Objectives. We studied the impact of clean indoor air law exemptions and pre-emption policies on the prevalence of a tobacco-specific lung carcinogen - 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) - among nonsmoking bar and restaurant workers. Methods. We collected urine specimens from 32 nonsmoking bar and restaurant workers from communities in Oregon where smoking is prohibited in bars and restaurants, and from 52 participants from communities in Oregon where smoking is allowed. Urine specimens collected before and after a workshift were analyzed for 3 NNK metabolites and reported as total 4-(methylnitrosamino) -1-(3-pyridyl)-1-butanol (NNAL). Urinalysis results from participants protected from workplace secondhand smoke were compared with results from participants who were exposed to it. Results. Participants exposed to workplace secondhand smoke were more likely to have any detectable level of NNAL (P=.005) and higher mean levels of NNAL (P < .001) compared with nonexposed participants. Increased levels of NNAL were also associated with hours of a single workplace exposure (P=.005). Conclusions. Nonsmoking employees left unprotected from workplace secondhand smoke exposure had elevated levels of a tobacco-specific carcinogen in their bodies. All workers - including bar and restaurant workers - should be protected from indoor workplace exposure to cancer-causing secondhand smoke.