Exposure to environmental tobacco smoke and risk of non-Hodgkin lymphoma in nonsmoking men and women.

Little is known about the risk of non-Hodgkin lymphoma (NHL) in nonsmokers who are exposed to environmental tobacco smoke (ETS). Previous research on NHL and ETS has not included men or examined doses of ETS exposure during childhood. The Cancer Prevention Study II Nutrition Cohort collected information on smoking habits and exposure to ETS during childhood and adulthood. Among 61,326 never-smoking men and women, 884 incident cases of NHL were identified between 1992 and 2009. Multivariable-adjusted relative risks and 95% confidence intervals were calculated using Cox proportional hazards regression to identify associations between ETS and NHL risk. Compared with no exposure to ETS as a child or an adult, childhood and/or adult ETS exposure was not associated with NHL overall. There was a positive association between the number of smokers in the house as a child (P for trend = 0.05) and exposure to 6 or more hours per week of ETS as an adult (relative risk = 2.37, 95% confidence interval: 1.12, 5.04) with follicular lymphoma risk. Adult ETS exposure was associated with a lower risk of diffuse large B-cell lymphoma (relative risk = 0.68, 95% confidence interval: 0.48, 0.97). This study suggests that adult and childhood ETS exposure may affect the risk of NHL, and that the associations differ by histological subtype.