Microplastics in drinking water: A neglected public health risk in tropical settings

Sir, Access to safe drinking water remains central to public health. While surveillance frameworks have traditionally prioritised microbial contamination, an emerging and insufficiently addressed threat is microplastics. These particles, typically <5 mm in size, have been identified in c.80% of drinking water sources globally, including bottled water, municipal supplies, and groundwater. ¹ They are non-degradable plastics: polyethene, polypropylene, polystyrene, polycarbonate, polyurethane, and polyamide, especially if containing chlorine atoms. They can cross cell membranes and remain in tissues, reproductive organs, GI tract, brain, kidneys, and liver.

Rapid urbanisation, inadequate waste management in dumps and landfills, and widespread reliance on single-use plastics accelerate environmental accumulation and fragmentation into microplastics, facilitating their entry into water systems. Despite growing evidence of exposure, microplastics remain absent from routine water quality assessments. ² Their potential role as vectors for toxic chemicals (pollutants and heavy metals) and microorganisms raises important concerns regarding long-term health effects.

In many low- and middle-income countries, inadequate segregation, open dumping, and limited recycling infrastructure facilitate the progressive breakdown of plastics into microplastics. ³ These particles enter water systems through surface runoff, sewage pathways, and environmental weathering. Populations relying on untreated or minimally treated water, particularly in peri-urban and rural settings, are therefore disproportionately exposed.

A key barrier to recognition is methodological. The detection and quantification of microplastics require advanced analytical techniques, including spectroscopic and microscopic methods, which are not widely accessible in resource-constrained settings. ² However, the absence of routine measurement should not be conflated with the absence of risk. The potential health implications, while still evolving, are biologically and increasingly plausible. Microplastics may function as carriers of heavy metals, endocrine-disrupting compounds, and microbial agents. ³ Experimental data suggest that chronic ingestion may induce inflammatory responses, oxidative stress, and disturbances in cellular homeostasis.^4,5 Emerging evidence from developing regions further suggests that microplastics in drinking water may exhibit significant sorptive capacity for environmental pollutants. ⁶ Although definitive epidemiological evidence remains limited, the trajectory of current findings warrants precaution rather than delay.

From a public health perspective, waiting for conclusive evidence before acknowledging risk may replicate patterns seen with other environmental exposures. A more pragmatic approach is justified. First, microplastics should be explicitly recognised within water safety discussions, even if quantitative thresholds are not yet defined. Second, targeted pilot surveillance in selected urban and peri-urban settings could generate contextually relevant baseline data. Third, upstream interventions are justified, particularly strengthening plastic waste management, improving segregation, and prohibiting single-use plastics. All offer tangible and immediately actionable benefits. ⁷

At the household level, filtration strategies are unlikely to reduce exposure, though boiling and coagulation-sedimentation may. At the municipal level, natural polysaccharide flocculants may be useful. At the national level, the limitation of plastic usage is essential. Addressing microplastics as a public health concern will ultimately require coordinated efforts across environmental science, policy, and healthcare systems.

Microplastics in drinking water represent an under-recognised but potential environmental health risk, particularly in low-income settings characterised by rapid urbanisation and infrastructural constraints. While important uncertainties remain, inaction based on incomplete evidence may prove deleterious. Early acknowledgement, coupled with pragmatic and context-sensitive interventions, offers an opportunity to address this emerging exposure before it becomes an entrenched public health challenge.

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