A recent study led by Yale University researchers, published in Environmental Health Perspectives, highlights a concerning connection between early-life exposure to two prevalent environmental pollutants—airborne fine particulate matter (PM2.5) and outdoor artificial light at night (O-ALAN)—and an increased risk of papillary thyroid cancer in children and young adults.
The research, a collaboration across multiple Yale departments and institutions nationwide, found a “significant association” between exposure to these pollutants during the perinatal period—the time from pregnancy to one year after birth—and a higher risk of developing thyroid cancer. The study focused on children and young adults up to 19 years old, with the findings suggesting that these environmental factors may contribute to the rising incidence of thyroid cancer in younger populations.
Dr. Nicole Deziel, the study’s lead author and an environmental epidemiologist at the Yale School of Public Health, expressed concern over the widespread nature of these exposures. “Fine particulate matter is a major component of urban air pollution from automobile traffic and industrial activity, while artificial light at night is a common feature in densely populated urban environments,” she said.
The research team analyzed data from 736 individuals diagnosed with papillary thyroid cancer before the age of 20, comparing them with 36,800 matched control participants. Using advanced geospatial and satellite modeling, the team assessed individual exposure levels to PM2.5 and O-ALAN based on participants’ residential locations in California. The study revealed that each 10 microgram per cubic meter increase in PM2.5 exposure raised the odds of developing thyroid cancer by 7%. The most significant associations were found among teenagers aged 15–19 and Hispanic children. Moreover, children born in areas with high levels of outdoor light at night had a 23%–25% higher likelihood of developing thyroid cancer.
“Thyroid cancer is one of the fastest-growing cancers in children and adolescents, but the causes remain largely unknown,” Dr. Deziel noted. “This study is the first large-scale investigation suggesting that early-life exposure to PM2.5 and O-ALAN may play a role in this alarming trend.”
The research team also included experts from Yale’s Departments of Biostatistics, Chronic Disease Epidemiology, and Pediatrics, along with researchers from the University of Southern California, UC Berkeley, and the American Cancer Society. Their collective expertise spans environmental exposure modeling, pediatric endocrinology, and cancer epidemiology.
Thyroid cancer in children often leads to extensive long-term health challenges. Compared to adults, children are frequently diagnosed at more advanced stages with larger tumors, and survivors may face issues such as temperature dysregulation, headaches, and mental fatigue, which can interfere with education, employment, and family life. These survivors are also more prone to anxiety and depression.
Both PM2.5 and O-ALAN are known environmental carcinogens that can disrupt endocrine systems and affect thyroid function. PM2.5 particles, being small enough to enter the bloodstream, can interfere with hormone signaling, including cancer pathways. Outdoor light at night has been shown to suppress melatonin and disturb circadian rhythms, which can also impact hormone-regulated cancer pathways.
The study also raises critical environmental justice concerns, noting that communities of color and low-income populations are disproportionately exposed to both air pollution and light pollution, contributing to the higher rates of thyroid cancer observed in Hispanic children.
The researchers stress the need for further studies to replicate and build upon these findings, advocating for improved exposure metrics and longitudinal research designs. In the meantime, Dr. Deziel emphasized the importance of addressing environmental factors in childhood cancer research. “Reducing exposure to air pollution and managing light pollution could be key steps in protecting children’s health,” she concluded.
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