Background: The role of environmental tobacco smoke (ETS) in the causation of lung and breast cancer has been repeatedly evaluated over recent years. In contrast, its impact on the risk of adult leukemia has received little attention.
Methods: We used the lifetime residential and occupational ETS exposure histories from a population-based sample of 1068 incident and histologically confirmed adult leukemia cases and 5039 population controls age 20 to 74 years to evaluate the relationship between ETS exposure and adult leukemia risk among nonsmokers in Canada. The duration of exposure and smoker-years index were used as indices of ETS exposure. We restricted our analysis to the 266 case and 1326 control subjects who reported being lifetime nonsmokers and provided residential ETS exposure history for at least 75% of their lifetime.
Results: No association was found for most leukemia subtypes, and in particular for acute myeloid leukemia. In contrast, the risk for chronic lymphocytic leukemia was clearly associated with ETS exposure, with an adjusted odds ratio of 2.3 (95% confidence interval = 1.2–4.5) for more than 83 smoker-years of residential exposure and 2.4 (1.3–4.3) for more than 72 smoker-years of occupational exposure. There was a dose–response relationship for chronic lymphocytic leukemia with both indices of exposure. Risk was not higher with recent exposure, using time-window-exposure analyses.
Conclusions: Regular long-term ETS exposure may be a risk factor for chronic lymphocytic leukemia.
From the *Département de médecine sociale et préventive, Faculté de Médecine, Université Laval, Sainte-Foy, Québec, Canada; †Institut national de santé publique du Québec, Sainte-Foy, Québec, Canada; and ‡Surveillance and Risk Assessment Division, Centre for Chronic Disease Prevention and Control, Public Health Agency of Canada, Ottawa, Ontario, Canada.
Received for publication 27 April 2004; final version accepted 12 May 2005.
Original funding for the NECSS provided through the Government of Canada’s Action Plan on Health and the Environment.
Supplemental material for this article is available with the online version of the journal at www.epidem.com; click on “Article Plus.”
Correspondence: Patrick Levallois, Direction des Risques Biologiques, Environnementaux et Occupationnels, INSPQ, 945 avenue Wolfe, 4e étage, Sainte-Foy, Québec, Canada, G1V 5B3. E-mail: email@example.com.