this would seem to be a relatively insensitive measure of exposure. Many people who are exposed to other peoples’ smoke may not always be married to smokers. Even if they are married to smokers, they are likely to be exposed to their spouses’ smoke for only a relatively small proportion of the day. The possibility exists that they may be exposed to other people’s smoke, for instance, at work, or while in other public places.

A study using urinary cotinine levels as a measure of exposure, however, showed that “marriage to a smoker” may identify individuals who are more exposed to tobacco smoke in general, not simply from their spouses (Wald and Ritchie, 1984). Table 12–2 shows that the exposure to other people’s smoke was greater for men married to smokers than for men married to nonsmokers (median hours of reported exposure of 21.1 and 6.5 hours per week, respectively). Of particular relevance for epidemiologic studies is the fact that exposure is greater outside the home as well as within the home. A reasonable interpretation of this fact is that men married to smokers might be more tolerant of other people’s smoke than men married to nonsmokers and are less likely to seek out smoke-free environments outside the home. Similar results, based on questionnaire information, have been reported by others (Friedman et al., 1983).

These results corroborate the use of a spouse’s smoking history as a method of classifying nonsmokers into groups that have different exposure levels to tobacco smoke. Using data from the