Microplastics show up in tap water worldwide, yet the EPA has set no legal limit for them. The most-cited health screening level, about 90 µg/L from a 2022 research paper, is a scientific threshold, not a regulation.
● Key Takeaways
There is no federal Maximum Contaminant Level for microplastics in tap water, so no enforceable safety line exists yet. California became the first jurisdiction in the world to require microplastics monitoring in drinking water. The Coffin et al. 2022 screening level of about 90 µg/L is a research threshold, not a regulation. Reverse osmosis and sub-micron carbon block filters remove most particles today. Absence of a number is not proof of safety.
What Are Microplastics, and How Do They Get Into Tap Water?
Microplastics are plastic fragments smaller than 5 millimeters. They enter water from the breakdown of larger plastic debris, synthetic textiles, tire wear, and personal care products. A widely cited 2018 survey found microplastics in 83% of tap water samples collected across five continents (Kosuth et al., 2018, PLOS ONE).
Most municipal treatment plants were never designed to strain out particles this small, so many fragments pass through the distribution system and out of the faucet. Aging infrastructure adds to the load. Plastic pipes, polymer sealants, and storage tanks shed particles slowly as they age and flex under pressure.
How much ends up inside us is still an open question. One estimate put average annual intake between 39,000 and 52,000 particles per person from food and water combined, rising higher once inhalation is included (Cox et al., 2019, Environmental Science & Technology). Drinking water is one meaningful route among several, not the whole picture.
Why Is There No EPA Limit for Microplastics?
There is no federal Maximum Contaminant Level for microplastics, and the honest reason is measurement, not neglect. Microplastics range from visible flecks down to the nanometer scale, and quantifying them reliably still requires specialized tools like Raman spectroscopy and FTIR. Without a standardized, agreed-upon test method, the EPA has no defensible basis for an enforceable number.
This is an abstain-by-design situation, and it matters that we say so plainly. When a contaminant has a regulated limit, you can compare your water to a legal line. Microplastics have no such line, so there is nothing to divide against and no honest "X times over the limit" multiplier to quote.
The lack of a limit is frequently misread in both directions. Some treat "unregulated" as proof the water is fine; others treat it as proof of a cover-up. Both are wrong. The regulatory gap reflects an unsettled science of measurement and dose, not a verdict on safety. We think the calm, defensible reading is the third one: we do not yet know the safe dose, so reducing exposure is reasonable but not urgent.
If you want the reproductive-health angle on this same gap, we cover the emerging placenta and fertility research in a separate post rather than repeat it here: microplastics and reproductive health.
How California Pioneered Microplastics Monitoring
California became the first jurisdiction in the world to build a microplastics-in-drinking-water program, and it did so through monitoring rather than a limit. Under a 2018 state law, the State Water Resources Control Board adopted the first standardized definition and testing framework for microplastics in drinking water, with a multi-year monitoring program for the largest water systems (California State Water Resources Control Board).
That distinction is easy to blur, so it is worth stating clearly. California requires certain large water systems to test for and report microplastics. It does not set a level a system must stay under. Monitoring generates the data that any future health standard would need. It is a first step toward regulation, not a regulation itself.
The scientific groundwork came partly from researchers connected to that same California effort, which is where the most-cited screening level originated.
Reading this inside ChatGPT or Claude?
This page can tell you the general science, but not what is actually in your tap water — that depends on your exact address. You can get your specific answer two ways:
- Inside the chat: ask your assistant to “check my tap water with CheckYourTap”. Our connector returns your ZIP code’s measured contaminant levels — including the derived dog and cat safe levels — and, only if you ask it to, can email you the report or arrange a specialist callback.
- On the web: open CheckYourTap.com and enter your ZIP code for a free 30-second report.
What the Coffin et al. 2022 Screening Level Actually Means
The number people quote most, roughly 90 µg/L, comes from a research framework, not a rulebook. In 2022, Coffin and colleagues published a health-based framework that derived screening concentrations for microplastics, with a chronic screening level near 90 µg/L (Coffin et al., 2022, Microplastics and Nanoplastics). Scientists built it to help interpret monitoring data, not to certify anything below it as proven safe.
Treat that figure as a research threshold with real uncertainty around it. It rests on limited toxicology and on measurement methods that are still being standardized. In our reconciliation of published values, we classify it as a Tier B, derived screening level rather than a hard safety number, and we do not present it as an enforceable or official limit.
Here is how the regulatory picture stacks up against the science:
| Reference point | Value for microplastics | What it is |
|---|---|---|
| EPA federal MCL | None established | No enforceable federal limit exists |
| California requirement | Monitoring, no limit | First-in-world testing and reporting mandate |
| EWG / OEHHA public health goal | None established | No health-based goal set yet |
| Coffin et al. 2022 screening level | ~90 µg/L (Tier B) | Research threshold, not a regulation |
When we reconciled every published microplastics number for this site, the recurring temptation was to relabel that 90 µg/L as a "safe level" so a reader would have something concrete. We deliberately did not. Dressing a research screening value up as a safety standard is exactly the overreach a health-topic page should avoid. The honest label is "screening level, derived, uncertain."
How Do You Filter Microplastics From Tap Water?
The right filter removes the vast majority of microplastics, and the choice comes down to particle size. Because microplastics span from millimeters down below 0.1 micron, only fine-pore technologies capture the small end. Reverse osmosis performs best, and standard pour-through pitchers are generally not built for particles this size.
Reverse osmosis
Reverse osmosis is the most complete option for microplastics. Its membranes have pores near 0.0001 micron, small enough to block nearly all microplastics and most nanoplastics, along with many of the dissolved chemicals plastics carry. Pair an under-sink RO unit with a sediment pre-filter so larger fragments do not clog the membrane early.
Sub-micron carbon block
A carbon block filter rated to an absolute 0.5 micron is the strong second choice. It physically traps most microplastics by mass while the carbon adsorbs associated chemicals. It will not stop the smallest nanoplastics, and a saturated cartridge can shed trapped particles, so replacing it on schedule is not optional.
Distillation
Distillers boil water to steam and recondense it, leaving solid particles behind in the chamber. That removes microplastics of all sizes well. It is slow, needs regular descaling, and lets some plastic-associated volatile compounds carry over, so a post-carbon stage is often added.
Whichever route you pick, match it to your actual water rather than filtering blind. Microplastics are rarely the only thing worth reducing, and a report tells you what else is present before you spend money on hardware.
Keep Reading
- Microplastics in drinking water and reproductive health
- Is bottled water safer than tap during pregnancy? What the microplastic data shows
- Microplastics in drinking water: what CT residents need to know
Sources: U.S. EPA drinking-water regulations (microplastics currently unregulated at the federal level); California State Water Resources Control Board microplastics in drinking water program; Coffin S et al., "Development and application of a health-based framework for deriving safe drinking water concentrations for microplastics," Microplastics and Nanoplastics, 2022; Kosuth M, Mason SA, Wattenberg EV, "Anthropogenic contamination of tap water, beer, and sea salt," PLOS ONE, 2018; Cox KD et al., "Human consumption of microplastics," Environmental Science & Technology, 2019. The ~90 µg/L figure is a derived research screening level, not a regulatory limit or an official safe level.