Tobacco Documents Online

~ _ ~Y A ~ /17/RCIt`7rn1 ~ COMMENTS ON THE CRS REPORT "ENVIRONMENTAL TOBACCO SMOKE AND LUNG CANCER RISK" ' 1. Using a"no-threshold" model, CRS estimates about 2800 lung cancer deaths per year in U.S. non4mokers; this estimate is nearly identical to EPA's own estimate of 3000. ' 2. Using a "threshold" model, CRS estimates about 500 lung cancer deaths per year, exclusively in individuals whose spouses smoke. EPA does not concur with the use of a threshold model for ETS for the following reasons: a. CRS presumes a potential threshold on the basis of the results of epidemiology studies which are not sufficiently sensitive to connote such an effect. b. ETS is a genotoxic carcinogen (i.e., a carcinogen that can irreversibly damage DNA, at conceivably minute exposures), and there is no demonstrated mechanistic basis for assuming a threshold. c. ETS has been observed fo cause cancer at typical environmental exposure levels! Exposure levels for which the CRS threshold model assumes there is no risk are not substantially different from those for which risks have been observed. (This is in contrast to the usual situation where environmental risks are extrapolated across several orders of magnitude in exposures, from high occupational exposures or from high-exposure animal bioassays.) CRS's threshold model is further flawed because it assumes too much precision from the epidemiology studies and does not allow any margin of safety for measurement errors or variabilities in human susceptibilities. Finally, when CRS assumes, under its threshold model, that there is no risk to individuals without spousal exposure, it wrongfully ignores the risk from occupational exposures, which are extremely variable and can be very high (e.g., bars and small, enclosed offices). 3. In general, CRS overemphasizes uncertainties and understates the strength and consistency of the evidence, for both lung cancer and childhood respiratory effects (probably for heart disease as well; however, EPA has not assessed the risks of ETS and heart disease). Furthermore, CRS overstates the potential bias from smoker status misclassification and from recall bias, and neglects the real downward bias from exposure misclassification. These issues were considered by the Science Advisory Board that reviewed EPA's risk assessment and unanimously concurred with EPA's conclusion that ETS is a known human carcinogen. 4. With respect to ETS and heart disease, CRS recommends that "Because of the potentially very large public health impact of ETS on heart disease, a comprehensive assessment and additional research program should be undertaken." EPA concurs with this recommendation. EPA contact person: Jennifer Jinot, 202-260-8913 I I I I I I I I I I I I I