463 records

Is my county in nonattainment for this pollutant?

463 records covering 139 row IDs, one fact each. Every value is transcribed from the source that states it and carries the sentence it was taken from: 1 source across 1 site, last checked 2026-10-05, due for re-check by 2027-04-03. Every record has a page of its own, quoting the line that states it.

About this data

Whether a US county is in 'nonattainment' for a given Clean Air Act pollutant (and if so, at what severity classification) drives real obligations for anyone building, permitting, or selling into that county: stricter new-source review, vehicle inspection and reformulated-fuel requirements, and federal highway-funding conditions all key off this status. EPA's Green Book is the single authoritative list, but it is a very long plain-text table with no per-county lookup and no API — a resident, contractor, or small manufacturer has to scan hundreds of rows by hand to find their county. Each record is one county x one pollutant NAAQS combination: whether it is designated nonattainment, the classification if the pollutant test has one (Marginal through Extreme for ozone; Moderate/Serious for PM), and the named nonattainment area it belongs to. Answers 'is [county] in nonattainment for ozone', 'what classification is [county] for PM-2.5', 'does building in [county] trigger nonattainment-area permitting'.

The data

Showing the first 400 of 463 records. Every record has its own page, with its source and the quoted line that states it; these list the rest.

• Records 1–400allegan-county-mi-serious · MICHIGAN · Allegan County · 8-Hour Ozone (2015) … san-joaquin-valley-ca-serious · CALIFORNIA · Tulare County · PM-2.5 (2006)
• Records 401–463san-joaquin-valley-ca-serious · CALIFORNIA · Fresno County · PM-2.5 (2012) … yuma-az-moderate · ARIZONA · Yuma County · PM-10 (1987)

Where this came from

Every record above links the page it was taken from and quotes the sentence that states it. These are the 1 source this dataset was assembled from.

• www3.epa.govhttps://www3.epa.gov/airquality/greenbook/ancl.html

Machine-readable

• data.jsonThe whole dataset — every record with its source URL and source quote.
• Open Knowledge Format bundleOne JSON object per line — every record's frontmatter and quoted span exactly as it is held here, in one fetch.
• data.csvThe same records as one flat table, for a spreadsheet or a dataframe. The last four columns are the source URL, the quoted sentence it was read from, the date we last checked it, and which columns are our reading rather than the page's words.
• How this is made and checkedWhat "verified against source" does and does not mean.

From your own code

Same records, same quotes, without scraping the page: refsource is on PyPI and npm. Each value comes back carrying the URL it was read from and the sentence on that page that states it — .source and .quote sit on the value itself rather than in a side channel, so the checking step is available instead of skipped.

pip install refsource
refsource lookup nonattainment-county-designations-by-pollutant row_id=allegan-county-mi-serious

npx -y refsource lookup nonattainment-county-designations-by-pollutant row_id=allegan-county-mi-serious

Set your AI assistant up to use this

Two files and no account. Put this in .mcp.json at the root of your project — Claude Code, Cursor, Windsurf, VS Code and Codex all read that file — and your assistant can look this dataset up instead of recalling it. The server is remote, keyless and read-only.

{
  "mcpServers": {
    "referencesource": {
      "type": "http",
      "url": "https://referencesource.org/mcp"
    }
  }
}

Add to Cursor · or, on the command line: claude mcp add --transport http referencesource https://referencesource.org/mcp --scope project

Then one line in the project's CLAUDE.md or AGENTS.md, so the assistant knows when to reach for it:

When a question needs "Current EPA nonattainment county designations by pollutant", call the referencesource MCP server at https://referencesource.org/mcp (tool `search_records`, dataset_slug `nonattainment-county-designations-by-pollutant`) instead of answering from memory — every record it returns carries its source URL and a verbatim quote from that page.

What each tool does, and the servers built over single registers: Connect your AI assistant.

463 records. last verified against source 2026-10-05. due for re-check by 2027-04-03.

Licence. US federal government work, no copyright (17 USC 105)