"Adults exposed to second-hand smoke -- which experts termed "a low-level lung carcinogen" -- had a slightly higher risk of lung cancer. The amount of cotinine -- a breakdown product of nicotine -- in their blood was only about 1 percent of that of active smokers. The research involved 650 patients with lung cancer and more than 1,500 healthy people of "all ages" up to 74."

Also, see:

Journal of the National Cancer Institute, Vol. 90, No. 19, October 7, 1998:

"An association between exposure to environmental tobacco smoke (ETS) and lung cancer risk has been suggested. To evaluate this possible association better, researchers need more precise estimates of risk, the relative contribution of different sources of ETS, and the effect of ETS exposure on different histologic types of lung cancer. To address these issues, we have conducted a case-control study of lung cancer and exposure to ETS in 12 centers from seven European countries.

RESULTS: ETS exposure during childhood was not associated with an increased risk of lung cancer. No clear dose-response relationship could be demonstrated for cumulative spousal ETS exposure. No increase in risk was detected in subjects whose exposure to spousal or workplace ETS ended more than 15 years earlier. Ever exposure to ETS from other sources was not associated with lung cancer risk. Risks from combined exposure to spousal and workplace ETS were higher for squamous cell carcinoma and small-cell carcinoma than for adenocarcinoma, but the differences were not statistically significant.

CONCLUSIONS: Our results indicate no association between childhood exposure to ETS and lung cancer risk. We did find weak evidence of a dose-response relationship between risk of lung cancer and exposure to spousal and workplace ETS. There was no detectable risk after cessation of exposure. "

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