What it is
Microplastics are plastic particles ranging from 5 millimeters down to 1 nanometer. The very smallest, under 1 micrometer, are called nanoplastics. EPA reports that they have been found in every ecosystem on the planet, and in food, beverages, and human and animal tissue.[1]
How it gets into water
Plastic is everywhere, so microplastics turn up in water sources, treatment systems and the containers we drink from. The World Health Organization's 2019 review found that wastewater treatment can remove more than 90% of microplastics, but it also identified major gaps in what's known about how many particles are present and where they come from.[2, 3]
Bottled water isn't a way around the problem. In a 2024 study, Columbia University researchers used a new imaging technique to count particles in bottled water and found about 240,000 detectable plastic particles per liter on average — about 90% of them nanoplastics. Counts ranged from roughly 110,000 to 370,000 per liter, 10 to 100 times higher than earlier estimates that couldn't see the smallest particles.[4, 5]
Why the numbers keep going up
Counting plastic you can't see is hard. Most earlier methods could only detect larger microplastics, so the smallest particles went uncounted. The Columbia team used stimulated Raman scattering microscopy, which can identify individual nanoplastic particles by their chemical signature.[4] As tools like this spread, expect estimates to keep changing — which is exactly why EPA is calling for standardized ways to collect, extract, count and identify these particles.[1] Better measurement doesn't mean the water suddenly changed. It means we're finally seeing what was there.
Health impacts
This is a young science, and it's moving fast. The most striking evidence so far comes from a 2024 study in the New England Journal of Medicine. Researchers examined plaque removed from the neck arteries of patients undergoing surgery and found microplastics and nanoplastics — mainly polyethylene — in 58.4% of them. Over an average follow-up of about 34 months, patients with plastic particles in their plaque had a higher risk of heart attack, stroke or death from any cause, with a hazard ratio of 4.53 — about 4.5 times the risk of those without detectable particles.[6]
That's an association, not proof of cause. The study was observational, and researchers are still working out what the findings mean. In 2019, WHO concluded that, based on the limited information available, microplastics in drinking water did not appear to pose a health risk at the levels then measured — while stressing that data on the smallest particles were extremely limited and calling for more research.[2] Since then, studies like these have shown far more particles, and far smaller ones, than earlier methods could detect.
What the law says vs. what health science says
There is no federal drinking water limit for microplastics today; they don't appear among EPA's regulated contaminants.[7] EPA says there's a pressing need to develop and standardize methods to collect, extract, count and identify microplastics — a necessary first step before anything can be regulated.[1]
That may be starting to change. In April 2026, NPR reported that EPA had flagged microplastics on a draft list of contaminants the agency is considering for drinking water regulation.[8] For now, the AquaGap™ for microplastics is a different kind of gap: not between a health goal and a legal limit, but between what scientists are finding and what anyone is required to measure.
What you can do
- Don't assume bottled is better. The 2024 Columbia study found hundreds of thousands of particles per liter in bottled water.[5]
- Follow the research. Measurement methods are improving quickly, and so is the evidence. We'll update this page as it does.
- Talk to your doctor if you have questions about your personal health risks.
- Know your water. Check your AquaScore™ to see what is measured and modeled at your address — and join the Guardians of H2O™ helping collect the data no one else has.
In the news
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Sources
- U.S. EPA. Microplastics Research.
- World Health Organization. WHO calls for more research into microplastics and a crackdown on plastic pollution (Aug. 22, 2019).
- World Health Organization. Microplastics in drinking-water (2019).
- PNAS. Qian et al., Rapid single-particle chemical imaging of nanoplastics by SRS microscopy, PNAS 121(3) (Jan. 2024).
- Columbia University Mailman School of Public Health. Bottled Water Can Contain Hundreds of Thousands of Nanoplastics (Jan. 2024).
- New England Journal of Medicine. Marfella et al., Microplastics and Nanoplastics in Atheromas and Cardiovascular Events, N Engl J Med 390:900–910 (Mar. 7, 2024).
- U.S. EPA. National Primary Drinking Water Regulations.
- NPR (news report). EPA flags microplastics, pharmaceuticals as contaminants in drinking water (Apr. 2, 2026).