Extreme VOCs in U.S. Drinking Water Systems

What this report shows

Volatile organic compounds (VOCs) are industrial chemicals that end up in water from solvent spills, dry cleaners, leaking fuel tanks, and — in the case of disinfection byproducts — the water treatment process itself. Each regulated VOC has a federal Maximum Contaminant Level (MCL). Benzene and trichloroethylene (TCE) are limited to 5 parts per billion; vinyl chloride to 2.

This report covers the extreme systems: public water systems where a VOC tested at 3 times its federal limit or more in EPA compliance monitoring. Samples include both source wells and treated water — a system with a heavily contaminated well may still serve safe water after treatment, but the contamination is real, the treatment burden is real, and the plume is nearby.

Where they are: CA (51), NY (20), PA (19), NC (9), LA (9), WI (8), IL (7), IN (7), FL (6), VA (6), CT (5), NJ (5), OK (4), MA (4), AK (4).

Coverage note: Mississippi submitted incomplete data to Six-Year Review 4, so MS systems are under-represented here. State drinking-water records fill that gap on request.

The 40 worst systems

Ranked by how far the governing chemical tested over its MCL. Solvent and fuel chemicals are ranked on their worst single sample; disinfection byproducts on the system's average.

How this was built

EPA collected every state's drinking-water compliance samples from 2012–2019 for its fourth Six-Year Review — 71 million records across roughly 140,000 systems. This report folds the 23 regulated VOC analytes down to one worst result per system, compares each against its MCL, and locates systems by the zip, city, or county they serve (EPA ECHO records, U.S. Census centroids). The same data drives the VOC layers on the iVerify draw tool.