Correlates of Positive Thyroid Peroxidase Antibodies Among Firefighters: A Cross-Sectional-Study

Abstract

Purpose Exposure to endocrine disrupting chemicals (EDCs) are associated with underactive thyroid glands, and possibly autoimmunity. Firefighters are exposed to EDCs from flame retardants; however, the prevalence and risk factor associations of thyroid antibodies among firefighters are unknown. Methods Firefighters attending professional health and safety conferences between November 2018 and January 2020, and with no prior diagnosis of thyroid disease were invited (n=278) to submit a health survey, blood samples, and complete a thyroid ultrasound. The survey assessed for sociodemographic and occupational characteristics, including a history of familial thyroid disease, smoking, firefighter tenure, and job rank, radiation exposure, and mitigation practices of occupational exposures. Serum thyroid peroxidase antibody (TPOAb) was also assessed. Results Approximately 39.9% firefighters evaluated had a positive TPOAb test. The mean age for those TPOAb positive was lower than those who tested negative (41.4 ±7.9 vs 43.1 ±7.9 years, p=0.07) but this difference was not significant. Firefighters with a family history of thyroid disease had a statistically significant higher prevalence of TPOAb compared to those without a family history (60.0% vs. 37.5%, p=0.02); this association remained significant after adjusting for sociodemographic and occupational factors (Odds Ratio 2.99; Confidence interval 1.31 – 6.85). Main conclusions The prevalence of TPOAb is high among firefighters in our study, and family history is a significant determinant of testing positive for TPOAb. Firefighters may benefit from TPOAb and thyroid stimulating hormone tests, and screening for family history of thyroid disease at baseline employee medical check-ups. This finding suggests the need for further studies.

A Review of the Association between Exposure to Flame Retardants and Thyroid Function

“…Articles were included if they met the following inclusion criteria: (1) provided measurements of serum, plasma, cord, placental, breast milk, or urine flame retardants, (2) provided measurements of serum, plasma, cord, placental, breast milk, or urine thyroid hormones (free thyroxine (fT4), total thyroxine (tT4), free triiodothyronine (fT3), total triiodothyronine (tT3), or thyroid-stimulating hormone (TSH)), (3) investigated the association between flame retardants and thyroid hormones within humans, or (4) investigated the association between flame retardants with thyroid-related antibodies or (5) cancer. Articles were excluded for the following reasons: (1) systematic reviews or meta-analyses, (2) non-human studies, (3) in vitro and preclinical studies, (4) missing statistical analysis, (5) studies not including flame retardants, and (6) studies without statistical analyses. Articles with incorrect or unspecified outcome variables included measurements of quantities of metals such as lead excretion or enzyme function like thyroid deiodinase activity as primary outcome variables were also excluded.…”

“…They are often used for household and industrial appliances (e.g., furniture, electronics), disbursed within building sites, and in transportation products such as cars and airplanes [ 4 ]. These chemicals have also been applied to the protective gear of firefighters to help mitigate the spread of fire [ 5 ]. Flame retardants have also been found in human foods and feces, as well as in human serum and urine samples [ 6 ].…”