Attributable lung cancer risk from radon in homes may be low
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《英国医生杂志》
EDITOR—Darby et al provide compelling evidence that indoor radon is an important contributor to the risk of lung cancer.1 However, the derived estimate of radon attributable lung cancers may have a low bias.
The authors estimate an increase in lung cancer risk of 16% for each incremental 100 Bq/m3 of radon from a pooling of the European residential case-control studies. They then estimate that radon may contribute to 9% of all lung cancers in those countries on the basis of an estimated average radon concentration of 59 Bq/m3 for 29 European countries. However, the relative risk per Bq/m3 was determined in each study for an exposure window of five to 35 years before ascertainment of the disease.
Typically, lung cancer will occur after the age of 55, so exposures received during childhood and young adulthood are not included. This would not be a problem if exposures occurring more than 35 years previously did not contribute appreciably to lung cancer risk. However, although the BEIR VI models do incorporate a fall-off in risk with time, the projected risk from childhood and young adult exposures are still about the same as for the population as a whole.2 3 As a result, more than 30% of the radon contribution to the population risk would be unaccounted for by the case-control studies.
This conclusion is based on model extrapolation; in reality, aside from very limited, and somewhat equivocal, data on Chinese tin miners,4 no direct information is available on risks from childhood exposures to radon. Also, if radon levels before the 30 year measurement window were highly correlated with the estimated average levels during the window, the error would be reduced since the measured average exposure rate would reflect the entire lifetime, rather than just 30 years. This is unlikely to be true in practice since people are unlikely to have lived in the same houses during childhood and early adulthood as they did for the 35 years before the incidence of lung cancer.
Jerome S Puskin, director
Puskin.Jerome@epamail.epa.gov
Center for Science and Risk Assessment, Radiation Protection Division, ORIA (6608J), US Environmental Protection Agency, Washington, DC 20460, USA
David J Pawel, statistician
Center for Science and Risk Assessment, Radiation Protection Division, ORIA (6608J), US Environmental Protection Agency, Washington, DC 20460, USA
Competing interests: None declared.
References
Darby S, Hill D, Auvinen A, Barros-Dios JM, Baysson H, Bochicchio F, et al. Radon in homes and risk of lung cancer: collaborative analysis of individual data from 13 European case-control studies. BMJ 2005;330: 223-6. (29 January.)
National Research Council. Committee on health risks of exposure to radon (BEIR VI). Health effects of exposure to radon. Washington, DC: National Academy Press, 1999.
Pawel DJ, Puskin JS. The U.S. Environmental Protection Agency's assessment of risks from indoor radon. Health Phys 2004;87: 68-74.
Xuan XZ, Lubin JH, Li JY, Li-Fen Y, Sheng LQ, Lan Y, et al. A cohort study in southern China of tin miners exposed to radon and radon decay products. Health Phys 1993;64: 120-131.
The authors estimate an increase in lung cancer risk of 16% for each incremental 100 Bq/m3 of radon from a pooling of the European residential case-control studies. They then estimate that radon may contribute to 9% of all lung cancers in those countries on the basis of an estimated average radon concentration of 59 Bq/m3 for 29 European countries. However, the relative risk per Bq/m3 was determined in each study for an exposure window of five to 35 years before ascertainment of the disease.
Typically, lung cancer will occur after the age of 55, so exposures received during childhood and young adulthood are not included. This would not be a problem if exposures occurring more than 35 years previously did not contribute appreciably to lung cancer risk. However, although the BEIR VI models do incorporate a fall-off in risk with time, the projected risk from childhood and young adult exposures are still about the same as for the population as a whole.2 3 As a result, more than 30% of the radon contribution to the population risk would be unaccounted for by the case-control studies.
This conclusion is based on model extrapolation; in reality, aside from very limited, and somewhat equivocal, data on Chinese tin miners,4 no direct information is available on risks from childhood exposures to radon. Also, if radon levels before the 30 year measurement window were highly correlated with the estimated average levels during the window, the error would be reduced since the measured average exposure rate would reflect the entire lifetime, rather than just 30 years. This is unlikely to be true in practice since people are unlikely to have lived in the same houses during childhood and early adulthood as they did for the 35 years before the incidence of lung cancer.
Jerome S Puskin, director
Puskin.Jerome@epamail.epa.gov
Center for Science and Risk Assessment, Radiation Protection Division, ORIA (6608J), US Environmental Protection Agency, Washington, DC 20460, USA
David J Pawel, statistician
Center for Science and Risk Assessment, Radiation Protection Division, ORIA (6608J), US Environmental Protection Agency, Washington, DC 20460, USA
Competing interests: None declared.
References
Darby S, Hill D, Auvinen A, Barros-Dios JM, Baysson H, Bochicchio F, et al. Radon in homes and risk of lung cancer: collaborative analysis of individual data from 13 European case-control studies. BMJ 2005;330: 223-6. (29 January.)
National Research Council. Committee on health risks of exposure to radon (BEIR VI). Health effects of exposure to radon. Washington, DC: National Academy Press, 1999.
Pawel DJ, Puskin JS. The U.S. Environmental Protection Agency's assessment of risks from indoor radon. Health Phys 2004;87: 68-74.
Xuan XZ, Lubin JH, Li JY, Li-Fen Y, Sheng LQ, Lan Y, et al. A cohort study in southern China of tin miners exposed to radon and radon decay products. Health Phys 1993;64: 120-131.