San Mateo County, CA

ZIP 94027

In ZIP 94027, 4 of the 12 things we check have at least one part graded D or F.

• Drinking water: California Water Service - Bear Gulch has 1 contaminant at or over an EPA legal limit; 14 contaminants are above health goals, led by pfos at 7.8× California’s Public Health Goal.
• Nearest Superfund site: Hewlett-Packard (620-640 Page Mill Road), 3.6 miles away (3 within 10 miles).
• Largest share of modeled toxic air from industry: Tesla Inc. (75%), mostly cobalt compounds.
• Fine particles (PM2.5) average 7.0 µg/m³; the WHO guideline is 5 and the EPA annual standard is 9.
• About 38,964 kg of agricultural pesticides are applied in the county each year.

Grades for ZIP 94027

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

Based on 4 census tracts · compiled October 25, 2026 · how each grade works and its sources

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