New York: Early-life exposure to small particle air pollution and outdoor artificial light at night could increase the risk of paediatric thyroid cancer, a new study led by researchers at Yale University in the US has suggested. 

The team found a “significant association” between exposure to ambient fine particulate matter air pollution (PM2.5) and outdoor artificial light at night (O-ALAN) and increased risk of papillary thyroid cancer in children and young adults up to 19 years old, according to the study published in Environmental Health Perspectives.

The exposures occurred during the perinatal stage of life, typically defined as the time from when pregnancy occurs up to a year after birth.

“These results are concerning, especially given how widespread both of these exposures are,” said Dr Nicole Deziel, an environmental epidemiologist with the Yale School of Public Health (YSPH) and the study’s lead author.

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, Deziel added.

The research team analysed data from 736 individuals diagnosed with papillary thyroid cancer before age 20 and 36,800 matched control participants based on birth year.

Using advanced geospatial and satellite modelling, the team assessed individual-level exposure to PM2.5 and O-ALAN based on residential location at birth. All of the study participants were from California.

The findings showed that for every 10 micrograms per cubic meter increase in PM2.5 exposure, the odds of developing thyroid cancer rose by 7 per cent overall.

The strongest association between exposure and thyroid cancer was found among teenagers (15–19 years of age) and Hispanic children. Similarly, children born in areas with high levels of exposure to outdoor light at night were 23–25 per cent more likely to develop thyroid cancer, according to the study.

"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 Deziel, an associate professor of epidemiology (environmental health sciences) and co-director of the Yale Center for Perinatal, Pediatric, and Environmental Epidemiology.

The 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.

The researchers emphasised that more work is needed to replicate and expand on their findings, ideally using improved exposure metrics and longitudinal designs. (IANS)