Passive smoking and lung cancer: epidemiological evidence and ongoing international collaborative studies.

Epidemiological studies which investigated the association between lung cancer in non-smokers and exposure to tobacco smoke are reviewed. Discordant results are discussed in the light of biases and misclassification. Design, materials and methods are presented of an ongoing international collaborative study to explore the relationship between recent exposure to passive smoking (P.S.), as assessed by interview, and cotinine and thiocyanate levels in urine.