Williamson County, TX

ZIP 78628

In ZIP 78628, 4 of the 12 things we check have at least one part graded D or F.

• Drinking water: Vista Oaks Mud meets every EPA legal limit; 7 contaminants are above health goals, led by bromodichloromethane at 262× California’s Public Health Goal.
• Closer to Superfund sites than 0% of U.S. neighborhoods, with no listed site within 10 miles of its center.
• Largest share of modeled toxic air from industry: Tesla Giga Texas (82%), mostly polycyclic aromatic compounds.
• Fine particles (PM2.5) average 8.3 µg/m³; the WHO guideline is 5 and the EPA annual standard is 9.
• About 204,705 kg of agricultural pesticides are applied in the county each year.

Grades for ZIP 78628

• Superfund sites nearbyA
• Factories and industrial sitesA to B
• Oil and gas wellsA to D
• Parks and nature nearbyB to C
• Air qualityC to D
• Drinking water qualityC
• Pesticide useC to F
• Neighborhood health statusA to C
• Past wildfire impactsA
• Past flood impactsA to B
• Noise levelsA to B
• Radiation signalsB to D

Based on 13 census tracts · compiled October 25, 2026 · how each grade works and its sources

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