Increased incidence of childhood leukemia in urban areas: a population-based case-control study.

Objective: We carried out a population-based case-control study to assess the possibility of an excess risk of childhood leukemia in urban areas, independently from road traffic pollution.

Methods: Study subjects were the 111 cases of childhood leukemia diagnosed from 1998 to 2011 among residents of two provinces of the northern Italian Emilia-Romagna region, and 444 controls matched by age and sex. Through mapping of the region carried out by remote sensing, we examined the percentage of urban or rural area in the 100-meter circular buffer around each child's house. We also modeled annual average exposure to benzene and PM10 from vehicular traffic at each residence.

Results: In a multivariate model adjusting for benzene and PM10, the odds ratio of leukemia associated with residence in a highly urbanized area and residential area (≥95% land use of this type near the child's home) was 1.4 (95% confidence intervals 0.8-2.4) and 1.3 (0.8-2.2), respectively. An increased risk was also found in association with the proximity to «dumps, scrap yards, and building sites». No association emerged with residence in rural areas or near industrial plants.

Conclusions: These results indicate that children living in urban areas experience an excess leukemia risk, independently from exposure to pollutants from vehicles.