Perinatal Exposures to Ambient Fine Particulate Matter and Outdoor Artificial Light at Night and Risk of Pediatric Papillary Thyroid Cancer.

BACKGROUND

Pediatric thyroid cancer incidence has been increasing globally, with environmental exposures being a hypothesized risk factor.

OBJECTIVE

We evaluated the association between pediatric thyroid cancer risk and perinatal exposure to ambient fine particulate matter (PM) with aerodynamic diameter () and outdoor artificial light at night (O-ALAN). Both are considered environmental carcinogens with evidence of thyroid function disruption, reported associations with thyroid cancer in adults, and concerns of distributive inequity. O-ALAN may also serve as a proxy for other outdoor air pollutants or urbanization.

METHODS

We conducted a case-control study of papillary thyroid cancer nested within a California birth cohort that included 736 cases diagnosed at 0-19 y of age and born in 1982-2011 and 36,800 controls frequency-matched on birth year. We assigned individual-level exposures for residence at birth for ambient concentrations from a validated, ensemble-based prediction model and O-ALAN using the New World Atlas of Artificial Night Sky Brightness. We calculated odds ratios (OR) and 95% confidence intervals (CI) using logistic regression adjusting for potential confounders and stratified by age and race/ethnicity.

RESULTS

We observed statistically significant associations between exposure and papillary thyroid cancer risk overall (OR per increase in , 95% CI: 1.01, 1.14), among the 15-19 y age group (; 95% CI: 1.00, 1.16), and among Hispanic children (; 95% CI: 1.02, 1.24). For O-ALAN, we observed statistically significantly increased odds of papillary thyroid cancer in higher exposure tertiles in comparison with the reference tertile in the overall population (tertile 2: , 95% CI: 1.04, 1.50; tertile 3: , 95% CI: 1.02, 1.50) and when modeled as a continuous variable ( per ). In age-stratified analyses, significant associations were observed among the 15-19 y age group, but not the 0-14 y age group. No significant differences were found by race/ethnicity.

DISCUSSION

This study provides new evidence suggesting associations between early-life exposure to and O-ALAN and pediatric papillary thyroid cancer. Given that O-ALAN may also represent other air pollutants or broader urbanization patterns, further research and refinements to exposure metrics are needed to disentangle these factors. https://doi.org/10.1289/EHP14849.