A newly released study of health risks from radon in Connecticut's drinking water supplies concludes that such exposure poses a minimal threat to public health, particularly when radon in the water is released into the household air, where it can be inhaled.
The study, "Radon in Connecticut: Quantitative Perspectives About Effects on Public Health," was conducted by a panel of experts convened by the Connecticut Academy of Science and Engineering (CASE) in response to an inquiry from the state Department of Public Utility Control (DPUC). The DPUC requested the study after receiving reports of radon in drinking water and requests for treatment of public drinking water supplies to reduce radon content. The panel was chaired by CASE member Jan A. Stolwijk, the Susan Dwight Bliss Professor Emeritus of Epidemiology at the School of Medicine.
The experts found that the major adverse health effect of radon is an increase in lung cancer risk resulting from inhalation. According to the report, some adverse health effects, primarily in the stomach, may result also from the ingestion of drinking water containing radon, although the effect is "expected to be less than for inhalation." The study also found that existing data on the health effects of ingested radon were not sufficient to yield a meaningful estimate of risk.
Radon is a naturally occurring radioactive isotope produced during the decay of uranium. Although most radon produced in the earth's crust remains in the soil and rock, some is constantly being released to ground water, where it can be carried into the outdoor atmosphere, the indoor atmosphere or drinking water.
Indoor radon exposure generally occurs when the radon that is mixed with indoor air
is inhaled. The isotope may come into the home from the outside atmosphere; be released from the soil gas under the house; or released into indoor air from the drinking water supply (during showers, laundry, or other household tasks). Exposure can also occur due to ingestion of radon in drinking water.
Radon exists in outside ambient air in concentrations of 0.1 to 0.4 picocuries per liter (pCi/l) of air. Indoor air in Connecticut has concentrations ranging from .1 to 38 pCi/l. Radon concentrations in Connecticut's ground water range from 50-500,000 pCi/l.
Surface water has very low radon concentrations and does not contribute significantly to population exposure, Stolwijk says. Connecticut's drinking water supplies come from three primary sources: private wells, public surface water supplies, and public ground (below surface) water supplies.
The report recommends that efforts to reduce the radon exposure in Connecticut be based on simultaneous considerations of exposure from both indoor air and drinking water supplies, and urges state officials to continue informing and advising the public of the risks of exposure and the remedies available for reducing exposure.
Noting that no standards for radon content in drinking water currently exist at the state, federal, or international level, the panel does not recommend development of a drinking water radon standard for Connecticut at this time.
The report notes that reduction of indoor radon concentrations resulting from soil gas infiltration is "the next most important strategy for lowering lung cancer risk" in the population, second only to reducing cigarette smoking, which is still "by far the most important contributor to overall lung cancer risk" in the United States.
CASE is a private, nonprofit corporation patterned after the National Academy of Sciences. It was chartered by the Connecticut General Assembly in 1976 and is limited by statute to 200 members, who must live or work in Connecticut. One of the principal functions of the academy is to provide science and technology information, as well as advice on public policy issues upon request of a government agency or private organization.
The summary and conclusions of the report are available on the CASE website at http://www.ctcase.org. The complete report is available from CASE at (860) 527-2161.