A new study led by researchers at Yale University suggests that children’s exposure at a young age to two common environmental pollutants—fine particulate matter air pollution and outdoor artificial light at night—may increase their risk of thyroid cancer.
The study—a collaborative project involving multiple faculties and institutions across Yale University in the U.S.—found a “significant association” between exposure to fine particulate matter air pollution (PM2.5) and outdoor artificial light at night (O-ALAN) and an increased risk of papillary thyroid cancer in children and young adults up to age 19. The exposures occurred during the perinatal life stage, typically defined as the period between the start of pregnancy and one year after birth.
“These findings are concerning, especially given how widespread both of these exposures are,” said Dr. Nicole Deziel, PhD, MHS , an environmental epidemiologist at the Yale School of Public Health (YSPH) and lead author of the study. “Fine particulate matter is found in urban air pollution from vehicle traffic and industrial activity, and artificial light at night is widespread, especially in densely populated urban areas.”
The research team analyzed data from 736 individuals diagnosed with papillary thyroid cancer before age 20, and data from 36,800 matched control subjects based on year of birth. Using advanced geospatial and satellite-based modeling, the team determined individual exposure to PM2.5 and O-ALAN based on residential address at birth. All study participants were from California.
The results showed that for every 10-microgram per cubic meter increase in PM2.5 exposure, the risk of developing thyroid cancer increased by 7% overall. The strongest association between exposure and thyroid cancer was found in teenagers (ages 15–19) and Hispanic children. Similarly, children born in areas with high levels of outdoor nighttime light exposure had a 23%–25% increased risk of developing thyroid cancer, according to the study.
"Thyroid cancer is among the fastest-growing cancers in children and adolescents, yet we know very little about the causes in this population," said Deziel, an 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 early-life exposures – particularly to PM2.5 and nighttime outdoor light – may play a role in this concerning trend."
