Environmental Radon and Cancer Correlations in Maine

Abstract

The distribution of 222Rn has been measured in the sixteen counties of Maine, U.S.A. by liquid scintillation counting of water samples from more than two thousand public and private wells. Three hundred and fifty of these wells have been characterized for geology and hydrology. Airborne radon has been measured in seventy houses with grab samples and in eighteen houses for 5-7 days each with continuously recording diffusion-electrostatic radon detectors. Concentrations of radon in water ranged from 20 to 180,000 pCi/l. Granite areas yielded the highest average levels (mean = 22,100 pCi/l.; n = 136), with considerable intra-granite variation. Metasedimentary rocks yielded levels characteristic of the lithology for metamorphic grades ranging from chlorite to andalusite. Sillimanite and higher-grade rocks yielded higher 222Rn levels, probably due to the intrusion of uranium-bearing pegmatites in these terranes. Airborne 222Rn in homes ranged from 0.05 to 210 pCi/l. At the high end of this range, doses will exceed recommended industrial limits. In some homes only a small fraction of the airborne 222Rn was due to the water supply. Average 222Rn levels in domestic water supplies for each of the 16 counties, calculated by areally averaging rock types and their associated 222Rn levels, were found to be significantly correlated with rates for all cancers combined and rates for lung and reproductive cancers in the counties. Although numerous factors other than cancer induction by indoor daughter exposures may be responsible for the observed correlations, these have not been investigated in detail.

Cancer Risks from Exposure to Radon in Homes

“…The estimated average background y-radiation per county has also been used as a proxy for potential indoor radon, since there tends to be a rather strong correlation between y-radiation and emanation of radon from the ground (70). Some other more-or-less positive studies have been based on measurements of Ra-226 in water (71) or levels of radon in water and indoor air (72). Some correlation studies have come out negative with regard to lung cancer, for example, studies from Canada (73), China (74), and France (75).…”

Potential health effects of indoor radon exposure.

“…Hess et al (15) have found that there is a correlation of radon in water supplies and radon in indoor air. This problem undoubtedly exists in other areas where deep wells are used for domestic water.…”

“…In Maine (15), artesian well water supplies in parts of the state have been found to have high concentrations of dissolved radon, and in some instances use of showers or dishwashers can increase indoor concentrations significantly. Hess et al (15) have found that there is a correlation of radon in water supplies and radon in indoor air.…”

Indoor Radon and Its Decay Products: Concentrations, Causes, and Control Strategies

“…As a result, very high radon concentrations can sometimes be found in associated water supplies. For example,s urvey of 222Rn concentrations in well-water in Maine found a range of 7 x 10 2 to 7 x 10 Bq/m 3 (20 to 180,000 pCi/l), while wells in granitic areas were found to average 8 x 10 5 Bq/m 3 (Hess et al 1983); and the average concentration in water from drilled wells in Finland has been found to be 6.3 x 10 5 Bq/m 3 (Asikainen and Kahlos 1980). With normal water use, the radon entering indoor air from water with such high concentrations can be expected to be significan t.…”