Exposure to environmental tobacco smoke (ETS) is associated with lung cancer, cardiovascular disease, and respiratory effects in studies of people who never smoked. [Levy, p. 148] Workers in bars, restaurants, and offices are exposed to environmental tobacco smoke, which is designated by IARC as a Group 1 human carcinogen. [Siemiatycki, p. 327] "The results of both study designs [case control and cohort] may be affected by inaccurate assessment of exposure to SHS, by inaccurate information on personal smoking habits that leads to classification of smokers as nonsmokers, by failure to assess and control for potential confounding factors, and by the misdiagnosis of a cancer at another site as a primary cancer of the lung." [Schottenfeld, p. 374] The best available biomarker for ETS is cotinine. "However, because the half-life for cotinine is about 17 h, it does not provide a valid marker for past ETS exposure. Therefore, unless a prospective study of ETS exposure and lung cancer in non-smokers is being conducted, there is presently no valid and reliable biomarker for past ETS exposure." [
PMID 12379877] Average levels of ETS exposure are comparable for home and unregulated work environments, but some bars and restaurants have exceptionally high levels. [
PMID 16880370] Producing tumors from cigarette smoke in experimental animals is difficult. "To compensate, the animals are treated with much higher doses of smoke than those humans in real life are usually exposed to. For example, most smoke inhalation studies in rodents administer doses of smoke with an average total particulate matter, which corresponds to a human smoking of 2-4 packs of cigarettes per day. . . . Consequently, although the causal link between SHS exposure and lung cancer development is well-established, the estimated risk for developing lung cancer consequent to SHS exposure remains somewhat debatable." [
PMID 18598930] Randomly selected participants from electoral rolls in central Italy included 977 smokers and 2402 nonsmokers. Of the nonsmokers, 882 were exposed to ETS, and 1520 were not, based on self-report. Average serum cotinine levels were 2.8 (ETS nonexposed nonsmokers), 4.4 (ETS exposed nonsmokers), and 277.3 (current smokers). [
PMID 12908713] "A recent study on women participating in a prenatal clinic in Philadelphia found that 73% of those who classified themselves as nonsmokers had urinary cotinine values above 80 ng/ml, the cutoff used to distinguish smokers from nonsmokers." [19125149] The difference was greater than 24% in five studies that compared prevalence estimates of smoking based on self-reported and measured values. [
PMID 19246437] The average urinary cotinine levels from hospitalized children aged 3 to 27 months was 0.44 ng/mg creatinine (no exposure), 4.10 (parents smoke outside the house), and 5.30 (parents smoke inside the house). [
PMID 11801622] See the hazardous job task, "Exposed to tobacco smoke working in unregulated bars, restaurants, or casinos."