Excretion of mutagens, nicotine and its metabolites in urine of cigarette smokers

Urine samples from 26 cigarette smokers on a restricteddiet were collected in the late afternoon. Urine extracts onXAD-2 resin were tested for mutagenicity in the microsusp-ension assay using Salmonella typhimurium strain TA98 inthe presence of metabolizing and deconjugating enzymes.Levels of urinary nicotine plus metabolites and cotininewere determined. Eighteen samples were clearly mutagenic,i.e. capable of doubling the number of spontaneousrevertants at one of the assayed doses of urine. Urinarymutagenic activity ranged from 193 to 8462 net revertants/mmol of creatinine, while urinary nicotine plus metabolitesand cotinine levels varied from 0.007 to 1366 and from0.011 to 0.297 mg/mmol creatinine. Urine samples withnicotine metabolite levels of 0.66mg/mmol creatinine had mean values ± SD of mutagenicactivity of 490 ± 222 (n = 10), 964 ± 560 (n = 9)and 2692 ± 2807 (n = 7) revertants/mmol of creatinine,respectively, the statistical comparison between the groupsbeing positive (Mann-Whitney tZ-test, P < 0.05). Themutagenic activity of urine samples from smokers correl-ated well with urinary nicotine plus metabolite levels (r =0.658, P < 0.01). A less close correlation was found betweenurinary mutagenic activity and other indicators of tobaccosmoke exposure, such as urinary cotinine (r = 0.504, P <0.05), number of cigarettes smoked during the day of urinecollection (r = 0.399, P < 0.05) and machine smoking-derived nicotine deliveries of the total number of cigarettessmoked (number of cigarettes multiplied by the nicotinecontent of each cigarette, as indicated by the manufacturer;r = 0.439, P < 0.05). These results suggest that themutagenic activity of smokers' urine may be predicted bythe urinary level of nicotine plus metabolites. The lowdegree of reliability of many presumptive indicators ofexposure to tobacco smoke and the different urinary excre-tion kinetics of tobacco smoke mutagens with respectto cotinine (a frequently used biomarker for monitoringexposure to tobacco smoke) are both emphasized.IntroductionIncreases in urinary mutagenicity have been observed inworkers exposed to specific genotoxic compounds and complexmixtures (Everson, 1986). Nevertheless, some lifestyle factorssuch as dietary habits (Baker et al, 1982; Sasson et al, 1985;Sousa et al, 1985; Doolittle et al, 1989), together with active(IARC, 1986) and passive smoking (Bos et al., 1983), havealso been reported to increase urinary mutagen levels. It istherefore important to check these confounding exposures