Table of Contents
Background
Microplastics (MPs) comprise tiny water-insoluble, solid plastic particles typically with a size ranging from 5 millimeters (mm) to 10 nanometers (nm), and are widely used in consumer products. Based on their chemical nature, MPs are classified into two major categories. Primary MPs are manufactured intentionally and mainly used in cosmetics and biomedical products etc. while secondary MPs refer to the type of MPs that are formed as a result of the breakdown of larger MPs through processes such as chemical weathering, mechanical breakdown, and digestive processes in animals. Chemically, MPs are stable in the environment and very difficult to degrade, making them pervasive in the environment and can be found in a range of ecosystems ranging from Antarctic tundra to tropical coral reefs as well as oceans, rivers, soil, air, and underground aquifers. In addition, levels of MPs have also been reported in food, beverages, and human and animal tissues.
Much of the research during the last two decades has emphasized monitoring MPs in various environmental compartments and assessing their impact on the environment and human health. Scientific literature suggests that MPs are also found in tap and bottled drinking water worldwide, making MPs a serious concern to public health. Their smaller size enables them to enter drinking water sources through various pathways. Once they are a part of water sources, their persistent chemical nature enables MPs to remain in drinking water systems indefinitely unless they are removed through suitable treatment methods. Various mechanisms have been suggested through which MPs can contaminate the drinking water sources. Notable sources of drinking water contamination from MPs include runoffs from agriculture, urban and industrial areas, conventional wastewater treatment plants, plastic consumables such as bottles and utensils, distribution systems atmospheric deposition, etc. Because of limited data available on the impact of MPs on human health associated with drinking water consumption, so far no MCL has been established for MPs in drinking water by major health organizations such as WHO and EPA.
Due to this, drinking water providers are routinely asked about the associated risks of MPs. To answer this, a recent study introduced the term “Threshold Microplastics Concentration” (TMC). However, exceeding the TMC did not necessarily indicate an immediate health risk but highlighted the need for a detailed risk assessment (Chowdhury, Schmidt et al. 2024). Further, WHO issued a report in 2019 stating that the current levels of MPs in drinking water do not pose serious health concerns. However, the need for further investigations was also highlighted since limited epidemiological evidence is available on this to establish a better understanding of the impact of MPs associated with drinking water consumption. Additionally, the EPA has shown a strong commitment to reducing the MP’s exposure and has been involved in various scientific investigations focusing on the presence and risks of MPs’ contamination in drinking water.
With more research data available, EPA will be able to develop federal standards or guidelines for microplastics in drinking water. In addition, MPs belong to an emerging class of contaminants and there are numerous ongoing studies to monitor the levels of MPs in aquatic bodies. Their chemical composition makes them vulnerable if consumed for longer periods therefore their levels in drinking water should not be overlooked and monitored regularly. If detected, the drinking water should be subjected to a suitable treatment method to remove it completely before being supplied to US consumers. A recently published review summarized the studies conducted on MPs in drinking water revealed that the highest abundance of MPs was detected in US tap water with 9.2 items/L compared with 22 countries (Zhang, Xu et al. 2020). It is certainly a concern to take the necessary steps to reduce the levels and routinely monitor the drinking water supply systems. MPs-associated health impacts through drinking water consumption are a growing concern and studies are being carried out and are not completely understood due to limited data availability. However, their physical and chemical nature and their potential to interact with other chemicals make them potentially harmful for human consumption.
Some notable associated health risks include their possible penetration into cellular barriers and tissues due to their very small size, their chemical composition involving bisphenols, phthalates, flame retardants, persistent organic chemicals (POPs), and metals whose toxicity is well established in the literature and can bioaccumulate in tissues and organs causing serious health issues including endocrine, neurological, developmental, respiratory, and other various health problems. Therefore, public water supply systems in the US should monitor MPs’ levels regularly to ensure MPs-free drinking water supply to the consumers.
Suggested mechanisms of MPs toxicity may include physical, chemical, and biological effects on humans. Smaller MPs (<100nm) may enter inside the cells disrupting cell membranes and inserting toxicity through inflammation, immune activation, and bioaccumulation pathways (Kim, Yu et al. 2021). Chemical additives such as bisphenols, phthalates, and flame retardants are often added with MPs during manufacturing processes, these additives may leach and be released into the body fluids such as stomach acids, enzymes, and tissues and can show toxicity (Godswill and Godspel 2019, López-Vázquez, Rodil et al. 2022).
Further, various environmental pollutants such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), persistent organic chemicals (POPs), and heavy metals can get absorbed onto MPs surface, and upon ingestion, they can contribute to numerous health problems (Lin, Li et al. 2022). Inside the human body, MPs along with the chemicals they carry, can trigger the production of reactive oxygen species (ROS) leading to damage to cellular components and oxidative stress (Das 2023). In addition, MPs can also induce genotoxicity which leads to increased cancer and other major disease risks (Das 2023, Winiarska, Jutel et al. 2024).
The fate of MPs inside the human body is solely dependent on their size. Large-size particles (>150 microns) are generally excreted out from the body with getting absorbed into the intestines. Whereas, small-size particles (1-10 microns) are so small that they get absorbed into the bloodstream and lymphatic systems from where they are transported to various organs and tissues and result in bioaccumulation leading to chronic health effects (Wu, Lin et al. 2022). However, more epidemiological research is warranted to fully understand the underlying mechanisms of MPs toxicity and associated disease development.
Detection Methods and Removal Strategies
It is challenging to quantify the MPs in drinking water due to diverse particle compositions, and advanced analytical techniques are required to differentiate organic and inorganic particles. A few notable methods for MPs analysis include microscopy-based methods comprising optical and fluorescence microscopy (Scircle and Cizdziel 2019, Nicolai, Pizzoferrato et al. 2022). Other methods are spectroscopy-based which comprise Fourier-Transform Infrared Spectroscopy (FTIR) capable of quantifying polymer types of MPs (Schymanski, Oßmann et al. 2021, De Frond, Hampton et al. 2022).
Raman spectroscopy is another widely used method that can identify MPs by measuring the scattering of laser light (Kniggendorf, Wetzel et al. 2019). Thermal methods involving Pyrolysis-Gas Chromatography Mass Spectrometry (Py-GC-MS) is also a commonly used method to measure MPs in drinking water. In Py-GC-MS, the sample is heated to high temperatures to break down the polymers into smaller molecules. The resulting breakdown products are then analyzed using GC and MS to identify the type of plastics present in the sample (Hermabessiere and Rochman 2021). However, this method is time-consuming and can also destroy the sample making this method less suitable for routine MPs monitoring.
Various methods have been developed so far to effectively filter or degrade MPs in drinking water. Among the widely used and most effective methods include filtration which is further categorized into various types based on the efficiency to remove MPs. Major types of filtration consist of sand filtration (>20 microns), membrane filtration such as microfiltration (0.1-10 microns), ultrafiltration (0.01-0.1 microns), nanofiltration (0.001-0.01 microns), reverse osmosis (RO) (<0.001 microns). RO is considered the most efficient method for removing almost all MPs in drinking water including nanoplastics (Shen, Song et al. 2020). Few other methods are also available to effectively remove MP residues in the drinking water.
These methods include electrocoagulation which uses an electric current to remove contaminants including MPs from water (Shen, Song et al. 2020), biological treatment using microbes in the form of biofilters (Cherniak, Almuhtaram et al. 2022) or through biodegradation (Miri, Saini et al. 2022), and advanced oxidation processes (AOPs) involve the use of highly reactive oxidizing agents such as H2O2, O3, and UV lights to degrade and remove MPs from drinking water (Kim, Sin et al. 2022, Dos Santos, Busquets et al. 2023). However, it is recommended to use a combination of different methods for the effective removal of MPs from drinking water.
Public Perspective
The following frequently asked questions (FAQs) try to address some general public concerns in the US related to MPs contamination in drinking water, especially in the NYC and NJ regions.
Our bodies naturally flush out the vast majority of MPs, but research has shown that some extremely small particles can remain in our systems. However, it is unclear whether MPs pose a danger to human health.
In vitro experiments with human cells and in vivo data generated with mice have shown that MPs elicit adverse health effects mainly by causing inflammation, oxidative stress, lipid metabolism disturbances, gut microbiota dysbiosis, and neurotoxicity.
Boiling and filtering calcium-containing tap water could help remove nearly 90% of the nano- and microplastics present.
Water filters are often used to filter out harmful contaminants such as chlorine and other chemicals. However, recent studies have found that RO water filters can also trap MPs which otherwise can be ingested by humans by getting into our food systems.
The only way to know if MPs are in your drinking water is to have your water tested by a certified laboratory. There are no at-home testing options (like strips) that can identify the presence of microplastics in a sample of water.
To effectively remove MPs from your drinking water, it is essential to use a water filtration method that is certified to specifically address MPs removal.
One of the easiest ways to avoid MPs in your drinking water is to avoid plastic bottles. Instead, you can use stainless steel or glass bottles. Use tap water instead of bottled water, if possible.
Different chemicals can leach from our plastic water bottles, knives, and dermatologic products to enter our bodies. These compounds are linked to serious health issues such as endocrine disruption, weight gain, insulin resistance, decreased reproductive health, and cancer.
Larger plastic pieces can leave your body through the natural process of elimination; however, smaller particles can be absorbed into your body and are toxic.
In the digestive system, MPs ingestion may lead to inflammation or an altered intestinal microbiome, resulting in an imbalance between beneficial and harmful bacteria and potentially leading to symptoms like abdominal pain, bloating, and changes in bowel habits.
Conclusion
MPs belong to a class of emerging contaminants widely used in the industries and manufacturing of consumer products. Their small size enables them to leach into water bodies from where humans ingest them through drinking water. Although epidemiological evidence to address the mechanisms associated with MPs in drinking water is scarce, their chemical nature, and ability to absorb numerous other contaminants such as PAHs, VOCs, and metals puts them under high-risk contaminants and demands regular monitoring in the drinking water supply systems.
So far, no regulatory levels have been established by the EPA due to limited data available for drinking water, however, the EPA is monitoring the reported levels in the US and is committed to setting MCLs as soon as sufficient evidence is available. Regular monitoring of drinking water supply systems should be carried out and if drinking water has MPs residues detected, the water must be subjected to a suitable treatment before being supplied to the consumers. Future studies must also emphasize monitoring the impact of ingested MPs in humans and correlate with various associated health outcomes to develop a better understanding of underlying mechanisms associated with MPs toxicity.
References
Cherniak, S. L., H. Almuhtaram, M. J. McKie, L. Hermabessiere, C. Yuan, C. M. Rochman and R. C. Andrews (2022). "Conventional and biological treatment for the removal of microplastics from drinking water." Chemosphere 288: 132587.
Chowdhury, O. S., P. J. Schmidt, W. B. Anderson and M. B. Emelko (2024). "Advancing evaluation of microplastics thresholds to inform water treatment needs and risks." Environment & Health.
Das, A. (2023). "The emerging role of microplastics in systemic toxicity: Involvement of reactive oxygen species (ROS)." Science of The Total Environment: 165076.
De Frond, H., L. T. Hampton, S. Kotar, K. Gesulga, C. Matuch, W. Lao, S. B. Weisberg, C. S. Wong and C. M. Rochman (2022). "Monitoring microplastics in drinking water: An interlaboratory study to inform effective methods for quantifying and characterizing microplastics." Chemosphere 298: 134282.
Dos Santos, N. d. O., R. Busquets and L. C. Campos (2023). "Insights into the removal of microplastics and microfibres by Advanced Oxidation Processes." Science of the Total Environment 861: 160665.
Godswill, A. C. and A. C. Godspel (2019). "Physiological effects of plastic wastes on the endocrine system (Bisphenol A, Phthalates, Bisphenol S, PBDEs, TBBPA)." International Journal of Bioinformatics and Computational Biology 4(2): 11-29.
Hermabessiere, L. and C. M. Rochman (2021). "Microwave‐Assisted Extraction for Quantification of Microplastics Using Pyrolysis–Gas Chromatography/Mass Spectrometry." Environmental Toxicology and Chemistry 40(10): 2733-2741.
Kim, J.-H., Y.-B. Yu and J.-H. Choi (2021). "Toxic effects on bioaccumulation, hematological parameters, oxidative stress, immune responses and neurotoxicity in fish exposed to microplastics: A review." Journal of Hazardous Materials 413: 125423.
Kim, S., A. Sin, H. Nam, Y. Park, H. Lee and C. Han (2022). "Advanced oxidation processes for microplastics degradation: A recent trend." Chemical Engineering Journal Advances 9: 100213.
Kniggendorf, A.-K., C. Wetzel and B. Roth (2019). "Microplastics detection in streaming tap water with Raman spectroscopy." Sensors 19(8): 1839.
Lin, L., H. Li, H. Hong, B. Yuan, X. Sun, L. He, C. Xue, H. Lu, J. Liu and C. Yan (2022). "Enhanced heavy metal adsorption on microplastics by incorporating flame retardant hexabromocyclododecanes: Mechanisms and potential migration risks." Water Research 225: 119144.
López-Vázquez, J., R. Rodil, M. J. Trujillo-Rodríguez, J. B. Quintana, R. Cela and M. Miró (2022). "Mimicking human ingestion of microplastics: Oral bioaccessibility tests of bisphenol A and phthalate esters under fed and fasted states." Science of the Total Environment 826: 154027.
Miri, S., R. Saini, S. M. Davoodi, R. Pulicharla, S. K. Brar and S. Magdouli (2022). "Biodegradation of microplastics: Better late than never." Chemosphere 286: 131670.
Nicolai, E., R. Pizzoferrato, Y. Li, S. Frattegiani, A. Nucara and G. Costa (2022). "A new optical method for quantitative detection of microplastics in water based on real-time fluorescence analysis." Water 14(20): 3235.
Schymanski, D., B. E. Oßmann, N. Benismail, K. Boukerma, G. Dallmann, E. Von der Esch, D. Fischer, F. Fischer, D. Gilliland and K. Glas (2021). "Analysis of microplastics in drinking water and other clean water samples with micro-Raman and micro-infrared spectroscopy: minimum requirements and best practice guidelines." Analytical and bioanalytical chemistry 413(24): 5969-5994.
Scircle, A. and J. V. Cizdziel (2019). "Detecting and quantifying microplastics in bottled water using fluorescence microscopy: A new experiment for instrumental analysis and environmental chemistry courses." Journal of Chemical Education 97(1): 234-238.
Shen, M., B. Song, Y. Zhu, G. Zeng, Y. Zhang, Y. Yang, X. Wen, M. Chen and H. Yi (2020). "Removal of microplastics via drinking water treatment: Current knowledge and future directions." Chemosphere 251: 126612.
Winiarska, E., M. Jutel and M. Zemelka-Wiacek (2024). "The potential impact of nano-and microplastics on human health: Understanding human health risks." Environmental Research: 118535.
Wu, P., S. Lin, G. Cao, J. Wu, H. Jin, C. Wang, M. H. Wong, Z. Yang and Z. Cai (2022). "Absorption, distribution, metabolism, excretion and toxicity of microplastics in the human body and health implications." Journal of Hazardous Materials 437: 129361.
Zhang, Q., E. G. Xu, J. Li, Q. Chen, L. Ma, E. Y. Zeng and H. Shi (2020). "A review of microplastics in table salt, drinking water, and air: direct human exposure." Environmental science & technology 54(7): 3740-3751.
- Yasir A. Rehman, Ph.D.
Dr. Rehman was born in Rawalpindi, Pakistan. He completed his MSc from PMAS – Arid Agriculture University Rawalpindi in 2011 where his thesis comprised a health risk assessment of subjects living in the vicinity of wastewater channels in urban settings and its relationship with the incidence of Malaria.
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OTHER RESEARCH ON WATER CONTAMINANTS BY DR. YASIR
