EPA Air Quality (AirNow)

EPA Air Quality (AirNow)

EPA AirNow provides real-time Air Quality Index (AQI) from 2500+ monitoring stations, forecasts for 500+ cities. Data by ZIP code, latitude/longitude, or monitoring area. Pollutants: O3, PM2.5, PM10, CO, NO2, SO2. AQI categories: Good (0-50), Moderate (51-100), USG (101-150), Unhealthy (151-200), Very Unhealthy (201-300), Hazardous (301+). Includes reporting area, date observed, and health category.

Data Model

• Current observations — real-time AQI readings by ZIP code or lat/lon with pollutant type, AQI value, and category.
• Forecasts — next-day AQI predictions for 500+ reporting areas with action day flags.
• Historical observations — past AQI readings for any date by ZIP code or lat/lon coordinates. Useful for trend analysis and comparing air quality across time periods.
• Monitoring sites — station metadata with location, parameters measured, and agency.

Gotchas

• Query by ZIP or lat/lon — observations require either zipCode or latitude+longitude, not both.
• Distance parameter — radius in miles from the query point to include stations (default 25).
• Format — must specify format=application/json for JSON responses.
• Rate limit — 500 requests per hour with a registered key.
• Date format — uses YYYY-MM-DDTHH for date parameters.