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Epidemiologic Notes and Reports Radon Exposure Assessment -- Connecticut

In 1985, indoor air radon (radon-222) levels were found to be elevated in households in Pennsylvania (1). Following this discovery, the Connecticut Department of Health Services (CDHS) received inquiries from citizens who requested that their household air be tested for the presence of radon. Because information regarding radon exposures in Connecticut did not exist, CDHS initiated a series of surveys/projects to characterize this potential problem.

In the first survey (Connecticut Radon Survey), carried out from 1985 through 1987, indoor radon sampling was done in 202 homes in 44 towns in areas with suspected high potential for radon. Indoor air radon levels in the homes were sampled using alpha-track devices (one per home) placed in the lowest lived-in area of each home for 3 months. Because radon levels are typically highest during the winter, all homes were sampled for radon in December, January, and February. Radon levels ranged from 0.1 picocuries per liter (pCi/L) to 24.6 pCi/L (geometric mean: 1.3 pCi/L) (Table 1). Eleven percent exceeded the Environmental Protection Agency (EPA) maximum exposure guideline of 4 pCi/L.

In the second survey (EPA-Connecticut Survey), EPA provided support for a survey of basement radon levels in Connecticut homes. From December 1986 through early March 1987, charcoal-testing devices were distributed to 1157 houses for placement in the basement or lowest livable area of each house for 2 days. In 168 towns, homes were selected in the order in which homeowners had requested an energy audit from an energy conservation organization. Housing characteristics, air infiltration rate, smoking habits of occupants, and house location were recorded when the devices were placed.

Of the basements tested, 19% exceeded the EPA guideline of 4 pCi/L (Table 1). The percentage of homes with levels greater than 4 pCi/L varied between regions (boundaries defined by the estimated geologic potential for radon presence). The age of the house was the strongest predictor of indoor radon levels, with mean radon concentration levels increasing with the average age of the homes. Based on the results of the EPA-Connecticut survey, CDHS issued an advisory in August 1987 that all Connecticut homeowners should have their houses tested for radon.

In December 1987, CDHS initiated the Household Testing Program (HTP). HTP provided free radon-testing devices and placement instructions to residents living in areas suspected of having high radon levels, measured radon concentrations in selected Connecticut municipalities, and examined the association between basement and living area radon concentrations.

Based on results of the previous two radon surveys and information on terrestrial radiation and bedrock geology, 53 municipalities were initially identified for the HTP. Of these, 38 were selected toparticipate in the HTP based on the ability of local health departments or other agencies to distribute testing devices. Each municipality was provided with 200 charcoal-testing devices for use in 100 volunteer households. For each home, one charcoal-testing device was placed in the basement or other lowest livable area, and the second device placed in the lowest lived-in area. The measurements detected a consistent 3:2 ratio between basement and living area radon concentrations. In addition, basement radon levels were strongly predictive of levels in lived-in areas (R2=0.48, p less than 0.00001).

Each of the three surveys detected higher radon levels in areas with granitic bedrock and lower radon levels in areas with sedimentary rock. Of all housing characteristics, only two (cinder-block foundation and house age) had statistically significant positive associations with radon levels. Energy-efficient homes did not have higher radon levels.

Alpha-track devices for follow-up long-term testing have been distributed to 340 households with lowest lived-in area radon concentrations greater than 4 pCi/L and/or basement radon concentrations greater than 20 pCi/L. Reported by: BF Toal, MSPH, CJ Dupuy, MS, LM Rothney, MPH, AJ Siniscalchi, MPH, DR Brown, ScD, Connecticut Dept of Health Svcs; MA Thomas, MS, Connecticut Dept of Environmental Protection. Office of the Director, Center for Environmental Health and Injury Control, CDC.

Editorial Note

Editorial Note: CDHS has collected data on indoor air radon levels in 5036 households. The data from the three Connecticut studies closely agree about both average radon levels detected and the percentage exceeding 4 pCi/L (Table 1). Based on the risk model from the Biological Effects of Ionizing Radiations IV report (2), results from the EPA-Connecticut Survey indicate that, in Connecticut, radon exposure may account for 280 excess cases of lung cancer per year.

The CDHS studies helped to quantify the magnitude of radon exposure in Connecticut, assisted in establishment of a radon program, and guided subsequent research and public education on radon health risks, screening, and mitigation techniques.

Until 1984, radon was considered a health hazard primarily for uranium and underground mining workers and for persons living in homes built on uranium mill tailing deposits or land reclaimed from phosphate mining. Based on EPA surveys of 1986-1989, however, exposure to radon and its short-lived decay products are estimated to exceed the EPA guideline (4 pCi/L) in greater than 8 million homes located in 25 states and Native American lands (EPA, unpublished data, 1989).

In the United States, 5000-20,000 deaths from radon exposure may be occurring yearly (3). For persons who are exposed at the EPA guidance level of 4 pCi/L over a lifetime, overall risk for lung cancer is approximately 1%-3%. Risk for lung cancer from radon exposure is greatest among smokers, although risks for nonsmokers are also substantial (approximately 15 per 1000 exposed). Smoking appears to interact synergistically with radon in causing lung cancer. Consequently, cessation of smoking represents a crucial prevention measure for reducing lung cancer risk, particularly among radon-exposed populations.


  1. CDC. Health hazards associated with elevated levels of indoor radon--Pennsylvania. MMWR 1985;34:657-8.

  2. National Research Council. Health risks of radon and otherinternally deposited alpha-emitters: BEIR IV. Washington DC: National Academy Press, 1988.

  3. Office of Air and Radiation/CDC. A citizen's guide to radon: what it is and what to do about it. Washington, DC: US Environmental Protection Agency, Office of Air and Radiation; US Department of Health and Human Services, Public Health Service, 1986. *One hundred seventy hours exposure to any combination of radon daughters in 1 liter of air that results in 1.3 X 105 million electron volts of potential alpha energy.

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