Effects of low mercury vapour exposure on the thyroid function in chloralkali workers

• Published in: Journal of applied toxicology Vol. 20; no. 6; pp. 483 - 489
• Main Authors: Ellingsen MD, Dag G., Efskind MD, Jon, Haug MD, Egil, Thomassen MSc, Yngvar, Martinsen MSc, Ivar, Gaarder MD, Per I
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.11.2000; Wiley
• Subjects: Adult; Aged; Biological and medical sciences; Biomarkers; Chemical and industrial products toxicology. Toxic occupational diseases; Chemical Industry; chloralkali; chloralkali industry; Humans; Inhalation Exposure - adverse effects; Iodine - blood; Iodine - urine; Male; Medical sciences; Mercury - toxicity; mercury vapour; Metals and various inorganic compounds; Middle Aged; Occupational Exposure - adverse effects; ratio free T4/free t3; Regression Analysis; reverse triiodothyronine; Selenium - blood; Selenium - urine; Thyroid Function Tests; Thyroid Gland - drug effects; Thyroid Hormones - blood; Toxicology; Tumor Necrosis Factor-alpha - metabolism; tumour necrosis factor-α; urinary iodine; Endocrinopathy; Human; Chemical industry; Vapor; Toxicity; Low dose; Cytokine; Thyroid gland; Occupational exposure; Inhalation; Heavy metal; Chronic; Thyroxine; Thyroid hormone; Triiodothyronine; Mercury; Tumor necrosis factor α; Occupational medicine
• ISSN: 0260-437X; 1099-1263
• DOI: 10.1002/1099-1263(200011/12)20:6<483::AID-JAT722>3.0.CO;2-I

Forty‐seven chloralkali workers exposed to mercury vapour for an average of 13.3 years were compared with 47 referents matched for age in a cross‐sectional study of thyroid function. The mean urinary mercury concentration in the exposed workers was low compared with other studies of chloralkali workers: 5.9 nmol mmol−1 creatinine (range 1.1–16.8) vs 1.3 nmol mmol−1 creatinine (range 0.2–5.0) in the reference group. The median serum concentration of reverse triiodothyronine (rT3) was statistically significantly higher in the exposed subjects compared with the referents (268 pmol l−1 and range 161–422 vs 240 pmol l−1 and range 129–352; P = 0.009). The difference between the exposed subjects and the referents was most pronounced in the highest exposed sub‐groups. The free thyroxine (T4)/free T3 ratio was also higher in the highest exposed subgroups compared with the referents. The median serum concentration of tumour necrosis factor alpha (TNF‐α) was lower in the exposed subjects (7.3 pg ml−1 and range 4.4–69.7 vs 8.0 pg ml−1 and range 6.0–34.6; P = 0.004). Exposed subjects with the lowest urinary iodine (<67.8 nmol mmol−1 Cr) had higher serum concentrations of reverse T3 and a higher free T4/free T3ratio than the other subjects, suggesting that a low concentration of iodine in urine may be a risk factor for increased serum concentrations of reverse T3 and the free T4/free T3 ratio in subjects exposed occupationally to mercury vapour. The study could indicate a slight effect of low mercury vapour exposure on the function of the enzyme type I iodothyronine deiodinase, possibly modified by comparatively low urinary iodine concentrations. Copyright © 2000 John Wiley & Sons, Ltd.