Microplastics have become an increasingly significant environmental and public health issue in recent years. Once primarily associated with marine pollution, these tiny particles are now commonly detected in freshwater sources and bottled and tap water. Their pervasive distribution, combined with the chemicals and biofilms they can transport, has heightened concerns about their potential effects on human health. As drinking water represents a major route of exposure, awareness and apprehension regarding microplastics continue to rise worldwide.1-4
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What are Microplastics?
Plastics are extensively used across industries due to their affordability, chemical stability, durability, and water resistance. Global plastic production has risen to 368 million tons annually, with projections reaching 33 billion tons by 2050. Yet, only 9% of plastic waste is recycled, and 79% is discharged into the environment. The discarded plastic waste accumulated over land, stagnant water bodies, and wastewater effluent/sludge eventually enters rivers.1,2
Environmental exposure degrades plastics into numerous tiny plastic fragments/particles, such as microplastics/microscopic fragments of plastic waste with particles less than 5 mm in size, and even nanoplastics with less than 1 µm in size. Microplastics differ in composition, density, shape, and size.1,2
Annual microplastic emissions are estimated at 10–40 million tons and could double by 2040. Microplastics are classified as primary microplastics, which are produced in less than 5 mm sizes for use in cosmetics and textiles, and secondary microplastics, which are formed by environmental breakdown.3,4
How Do Microplastics Get into Water?
Microplastics in surface water, groundwater, and wastewater have raised serious concerns about the potential contamination of drinking water. Microplastics enter drinking-water sources through various pathways, with surface run-off and wastewater effluent, both treated and untreated, being the primary contributors. These pathways include rain-induced run-off, treated and untreated sewage discharge, industrial effluents, degraded plastic waste, and atmospheric deposition.1,4
Primary microplastics, used in products like medicines and cosmetics, often enter domestic wastewater after use. Most wastewater treatment plants are not designed for complete microplastic removal. Hence, a large amount ends up in the effluent discharged into freshwater bodies and becomes part of the fresh/drinking water supply chain.4
The rise in microplastic levels in the Chicago River has been linked to effluents from adjacent wastewater treatment facilities. Components of water treatment and distribution systems—often made of plastic materials like polyethylene and polyvinyl chloride can degrade and lead to microplastic contamination.4
While primary microplastics contribute around 15–31% of total microplastics in drinking water, almost 69–81% are secondary microplastics. These originate from the breakdown of larger plastic/macroplastic waste in landfills and open dumps. Leachate from these sites carries microplastics that seep along with the water and contaminate surface and groundwater systems.4
Hence, microplastics are present in surface-derived drinking water and also in groundwater, although in smaller concentrations. Drinking water contains fragment and fiber-shaped microplastics, with polyethylene terephthalate, polyethylene, polyvinylchloride, and polypropylene being the most common polymer types in it.4
What are the Dangers of Microplastics?
Microplastic ingestion in humans primarily occurs through contaminated drinking water. Once ingested, some particles get excreted through bile, urine, or faeces due to their resistance to degradation. The microplastic elimination rate depends on size, shape, polymer type, and associated chemicals. However, microplastics can bioaccumulate in secondary organs after translocating from the gut with chronic/cumulative exposure, causing tissue obstruction due to their persistence in the body.4
This bioaccumulation raises significant public health concerns as microplastics are now prevalent in various environmental matrices and drinking water.
In the gastrointestinal system, microplastics trigger inflammatory responses, disrupt cellular functions, increase gut permeability, and alter microbial composition and metabolism. Their surface protein corona may facilitate their passage through the gastrointestinal tract.
A small portion of these particles may enter the bloodstream through the gastrointestinal wall and circulate to various organs and tissues, a process supported by in vivo studies.2
Recent findings reveal microplastic presence in human blood, placenta, breast milk, and lungs. Microplastic exposure causes adverse effects like oxidative stress, genotoxicity, inflammation, necrosis, and apoptosis, which may lead to tissue damage, fibrosis, or malignancy.2
Animal studies have displayed that polystyrene microplastics accumulate in the kidney, lungs, and intestine, leading to oxidative stress, altered lipid and energy metabolism, and neurotoxicity. Circulating microplastics have also been associated with pulmonary hypertension and vascular dysfunction, underscoring the potential for systemic health effects.2,4
Challenges in Removing Microplastics
The removal of microplastics from drinking water remains a major challenge due to constrained technical parameters and unclear removal mechanisms.
Detection of very small particles (<10 μm) and those in low concentrations, whether spherical or fragmented, is particularly difficult with current methodologies. Sample contamination during collection and laboratory processing further complicates accurate analysis.
A key issue is the lack of standardized analytical methods for sampling, identifying, and quantifying microplastics in drinking water. There is no consensus on the sample size, units of measurement, or pretreatment procedures needed to eliminate interference from non-plastic substances like salts. Existing quality assurance and control methods also require review and updates to ensure accurate and consistent microplastic assessments.2,3
Quick Guide to Microplastics in Drinking Water
Video Credit: Tap Score/YouTube.com
Latest Research in Microplastic Removal
Conventional treatment methods are effective to some extent in removing microplastics due to their physical similarity to suspended particulates. Among these, coagulation-precipitation is the most crucial process, with removal efficiencies reported between 17% and 71%.
One study showed coagulation-sedimentation reduced microplastics from 6614 to 3472 microplastics/L (40.5–54.5% efficiency). Another found air flotation removed up to 83% of microplastics.2 Advanced treatment technologies, such as membrane separation, effectively remove microplastics from water.
A study showed that ultrafiltration and reverse osmosis reduced microplastic levels from 2.2 microplastics/L to 0.28 microplastics/L and 0.21 microplastics/L, respectively. While promising for drinking water purification, further research must consider economic feasibility and membrane contamination risks.2
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A paper recently published in the Polish Journal of Environmental Studies proposed practical quality assurance and quality control (QA/QC) techniques to improve the accuracy of microplastic analysis. It addressed the lack of standardized/efficient QA/QC measures for sampling and analysis, which has hindered consistent environmental research on microplastics.
The study highlighted that microplastic research remains in its early stages, with varied and sometimes controversial methods used for sampling and laboratory analysis.
By comparing different approaches, the authors introduced a set of QA/QC measures to enhance the reliability and precision of analytical data for microplastics.2
Do Reusable Water Bottles Contain Microplastics?
Water stored in reusable plastic water bottles is not free from microplastic contamination. A study in the Journal of Hazardous Materials investigated chemical migration into water stored in reusable plastic bottles—new, used, and dishwasher-washed—over 24 hours.
Using liquid chromatography–high-resolution mass spectrometry, researchers identified over 3,500 compounds related to dishwashing, with 430 persisting even after flushing. More than 400 plastic-related compounds were detected, including oligomers from biodegradable polyester (polycaprolactone) and aromatic amines, possibly introduced as slip agents or antioxidants.5
Many of these chemicals had not previously been reported in bottled water. Used bottles release primarily plasticizers, antioxidants, and photoinitiators, the latter raising concern for potential endocrine-disrupting effects.
Overall, dishwashing significantly increased the leaching of plastic-related compounds, and subsequent flushing only halved their intensity, highlighting possible health risks associated with repeated use of plastic bottles.5
Continued Research in Microplastics in Drinking Water Needed
The widespread presence of microplastics in drinking water, originating from environmental pollution and everyday plastic use, poses significant health and environmental concerns.
Despite some removal by conventional and advanced treatment methods, the lack of standardized detection and analysis techniques hampers effective mitigation. Continued research and stricter quality control are essential to safeguard public health and ensure cleaner drinking water.
References and Further Reading
- Microplastics in drinking-water [Online] Available at https://cdn.who.int/media/docs/default-source/wash-documents/microplastics-in-dw-information-sheet190822.pdf (Accessed on 05 May 2025)
- Liu, H. et al. (2024). Microplastics in Drinking Water: Current Knowledge, Quality Assurance and Future Directions. Polish Journal of Environmental Studies, 33(5). DOI: 10.15244/pjoes/183443, https://www.pjoes.com/Microplastics-in-Drinking-Water-nCurrent-Knowledge-Quality-Assurance-nand-Future,183443,0,2.html
- Rodríguez-Barroso, R., Cruceira, A., Coello, M. D., Quiroga, J. M., & Egea-Corbacho, A. (2025). Microplastics in Drinking Water. Efficiency Of Treatment And Distribution Of A Drinking Water Distribution Cycle. Cleaner Engineering and Technology, 100972. DOI: 10.1016/j.clet.2025.100972, https://www.sciencedirect.com/science/article/pii/S2666790825000953
- Singh, S., Trushna, T., Kalyanasundaram, M., Tamhankar, A. J., & Diwan, V. (2022). Microplastics in drinking water: a macro issue. Water Supply, 22(5), 5650-5674. DOI: 10.2166/ws.2022.189, https://iwaponline.com/ws/article/22/5/5650/88579/Microplastics-in-drinking-water-a-macro-issue
- Tisler, S., Christensen, J. H. (2022). Non-target screening for the identification of migrating compounds from reusable plastic bottles into drinking water. Journal of Hazardous Materials, 429, 128331. DOI: 10.1016/j.jhazmat.2022.128331, https://www.sciencedirect.com/science/article/pii/S0304389422001194
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