Radon in Maine Well Water

The same granite bedrock that gives Maine its arsenic problem also produces radon — a radioactive gas that dissolves in well water and enters your home's air.

How Radon Gets in Your Water

Radon is produced by the natural radioactive decay of uranium in rock. Maine's granitic bedrock contains uranium, which continuously produces radon gas. When groundwater flows through fractures in this bedrock, it picks up dissolved radon.

When you use that water in your home — showering, doing dishes, running the washing machine — radon gas is released into your indoor air. The primary health risk from radon in water is actually an airborne exposure, not from drinking the water.

The Health Risk

Radon is the second leading cause of lung cancer in the United States, after smoking. The EPA estimates that radon in indoor air causes approximately 21,000 lung cancer deaths per year.

Radon in water contributes to indoor air radon levels. The EPA estimates that 10,000 pCi/L of radon in water contributes approximately 1 pCi/L to indoor air. While this is typically a smaller contribution than radon entering through the foundation, it adds to the total exposure.

Maine's Radon Geology

Maine has some of the highest radon levels in the country because of its bedrock geology. The same granitic and metamorphic formations that produce arsenic also produce radon and uranium. These three contaminants frequently co-occur in Maine wells.

If your well has elevated arsenic, there's a good chance it also has elevated radon and uranium. Test for all three.

Should You Test?

If you're on a private well in Maine, yes. Especially if:

• Your home has been tested for indoor air radon and levels are elevated (above 4 pCi/L)
• Your well is drilled into bedrock (as opposed to sand and gravel)
• Your well has tested positive for arsenic or uranium (same geological source)

Testing

Radon in water testing is available through most Maine water testing labs. It typically costs $25-$50. The sample must be collected carefully (radon is a gas and escapes easily from water) and delivered to the lab quickly.

See our testing guide for lab contacts.

Treatment Options

Treatment	Typical Cost	Notes
Aeration system	$3,000-$5,000	Bubbles air through water to release radon gas, then vents it outside. Most effective method (95-99% removal).
Granular activated carbon (GAC)	$1,000-$3,000	Adsorbs radon. Less effective than aeration for high levels. Creates mildly radioactive spent carbon requiring proper disposal.