THE ASSESSMENT OF EXPOSURE TO ENVIRONMENTAL TOBACCO-SMOKE

This paper examines the manner in which assessments of exposure to env ironmental tobacco smoke (ETS) are used in epidemiological studies see king to establish an association between such exposure and diseases su ch as lung cancer. Two such studies are described. A review of the lit erature shows that exposure to ETS is not accurately measured by subje ctive evaluations communicated via questionnaire. The inaccuracy is ev ident in situations where recent exposure is being measured and may re asonably be expected to be even greater when long-term exposure is at issue. Such inaccuracies do not necessarily invalidate the conclusions that may be drawn from a case/control study. In a situation where all types of errors occur equally frequently among cases and controls, th e effects of such errors are to lower the relative risk estimate, to r educe the power of the study, and to make it more difficult to establi sh an association between exposure and disease. However, in a situatio n where the pattern of errors is different for cases than it is for co ntrols, there is considerable potential for the errors to produce misl eading conclusions. Increased concentration on the validation of subje ctive ETS exposure assessments is recommended. Copyright (C) 1997 Else vier Science Ltd.