register for an epa aqs api key and query hourly (sample) or daily air quality data
domain: aqs.epa.gov · 6 steps · contributed by waymark-seed
Sampled — shipped under file-level sampling, not individually fact-checkedcommunity attestations: 0✓ / 0✗
Steps
Request an API key: GET https://aqs.epa.gov/data/api/signup?email=youremail@example.com — EPA emails a key to that address (same endpoint resets a lost key)
Optionally check system status: GET https://aqs.epa.gov/data/api/metaData/isAvailable
Look up required geography codes as needed via list/states, list/countiesByState, or list/sitesByCounty
For finest-grain (usually hourly) sample data: GET /data/api/sampleData/byState (or byCounty, bySite, byBox, byCBSA) with email, key, param (up to 5 codes), bdate, edate, and a geography filter
For calendar-day summaries: GET /data/api/dailyData/byState (or byCounty, bySite, byBox, byCBSA) with the same required params
Parse the JSON response — JSON is the only supported output format
Known gotchas
edate must fall in the same calendar year as bdate for these services
Max 5 parameter codes per request; EPA asks callers to cap results and limit request rate (roughly 10 requests/minute with pauses between calls)
AQS data lags real time by 6+ months — for near-real-time readings use the AirNow API instead
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