Los Angeles County, CA

ZIP 91791

In ZIP 91791, 7 of the 12 things we check have at least one part graded D or F.

• Drinking water: Valencia Heights Water Co. has 2 contaminants at or over an EPA legal limit; 15 contaminants are above health goals, led by pfoa at 1,029× California’s Public Health Goal.
• Nearest Superfund site: San Gabriel Valley (area 4), 3.8 miles away (3 within 10 miles).
• Largest share of modeled toxic air from industry: Sterigenics-Ontario Facility (23%), mostly ethylene oxide.
• Fine particles (PM2.5) average 13.6 µg/m³; the WHO guideline is 5 and the EPA annual standard is 9.
• About 250,208 kg of agricultural pesticides are applied in the county each year.

Grades for ZIP 91791

• Superfund sites nearbyD to F
• Factories and industrial sitesD to F
• Oil and gas wellsC to F
• Parks and nature nearbyB to D
• Air qualityF
• Drinking water qualityC to F
• Pesticide useB to C
• Neighborhood health statusA to C
• Past wildfire impactsD
• Past flood impactsA to C
• Noise levelsA to B
• Radiation signalsC

Based on 11 census tracts · compiled October 25, 2026 · how each grade works and its sources

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