Microplastics in Drinking Water: An Invisible Threat with Growing Consequences

Microplastics have rapidly shifted from an obscure scientific topic of interest to a defining environmental and public health concern. While microplastics were once believed to be confined to oceans and landfills, these tiny particles are found in the air we breathe, the food we eat, and the water we drink. As research accelerates, so does public awareness. According to the 2025 Waterdrop Annual Water Survey, microplastics have now become the most feared water contaminant among US consumers, surpassing other hazardous contaminants such as lead and PFAS.

Microplastics are small plastic particles measuring less than 5 millimeters in size.[1]As a reference, a grain of rice is about 5 millimeters. Microplastics originate either as intentionally manufactured small particles, such as microbeads in cosmetics, or as fragments that break off from larger plastic items.[2] Nanoplastics are even smaller pieces, measuring less than 100 nanometers, and these smaller particles can penetrate biological tissues more readily.

Because of their small size, microplastics can easily travel through water systems, soil, air, and living organisms. [3] Their small scale also makes them extremely difficult to remove once they enter the environment.

Global overabundance of plastic is the root problem that drives microplastics contamination. Between 1950 and 2015 an estimated 6.3 billion tons of plastic waste were generated with 79% either buried or discarded in the environment.[2]Over time, these materials break down into small particles through sunlight, heat, and/or mechanical stress. Microplastics tend to accumulate in landfills and garbage dumps, soil, water sources (rivers, lakes and streams), and in dust.[2]These particles can remain in the soil for decades or be transported by wind or water, which can lead to spread far beyond their original source.[3]

Microplastics can also originate from common household and industrial sources. Synthetic fabrics shed microfibers during washing, and some personal care products, such as exfoliants, contain microbeads.[4]Indoor environments contain particles from insulation and furnishings.[5]Microplastics have even been detected in freshly fallen snow![6]Unfortunately, the ubiquity of plastic in our modern lives ensures that microplastics are continuously generated and dispersed throughout our environment, making it easy to encounter them in everyday life.

As we discussed, microplastics are found in nearly every part of the environment, and they are used in almost every consumer product category. There are many ways in which microplastics can enter our bodies. They can be inhaled in both indoor and outdoor environments.[7] Several studies have also detected microplastics in food including seafood, salt, honey, sugar, and fruits and vegetables.[8] Finally, a global study found that up to 83% of tap water samples contained microplastics.[1] If you think bottled water is safer, think again. Bottled water may contain even higher concentrations of microplastics, due to shedding from plastic bottles and caps.[9]

Microplastics can enter drinking water through many routes. Microplastics can enter lakes, rivers, and the groundwater supply from storm water runoff, industrial discharge, and discarded and degraded litter.[10] Municipal treatment plants can remove many water contaminants, however, because of their small size microplastics can often slip through filtration systems. Even after treatment, microplastics can enter our drinking water through plastic water pipes, plastic filters, and other pieces of household plumbing systems.[10, 11] In summary, microplastic contamination can happen at multiple points between the source and the tap.

Although research is ongoing and more research is needed, evidence increasingly suggests that microplastics can affect multiple human organ systems. Ingested microplastics may cause nausea, vomiting, abdominal pain, and changes in the gut microbiota.[12] Many plastics contain endocrine-disrupting chemicals, such as BPA and phthalates.

These chemicals in the plastic may interfere with human hormone regulation, potentially contribution to metabolic disorders, developmental abnormalities, and thyroid dysfunction.[13] These chemicals within microplastics have also been linked to reduced fertility and altered reproductive development. Finally, microplastics can trigger chronic inflammation, oxidative stress, and immune dysregulation.[14]

Because of the potential health risks, consumers are increasingly seeking ways to protect themselves from microplastics exposure. Several methods exist to reduce microplastics, though their effectiveness varies (please note this discussion is not all inclusive). Activated charcoal filters can capture and eliminate some microplastics, but the performance varies across brand and design.[15] These charcoal filters are typically low-to-mid cost and are generally accessible.

Distillation removes microplastics by evaporating water, leaving the contaminants behind.[16] However, this method is energy-intensive, costly, and impractical for most households. Reverse osmosis is an effective way for removing microplastics. Reverse osmosis membranes typically have extremely small pore sizes, which are capable of filtering out particles far smaller than typical microplastics.[17] There is some literature that shows the reverse osmosis systems can achieve higher removal rates compared to other filtration methods, although more research is needed.

Reverse osmosis is a high-pressure water purification system that forces water through a semi-permeable membrane to separate water molecules from dissolved and suspended contaminants. Standard reverse osmosis membranes in drinking water filtration systems have extremely small pore sizes, typically 0.001 microns or less. By contrast, microplastics are much larger, and as discussed are typically 5 millimeters (or 5,000 microns) in size or less.

Because microplastics are typically thousands of times bigger than the openings in a reverse osmosis membrane, these systems can effectively block microplastics from passing through the membrane. Many systems report >99% efficiency in removing contaminants in well-maintained systems. While more research needs to be conducted, based on size, reverse osmosis systems are likely capable of filtering even nanoplastics.

Microplastics have become a defining environmental and public health issue. Their presence in drinking water is well-documented, widespread, and increasingly concerning to consumers. Scientific research continues to uncover and examine potential health risks, from endocrine disruption to immune system effects.

The 2025 Waterdrop Annual Water Quality Survey confirms that Americans are paying attention. Microplastics now top the list of feared contaminants, and consumers are taking action and carefully considering ways to reduce their exposure to microplastics.

As plastic production continues and environmental contamination grows, microplastics will remain a pressing challenge. However, with rising awareness, improved filtration techniques, and stronger regulatory efforts, individuals and communities can take meaningful steps to safeguard their water and their health.

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