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

Abstract

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 $\le 2.5\mu m$ (${\mathrm{PM}}_{2.5}$) 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 ${\mathrm{PM}}_{2.5}$ 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 ${\mathrm{PM}}_{2.5}$ exposure and papillary thyroid cancer risk overall (OR per $10{\text{-}\mu g/m}^3$ increase in ${\mathrm{PM}}_{2.5}=1.07$, 95% CI: 1.01, 1.14), among the 15-19 y age group ($\text{OR}=1.08$; 95% CI: 1.00, 1.16), and among Hispanic children ($\text{OR}=1.13$; 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: $\text{OR}=1.25$, 95% CI: 1.04, 1.50; tertile 3: $\text{OR}=1.23$, 95% CI: 1.02, 1.50) and when modeled as a continuous variable ($\text{OR}=1.07$ per $1{\text{mcd}/m}^2$). 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 ${\mathrm{PM}}_{2.5}$ 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.

Figure 1.

Odds ratios and 95% confidence intervals for pediatric papillary thyroid cancer in relation to perinatal exposure to ambient ${\mathrm{PM}}_{2.5}$ concentrations as tertiles of exposure or with ${\mathrm{PM}}_{2.5}$ modeled as a continuous variable (per $10{\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$), overall and by age group, and race/ethnicity within a nested case–control study in California ($n=736$ cases, 36,800 controls). Models for the overall population and age groups were adjusted for sex, race, birth weight, gestational age, birth order, birth year, maternal age, mother’s birthplace, maternal education, history of C-section, and paternal age. Models for different racial and ethnic groups adjusted for the same covariates except race and ethnicity.

Figure 2.

Odds ratios and 95% confidence intervals for pediatric papillary thyroid cancer in relation to perinatal exposure to outdoor artificial light at night (second and third tertiles compared with first tertile, or with light modeled as a continuous variable, per $1{\text{\hspace{0.17em}mcd}/\mathrm{m}}^2$), overall and by age group, and race/ethnicity within a nested case–control study in California ($n=736$ cases, 36,800 controls). Models for the overall population and different age groups were adjusted for sex, race, birth weight, gestational age, birth order, birth year, maternal age, mother’s birthplace, maternal education, history of Cesarean-section, and paternal age. Models for different racial and ethnic groups adjusted for the same covariates except race and ethnicity.