Air pollution exposure linked to thyroid function in general population

Exposure to ambient air pollution is associated with thyroid function in the general population, reveals a recent study, noting that such association is more pronounce in older or overweight or obese adults.

The investigators used a nationwide sample of Korean adults to examine the association between exposure to air pollution and thyroid function, and whether such association differed between subgroups stratified according to age or body mass index.

A total of 4,704 adults were included in the final analysis, which used each person’s annual average exposure to four air pollutants: particulate matter with an aerodynamic diameter less than or equal to 10 μm (PM₁₀), nitrogen dioxide (NO₂), sulfur dioxide, and carbon monoxide (CO). Serum thyrotropin (TSH) and free thyroxine (FT4) concentrations were used as indicators of thyroid function according to age and body mass index.

The annual average exposure to NO₂ and CO appeared to induce an elevated TSH and reduced FT4 concentrations after adjusting for possible confounding factors (p<0.05 for all). Apart from these two pollutants, PM₁₀ exposure also correlated with TSH level (p=0.03) in men.

In age-stratified analysis, exposure to NO₂ and CO had stronger effects in older than in younger adults. Exposure to these air pollutants correlated with serum TSH and FT4 concentrations in people who were overweight or obese, but not in those of normal weight.

This is the first study to provide evidence of a link between air pollution and thyroid function in the general population, according to the investigators.