St Louis County, Missouri: drinking water report. St. Louis County (separate from the City of St.
St. Louis County (separate from the City of St. Louis) serves about 1 million residents in the suburban ring surrounding the city. Missouri American Water is the primary provider, drawing from the Missouri and Meramec Rivers. Some communities operate independent systems. The county's complex jurisdictional structure – over 80 municipalities – means water service is fragmented across multiple providers.
The Missouri River carries agricultural runoff from the Great Plains, while the Meramec River drains a mix of forested, suburban, and former mining landscapes. UCMR5 data shows low-level PFAS detections in county systems. Missouri does not have state-specific PFAS standards.
According to the Missouri Department of Natural Resources' 2024 compliance data, county systems met federal standards. Atrazine – a common agricultural herbicide – is a seasonal contaminant in Missouri River water, though treatment reduces it below MCLs. The legacy of lead mining in the broader region also means some soils carry elevated lead, though this affects soil and dust more than treated drinking water.
With over 80 municipalities, your provider and source water may differ from your neighbor's. Identifying your specific system is step one.
Check your water to see data for your provider. Activated carbon handles taste, atrazine, and some PFAS. Our water filter guide covers options. Pull your detailed report, and visit our Missouri page for statewide data.
Drinking water is one exposure route. These federal datasets also cover St Louis County, MO.
The EPA places St Louis County, MO in Zone 2 - a moderate-risk category, with a predicted average indoor radon level between 2 and 4 pCi/L. Zone maps predict an area's radon potential from geology and existing indoor readings; they say nothing about a specific house. Testing is the only way to know your own level.
70% of homes in St Louis County, MO were built before 1980, and 16% before 1950. Residential lead paint was banned in 1978, so housing age is the strongest available proxy for lead-paint exposure. This describes the county's housing stock, not any one home.
Modelled annual fine-particle pollution (PM2.5) in St Louis County, MO averages 8.6 µg/m³, within the EPA's annual standard of 9 µg/m³. These are CDC modelled county estimates rather than readings from a specific monitor.
How radon zones work · Air quality by county · Lead exposure guide