Association between long-term exposure to environmental coarse particulate matter and the prevalence of thyroid disorders: a cross-sectional study in China.

BACKGROUND

Evidence linking long-term exposure to particulate matter with thyroid dysfunction is increasing, but data on particulate matter 10 micrometers or less (PM10) exposure and thyroid disorders remain limited.

METHODS

73,900 subjects aged ≥ 18 years from a nationwide population-based study were included. Thyroid disorders were determined using standardized biochemical testing and thyroid ultrasound examination. Individual long-term PM10 exposure was estimated at a 1 × 1 km spatial resolution using a Space-Time Extra Trees model, and the five-year average concentration preceding enrollment was assigned to each participant's residential address. Weighted estimates were calculated to account for the complex sampling design.

RESULTS

The average long-term exposure to PM10 at residential addresses was 111.74 µg/m3, ranging from 35.08 µg/m³ to 374.8 µg/m³. Compared with those in the first quartile (35.08 to 75.50 µg/m³), participants in the highest PM10 quartile (130.80 to 374.80 µg/m³) had higher odds of overt hypothyroidism (OR 1.36 [CI 1.03-1.79]), subclinical hypothyroidism (1.14 [1.04-1.25]), autoimmune thyroiditis (1.10 [1.01-1.20]) and thyroglobulin antibody positivity (1.24 [1.12-1.37]). Each 10 µg/m³ increase in the PM10 concentration was associated with higher odds of overt hypothyroidism (OR 1.16 [1.07-1.25]) and subclinical hypothyroidism (1.07 [1.04-1.10]). TgAb positivity showed an increasing exposure-response pattern across PM10 concentrations. No consistent significant associations were observed for overt hyperthyroidism, subclinical hyperthyroidism, Graves' disease, or thyroid peroxidase antibody positivity.

CONCLUSION

Long-term PM10 exposure was associated with higher odds of overt hypothyroidism, subclinical hypothyroidism, autoimmune thyroiditis, and TgAb positivity among Chinese adults. These findings suggest that coarse particulate pollution may be a modifiable environmental factor related to hypothyroidism and thyroid autoimmunity.