Ambient air pollution and thyroid function in Spanish adults. A nationwide population-based study (Di@bet.es study)

Abstract

Background Recent reports have suggested that air pollution may impact thyroid function, although the evidence is still scarce and inconclusive. In this study we evaluated the association of exposure to air pollutants to thyroid function parameters in a nationwide sample representative of the adult population of Spain. Methods The Di@bet.es study is a national, cross-sectional, population-based survey which was conducted in 2008-2010 using a random cluster sampling of the Spanish population. The present analyses included 3859 individuals, without a previous thyroid disease diagnosis, and with negative thyroid peroxidase antibodies (TPO Abs) and thyroid-stimulating hormone (TSH) levels of 0.1-20 mIU/L. Participants were assigned air pollution concentrations for particulate matter <2.5μm (PM2.5) and Nitrogen Dioxide (NO2), corresponding to the health examination year, obtained by means of modeling combined with measurements taken at air quality stations (CHIMERE chemistry-transport model). TSH, free thyroxine (FT4), free triiodothyronine (FT3) and TPO Abs concentrations were analyzed using an electrochemiluminescence immunoassay (Modular Analytics E170 Roche). Results In multivariate linear regression models, there was a highly significant negative correlation between PM2.5 concentrations and both FT4 (p<0.001), and FT3 levels (p<0.001). In multivariate logistic regression, there was a significant association between PM2.5 concentrations and the odds of presenting high TSH [OR 1.24 (1.01-1.52) p=0.043], lower FT4 [OR 1.25 (1.02-1.54) p=0.032] and low FT3 levels [1.48 (1.19-1.84) p=<0.001] per each IQR increase in PM2.5 (4.86 μg/m3). There was no association between NO2 concentrations and thyroid hormone levels. No significant heterogeneity was seen in the results between groups of men, pre-menopausal and post-menopausal women. Conclusions Exposures to PM2.5 in the general population were associated with mild alterations in thyroid function.

The impact of environmental factors and contaminants on thyroid function and disease from fetal to adult life: current evidence and future directions

“…The findings in newborns/infants are, however, in agreement with the data collected in adults, as shown in the Di@bet.es study ( 35 ), where a significant negative association between exposures to PM 2.5 and thyroid hormone levels was described, moreover, with relatively low PM 2.5 concentration ranges, well below the existing European Ambient Air Quality Directive target values (PM 2.5 <25 µg/m 3 ) ( 20 ). To date, the WHO guidelines recommend a maximum annual PM 2.5 exposure < 5 µg/m 3 ( 16 ).…”

Urinary Iodine Metabolomics as a Novel Tool for Understanding Environmentally Induced Thyroid Hormone Metabolic Alteration

“…11−13 Epide-miological studies have also shown associations between environmental factors (e.g., air pollution) and changes in the HPT axis. 14 These results require a better understanding of the environmental etiology of TH dysfunction to inform preventive strategies. Unfortunately, there is no human evidence to date on which and how far pollutants would disturb peripheral TH metabolism beyond deiodination, largely due to the lack of sensitive markers to indicate metabolic variations.…”

“…Increasing numbers of environmental chemicals have been suggested as thyroid disruptors . Animal studies with large doses of exposure have revealed significant changes in circulating TH levels partially via interference with the HPT axis and iodine-centered peripheral metabolism. − Epidemiological studies have also shown associations between environmental factors (e.g., air pollution) and changes in the HPT axis . These results require a better understanding of the environmental etiology of TH dysfunction to inform preventive strategies.…”