Preliminary Studies on Thyroid Function in Welders

Abstract

During welding operation, workers are exposed to welding fumes containing various toxic metals and their oxides, certain gases, radiation, and high temperature") . Health hazards and biological effects associated to these exposures have been extensively studied'-'), however, thyroid function has received very little attention. There are a few reports available, which indicate that some metals including aluminium, cadmium, lead, and mercury can alter thyroid function','). In addition, exposure to radiation, and high temperature are also known to have their impact on thyroid function. Studies reported') earlier from this Institute indicated that metals like manganese , iron, and zinc form the main constituents of welding fumes while chromium, nickel, copper, cadmium, and lead were found in trace amounts; significantly higher levels of these metals including chromium, nickel, copper, and cadmium were also found in blood of welders.Keeping in view the above facts, we have conducted a pilot study to assess thyroid function in welders working in small-scale industrial settings. Subjects and MethodsTwenty healthy male welders with an average age of 38.4 ± 8.67 yr (mean ± SD), having average occupational exposure of 13.5 ± 5.2 yr (mean ± SD), and performing manual electric arc and/or gas welding participated in the study. Job operation mainly included welding and cutting of iron objects. Simultaneously, an equal number of control subjects, matched with age, sex, socio-economic status and having no previous occupational exposure to welding profession or other chemicals were also studied. All subjects were interviewed for their life-style, and their occupational history was recorded. Intravenous blood samples (6-8 ml) from both the groups were drawn in a morning session. Serum was separated by centrifugation and used for hormonal analysis. Serum thyrotropin (thyroid stimulating hormone, TSH) was estimated by solid phase immunoradiometric assay (TSH/IRMA)7). Serum total T 3 ( TT3)8 and total T4 (TT4)9) were measured by radio immunoassay (RIA). Assay sensitivity (n=5) as determined by the lowest standard, different from zero (t-test), was 0.58 ng/dl for T3; 0.2 µg/dl for T4; and 0.03 µIU/ml for TSH, respectively. Intra-assay coefficients of variation (CVs) for reference sera (n=5 each) with T4 concentrations of 7.5 and 15 pg/dl were 3.4% and 4.8%, respectively. Similarly for T3 reference sera, (1.3 ng/ml) and TSH reference sera (30 /AU/ml); the values of CVs (n=5 each) were 4.3% and 4.6%, respectively. Statistical analysis was performed using Student's `t' test. ResultsLevels of TSH were increased significantly (p<0.02) in welders compared with non-welders. The average level of TSH was determined to be 2.61 ± 1.93 /AU/ml (mean ± SD) and ranged from 0.74-7.34 AU/m.1 in welders, while it was quite lower (1.71 ± 0.63 µIU/ml) in non welders and varied in a narrow range (0.81-3.20 µIU/ ml). However, total T3 (TT3) and total T4 (TT4) levels remained almost unchanged.Based on the individual TSH measurements, 4 of the 20 welders (s...

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