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 presents a mixture of findings, but to date few studies have used a sophisticated emissions-based model to assess pollution exposures in pregnancy and early childhood. Aims: The purpose of this study was to estimate risk of a number of different childhood cancers from traffic-related air pollution exposure in pregnancy and early childhood (<1 year of age). Methods: The present study included children younger than age 6 identified in the California cancer registry (born 1998-2007) who could be linked to a California birth certificate (N=3590). 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 at the child’s residence at birth during each trimester of pregnancy and in the first year of life. To confirm our results, we additionally examined associations with particulate matter (PM2.5) pollution, as measured by community-based air pollution monitors, and a simple measure of traffic density, for the purpose of comparing our findings to previous studies. Results: Using unconditional logistic regression, a per interquartile range increase in exposure to traffic-related pollution from CALINE4 was associated with increases in acute lymphoblastic leukemia [ALL; 1st trimester OR=1.05, 95% confidence interval (CI): 1.00, 1.09), retinoblastoma (1st trimester OR=1.11, 95% CI 1.02, 1.21), particularly bilateral retinoblastoma (OR=1.15, 95% CI 1.01, 1.32), and germ cell tumors (OR=1.15, 95% CI 1.04, 1.29). CALINE4 estimates were highly correlated across trimesters and the 1st year of life, making it difficult to discern the most important period for exposure. Similar patterns were observed in PM2.5 analyses for both ALL and retinoblastoma. Conclusions: Our findings support a relation between early exposure to traffic pollution and several childhood cancers.