Volatile organic compounds exposure with risk of thyroid function in U.S. general population: 2007-2012 NHANES

The link between exposure to environmental hazards and thyroid function has been relatively well established. However, evidence on environmental exposure to volatile organic compounds (VOCs) and thyroid function in the general population remains unclear.

To assess the impact of individual and joint effects of VOCs exposure on thyroid function in a representative sample of U.S. general population.

The findings from the WQS suggested a positive correlation between VOCs co-exposure and FT3 (β = 0.033, 95 % CI: 0.014, 0.025), as well as a negative correlation with FT4/FT3 (β = -0.084, 95 % CI: -0.127, -0.040). Specifically, 1,4-dichlorobenzene (29.2 %) was identified as the primary contributor to elevated serum FT3 concentrations, while tetrachloroethylene, 2,5-dimethylfuran, and furan (18.3 %) were the major contributors to the decreased FT4/FT3 ratio. Thyroid hormones, including FT3 and FT4, are key indicators of thyroid function, with the FT4/FT3 ratio serving as an important marker of thyroid homeostasis. Subgroup analysis showed a positive association between VOC exposure and FT3 in females (β = 0.045, 95 % CI: 0.019, 0.071), with 1,4-dichlorobenzene as the strongest contributor. In participants aged ≥ 60 years, VOC exposure was positively associated with FT3 (β = 0.107, 95 % CI: 0.006, 0.208) and negatively with FT4/FT3 (β = -0.103, 95 % CI: -0.202, -0.003). In this subgroup, ethylbenzene and 1,4-dichlorobenzene were the major contributors to FT3, while o-xylene was the primary contributor to the FT4/FT3 ratio. No significant associations were found in males or participants < 60 years.

These results suggest that VOCs exposure has a detrimental impact on thyroid function, especially in females and individuals aged 60 years and older. VOCs exposure may accelerate the onset of thyroid function impairment and lead to changes in thyroid hormone levels. This study may inform the development of early monitoring and regulatory measures for VOCs exposure, thereby reducing the incidence of thyroid dysfunction.