Charles County, Maryland: drinking water report. Charles County sits in southern Maryland along the Potomac River, encompassing communities like Waldorf,
Charles County sits in southern Maryland along the Potomac River, encompassing communities like Waldorf, La Plata, and Indian Head. Most residents rely on groundwater wells or small community water systems drawing from the Patuxent and Aquia aquifers, though some areas near the river use surface water sources. The county's mix of suburban development and rural areas creates a patchwork of water supply systems, from municipal utilities serving denser populations to thousands of private wells in less developed zones.
Charles County faces water quality challenges typical of the Chesapeake Bay region, where agricultural runoff, aging infrastructure, and naturally occurring contaminants intersect. The Potomac aquifer system that underlies much of the county contains elevated levels of radium and uranium in some locations, a geological reality across Maryland's Coastal Plain. These naturally occurring radioactive elements leach from bedrock into groundwater, particularly affecting deeper wells. The EPA's UCMR monitoring has flagged radionuclides as a concern in similar hydrogeologic settings throughout the mid-Atlantic, and Charles County's geology follows this pattern.
Lead exposure remains a concern in older neighborhoods where service lines and household plumbing installed before the 1980s still exist. While public water systems must test at the tap under the Lead and Copper Rule, the thousands of private wells scattered across rural Charles County receive no mandatory testing or treatment. These wells are the homeowner's responsibility, and many have never been tested for the full range of potential contaminants. Nitrate contamination from septic systems and agricultural operations also poses risks in areas with dense well networks and limited sewer infrastructure.
PFAS contamination has emerged as a statewide concern in Maryland, with military installations and industrial sites identified as sources. Indian Head Naval Support Facility, located within Charles County, has used aqueous film-forming foams containing PFAS for decades. The Maryland Department of the Environment has expanded PFAS testing requirements, and communities near defense installations typically show detectable levels of these persistent chemicals. Surface water from the Potomac River, which supplies some county residents, can carry PFAS and other contaminants from upstream sources throughout the watershed.
Test your water regardless of your source, whether you're on a public system or private well. Private well owners should test annually for basic contaminants and every three to five years for a broader panel including radionuclides, nitrates, and volatile organic compounds. Check your water to see current data for your ZIP code, review our water filter guide to find treatment options matched to your specific contaminants, and read the detailed report for comprehensive testing information. The Maryland state page provides additional context on statewide water quality trends and regulatory requirements.
Drinking water is one exposure route. These federal datasets also cover Charles County, MD.
The EPA places Charles County, MD 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.
30% of homes in Charles County, MD were built before 1980, and 5% 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 Charles County, MD averages 7.2 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