Air Quality in Norristown, PA: Moderate (77 AQI)
AQI 77 · Moderate · Ozone · Updated
Norristown's air quality is moderate. Unusually sensitive people should consider reducing prolonged outdoor exertion.
Data: EPA AirNow, FEMA National Risk Index Last verified:
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. Norristown's average AQI of 77 falls in the "Moderate" range.
Air Quality by ZIP Code in Norristown
AQI varies across Norristown's 3 ZIP codes based on proximity to pollution sources and local geography.
| ZIP Code | AQI | Category | Wildfire | Mold | |
|---|---|---|---|---|---|
| 19401 | 77 | Moderate | 13 | 66 | View report → |
| 19403 | 77 | Moderate | 18 | 60 | View report → |
| 19404 | 77 | Moderate | 18 | 31 | View report → |
Air Quality Overview
Norristown, Pennsylvania has moderate air quality with an average AQI of 77. 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 Ozone.
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: Ozone
Ground-level ozone forms when pollutants from cars, power plants, and industrial facilities react with sunlight. Unlike stratospheric ozone, ground-level ozone is harmful to breathe.
Health effects of ozone exposure:
- Irritation of the respiratory system
- Reduced lung function
- Aggravation of asthma and chronic lung diseases
- Increased susceptibility to respiratory infections
Peak times: Ozone levels are typically highest on hot, sunny afternoons. Exercise outdoors in the morning when levels are lower.
Air Quality by ZIP Code in Norristown
AQI varies across Norristown's 3 ZIP codes based on proximity to pollution sources, traffic patterns, and local geography:
| ZIP Code | AQI | Category | Wildfire Risk | Mold Score |
|---|---|---|---|---|
| 19401 | 77 | Moderate | 13 | 66 |
| 19403 | 77 | Moderate | 18 | 60 |
| 19404 | 77 | Moderate | 18 | 31 |
Wildfire Smoke Risk
Norristown has an elevated wildfire smoke risk with an average smoke risk score of 16 (scale 0-100). There have been 32 fires recorded within 100 km of city ZIP codes.
| Metric | Value |
|---|---|
| Avg. smoke risk score | 16 |
| Max smoke risk score | 18 |
| Fires within 100 km | 32 |
| 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
Norristown has an average mold risk score of 52 out of 100, with 2 ZIP codes in the high-risk category.
| Factor | Value |
|---|---|
| Mold risk score | 52/100 |
| Average humidity | 63% RH |
| High-risk ZIPs | 2 |
| Peak season | balanced |
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 77), 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
Norristown vs. Nearby Pennsylvania Cities
How Norristown's air quality compares to nearby cities:
| City | AQI | Category | Population |
|---|---|---|---|
| Norristown | 77 | Moderate | 87,066 |
| Mechanicsburg | 54 | Moderate | 83,963 |
| Easton | 46 | Good | 91,876 |
| Wilkes Barre | 37 | Good | 77,959 |
ZIP Codes in Norristown
Norristown covers 3 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
Source reporting periods vary. See each cited source for its publication schedule.