Parental smoking, CYP1A1 genetic polymorphisms and childhood leukemia (Quebec, Canada)

Objective: To evaluate the effect of parental smoking on childhood acute ly mphoblastic leukemia and to determine if it is modified by child genetic po lymorphisms. Methods: We carried out a case-control study in Quebec, Canada, including 4 91 incident cases aged 0-9 years and as many healthy controls matched on ag e and sex. Each parent was interviewed separately with respect to smoking h abits during and after pregnancy. In addition, we carried out a case-only s ubstudy with 158 cases classified according to presence or absence of the a lleles *2A, *2B, and *4 in the CYP1A1 gene. Results: There were small risk increases with maternal smoking during the l ater trimesters. Interaction odds ratios were increased (although often not significantly) for the CYP1A1*4 allele at high levels of maternal smoking in the last trimesters and at low level of paternal postnatal smoking, and decreased for the CYP1A1*2B allele. The latter appeared to confer a protect ive advantage at low levels for maternal prenatal smoking and at high level s for paternal postnatal smoking. Conclusions: Reported smoking habits showed no association with leukemia; r isks for genetic polymorphisms lacked precision but indicated that the effe ct of parental smoking could be modified by variant alleles in the CYP1A1 g ene.