Estimating Exposure to Environmental Tobacco Smoke

To the Editor. —Dr Pirkle and colleagues¹ deserve congratulations for measuring serum cotinine (a metabolite of nicotine) in 10 642 persons aged 4 years and older. The new chemical analytic method used has an amazingly low detection limit of 0.05 ng/mL, which is far better than the 1 ng/mL levels we and many others have been able to attain. We are one of the research groups cited that found nicotine in vegetables.^2,3 In the spirit of promoting good science, I question the authors' conclusion that the contribution of dietary nicotine is negligible in persons with no reported home or work environmental tobacco smoke (ETS) exposure.

I would strongly encourage Pirkle et al to use such an exquisitely sensitive chemical method to determine the role of dietary nicotine by direct clinical study of adult nonsmokers rather than ruling out dietary nicotine using statistical multiple regression models. Based on regression