Microplastics in Tap Water by US City: 2026 Guide

Last updated: June 1, 2026

What we actually know about US city tap water

The 2017 Orb Media investigation, in partnership with the University of Minnesota School of Public Health, remains the most-cited per-city dataset for US tap water. Their sampling found microplastics in every one of the 33 US sites tested, including Manhattan, Washington DC (the EPA building, the US Capitol, and Trump Tower), Chicago, and Boston. The detection rate of 94% across the broader US sample was the highest of the 14 countries Orb tested.

Since 2017, individual academic studies have sampled specific utilities — Chicago, Cleveland, Denver, San Francisco Bay Area — and the EPA, USGS, and individual state agencies have begun broader monitoring. California adopted the first statewide microplastic drinking-water monitoring rule in 2022 with reporting phased in 2025-2026. As of mid-2026 we still don't have a comprehensive head-to-head city ranking — but we have enough proxy and direct data to characterise the major metros.

US cities with the cleanest tap water

Portland, Oregon — Bull Run watershed

Portland draws from the Bull Run watershed, a federally protected forested reservoir system in the Cascades. Until recently Portland delivered Bull Run water without conventional filtration — the source was that clean. A federal LT2 rule now requires Portland to build filtration by 2027, but the source water itself remains among the cleanest tap-water inputs in the country. Bull Run microplastic load is below US averages and very likely below most international tap-water averages.

Seattle, Washington — Cedar and Tolt watersheds

Seattle Public Utilities draws from the Cedar River and South Fork Tolt watersheds, both protected mountain reservoirs. Treatment uses ozone, UV, and chlorine — among the most advanced multi-barrier treatment chains in the country. Independent sampling of Seattle tap water has shown low microplastic counts relative to US averages.

New York City — Catskill / Delaware reservoirs

Despite the city's density, NYC tap water comes from one of the largest and cleanest unfiltered municipal supplies in the country. The Catskill / Delaware reservoir system spans 2,000 square miles of protected forested land 100+ miles north of the city. NYC has a Filtration Avoidance Determination from the EPA — one of only a handful of major US cities allowed to operate unfiltered. UV disinfection was added in 2013 at the Catskill / Delaware UV facility. Local distribution-system contamination does add some microplastic load between Westchester and your tap.

San Francisco — Hetch Hetchy

San Francisco draws from Hetch Hetchy reservoir in Yosemite National Park. Like NYC, SF has historically operated without conventional filtration of the Hetch Hetchy source because the Yosemite watershed is that protected. UV disinfection was added in 2011. Hetch Hetchy water is among the cleanest tap-water sources in the US.

Boston — Quabbin and Wachusett reservoirs

Massachusetts Water Resources Authority serves Boston and 50+ surrounding communities from the Quabbin and Wachusett reservoirs in central Massachusetts — both protected forested supplies. MWRA uses ozone, UV, and chlorine. Independent sampling has shown low microplastic indicators.

US cities with higher microplastic load

Houston — Trinity River system

Houston Public Works draws primarily from the Trinity River system (Lake Houston, Lake Conroe, Lake Livingston) plus groundwater wells. The Trinity drains a heavily urbanised watershed with agricultural and industrial input. Combined with the Gulf coast humidity and the concentration of petrochemical industry in the Houston metro, Houston shows elevated tap-water microplastic indicators. Houston also has aging distribution piping in many older neighbourhoods.

Phoenix and Tucson — Colorado River / Salt River

Phoenix draws from the Salt River Project (Salt and Verde rivers) and a Central Arizona Project allocation of Colorado River water. Tucson is heavily dependent on CAP Colorado River water. The Colorado River is the dominant source water for ~40 million people across seven Western states, and its raw-water microplastic load has been rising with watershed development. Phoenix utilities use advanced treatment (Val Vista, Squaw Peak, Verde, and Deer Valley plants), but the input load is higher than upland-reservoir cities.

New Orleans — Mississippi River

New Orleans Sewerage and Water Board draws directly from the Mississippi River, the largest drainage basin in North America. The Mississippi carries agricultural, industrial, and urban plastic load from 31 states and two Canadian provinces by the time it reaches New Orleans. The city is also Gulf coast with the associated humidity-driven plastic breakdown and atmospheric deposition. New Orleans tap water is among the higher-load US municipal supplies.

Los Angeles — State Water Project + Colorado River + local

LADWP draws from a portfolio: about 50% imported State Water Project (Northern California), ~20% Colorado River via Metropolitan Water District, ~10% Eastern Sierra Mountain runoff via the LA Aqueduct, and the rest from local groundwater. The imported components mean LA inherits whatever microplastic load the source watersheds carry. The Eastern Sierra water is among the cleanest; Colorado River the highest. LADWP runs modern treatment, but end-of-tap exposure depends partly on which source dominates your neighbourhood that month.

US cities in the middle of the range

Chicago and Milwaukee — Lake Michigan

Chicago's Jardine and South water plants draw from Lake Michigan, as does Milwaukee Water Works. Lake Michigan has documented microplastic concentrations from urban runoff and atmospheric deposition, but the volume of the lake provides significant dilution. Both cities operate modern multi-barrier treatment. Net microplastic load sits mid-range for US municipal supplies — better than river-fed Gulf cities, higher than upland- reservoir cities.

Denver — South Platte and mountain reservoirs

Denver Water draws from a combination of South Platte River diversions and mountain reservoirs (Dillon, Williams Fork, Cheesman). The mountain reservoir components keep Denver in the lower-mid range for microplastic load. Treatment is modern.

Atlanta — Chattahoochee River

Atlanta Department of Watershed Management draws from the Chattahoochee River. River-sourced and with a moderately developed upstream watershed, Atlanta sits mid-range. Treatment is good.

Philadelphia — Delaware and Schuylkill rivers

Philadelphia Water draws from the Delaware and Schuylkill rivers. Both source waters carry urban and industrial load from the upstream metro. Philly's treatment is modern but the source load and very old distribution piping in the urban core combine to put Philadelphia in the middle-to-upper US range.

Quick-reference city comparison

Note: relative load is a directional proxy combining source-water type, treatment maturity, distribution-piping age, and independent microplastic sampling where it exists. It is not a measurement and should not be used to compare utility performance directly. Check your local Consumer Confidence Report for utility-specific contaminant data.

Why your specific home matters more than your city

Even within a single city, microplastic exposure at your tap depends on:

• Service-line material — plastic (PVC, HDPE, PEX) service lines shed more microplastics into the home than copper or iron mains.
• Home plumbing — PEX and CPVC plastic plumbing inside the walls adds load. Older copper plumbing adds less plastic but introduces other concerns.
• Hot water heater — plastic-lined hot water heaters and plastic dip tubes are a significant source.
• Faucet aerator and fixtures — most modern aerators have plastic components. Cheap fixtures often use higher-plastic-content internal parts.
• Time-of-day flow — first-draw water that's been sitting in the line overnight has higher contact load than flushed water.

Practical advice for any US city

1. Find your local Consumer Confidence Report. Every public utility publishes one by July 1. Look up source-water type, treatment process, and any PFAS detections.
2. Cross-check the EWG Tap Water Database at ewg.org/tapwater for utility-specific contaminant compliance.
3. Install a point-of-use filter. The right tier depends on your daily volume — see our best pitcher filters ranked, best RO systems, and best water filters overall.
4. Flush before first draw. Run the tap for 30 seconds before filling a glass first thing in the morning, especially in older buildings.

See also: microplastics in tap water by US state, microplastics in drinking water by country, and microplastics in tap water (overview).