Exposure to professional pest control treatments and the risk of childhood acute lymphoblastic leukemia

Previous studies suggest that exposure to pesticides increases the risk of childhood acute lymphoblastic leukemia (ALL). The aim of this analysis was to investigate whether professional pest treatments in or around the home before birth or during childhood increased the risk of childhood ALL. Data from 388 cases and 870 frequency-matched controls were analyzed using unconditional logistic regression, adjusting for study matching variables and potential confounders, to calculate odds ratios (ORs). A meta-analysis of our findings with the published findings of previous studies was also conducted. The ORs for any professional pest control treatments were 1.19 (95% CI 0.83, 1.69) in the year before pregnancy, 1.30 (95% CI 0.86, 1.97) during pregnancy and 1.24 (95% CI 0.93, 1.65) for those done after the child's birth. The ORs for exposure after birth were highest when it occurred between the ages of two and three years. ORs were elevated for termite treatments before birth. ORs were higher for pre-B than T cell ALL and for t(12;21) (ETV6-Runx-1) than other cytogenetic sub-types. The pooled OR from a meta-analysis of our study with three previous studies of professional pest control treatments during pregnancy was 1.37 (95% CI 1.00, 1.88). Our results, and those of our meta-analysis, provide some evidence of a modestly increased risk of ALL for professional pest control treatments done during the index pregnancy and possibly in the child's early years. The analysis of pooled data from international collaborations may provide more certainty regarding these potentially important associations.