San Mateo County, CA

ZIP 94028

In ZIP 94028, 3 of the 12 things we check have at least one part graded D or F.

• Drinking water: Santa Clara Valley Water District meets every EPA legal limit; 14 contaminants are above health goals, led by pfos at 3.7× California’s Public Health Goal.
• Nearest Superfund site: Intersil Inc./siemens Components, 6.5 miles away (3 within 10 miles).
• Largest share of modeled toxic air from industry: Tesla Inc. (70%), mostly cobalt compounds.
• Fine particles (PM2.5) average 6.1 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 94028

• Superfund sites nearbyD to F
• Factories and industrial sitesB
• Oil and gas wellsA
• Parks and nature nearbyB to C
• Air qualityA
• Drinking water qualityA to F
• Pesticide useC to D
• Neighborhood health statusB
• Past wildfire impactsA to C
• Past flood impactsA
• Noise levelsA to C
• Radiation signalsC

Based on 2 census tracts · compiled September 10, 2026 · how each grade works and its sources

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