Weekly patterns in smoking habits and influence on urinary cotinine and mutagenicity levels: Confounding effect of nonsmoking policies in the workplace

Lifestyle factors such as smoking have been shown to influence urinary muta genicity, Therefore, these factors have to be considered carefully when eva luating occupational genotoxic exposures. We investigated day-today variabi lity in active and passive tobacco smoke exposure by studying urinary cotin ine levels and determined their influence on observed urinary mutagenicity, Urinary cotinine was assessed for 105 subjects employed in the rubber manu facturing industry in the Netherlands on Sunday, Wednesday, and Thursday. U rinary mutagenicity was measured by the Salmonella typhimurium strain YG104 1 with metabolic activation for the Sunday urine sample and a pooled weekda y urine sample. A sharp decrease in urinary cotinine concentration was obse rved during the week compared to Sunday for smokers (39%; P < 0.01) and non smokers (23%), Different smoking habits on Sunday resulted in higher regres sion coefficients for categorical proxies for smoking habits and urinary mu tagenicity Levels. However, regression coefficients for urinary cotinine an d urinary mutagenicity were similar for the Sunday and weekday urine sample s (<beta> = 0.29 and beta = 0.28, respectively). Consequently, these estima tes were used to adjust urinary mutagenicity for tobacco smoke intake. Coti nine-adjusted urinary mutagenicity levels were comparable between smokers a nd nonsmokers, and a similar increase in urinary mutagenicity of 39% and 34 %, respectively, was observed for both smokers and nonsmokers due to occupa tional genotoxic exposures or other changes in lifestyle factors. These res ults indicate that the introduction of nonsmoking policies in the workplace has reduced exposure to mainstream and environmental tobacco smoke, result ing in a temporal variation in lifestyle-related mutagenicity, Therefore, a dequate adjustment for daily tobacco smoke exposure is a necessity when usi ng the urinary mutagenicity assay to evaluate possible genotoxic exposures in the workplace.