DHHS → MeCDC → Environmental and Community Health → EOHP → Real Estate Fact Sheets → FAQs About Radon in Air
Frequently Asked Questions:
2 pCi/L Recommendation for Radon in Air
The Maine CDC is emphasizing the 2 pCi/L as the current recommended clean up level for air in Maine. More information about radon can be found at the Maine Radon Homepage.
Why is Maine emphasizing a radon cleanup level of 2 pCi/L?
Any radon exposure has some risk of causing lung cancer. The lower the radon level in your home, the lower your family's risk of lung cancer. The U.S. Congress has set a long-term goal that indoor radon levels be no more than outdoor levels; about 0.4 pCi/L of radon is normally found in the outside air. While this goal is not yet technologically achievable in all cases, most homes can be reduced to 2 pCi/L or below. The U.S. Environmental Protection Agency (EPA) recommends fixing your home if a long-term test or average of two short-term tests show radon levels of 4 pCi/L or higher. Because radon levels in most homes can be reduced to 2 pCi/L or below with today's technology, EPA has suggested considering fixing your home at levels between 2 and 4 pCi/L. The Maine CDC is now recommending fixing your home if long-term test or average of two short-term tests show air results above 2 pCi/L.
Why is Maine Choosing to Emphasize the 2 pCi/L clean up level now?
Historically, much of the concern about radon came from studies of uranium miners exposure to relatively high levels of radon gas. Over the past decade, there have been several very good epidemiological studies of people exposed to radon in their homes showing an increased risk of lung cancer. In recent years there have also been attempts to pool the many studies together to provide yet stronger evidence for the link beteen radon exposure in the home and lung cancer. These studies, coming from North America, Europe and China, confirm that the risks of radon at levels currently considered acceptable are indeed of public health concern. For example, even at an air level of 2 pCi/L, the estimated cancer risk for a mixed population of smokers and non-smokers is 1 excess cancer for every 100 exposed people (i.e., a risk of 1 per 100). For more information about these studies, see the Maximum Exposure Guideline for Radon in Drinking Water (MeCDC 2006).
Can Mitigators Clean up to 2 pCi/L?
There have been improvements in efficiency and technology since the 4 pCi/L technology based action level was established as a in 1986. EPA’s Citizen’s Guide to Radon (EPA 2005) states, “most homes today can be reduced to 2 pCi/L or below.” Additionally, an informal survey of Maine radon mitigators suggests that in the majority of cases 2 pCi/L is achievable.
EPA 1992. Technical Support Document for the 1992 Citizen’s Guide to Radon. EPA 400-R-92-011
EPA 2005. A Citizen's Guide to Radon: The Guide to Protecting Yourself and Your Family From Radon. https://www.epa.gov/radon/pubs/citguide.html
MECDC (2005). Maximum Exposure Guideline for Radon in Drinking Water. Maine Center for Disease Control. Environmental and Occupational Health Program.