Radioactive rocks under our homes can be dangerous – Milford-Orange Times
By Dan May
On our land
The COVID surges that occur as people move indoors for the winter and gather with family and friends for the holidays are a reminder that indoor air quality can be a health hazard. This is true not only for infectious diseases, but also for indoor air contaminants. The concentration of many pollutants indoors exceeds the concentration outdoors. Most people also spend more than 90% of their time indoors, and for vulnerable groups like infants, the elderly and people with chronic conditions, this proportion is likely higher.
Most indoor contaminants come from human behavior (second-hand smoke, aerosols), HVAC systems that allow mold to build up, and/or the presence of hazardous materials that can become airborne (such as dust from old paint lead) or released as gas from furniture or building materials. Many health effects are linked to poor indoor air quality, including an increasing incidence of asthma.
However, one pollutant of concern is only of natural origin: radon. It is an invisible, odorless and radioactive gas. It is present at low levels in the atmosphere but can increase in concentration to dangerous levels in buildings – especially single family homes. Long-term exposure to high levels of radon can cause lung cancer, with up to 20% of lung cancer cases in the United States likely due to radon.
Radon is a radioactive element formed when the element uranium slowly undergoes radioactive decay through a multi-step series to eventually form the stable element lead. This decay process was studied by Marie Curie about a century ago, and the concentration of radon present in the air is now measured in terms of picoCuries per liter of air.
Radon is an inert gas that does not combine chemically with any other element. When it appears during this decay series, it can leak from rocks that originally contained uranium into the atmosphere or enter homes through foundation floors and walls, pump pits sump, underground water well systems and other connections between the house and the basement.
Radon is very unstable, with a half-life of about four days before it decays releasing alpha and gamma radiation into another radioactive element called polonium. Polonium is also a toxic poison, used by Russia in several notorious assassinations. Radiation damage and polonium toxicity impact cells when radon atoms decay in an individual’s lungs.
In 2020, the US Department of Health and Human Services formulated environmental health goals in a document called Healthy People 2020. Two goals related to radon exposure: increase the proportion of existing homes at risk of radon exposure radon with radon mitigation systems; and increase the proportion of new single-family homes built in areas with high radon potential with radon-reducing features.
Both goals focus on homes located in areas with high radon potential. The focus on single family homes is because most residential HVAC systems do not bring in fresh air at the rate of commercial air handlers or other large buildings. The emphasis on areas with high radon potential is due to the fact that radon is linked to geology. Since the underlying rock types vary by location and generally have different concentrations of uranium, the amount of radon released by the ground varies from location to location.
Connecticut public health agencies produced maps of indoor radon potential based on underlying bedrock, overlying glacial or river sediments, and/or groundwater uranium measurements in the 1990s. Areas of low radon potential in this region included river valleys such as those adjacent to the West River or the Quinnipiac River, as well as the glacial lake deposits that underlie downtown New Haven.
West Haven’s radon potential is also considered low, largely because it sits above ancient volcanic rocks with only traces of uranium. In contrast, the coastal areas of East Haven and Branford are built on granitic rocks and derived sediments. The higher uranium concentrations inherent in these materials suggest a high radon potential, with 40% or more of homes likely to need mitigation.
Milford, Orange, Woodbridge and Hamden are considered to have moderate indoor radon potential, with measurements needed for perhaps one in four homes. However, public health agencies continue to update potential old cards with home testing. The results can be very specific to a given dwelling site and type of construction.
If you have never had your home tested or are planning to move to another house in the area, a radon test is good protection. Mid-winter is the perfect time to test. Contact your local or national public health unit for what is often a free test.
Dan May is a geologist and professor of environmental science at the University of New Haven. He can be contacted at [email protected]