt, but dwarfed perhaps by the even more gargantuan more than 787,000 tons of microplastics that China is expected to have in its waterways as of this year.⁷ Evidently, the microplastic problem is one that is a globally-shared experience.

It is estimated that in 2024, nearly two hundred and twenty two million tonnes of plastic waste will be created of which over 70 million tonnes will invariably find its eventual resting place to be in nature.⁷

As such, studies show that humans consume on average 50,000 particles of microplastic per year - a number that is found to increase significantly if bottled water is being consumed.⁸

It is therefore evident that we are facing a mounting challenge in the face of microplastics - unfortunately, due to the novelty of this issue, there is a lack of thorough understanding about its intricacies. This review serves three main objectives. Firstly, it consolidates scientifically noteworthy discoveries to provide a comprehensive understanding of the subject. Secondly, it delves into the human repercussions of microplastic ingestion. Lastly, it illuminates the deficiencies in current research and highlights areas where further investigation is needed to enhance our collective understanding

Materials and Methods

A literature review was conducted on Indexing services (SCOPUS and PUBMED). Pertinent studies, prioritising original research, review articles and meta-analyses were identified. The exclusion criterion included papers not published in English(or where full-text translation was not available), proposal and opinion papers. Papers from before 2018 and papers that failed to reject the null hypothesis were excluded so as to maintain this review to only statistically significant findings. Lastly, papers that were found to have strong biases that may influence the findings and studies conducted exclusively on non-human populations/cells were excluded. The author then conducted a thorough evaluation of each study to ensure relevance and significance. After deduplication of results and implementation of the exclusion criterion, a total of 58 papers were shortlisted for this review. The PRISMA flow diagram is available in Figure 1. The keywords used for this literature search were “microplastic”, “human health”, “nanoplastic”, “pathogens”, “bioaccumulation”, “ antibiotic resistant”.

Results

The proliferation of microplastics presents a growing challenge. Their remarkable durability means they can persist in the environment for decades without notable degradation.⁴

Humans may be exposed to microplastics either directly or indirectly. For instance, humans may indirectly consume contaminated marine or terrestrial animals6 or face direct exposure via direct ingestion or even inhalation.⁹

Microbial Infiltration and the Marine Biosphere

It's important to acknowledge that while the ingestion and buildup of microplastics in biological organisms pose inherent challenges, these are further complicated by co-ingestion of potential sources of illness. For instance, it is known that microplastics have an exceptionally long half-life, like all other forms of plastic. The half-life of the estimated half-life of high-density polyethylene ranges from 58 to 1,200 years depending on environmental and intrinsic factors.¹⁰ In contrast, microbial attachment to plastic surfaces occurs within a matter of minutes.¹¹

Of course, this is a worrying finding : microplastics can therefore persist for decades with colonies of attached microbes, waiting for biological ingestion.

Another note-worthy characteristic of microplastics is that they readily form biofilms.¹² Biofilm formation is a complex process that includes microbial attachment, release of polymeric proteins and proliferation of microbial colonies in subsequently formed biofilms.¹³ Intrinsic physical properties of plastics such as hydrophobicity and microscopic “roughness” may influence and promote biofilm formation.¹³ Additionally, Fungi, Algae and Bacteria are all usually found in biofilms.¹⁴ This type of multi-microbial cocktail is of potentially disastrous effects in case of human consumption.

A study of biofilms that form on microplastics has shown the presence of pathogenic bacteria such as Pseudomonas, Vibrios and Acinetobacter.¹⁵ These microbial-infested microplastics are then readily uptaken by marine life, including marine species that are of interest for human consumption.¹⁶

Interestingly, it is not as though these microbes lay benign within marine hosts and only cause disease in humans. They are in fact responsible for major marine ecological disruptions too. For instance, Vibrio are a large contributor to bivalve (e.g. mussels) mortality.¹⁷

This comes at a great ecological and subsequent human cost, too. As the human population expands, we look for ways to ramp up food production to combat global food insecurity ; the top sector of growing food production is aquaculture,17 and when the marine ecology is invariably damaged, it contributes to a growing food insecurity problem.

Microplastics are also intrinsically harmful in nature and this is amplified by their tendency to accumulate. They enter the marine food chain and bioaccumulate in organisms. They are toxic, accumulate in all levels of the food chain and cause detrimental health effects including potentially causing death.^18,19

Another way in which microbes may thrive in microplastics is the case of microbes that are present in the air - they may attach to microplastics (that are also present in the air) and be sheltered from potentially lethal ultraviolet radiation20 and therefore flourish and be eventually ingested by humans. Microplastics in the air may be a consequence of agricultural erosion, a byproduct of waste-management, degradation of synthetic fabrics and so on.²¹

Antibiotic Resistance

Microplastics may also adsorb other harmful contaminants such as antibiotics.²² This further compounds the issue of microplastic pollution and brings us to the next important sequelae of microplastic prevalence - the spread of antibiotic resistant bugs and genes.²²

Antibacterial resistant Escherichia coli were found to be readily available farm wastewater in China.²³ Similarly, microbes resistant to beta-lactams were readily found in Ireland and associated with microplastic ingestion.²⁴

In addition to serving as carriers for antibiotic-resistant pathogens,25 microplastics also significantly contribute to the dissemination of antibiotic-resistant bacteria, with levels up to 5000 times higher on microplastics compared to water.²⁶ This holds immense significance, as while the microbial loads on microplastics may appear insufficient to cause immediate pathogenicity—E. coli typically requires a load of 105 Colony Forming Units per particle for disease onset, whereas microplastics typically contain a maximum of 104 Colony Forming Units per particle27 —it's crucial to contextualise their role in harbouring antibiotic-resistant genes.²⁸ Despite potentially sub-threshold microbial loads, microplastics carry genetic elements capable of conferring antibiotic resistance to other microbes, including those commonly found in the human digestive tract or other pathogenic strains. This underscores the critical importance of considering microplastics' contribution to rising antibiotic resistance trends and considering the multiple approaches via which microplastics may contribute to pathogenicity.

Human Exposure and Detrimental Effects

It is evident that human beings are being exposed to an abundance of microplastics.²⁹

Human beings may be exposed to microplastics in a myriad of different ways. Studies show that an estimated 80g of microplastics per day may be consumed by humans from fruits and vegetables grown on polluted soil alone!30 Further, humans also risk exposure to microplastics from recreational aquatic bodies like swimming pools where there is a high usage of plastic products like spandex swimming suits, plastic swimming goggles and so on that may leech microplastics into the water.³¹

Another avenue through which humans may encounter microplastic exposure became apparent during the recent COVID-19 pandemic. Our increased dependence on disposable plastic items such as face masks, personal protective equipment, and face shields, coupled with their disposal in vast landfills, exacerbates the microplastic problem.³² These plastics, resistant to rapid degradation, release microplastic particles that can contaminate soil and water, and may even disperse through the air. Moreover, the COVID-19 pandemic has highlighted that pathogens, especially viruses, tend to endure longer on plastic surfaces compared to others.³³ For instance, SARS-CoV-2 RNA was found to persist on face masks for up to a month,34 reinforcing the notion that microplastics (and plastics in general) can prolong the survival of pathogens.

As mentioned earlier, human beings may also be exposed to microplastics via inhalation.⁹ This is cause for concern as it was shown that microplastics may induce apoptosis, disrupt protein expression and arrest the cell cycle in epithelial cells of the lungs.³⁵ Further, higher microplastic levels have been linked with a higher risk of chronic obstructive pulmonary disease.³⁶

Microplastics have also been shown to exert oxidative stress,37 and apoptosis on human cells.³⁸ In addition, they may promote the release of pro-inflammatory chemicals such as Interleukin 6 and activate the immune response.³⁹ Further, human lymphocytes are shown to be particularly vulnerable to microplastic induced toxicity, a finding that raises concern for potential disruption to the homeostatic immune system.⁴⁰ There is also evidence that microplastics may be a cause of genotoxicity to human cells.⁴¹

Microplastics have also been discovered in human blood,42 further cementing the idea that they may travel around the body and accumulate in various different organs. This is further problematic still because microplastics have been shown to cause direct cytotoxic damage to cells lining the vessel walls, namely vascular endothelial cells.⁴³

Further, in-vitro experiments have also shown that microplastics - owing to their physical properties - may be directly hemolytic to human red blood cells.⁴⁴

Human exposure to microplastics and the subsequent ingestion of them is further solidified by the existence of microplastics in human faecal matter.⁴⁵ The human gut microbiota was also shown to be altered via the influence of microplastic exposure, an effect that may be potentially linked to the ability of microplastics to form biofilms.⁴⁶ This is an interesting finding that may potentially explain why higher concentrations of microplastics in faecal matter were found to be linked with a higher prevalence of inflammatory bowel disease in study subjects.⁴⁷ Further, microplastics were also linked with impaired gastrointestinal lipid absorption.⁴⁸

There is also some emerging evidence that microplastics could act as a cancer risk factor for humans, specifically in a gastro-intestinal environment but more high quality research is required before any concrete conclusions can be made.⁴⁹

Potential intrauterine exposure is another domain of concern with respect to microplastic exposure. Microplastics were found in the placenta50 and meconium51 acquired from infants born via caesarean deliveries. Although worrisome on its own, this cause for concern is further compounded when considering that human ventricular valve development is shown to be significantly affected by microplastic exposure.⁵² That being said, there is much to be discussed about the potential for contamination of samples and the issues with sample collection as a whole that may put into question some of the findings of microplastics in meconium and placenta. This will be further discussed in the “Future Research'' subsection of this paper.

Propagation

Microplastics are not susceptible to easy environmental degradation. They may travel very far distances in the ocean and this is cause for concern because of their ability to carry pathogens, antibiotic resistance and their inherent ability to accumulate. There is therefore a potential for increased outbreaks of disease and easier propagation of foreign, non-indigenous pathogens.⁵³

This is perhaps best seen in the results of a study that looked at the stool sample of a rural village in Indonesia - as many as 63% of participants were found to have microplastics in their gastrointestinal tracts.⁵⁴

The implications of this finding are concerning, indicating the significant exposure to and ingestion of microplastics even within rural farming communities. This underscores the environmental cumulative burden of the issue, as microplastics, potentially originating from distant marine sources, persist without degradation and find their way into communities. Thus, it suggests that despite minimal plastic usage or waste generation within these communities, they remain susceptible to microplastic ingestion.

Floating microplastics might also facilitate the spread of invasive species across natural boundaries.⁵⁵ This occurrence has the potential to significantly modify the native ecological balance of an area and cause disturbances to its indigenous biological communities.

As previously discussed, microplastics serve not only as surfaces for pathogenic species to attach to but also actively promote their proliferation and spread.⁵⁶ This significantly amplifies the potential for microplastic-bound pathogens to enhance their virulence, as the conducive environment provided by microplastics can facilitate the rapid multiplication of these harmful microorganisms. Consequently, this heightened virulence poses an increased risk of potentially devastating effects on ecosystems and human health.

Further Research

Research into the potentially harmful effects of microplastics faces a variety of challenges. First, there isn’t a universally accepted, established method for sample collection that can ensure no sample contamination.

This is an issue in a lot of research studies - sample collection, storage and analysis, all invariably use plastic materials in multiple steps of the process, and this can very easily contaminate the sample and skew the accuracy of results.⁵¹

Additionally, microplastics, owing to their small size and chemical inertness are extremely difficult to meaningfully test hypotheses upon, at least in humans.⁵⁷

Yet another hurdle in the field of research is the vast diversity in the types of microplastics. Plastics and by extension, microplastics are of a variety of different types and may have different properties, physical and chemical. To then try to hypothesise an umbrella assumption that blankets all of their effects is a daunting task, perhaps one that isn’t even doable.

Lastly, it is absolutely essential to segregate the effects caused by microplastics owing to their inherent qualities, from effects caused by additives or attached pathogens.⁵⁸

Novel research methods need to be developed and concise questions need to be asked in order to determine precisely whether the potential disease-causing aspect of microplastics is an inherent, fundamental quality or is attributable to attached pathogens or other additives.

Conclusion

In conclusion, the pervasive presence of microplastics poses significant challenges to both the environment and human health. As evidenced by this review, microplastics have infiltrated various ecosystems, from marine environments to terrestrial food webs, and have become a ubiquitous presence in everyday life.

The implications of microplastic pollution are far-reaching and multifaceted. Not only do microplastics persist in the environment for decades, but they also have the potential to accumulate in organisms, leading to detrimental effects on ecosystems and biodiversity. Additionally, human exposure to microplastics through various routes, including ingestion and inhalation, raises concerns about potential health risks.

Human exposure to microplastics poses significant health risks, including potential respiratory and gastrointestinal effects, as well as implications for systemic inflammation and immune function. There is also concern regarding transplacental transmission of microplastics in humans. Future research should focus on elucidating the full extent of these health impacts and exploring potential interventions to mitigate them.

Addressing the issue of microplastic pollution requires concerted efforts from all sectors of society. Strategies to mitigate microplastic pollution must include improved waste management practices, the development of environmentally friendly alternatives to plastic, and public awareness campaigns to reduce plastic consumption.

Furthermore, collaborative interdisciplinary research is needed to better understand the full extent of the environmental and health impacts of microplastics. This research should prioritise comprehensive characterization of microplastics, mechanistic studies to elucidate their biological effects, and the development of strategies to mitigate their impact on ecosystems and human health. Overcoming methodological challenges, such as sample contamination and the diverse nature of microplastics, is essential to advancing our understanding of this complex issue. It's crucial to distinguish between the effects triggered by the inherent qualities of microplastics and those induced by additives or attached pathogens.

Ultimately, addressing the challenge of microplastic pollution requires a collective effort to reduce plastic use, improve waste management practices, and develop sustainable alternatives. Only through coordinated action can we effectively protect the environment and safeguard human health for future generations.

Acknowledgements

There are no acknowledgements to be made.

Conflicts of Interest

There are no conflicts of interest to be declared.

References

1. Osman AI, Hosny M, Eltaweil AS, Omar S, Elgarahy AM, Farghali M, et al. Microplastic sources, formation, toxicity and remediation: a review. Environmental chemistry letters. 2023 Apr 4;1–41.

2. Frias JPGL, Nash R. Microplastics: Finding a consensus on the definition. Marine Pollution Bulletin. 2019 Jan;138:145–7.

3. Xiang Y, Jiang L, Zhou Y, Luo Z, Zhi D, Yang J, et al. Microplastics and environmental pollutants: Key interaction and toxicology in aquatic and soil environments. Journal of Hazardous Materials. 2022 Jan;422:126843.

4. Schymanski D, Goldbeck C, Humpf HU, Fürst P. Analysis of microplastics in water by micro-Raman spectroscopy: Release of plastic particles from different packaging into mineral water. Water Research. 2018 Feb;129:154–62.

5. Peng L, Fu D, Qi H, Lan CQ, Yu H, Ge C. Micro- and nano-plastics in marine environment: Source, distribution and threats — A review. Science of The Total Environment. 2020 Jan;698:134254.

6. Waring RH, Harris RM, Mitchell SC. Plastic contamination of the food chain: A threat to human health? Maturitas. 2018 Sep;115:64–8.

7. EA - Earth Action. Plastic Overshoot Day – Report 2024 [Internet]. http://plasticovershoot.earth/. EA – Earth Action, Lausanne, Switzerland; 2024. Available from: https://plasticovershoot.earth/wp-content/uploads/2024/04/EA_POD_report_2024.pdf

8. Cox KD, Covernton GA, Davies HL, Dower JF, Juanes F, Dudas SE. Human Consumption of Microplastics. Environmental Science & Technology. 2019 Jun 5;53(12):7068–74.

9. Gasperi J, Wright SL, Dris R, Collard F, Mandin C, Guerrouache M, et al. Microplastics in air: Are we breathing it in? Current Opinion in Environmental Science & Health. 2018 Feb;1:1–5.

10. Chamas A, Moon H, Zheng J, Qiu Y, Tabassum T, Jang JH, et al. Degradation Rates of Plastics in the Environment. ACS Sustainable Chemistry & Engineering. 2020 Feb 3;8(9):3494–511.

11. Dudek KL, Cruz BN, Polidoro B, Neuer S. Microbial colonization of microplastics in the Caribbean Sea. Limnology and Oceanography Letters. 2020 Jan 6;5(1):5–17.

12. Wang J, Guo X, Xue J. Biofilm-Developed Microplastics As Vectors of Pollutants in Aquatic Environments. Environmental Science & Technology. 2021 Sep 23;

13. Sharma VK, Ma X, Lichtfouse E, Robert D. Nanoplastics are potentially more dangerous than microplastics. Environmental Chemistry Letters. 2022 Nov 9;21(4):1933–6.

14. Boudarel H, Mathias JD, Blaysat B, Grédiac M. Towards standardized mechanical characterization of microbial biofilms: analysis and critical review. npj Biofilms and Microbiomes. 2018 Aug 20;4(1).

15. Mughini-Gras L, van der Plaats RQJ, van der Wielen PWJJ, Bauerlein PS, de Roda Husman AM. Riverine microplastic and microbial community compositions: A field study in the Netherlands. Water Research. 2021 Mar;192:116852.

16. Fernández Severini MD, Villagran DM, Buzzi NS, Sartor GC. Microplastics in oysters (Crassostrea gigas) and water at the Bahía Blanca Estuary (Southwestern Atlantic): An emerging issue of global concern. Regional Studies in Marine Science. 2019 Nov;32:100829.

17. Bowley J, Baker-Austin C, Porter A, Hartnell R, Lewis C. Oceanic Hitchhikers – Assessing Pathogen Risks from Marine Microplastic. Trends in Microbiology. 2021 Feb;29(2):107–16.

18. Hipfner JM, Galbraith M, Tucker S, Studholme KR, Domalik AD, Pearson SF, et al. Two forage fishes as potential conduits for the vertical transfer of microfibres in Northeastern Pacific Ocean food webs. Environmental Pollution. 2018 Aug;239:215–22.

19. Caron AGM, Thomas CR, Berry KLE, Motti CA, Ariel E, Brodie JE. Ingestion of microplastic debris by green sea turtles (Chelonia mydas) in the Great Barrier Reef: Validation of a sequential extraction protocol. Marine Pollution Bulletin. 2018 Feb;127:743–51.

20. Prata JC. Airborne microplastics: Consequences to human health? Environmental Pollution. 2018 Mar;234:115–26.

21. Campanale, Massarelli, Savino, Locaputo, Uricchio. A Detailed Review Study on Potential Effects of Microplastics and Additives of Concern on Human Health. International Journal of Environmental Research and Public Health. 2020 Feb 13;17(4):1212.

22. Li J, Zhang K, Zhang H. Adsorption of antibiotics on microplastics. Environmental Pollution. 2018 Jun;237:460–7.

23. Liu C, Liu Y, Feng C, Wang P, Yu L, Liu D, et al. Distribution characteristics and potential risks of heavy metals and antimicrobial resistant Escherichia coli in dairy farm wastewater in Tai’an, China. Chemosphere. 2021 Jan;262:127768.

24. Moore RE, Millar BC, Moore JE. Antimicrobial resistance (AMR) and marine plastics: Can food packaging litter act as a dispersal mechanism for AMR in oceanic environments? Marine Pollution Bulletin. 2020 Jan;150:110702.

25. Amaral-Zettler LA, Zettler ER, Mincer TJ. Ecology of the plastisphere. Nature Reviews Microbiology. 2020 Jan 14;18(3):139–51.

26. Zhang Y, Lu J, Wu J, Wang J, Luo Y. Potential risks of microplastics combined with superbugs: Enrichment of antibiotic resistant bacteria on the surface of microplastics in mariculture system. Ecotoxicology and Environmental Safety. 2020 Jan;187:109852.

27. Boni W, Parrish K, Patil S, Fahrenfeld NL. Total coliform and Escherichia coli in microplastic biofilms grown in wastewater and inactivation by peracetic acid. Water Environment Research. 2020 Sep 9;93(3):334–42.

28. Guo X pan, Sun X li, Chen Y ru, Hou L, Liu M, Yang Y. Antibiotic resistance genes in biofilms on plastic wastes in an estuarine environment. Science of The Total Environment. 2020 Nov;745:140916.

29. McIlwraith HK, Kim J, Helm P, Bhavsar SP, Metzger JS, Rochman CM. Evidence of Microplastic Translocation in Wild-Caught Fish and Implications for Microplastic Accumulation Dynamics in Food Webs. Environmental Science & Technology. 2021 Sep 9;55(18):12372–82.

30. Ebere EC, Wirnkor VA, Ngozi VE. Uptake of Microplastics by Plant: a Reason to Worry or to be Happy? [Internet]. unknown. 2019. Available from: https://www.researchgate.net/publication/334083970_Uptake_of_Microplastics_by_Plant_a_Reason_to_Worry_or_to_be_Happy

31. Stovall JK, Bratton SP. Microplastic Pollution in Surface Waters of Urban Watersheds in Central Texas, United States: A Comparison of Sites With and Without Treated Wastewater Effluent. Frontiers in Analytical Science. 2022 Feb 17;2.

32. Tiwari BR, Lecka J, Pulicharla R, Brar SK. Microplastic pollution and associated health hazards: Impact of COVID-19 pandemic. Current Opinion in Environmental Science & Health. 2023 Aug;34:100480.

33. van Doremalen N, Bushmaker T, Morris DH, Holbrook MG, Gamble A, Williamson BN, et al. Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1. New England Journal of Medicine. 2020 Apr 16;382(16):1564–7.

34. Córdoba-Lanús E, García-Pérez O, Cazorla-Rivero S, Rodríguez-Esparragón F, Piñero JE, Clavo B, et al. Persistence of SARS-CoV-2 infection on personal protective equipment (PPE). BMC Infectious Diseases. 2021 Nov 19;21(1).

35. Xu M, Halimu G, Zhang Q, Song Y, Fu X, Li Y, et al. Internalization and toxicity: A preliminary study of effects of nanoplastic particles on human lung epithelial cell. Science of The Total Environment. 2019 Dec;694:133794.

36. Dong CD, Chen CW, Chen YC, Chen HH, Lee JS, Lin CH. Polystyrene microplastic particles: In vitro pulmonary toxicity assessment. Journal of Hazardous Materials. 2020 Mar;385:121575.

37. Danopoulos E, Twiddy M, West R, Rotchell JM. A rapid review and meta-regression analyses of the toxicological impacts of microplastic exposure in human cells. Journal of Hazardous Materials. 2022 Apr;427:127861.

38. Yee MSL, Hii LW, Looi CK, Lim WM, Wong SF, Kok YY, et al. Impact of Microplastics and Nanoplastics on Human Health. Nanomaterials. 2021 Feb 16;11(2):496.

39. Han S, Bang J, Choi D, Hwang J, Kim T, Oh Y, et al. Surface Pattern Analysis of Microplastics and Their Impact on Human-Derived Cells. ACS Applied Polymer Materials. 2020 Aug 28;2(11):4541–50.

40. Salimi A, Alavehzadeh A, Ramezani M, Pourahmad J. Differences in sensitivity of human lymphocytes and fish lymphocytes to polyvinyl chloride microplastic toxicity. Toxicology and Industrial Health. 2022 Feb;38(2):100–11.

41. Çobanoğlu H, Belivermiş M, Sıkdokur E, Kılıç Ö, Çayır A. Genotoxic and cytotoxic effects of polyethylene microplastics on human peripheral blood lymphocytes. Chemosphere. 2021 Jun;272:129805.

42. Zuri G, Karanasiou A, Lacorte S. Human biomonitoring of microplastics and health implications: A review. Environmental Research. 2023 Nov;237:116966.

43. Lu YY, Li H, Ren H, Zhang X, Huang F, Zhang D, et al. Size-dependent effects of polystyrene nanoplastics on autophagy response in human umbilical vein endothelial cells. Journal of Hazardous Materials. 2022 Jan;421:126770.

44. Hwang J, Choi D, Han S, Jung SY, Choi J, Hong J. Potential toxicity of polystyrene microplastic particles. Scientific Reports. 2020 Apr 30;10(1).

45. Schwabl P, Köppel S, Königshofer P, Bucsics T, Trauner M, Reiberger T, et al. Detection of Various Microplastics in Human Stool. Annals of Internal Medicine. 2019 Oct 1;171(7):453–7.

46. Tamargo A, Molinero N, Reinosa JJ, Alcolea-Rodriguez V, Portela R, Bañares MA, et al. PET microplastics affect human gut microbiota communities during simulated gastrointestinal digestion, first evidence of plausible polymer biodegradation during human digestion. Scientific Reports. 2022 Jan 11;12(1).

47. Yan Z, Liu Y, Zhang T, Zhang F, Ren H, Zhang Y. Analysis of Microplastics in Human Feces Reveals a Correlation between Fecal Microplastics and Inflammatory Bowel Disease Status. Environmental Science & Technology. 2021 Dec 22;56(1):414–21.

48. Tan H, Yue T, Xu Y, Zhao J, Xing B. Microplastics Reduce Lipid Digestion in Simulated Human Gastrointestinal System. Environmental Science & Technology. 2020 Aug 14;54(19):12285–94.

49. Bonanomi M, Salmistraro N, Porro D, Pinsino A, Colangelo AM, Gaglio D. Polystyrene micro and nano-particles induce metabolic rewiring in normal human colon cells: A risk factor for human health. Chemosphere. 2022 Sep;303:134947.

50. Ragusa A, Svelato A, Santacroce C, Catalano P, Notarstefano V, Carnevali O, et al. Plasticenta: First evidence of microplastics in human placenta. Environment International. 2021 Jan;146:106274.

51. Braun T, Ehrlich L, Henrich W, Koeppel S, Lomako I, Schwabl P, et al. Detection of Microplastic in Human Placenta and Meconium in a Clinical Setting. Pharmaceutics. 2021 Jun 22;13(7):921.

52. Bojic S, Falco MM, Stojkovic P, Ljujic B, Gazdic Jankovic M, Armstrong L, et al. Platform to study intracellular polystyrene nanoplastic pollution and clinical outcomes. Stem Cells. 2020 Jul 2;38(10):1321–5.

53. Simkanin C, Carlton JT, Steves B, Fofonoff P, Nelson JC, Clarke Murray C, et al. Exploring potential establishment of marine rafting species after transoceanic long‐distance dispersal. Global Ecology and Biogeography. 2019 Jan 28;28(5):588–600.

54. Wibowo AT, Nugrahapraja H, Wahyuono RA, Islami I, Haekal MH, Fardiansyah Y, et al. Microplastic Contamination in the Human Gastrointestinal Tract and Daily Consumables Associated with an Indonesian Farming Community. Sustainability. 2021 Nov 19;13(22):12840.

55. Rech S, Thiel M, Borrell Pichs YJ, García-Vazquez E. Travelling light: Fouling biota on macroplastics arriving on beaches of remote Rapa Nui (Easter Island) in the South Pacific Subtropical Gyre. Marine Pollution Bulletin. 2018 Dec;137:119–28.

56. Guo X, Wang J. The chemical behaviors of microplastics in marine environment: A review. Marine Pollution Bulletin. 2019 May;142:1–14.

57. da Silva Brito WA, Mutter F, Wende K, Cecchini AL, Schmidt A, Bekeschus S. Consequences of nano and microplastic exposure in rodent models: the known and unknown. Particle and Fibre Toxicology. 2022 Apr 21;19(1).

58. Xu JL, Lin X, Wang JJ, Gowen AA. A review of potential human health impacts of micro- and nanoplastics exposure. Science of The Total Environment. 2022 Dec;851:158111.