title: Effects of low mercury vapour exposure on the thyroid function in chloralkali workers.
abstract: 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-alpha) 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 T 3 and a higher free T4/free T3 ratio 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.
authors.affiliation: National Institute of Occupational Health, PO Box 8149 Dep, N-0033 Oslo, Norway. dag.ellingsen@stami.no
authors.forename: D G
authors.initials: DG
authors.lastname: Ellingsen
authors.forename: J
authors.initials: J
authors.lastname: Efskind
authors.forename: E
authors.initials: E
authors.lastname: Haug
authors.forename: Y
authors.initials: Y
authors.lastname: Thomassen
authors.forename: I
authors.initials: I
authors.lastname: Martinsen
authors.forename: P I
authors.initials: PI
authors.lastname: Gaarder
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers; D002617:Chemical Industry; D006801:Humans; D019570:Inhalation Exposure / Q000009:adverse effects*; D007455:Iodine / Q000097:blood / Q000652:urine; D008297:Male; D008628:Mercury / Q000633:toxicity*; D008875:Middle Aged; D016273:Occupational Exposure / Q000009:adverse effects*; D012044:Regression Analysis; D012643:Selenium / Q000097:blood / Q000652:urine; D013960:Thyroid Function Tests; D013961:Thyroid Gland / Q000187:drug effects*; D013963:Thyroid Hormones / Q000097:blood; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D015415:Biomarkers; D013963:Thyroid Hormones; D014409:Tumor Necrosis Factor-alpha; D007455:Iodine; D008628:Mercury; D012643:Selenium