Steinmaus and Smith Respond to "Proximity to Gasoline Stations and Childhood Leukemia"

Benzene is an established cause of adult leukemia, but its role in childhood leukemia is less clear. In a recent meta-analysis, we identified associations of childhood leukemia with occupational and household product benzene exposure and traffic-related pollution. Residential proximity to gasoline stations or automobile repair facilities may be another source of benzene, and in 3 studies assessing these sources, we identified a summary relative risk of 1.59 (95% confidence interval: 0.70, 3.62). Although not statistically significant, this summary relative risk was of a magnitude similar to that of our other positive findings. In this issue of the Journal (Am J Epidemiol 2017;185(1):5-7), Dr. Infante suggested that meta-analyses of studies on childhood leukemia and proximity to gasoline stations should involve some criteria that differ from those we used. These suggested criteria involved combining leukemia subtypes, excluding automobile repair facilities, and using nonleukemia cancers as control subjects. We redid our meta-analysis using these new criteria and obtained a summary relative risk of 2.42 (95% confidence interval: 1.51, 3.89). Overall, although this result should be interpreted in light of the relatively small sample size (3 studies) and its post-hoc nature, it provides additional new evidence for associations of childhood leukemia with both residential proximity to gasoline stations and exposure to benzene.