Portland, Maine – A dangerous gas could be building inside Portland-area homes right now as cool spring nights keep windows shut, allowing radon—known as the “invisible killer”—to accumulate within enclosed spaces. The risk can increase within hours when airflow is limited, especially during early spring temperature swings.
According to the U.S. Environmental Protection Agency, radon is a radioactive gas that forms naturally in soil and seeps into homes through foundation cracks, sump pumps, and crawl spaces. Maine remains one of the highest-risk states in the country, with data showing about 33% of homes test above the EPA action level of 4 picocuries per liter.
Across Cumberland County, older homes with basements are particularly vulnerable this time of year. In Portland, South Portland, and Westbrook, residents often keep homes sealed overnight due to lingering cold, trapping radon indoors. The Maine CDC warns that long-term exposure is the second leading cause of lung cancer in the U.S., linked to roughly 21,000 deaths annually.
Unlike carbon monoxide, radon exposure produces no immediate symptoms. Health officials stress that short-term test kits, which provide results within two to four days, are the only reliable way to detect elevated levels. Mitigation systems can reduce indoor concentrations by up to 99 percent when installed properly.
Residents are urged to test homes now as conditions through April continue to favor indoor buildup. Free and low-cost kits remain available statewide, and additional public health alerts could be issued if elevated readings persist into early summer.
