Perinatal and early-life exposure to ambient fine particulate matter air pollution (PM2.5) and outdoor artificial light at night (O-ALAN) may be associated with a statistically significant increased risk of papillary thyroid cancer in children and young adults up to 19 years old, according to the results of a study published in Environmental Health Perspectives.
The incidence of pediatric thyroid cancer has been increasing globally, and exposure to air pollution and artificial light is a hypothesized risk factor.
“These results are concerning, especially given how widespread both of these exposures are,” stated lead study author Nicole Deziel, PhD, MHS, an environmental epidemiologist at Yale School of Public Health. “Fine particulate matter is found in urban air pollution due to automobile traffic and industrial activity, and artificial light at night is common, particularly in densely populated urban areas.”
"Thyroid cancer is among the fastest growing cancers among children and adolescents, yet we know very little about what causes it in this population," said Dr. Deziel, who is also Associate Professor of Epidemiology (environmental health sciences) and Co-Director of the Yale Center for Perinatal, Pediatric, and Environmental Epidemiology. "Our study is the first large-scale investigation to suggest that these exposures early in life—specifically to PM2.5 and outdoor light at night—may play a role in this concerning trend."
Study Methods and Results
Investigators conducted a case-control study of 736 cases from a cluster of papillary thyroid cancer in California. All patients were born between 1982 and 2011 and were diagnosed between 0 and 19 years of age. Additionally, investigators analyzed 36,800 controls that were matched by birth year. Exposure levels were assigned using a validated, ensemble-based prediction model plus the New World Atlas of Artificial Night Sky Brightness.
Statistically significant associations were found between exposure to PM2.5 and papillary thyroid cancer risk (odds ratio [OR] per 10-μg/m3 increase in PM2.5 = 1.07; 95% confidence interval [CI] = 1.01–1.14). Particularly among the 15 to 19 year old age group, the odds ratio was increased at 1.08 (95% CI = 1.00–1.16), and among Hispanic children (OR = 1.13; 95% CI = 1.02–1.24).
In terms of O-ALAN exposure, statistically significant increased risk of papillary thyroid cancer was observed in higher exposure tertiles compared with the controls. Children born in areas with high levels of exposure to O-ALAN were 23% to 25% more likely to develop papillary thyroid cancer. No significant differences were found by race/ethnicity.
The study authors concluded that as O-ALAN may represent other air pollutants or broader urbanization patterns, and that further research and refinements to exposure metrics are needed to understand the impact of these exposures.
“Our results point to the critical importance of addressing environmental factors in childhood cancer research. Reducing exposures to air pollution and managing light pollution could be important steps in protecting children's health,” Dr. Deziel concluded.
Disclosure: For full disclosures of the study authors, visit ehp.niehs.nih.gov.
