Editorial policy

Every quantitative claim comes from a named federal data release, and the release, its vintage and its limits are stated on the methodology page. Where a source suppresses or omits a value, the page shows a dash. We do not interpolate, we do not substitute a state average for a missing county, and we do not fill gaps with an estimate of our own.

• Any statement that a specific home, address or building is safe or unsafe. A county zone cannot support that claim, and no page here will make it.
• A symptom checker, risk calculator or any tool that outputs a conclusion about an individual's health. We publish criteria as published; we do not apply them to you.
• Supplement or treatment claims of any kind.
• Rankings dressed up as severity when they are really rankings by population or by a single year. Where a ranking is one of those, the page says so in the table's own source note.

We earn money by connecting homeowners with certified radon measurement and mitigation contractors, and from clearly labelled affiliate links on hardware. Neither of those relationships influences a figure on this site, because the figures are not ours to influence - they come out of a government file.

A contractor cannot pay to have a county described as higher risk than the EPA describes it. There is no arrangement under which that could happen, and if one were ever offered it would be refused.

We take no per-referral payment involving any laboratory, clinic, treatment facility, insurer or medical equipment supplier, and we run no Medicare or Medigap lead generation.

Errors get fixed and the fix gets dated. If a figure was wrong in the underlying federal release and the agency has since revised it, the next data build picks up the revision and the build date on every page changes with it.

This site reports environmental and public-health measurements. It is not medical advice, diagnosis or treatment, and it is not a substitute for a clinician. Population statistics describe populations. They do not describe you.