Air pollution and thyroid abnormalities: Systematic review and meta-analysis

Abstract

Background Air pollution exposure can trigger a wide range of thyroid dysfunction in different population groups. This systematic review and meta-analysis aimed to find the association between air pollution and thyroid dysfunction in the general population and neonate, pregnant and cancerous people. Methods Electronic databases, including Web of Science, PubMed, Scopus, and Embase, were searched for all published articles from 27 October 2021. The Newcastle Ottawa Scale checklist was used to assess the quality of individual studies. Relevant demographic data and the intended results of the selected studies were extracted, and their adjusted odds ratios were pooled using random and fixed effect analysis based on the heterogenicity index. Results After applying the search strategies, twenty-six articles were included in our study. Overall, the association between air pollution and thyroid cancer, neonatal hypothyroidism, maternal thyroid function, and thyroid function in the general population was discussed in four, eight, ten, and four studies, respectively. There was a significant association between PM2.5 exposure and maternal hypothyroxinemia with pooled OR of 1.241 (95%CI, 1.089–1.415), p-value < 0.001. No positive relationship existed between NO2 exposure and maternal hypothyroxinemia with pooled OR of 1.007 (95%CI, 0.840–1.207), p-value = 0.941. The investigation of the relationship between PM2.5 exposure and congenital hypothyroxinemia showed a significant association between them, with pooled OR of 1.017 (95%CI, 1.002–1.032), p-value = 0.024. Conclusions Air pollution could influence thyroid function, especially in pregnant women and newborn infants. This study and similar investigations provide evidence of air pollution toxicity for healthcare systems.