Outdoor artificial light at night, air pollution, and childhood acute lymphoblastic leukemia

Abstract

BACKGROUND AND AIM: Acute lymphoblastic leukemia (ALL) is the most common form of cancer in children. An environmental exposure that has been previously associated with childhood ALL is air pollution but less is known about the association with artificial light at night (ALAN), another pervasive pollutant, particularly in urban areas. ALAN is believed to disrupt circadian rhythm and potentially lead to detrimental health outcomes. We sought to evaluate the risk of ALAN and air pollution in a large population-based case-control study of childhood ALL in California. METHODS: The California Linkage Study of Early-Onset Cancers is a large linkage study in the state of California. Childhood cancers identified in the California Cancer Registry are linked to birth records and 50 controls were randomly selected by year of birth. Between 2000-2015, a total of 2,782 cases and 139,100 controls were identified for this analysis. ALAN was assessed using the New World Atlas of Artificial Night Sky Brightness and PM2.5 with an ensemble-based air pollution model. Exposures were assigned to each participant’s geocoded residential addresses at birth. The associations between ALAN, PM2.5 and childhood leukemia were assessed using logistic regression from which odds ratios (OR) and 95% confidence intervals (95% CI) were calculated. RESULTS:After adjusting for known risk factors at birth (e.g. delivery by C-section), ALAN was associated with a 1.15 increased risk of childhood leukemia in Hispanic participants (95% CI 1.02-1.30) residing in the highest tertile of ALAN. There was an elevated risk of ALL among non-Hispanic White participants and PM2.5 (OR per 10 ug/m3 1.23, 95% CI 0.98-1.55) but not in Hispanic participants (OR per 10 ug/m3 1.04, 95% CI 0.90-1.21). CONCLUSIONS:ALAN was associated with increased ALL risk among Hispanic children. Further work is needed to understand the difference in risk of ALL associated with ALAN and air pollution among Hispanic and non-Hispanic children. KEYWORDS: light pollution, air pollution, cancer and cancer precursors, children's environmental health, epidemiology