Radon in Maine Homes: The Invisible Guest You Can Kick Out

Michael Marquis
Nov 25
4 min read

Radon: Silent, Invisible, and Very Much a Thing in Maine

If the phrase “radioactive gas under your house” gives you horror-movie vibes, you’re not entirely wrong.

Radon is a naturally occurring, radioactive gas that sneaks into homes from the soil. You can’t see, smell, or taste it — but prolonged exposure dramatically increases lung-cancer risk. The EPA estimates radon causes 21,000 lung cancer deaths each year, making it the #1 cause of lung cancer in non-smokers in America.

In short, if asbestos had an evil ghost cousin, it’d be radon.

And here’s where Maine gets the spotlight: Our beloved Pine Tree State has some of the highest radon concentrations in the country — a perfect storm created by old housing, rocky soil, and long winters with windows locked up tight.

With the oldest housing stock in the United States (the median year built in Maine is older than in any other state), many homes lack modern radon-resistant construction features. Combine that with lots of basement living, old foundations, and granite-rich soil… boom: ideal radon pathway.

The good news? Testing is simple. Fixes are effective. And HarborLight Property Inspections is here to help.

Let’s break it down:

Why Maine Is a Radon Hot Zone

You can’t rely on your neighbor’s test… or your neighbor’s neighbor’s test. Radon is hyper-localized. You can have one house at 1.2 pCi/L, and the house next door is sitting at 18+ pCi/L.

And that’s not theoretical — we’ve seen it.

Mini Case Studies from Right Here in Vacationland

✅ Portland — Deering Center Duplex A landlord prepping for turnover requested radon screening. One unit measured at 1.8 pCi/L, while the garden-level unit clocked in at 9.6 pCi/L — more than double EPA’s 4.0 action threshold. The lower unit was fully occupied. The tenant had no idea.

✅ Brunswick — 1950s Cape Homebuyer had already scheduled inspection. Foundation cracks + finished basement triggered radon add-on. Test returned 6.4 pCi/L. Mitigation system installed post-closing dropped levels to 1.1 pCi/L. Basement now safe to use for kids’ playroom.

✅ Lewiston — 3-Unit Housing Stock Seller disclosed prior radon test “years ago — no issue.” New test: 12.7 pCi/L. Buyer negotiated $1,550 mitigation concession; system installed pre-close, tenants unaffected.

Key takeaway: Radon is unpredictable. The only way to know is to test.

Who Should Be Paying Attention?

Short answer: everyone.

Homeowners

Because exposing your family to radon for years is a no-brainer, bottom line.

Landlords

Radon is increasingly referenced in housing safety conversations, and high concentrations represent a potential liability. Testing + mitigation is becoming industry standard — especially for basement or first-floor units.

Investors

If you plan on adding bedrooms or finishing basements (a very Maine thing, btw), you need to know radon levels first.

Real Estate Agents

You’re in the risk-reduction business. Radon testing is a must-recommend for client health + smooth transactions. And it’s a solid value-add to your brand.