Does prenatal exposure to multiple airborne and tap-water pollutants increase neonatal thyroid-stimulating hormone concentrations? Data from the Picardy region, France

The association between particulate matter 2.5 and thyroid function and thyroid cancer: a meta-analysis

PURPOSE

Recent studies indicate a potential link between exposure to atmospheric particulate matter 2.5 (PM2.5) and thyroid function, though epidemiological conclusions remain inconsistent. This comprehensive systematic review and meta-analysis aims to clarify the connection between PM2.5 levels and the risks of thyroid function and thyroid cancer.

METHODS

Using the medical subject headings "PM2.5" and "thyroid hormones" along with their associated free words, publications from the Web of Science, Embase, Cochrane Library, and PubMed up to April 2024 were searched. The study protocol has been registered on PROSPERO (CRD42024554220).

RESULTS

A total of 1322 articles were collected from databases, of which 27 studies were included in the analysis. The findings indicated that exposure to PM2.5 was a significant risk factor for hypothyroidism, increasing the incidence risk by 0.15 (95% CI 1.08, 1.23, P < 0.001). PM2.5 exposure levels were significantly higher in Asian populations than in European populations; each incremental increase in PM2.5 exposure resulted in a rise in TSH by 0.27 mIU/L (95% CI 0.07, 0.47, P = 0.008) and a decrease in FT4 by 0.21 pmol/L (95% CI - .35, - 0.07, P = 0.004). Additionally, in susceptible pregnant women, each incremental increase in PM2.5 exposure during pregnancy was associated with a rise in TSH levels by 0.08 mIU/L (95% CI - 0.02, 0.17, P < 0.001) and a decrease in FT4 levels by 0.09 pmol/L (95% CI - 0.23, 0.05, P = 0.210).

CONCLUSION

Our research establishes PM2.5 exposure as a risk factor for diminished thyroid function. In Asian populations, the average level of PM2.5 exposure is high, significantly affecting thyroid hormones (TSH, FT4). Particular attention to PM2.5 exposure levels during pregnancy is essential to reduce the risk of thyroid dysfunction.

Congenital and acquired hypothyroidism: Temporal and spatial trends in France from 2014 to 2019

PURPOSE

To assess the incidence of congenital hypothyroidism (CH) and acquired hypothyroidism (AH) between 2014 and 2019 in continental France.

METHODS

New cases of CH and AH were identified using the French National Health Data System (Système Nationale des Données de Santé, SNDS). Temporal trends were studied using linear regression models. Spatial distributions were studied using Moran's global index (I) and the statistical method and local indicators of spatial association.

RESULTS

The incidence of permanent CH in females increased by 8.9 % per year (2014: 36.9 [31.1-43.7] per 100,000 birth-years vs. 2019: 51 [43.9-59.3] per 100,000 birth-years, p < 0.01). The incidence of AH decreased between 2014 and 2019 for both females (2014: 535.7 [533.2-538.2] per 100,000 person-years vs 2019: 335.5 [333.6-337.4] per 100,000 person-years, p < 0.01) and males (2014: 197.5 [195.9-199] per 100,000 person-years vs 2019: 141.7 [140.4-142.9] per 100,000 person-years, p < 0.01). The incidence of hypothyroidism was high in the Nord-Pas-De-Calais and Lorraine regions (CH and AH).

CONCLUSIONS

The incidence of permanent CH in females has increased over time. AH incidence decreased. It seems necessary to investigate environmental factors in the disparity of incidence distribution.

Prenatal exposure to air pollution and maternal and fetal thyroid function: a systematic review of the epidemiological evidence

BACKGROUND

Exposure to ambient air pollution is a top risk factor contributing to the global burden of disease. Pregnant persons and their developing fetuses are particularly susceptible to adverse health outcomes associated with air pollution exposures. During pregnancy, the thyroid plays a critical role in fetal development, producing thyroid hormones that are associated with brain development. Our objective is to systematically review recent literature that investigates how prenatal exposure to air pollution affects maternal and fetal thyroid function.

METHODS

Following the Navigation Guide Framework, we systematically reviewed peer-reviewed journal articles that examined prenatal exposures to air pollution and outcomes related to maternal and fetal thyroid function, evaluated the risk of bias for individual studies, and synthesized the overall quality and strength of the evidence.

RESULTS

We found 19 studies that collected data on pregnancy exposure windows spanning preconception to full term from 1999 to 2020 across nine countries. Exposure to fine particulate matter (PM2.5) was most frequently and significantly positively associated with fetal/neonatal thyroid hormone concentrations, and inversely associated with maternal thyroid hormone concentrations. To a lesser extent, traffic-related air pollutants, such as nitrogen dioxide (NO2) had significant effects on fetal/neonatal thyroid function but no significant effects on maternal thyroid function. However, the body of literature is challenged by risk of bias in exposure assessment methods and in the evaluation of confounding variables, and there is an inconsistency amongst effect estimates. Thus, using the definitions provided by the objective Navigation Guide Framework, we have concluded that there is limited, low quality evidence pertaining to the effects of prenatal air pollution exposure on maternal and fetal thyroid function.

CONCLUSION

To improve the quality of the body of evidence, future research should seek to enhance exposure assessment methods by integrating personal monitoring and high-quality exposure data (e.g., using spatiotemporally resolved satellite observations and statistical modeling) and outcome assessment methods by measuring a range of thyroid hormones throughout the course of pregnancy.

Associations between short-term exposure to air pollution and thyroid function in a representative sample of the Korean population

BACKGROUND

Disruption of thyroid function can profoundly affect various organ systems. However, studies on the association between air pollution and thyroid function are relatively scarce and most studies have focused on the long-term effects of air pollution among pregnant women.

OBJECTIVES

This study aimed to explore the associations between short-term exposure to air pollution and thyroid function in the general population.

METHODS

Data from the Korea National Health and Nutrition Examination Survey (2013-2015) were analyzed (n = 5,626). Air pollution concentrations in residential addresses were estimated using Community Multiscale Air Quality models. The moving averages of air pollution over 7 days were set as exposure variables through exploratory analyses. Linear regression and quantile g-computation models were constructed to assess the effects of individual air pollutants and air pollution mixture, respectively.

RESULTS

A 10-ppb increase in NO2 (18.8-μg/m3 increase) and CO (11.5-μg/m3 increase) was associated with 2.43% [95% confidence interval (CI): 0.42, 4.48] and 0.19% (95% CI: 0.01, 0.36) higher thyroid-stimulating hormone (TSH) levels, respectively. A 10-μg/m3 increase in PM2.5 and a 10-ppb increase in O3 (19.6-μg/m3 increment) were associated with 0.87% (95% CI: 1.47, -0.27) and 0.59% (95% CI: 1.18, -0.001) lower free thyroxine (fT4) levels, respectively. A simultaneous quartile increase in PM2.5, NO2, O3, and CO levels was associated with lower fT4 but not TSH levels.

CONCLUSIONS

As the subtle changes in thyroid function can affect various organ systems, the present results may have substantial public health implications despite the relatively modest effect sizes. Because this was a cross-sectional study, it is necessary to conduct further experimental or repeated-measures studies to consolidate the current results.

A comprehensive review on endocrine toxicity of gaseous components and particulate matter in smog

Smog is a form of extreme air pollution which comprises of gases such as ozone, sulfur dioxide, nitrogen and carbon oxides, and solid particles including particulate matter (PM2.5 and PM10). Different types of smog include acidic, photochemical, and Polish. Smog and its constituents are hazardaous to human, animals, and plants. Smog leads to plethora of morbidities such as cancer, endocrine disruption, and respiratory and cardiovascular disorders. Smog components alter the activity of various hormones including thyroid, pituitary, gonads and adrenal hormones by altering regulatory genes, oxidation status and the hypothalamus-pituitary axis. Furthermore, these toxicants are responsible for the development of metabolic disorders, teratogenicity, insulin resistance, infertility, and carcinogenicity of endocrine glands. Avoiding fossil fuel, using renewable sources of energy, and limiting gaseous discharge from industries can be helpful to avoid endocrine disruption and other toxicities of smog. This review focuses on the toxic implications of smog and its constituents on endocrine system, their toxicodynamics and preventive measures to avoid hazardous health effects.