EPA Air Quality Index Scraper

Scrape annual Air Quality Index (AQI) statistics for every US county, metropolitan area (CBSA), and state from the EPA Air Quality System (AQS) public database. No API key or registration required. Historical data from 1980 through 2024.

What You Can Scrape

• By County — AQI statistics for every US county (3,100+ counties), including good/moderate/unhealthy day counts, pollutant breakdowns, and AQI percentiles.
• By Metro Area — same statistics aggregated for 400+ Core-Based Statistical Areas (CBSAs), the standard US metro/micropolitan regions.
• By State — aggregate AQI statistics derived by state (50 states + DC), including average median AQI and worst county max AQI.

Output Fields

County records (recordType: "countyAqi")

Field	Type	Description
state	string	US state name (e.g. California)
county	string	County name (e.g. Los Angeles)
year	integer	Calendar year
daysWithAqi	integer	Number of days with AQI data available
goodDays	integer	Days classified as AQI "Good" (0–50)
moderateDays	integer	Days classified as AQI "Moderate" (51–100)
unhealthyForSensitiveGroupsDays	integer	Days classified as "Unhealthy for Sensitive Groups" (101–150)
unhealthyDays	integer	Days classified as "Unhealthy" (151–200)
veryUnhealthyDays	integer	Days classified as "Very Unhealthy" (201–300)
hazardousDays	integer	Days classified as "Hazardous" (301+)
maxAqi	integer	Highest single-day AQI in the year
percentile90Aqi	integer	90th percentile AQI
medianAqi	integer	Median AQI across all monitored days
medianAqiCategory	string	Health category label for median AQI
daysCo	integer	Days where CO was the primary pollutant
daysNo2	integer	Days where NO2 was the primary pollutant
daysOzone	integer	Days where ozone was the primary pollutant
daysPm25	integer	Days where PM2.5 was the primary pollutant
daysPm10	integer	Days where PM10 was the primary pollutant
dominantPollutant	string	Pollutant with the most monitoring days
sourceUrl	string	EPA AQS zip file URL for this year
scrapedAt	string	UTC timestamp when record was scraped
recordType	string	Always "countyAqi"

Metro area records (recordType: "metroAqi")

Same fields as county records, plus:

Field	Type	Description
cbsa	string	CBSA name (e.g. Los Angeles-Long Beach-Anaheim, CA)
cbsaCode	string	CBSA numeric code
stateAbbreviations	array	State abbreviations in this CBSA

State records (recordType: "stateAqi")

Field	Type	Description
state	string	US state name
year	integer	Calendar year
countyCount	integer	Number of counties included in the aggregation
avgMedianAqi	integer	Average of county median AQI values
avgMedianAqiCategory	string	Health category for average median AQI
stateMaxAqi	integer	Highest max AQI among all counties
avgDaysWithAqi	integer	Average days with monitoring data per county
totalGoodDays	integer	Sum of good days across all counties
totalUnhealthyDays	integer	Sum of unhealthy days across all counties

Input Parameters

Parameter	Type	Default	Description
mode	select	byCounty	byCounty, byMetro, or byState
year	integer	2024	Year to fetch (1980–2024)
years	array	—	Multiple years for a single run
stateFilter	string	—	Filter to one state (e.g. California)
minMedianAqi	integer	—	Minimum median AQI
maxMedianAqi	integer	—	Maximum median AQI
minDaysWithAqi	integer	—	Minimum monitoring days
minMaxAqi	integer	—	Minimum max AQI (find worst air quality)
pollutantFilter	select	—	Filter by dominant pollutant: co, no2, ozone, pm25, pm10
sortBy	select	medianAqi	Sort field: medianAqi, maxAqi, unhealthyDays, goodDays, daysWithAqi, state
maxItems	integer	500	Maximum records to emit

Example Inputs

Counties with worst air quality in California for 2023

{
  "mode": "byCounty",
  "year": 2023,
  "stateFilter": "California",
  "sortBy": "medianAqi",
  "maxItems": 50
}

All US metro areas for 2024 sorted by worst AQI

{
  "mode": "byMetro",
  "year": 2024,
  "sortBy": "maxAqi",
  "maxItems": 100
}

Historical data: California AQI by county for 2015–2024

{
  "mode": "byCounty",
  "years": ["2015", "2016", "2017", "2018", "2019", "2020", "2021", "2022", "2023", "2024"],
  "stateFilter": "California",
  "maxItems": 5000
}

State-level summary for 2024

{
  "mode": "byState",
  "year": 2024,
  "sortBy": "medianAqi",
  "maxItems": 51
}

Find counties with the most PM2.5 pollution days

{
  "mode": "byCounty",
  "year": 2023,
  "pollutantFilter": "pm25",
  "sortBy": "medianAqi",
  "maxItems": 100
}

Use Cases

• Air quality research — analyze long-term trends in US air quality at county and metro levels.
• Public health — identify areas with high numbers of unhealthy air days for sensitive populations.
• Policy analysis — compare AQI improvements across states and metro areas over time.
• Environmental journalism — find the cleanest and most polluted areas in the US.
• Real estate / relocation — evaluate air quality history when choosing where to live.
• Academic research — build datasets linking air quality to health outcomes, demographics, or economic activity.

AQI Health Categories

AQI Range	Category
0–50	Good — Air quality is satisfactory
51–100	Moderate — Acceptable quality; some pollutants may concern sensitive people
101–150	Unhealthy for Sensitive Groups — At-risk populations may experience health effects
151–200	Unhealthy — Everyone may experience health effects
201–300	Very Unhealthy — Health warnings of emergency conditions
301+	Hazardous — Serious health effects for entire population

Data Source

Data comes directly from the EPA Air Quality System (AQS) public bulk data files, which are freely available without registration or API keys. Data is published annually and covers all EPA monitoring stations across the United States.

FAQ

Does this require an API key? No. The EPA AQS bulk data files are publicly accessible ZIP archives — no registration or API key is needed.

What years are available? Annual AQI data is available from 1980 through 2024. Set year or provide a list in years.

How current is the data? Annual data is published by the EPA for the previous year. The most recent available year is typically published by Q2 of the following year.

How many counties does the US have? The US has approximately 3,143 counties/county-equivalents. Not all have EPA monitoring stations, but 2,000+ typically appear in the annual dataset.

What is a CBSA? A Core-Based Statistical Area is the standard US geographic unit for metropolitan and micropolitan statistical areas, defined by the US Office of Management and Budget. The AQI dataset covers 400+ CBSAs.

Can I get data for multiple years at once? Yes — use the years input to provide a list of years. Each year is fetched as a separate EPA download and all records are emitted in the same run.