TABLE ES-2 Estimated attributable risk (ARa) for lung-cancer death from domestic exposure to radon using 1985-89 U.S. population mortality rates based on selected risk models

Model

Population

Ever-smokersb

Never-smokersb

Males

 

 

 

Committee's preferred models

 

 

 

Exposure-age-concentration

0.141

0.125

0.258

Exposure-age-duration

0.099

0.087

0.189

Other Models

 

 

 

CRRc (<0.175 Jhm-3; <50 WLM)

0.109

0.096

0.209

BEIR IV

0.082

0.071

0.158

Females

 

 

 

Committee's preferred models

 

 

 

Exposure-age-concentration

0.153

0.137

0.269

Exposure-age-duration

0.108

0.096

0.197

Other Models

 

 

 

CRRc (<0.175 Jhm-3; <50 WLM)

0.114

0.101

0.209

BEIR IV

0.087

0.077

0.163

a AR = the risk of lung-cancer death attributed to radon in populations exposed to radon divided by the total risk of lung-cancer death in a population.

b Based on a submultiplicative relationship between tobacco-smoking and radon.

c CRR = constant relative risk.

portionately to AR. Only 13% of the calculated AR is estimated to be contributed by the 50% of homes below the median concentration of about 25 Bqm-3 (0.7 pCiL-1) and about 30% by homes below the mean of about 46 Bqm-3 (1.25 pCiL-1). Homes above 148 Bqm-3 (4 pCiL-1), the current action level established by the Environmental Protection Agency, contribute about 30% percent of the AR. This contribution to the total AR is indicative of the potential magnitude of avoidable deaths with a risk management program based on the current action guideline. While 10–15 percent of all lung-cancers are estimated to be attributable to indoor radon, eliminating exposures in excess of 148 Bqm-3 (4 pCiL-1) would prevent about 3 to 4 percent of all lung-cancers, or, about one-third of the radon-attributable lung-cancers.

The ARs were re-estimated with assumption of thresholds, levels below which cancer risk is not increased, at 37, 74, or 148 Bqm-3 (1, 2, or 4 pCiL-1). Even though the committee assumed that risk was most likely linear with exposure at lower levels, this analysis was conducted to illustrate the impact of assuming a threshold on risk-management decisions. Assuming an action level of 148 Bqm-3 (4 pCiL-1) for mitigation, postulating a threshold reduces the total number of lung-cancer deaths that are attributable to indoor radon and also the number of lung-cancer deaths that can be prevented by reducing levels in homes to zero. For assumed thresholds below 148 Bqm-3 (4 pCiL-1), there is little impact on the



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