[Exposure to tobacco smoke in a Japanese urban population. An analysis using biochemical markers of smoking]

An epidemiological study in an urban population was conducted to investigate exposure to tobacco smoke using two biochemical markers of smoking. In 1993 and 1994, expired air carbon monoxide (EACO) concentrations were determined with a small portable CO monitor for 4,619 subjects aged 30 and over, who had been randomly selected from residents of S-city in Osaka Pref, and who had received a health examination for cardiovascular disease at the National Cardiovascular Center. Urinary cotinine (UCOT) concentrations were determined using gas chromatography for 480 subjects, who were nonsmokers, and who had received a health examination during Sep. and Nov. in 1994. They also completed a questionnaire about smoking habits and potential of passive smoking. In this study smoking prevalences were 45% in men and 11% in women according to the questionnaire. Among nonsmokers 55% of men and 46% of women reported some degree of exposure to tobacco smoke. The EACO levels were related to the number of cigarettes smoked per day in a dose-response fashion. The time elapsed since last smoked and the usual depth of inhalation, in addition to the number of cigarettes, had effects to EACO level. The optimal EACO cut-off points selected to differentiate smokers and nonsmokers were between 6 and 7 ppm for men, and 5 and 6 ppm for women with a sensitivity and a specificity of about 90%. The hours spent with tobacco smoke at home, whether there was a smoking spouse or not, and the time elapsed since last inhalation of smoke affected EACO level in nonsmokers. The frequency of going to an amusement place, a bar or a restaurant, and the hours spent with tobacco smoke in a work place had effects on UCOT level in non-smokers. The proper use of biochemical markers for tobacco smoke may be of value in developing more effective strategies for smoking problems control.