Urine Mutagenicity as a Measure of Exposure to Tar

Abstract

To the Editor.— In the recent article by Benowitz et al1entitled Reduced Tar, Nicotine, and Carbon Monoxide Exposure While Smoking Ultralow- but Not Low-Yield Cigarettes, the authors suggest that may be quantitatively measured as urine mutagenicity. Neither the literature2-4nor the authors' own data support this assumption. The authors state that relative tar exposure was estimated by urine mutagenicity, simply assuming that urine mutagenicity offers a predictive measure of tar exposure. The validity of this assumption is called into question by the authors' own data. The authors state that group 1 smokers tended to be heavier smokers, based on higher admission blood levels of cotinine... and plasma thiocyanate. Yet, when the mutagenic activity of the two groups when smoking their usual brand of cigarette is compared, the urine of the heavier smokers is substantially less mutagenic (Table). Differences in urine mutagenic activity can be due