---
title: "EPA radon zone by county"
method: POST
path: "/api/locus_radon_zone"
tags: ["environment", "radon", "housing", "read-only", "free", "free"]
---

# EPA radon zone by county

`POST /api/locus_radon_zone`

## Request

- Base URL: `https://api.locus.report`
- URL: `https://api.locus.report/api/locus_radon_zone`
- Auth: none required

EPA Map of Radon Zones county zone 1, 2, or 3 for a US point or state and county. For testing or disclosure follow-up: Zone 1 carries a radon overhang watch item. County potential, not a building reading, health claim, or property safety finding.
Use this when you can call Locus free tools (REST tools/call or MCP).
Use locus-radon-zone instead when your client can only call paid x402 routes; it returns the same records. Direct flat-body route for this one free resource; no API key, payment, or catalog wrapper. Return only the cited bounded evidence described here; this route never produces a paid brief or full report.

## Request body

- object
  - `address` string: Optional US street address; used to derive county when state+county or lat/lng are not provided.
  - `latitude` number: Optional decimal latitude; provide with longitude to derive county from the point.
  - `longitude` number: Optional decimal longitude; provide with latitude to derive county from the point.
  - `state` string: Optional two-letter state code; provide with county to skip point resolution.
  - `county` string: Optional county name, e.g. Wake County; provide with state to skip point resolution.

## Response `200`

Free cited evidence response.

- object

## Other responses

- `400`: Invalid request body.
- `429`: Rate limited.

---

[API](https://skmtc.dev/locus/apis/locus-api.md) · [All operations](https://skmtc.dev/locus/apis/locus-api/llms.txt) · [OpenAPI document](https://skmtc.dev/locus/apis/locus-api/revisions/ba7786b74adb?raw)