---
title: "EPA radon zone by county"
method: POST
path: "/api/locus-radon-zone"
tags: ["environment", "radon", "housing", "read-only", "paid", "x402", "category:hazard"]
---

# 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: one of:
  - API key in header `PAYMENT-SIGNATURE`
  - API key in header `Authorization`

EPA Map of Radon Zones county designation (1, 2, or 3) for an address, point, or state and county, for buyer, owner and lender agents. Returns the same records as locus_radon_zone. Use this when your client can only call paid x402 routes. Use locus_radon_zone instead when you can call Locus free tools (REST tools/call or MCP).

## 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`

Atomic read result. A substantive result is paid; an empty/out-of-coverage result carries charged:false (x402 settlement suppressed).

- object

## Other responses

- `400`: Invalid request body.
- `402`: Payment Required. For x402 v2, repeat the identical request with a valid PAYMENT-SIGNATURE header (legacy X-PAYMENT is accepted for compatibility), or use Authorization: Payment for MPP Tempo when advertised in x-payment-info.offers.

---

[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)