Air Quality in South San Francisco, CA: Moderate (53 AQI)
AQI 53 · Moderate · PM2.5 · Updated 2026-07-18
South San Francisco's air quality is moderate. Unusually sensitive people should consider reducing prolonged outdoor exertion.
Data: EPA AirNow, FEMA National Risk Index Last verified: 2026-07-18
What is AQI?
The Air Quality Index (AQI) is a standardized scale from 0 to 500 that measures air pollution levels. 0-50 is "Good," 51-100 is "Moderate," 101-150 is "Unhealthy for Sensitive Groups," and above 150 is "Unhealthy" for everyone. AQI tracks five major pollutants: ground-level ozone, particulate matter (PM2.5 and PM10), carbon monoxide, sulfur dioxide, and nitrogen dioxide. South San Francisco's average AQI of 53 falls in the "Moderate" range.
How do wildfires affect air quality?
Wildfire smoke contains fine particulate matter (PM2.5) that can travel hundreds of miles and dramatically spike AQI readings. During fire season, even cities far from active fires can experience unhealthy air. HEPA air purifiers (rated for PM2.5) are the most effective indoor protection. Check AirNow.gov for real-time conditions during fire season.
Air Quality by ZIP Code in South San Francisco
AQI varies across South San Francisco's 2 ZIP codes based on proximity to pollution sources and local geography.
| ZIP Code | AQI | Category | Wildfire | Mold | |
|---|---|---|---|---|---|
| 94080 | 53 | Moderate | 22 | 43 | View report → |
| 94083 | 53 | Moderate | 22 | 17 | View report → |
Air Quality Overview
South San Francisco, California has moderate air quality with an average AQI of 53. Air quality is acceptable, though some pollutants may be a concern for a small number of people who are unusually sensitive to air pollution. The dominant pollutant is PM2.5.
The Air Quality Index (AQI) is an EPA-standardized scale from 0 to 500. Values below 50 are "Good," 51-100 "Moderate," 101-150 "Unhealthy for Sensitive Groups," 151-200 "Unhealthy," 201-300 "Very Unhealthy," and above 300 "Hazardous."
Dominant Pollutant: PM2.5
PM2.5 (fine particulate matter) consists of particles smaller than 2.5 micrometers - about 30 times thinner than a human hair. These particles can penetrate deep into the lungs and enter the bloodstream.
Health effects of PM2.5 exposure:
- Short-term: coughing, shortness of breath, aggravated asthma
- Long-term: reduced lung function, cardiovascular disease, premature death
- Most vulnerable: children, elderly, people with heart or lung disease
Common sources in urban areas: vehicle exhaust, construction dust, industrial emissions, wildfire smoke, residential wood burning.
Air Quality by ZIP Code in South San Francisco
AQI varies across South San Francisco's 2 ZIP codes based on proximity to pollution sources, traffic patterns, and local geography:
Wildfire Smoke Risk
South San Francisco has an elevated wildfire smoke risk with an average smoke risk score of 22 (scale 0-100). There have been 2 fires recorded within 100 km of city ZIP codes.
| Metric | Value |
|---|---|
| Avg. smoke risk score | 22 |
| Max smoke risk score | 22 |
| Fires within 100 km | 2 |
| High-risk ZIP codes | 0 |
Wildfire smoke contains PM2.5, carbon monoxide, and volatile organic compounds. Even short-term exposure can trigger asthma attacks and respiratory distress.
Indoor Mold Risk
South San Francisco has an average mold risk score of 30 out of 100.
| Factor | Value |
|---|---|
| Mold risk score | 30/100 |
| Average humidity | 57% RH |
| High-risk ZIPs | 0 |
| Peak season | winter high |
Mold risk is influenced by humidity levels, housing age (older homes have more moisture issues), flood history, and water infrastructure quality. Indoor humidity above 60% creates favorable conditions for mold growth.
Signs of mold problems: musty odors, visible growth on walls or ceilings, worsening allergies indoors, condensation on windows. Professional mold testing ($300-$600) can identify hidden issues.
Health Recommendations
With moderate air quality (AQI 53), most people can be active outdoors. Sensitive groups should take precautions:
- Sensitive groups (asthma, COPD, heart disease): consider reducing prolonged outdoor exertion
- Keep windows closed on high-pollution days
- Use a HEPA air purifier in main living areas
- Check AirNow.gov before outdoor exercise
South San Francisco vs. Nearby California Cities
How South San Francisco's air quality compares to nearby cities:
| City | AQI | Category | Population |
|---|---|---|---|
| South San Francisco | 53 | Moderate | 65,036 |
| Lynwood | 56 | Moderate | 64,918 |
| Arcadia | 58 | Moderate | 65,247 |
| Woodland | 47 | Good | 65,976 |
ZIP Codes in South San Francisco
South San Francisco covers 2 ZIP codes. Air quality can vary by neighborhood based on proximity to highways, industrial areas, and green spaces. Check your specific ZIP code for localized data.
Data Sources
- Air quality: EPA AirNow - real-time and historical AQI data
- Wildfire risk: FEMA National Risk Index
- Mold risk: Derived from EPA, FEMA, Census ACS (humidity, housing age, flood history)
- Monthly AQI: EPA Air Quality Statistics
Updated daily.