St. Mary's County, MD

ZIP 20634

In ZIP 20634, 6 of the 12 things we check have at least one part graded D or F.

• Drinking water: Hunting Quarters meets every EPA legal limit; 4 contaminants are above health goals, led by arsenic at 921× California’s Public Health Goal.
• Nearest Superfund site: Patuxent River Naval Air Station, 3.1 miles away (2 within 10 miles).
• Largest share of modeled toxic air from industry: Stella-Jones Corp (70%), mostly arsenic compounds.
• Fine particles (PM2.5) average 6.5 µg/m³; the WHO guideline is 5 and the EPA annual standard is 9.
• About 64,785 kg of agricultural pesticides are applied in the county each year.

Grades for ZIP 20634

• Superfund sites nearbyD to F
• Factories and industrial sitesA to B
• Oil and gas wellsA
• Parks and nature nearbyC to D
• Air qualityA
• Drinking water qualityC to D
• Pesticide useD to F
• Neighborhood health statusB to D
• Past wildfire impactsA
• Past flood impactsD
• Noise levelsA
• Radiation signalsC

Based on 5 census tracts · compiled September 10, 2026 · how each grade works and its sources

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