Childhood Cancer and Traffic-Related Air Pollution Exposure in Pregnancy and Early Life

Abstract

Background: The literature on traffic-related air pollution and childhood cancers is inconclusive, and little is known on rarer cancer types.Objectives: We sought to examine associations between childhood cancers and traffic-related pollution exposure.Methods: The present study included children < 6 years of age identified in the California Cancer Registry (born 1998–2007) who could be linked to a California birth certificate (n = 3,590). Controls were selected at random from California birthrolls (n = 80,224). CAlifornia LINE Source Dispersion Modeling, version 4 (CALINE4) was used to generate estimates of local traffic exposures for each trimester of pregnancy and in the first year of life at the address indicated on the birth certificate. We checked our findings by additionally examining associations with particulate matter (≤ 2.5 μm in aerodynamic diameter; PM2.5) pollution measured by community-based air pollution monitors, and with a simple measure of traffic density.Results: With unconditional logistic regression, a per interquartile range increase in exposure to traffic-related pollution during the first trimester (0.0538 ppm carbon monoxide, estimated using CALINE4) was associated with acute lymphoblastic leukemia [ALL; first trimester odds ratio (OR) = 1.05; 95% CI: 1.01, 1.10]; germ cell tumors (OR = 1.16; 95% CI: 1.04, 1.29), particularly teratomas (OR = 1.26; 95% CI: 1.12, 1.41); and retinoblastoma (OR = 1.11; 95% CI: 1.01, 1.21), particularly bilateral retinoblastoma (OR = 1.16; 95% CI: 1.02, 1.33). Retinoblastoma was also associated with average PM2.5 concentrations during pregnancy, and ALL and teratomas were associated with traffic density near the child’s residence at birth.Conclusions: We estimated weak associations between early exposure to traffic pollution and several childhood cancers. Because this is the first study to report on traffic pollution in relation to retinoblastoma or germ cell tumors, and both cancers are rare, these findings require replication in other studies.Citation: Heck JE, Wu J, Lombardi C, Qiu J, Meyers TJ, Wilhelm M, Cockburn M, Ritz B. 2013. Childhood cancer and traffic-related air pollution exposure in pregnancy and early life. Environ Health Perspect 121:1385–1391; http://dx.doi.org/10.1289/ehp.1306761

Childhood cancer and residential exposure to highways: a nationwide cohort study

“…Consistent with our findings, previous studies looking at CNS tumours found no [29][30][31] or only weak evidence [28] of an increased risk associated with proximity to highly trafficked roads. To our knowledge, only three other studies have investigated lymphoma in relation to traffic exposure [11,28,29]. Consistent with our study, they found no evidence of an association.…”

“…Due to the small number of AML cases in our study, we did not perform separate analyses for AML. Another recent case-control study from California using modelled carbon monoxide as a proxy for traffic related pollution showed a positive association for ALL but not for CNS tumours [11]. A Danish case-control study found an increased risk with higher levels of modelled nitrogen monoxide and benzene for Hodgkin's lymphoma, but not for leukaemia or CNS tumours [29].…”

“…Most studies investigating exposure to specific traffic related pollutants support an association with childhood leukaemia [9][10][11][12][33][34][35][36][37]]. An ecological study from Texas [35] and a recent case-control study from California [37] found increased risks of childhood leukaemia associated with elevated air concentrations of benzene.…”

“…Several studies have investigated whether traffic related pollution is associated with an increased risk of childhood cancer [7][8][9][10][11][12]. The focus has been on leukaemia, and specifically acute lymphoblastic leukaemia (ALL), and tumours of the central nervous system (CNS).…”

The importance of the exposure metric in air pollution epidemiology studies: When does it matter, and why?

“…Heck et al examined associations between childhood cancers and traffic-related exposures to PM 2.5 and CO, both in utero, and during the child's first year. The CALINE model, traffic density metrics, and monitor measurements were all used as exposure metrics, with weak associations found between exposure metrics and several childhood cancers (Heck et al 2013).…”