Effect of occupational exposure to extremely low frequency electromagnetic fields on level of thyroid hormones effective on fatigue

Background: The aim of this study was to assess exposure to extremely low frequency electromagnetic fields (ELF-EMFs) and its effects on secretion of thyroid hormones associated with symptoms of fatigue on electric arc welding workers. Methods: This study was carried out on two groups including 35 welders (as exposed) and 35 non-welders (as control). Extremely low frequency electromagnetic fields were measured according to guideline compiled by the National Institute for Occupational Safety and Health (NIOSH) using a calibrated ELF meter. The level of Triiodothyronine hormone (T3), thyroxine hormone (T4) and thyroid stimulating hormone (TSH) secretion were studied on both exposed and unexposed groups through the enzyme-linked immunosorbent assay (ELISA). Samn-Perelli fatigue scale questionnaire was completed by two groups. Analysis was performed using SPSS V 20 software and analytical statistics including t-test, chi-squared test, Analysis of variance (ANOVA) and the Pearson correlation coefficient.  Results: The thyroid hormones had lower level in the exposed group than the non-welders. Mean difference of T4 and TSH hormones between the two groups was statistically significant (p <0.05). The prevalence of the hormone disruption compared with their normal range and the levels of fatigue in welders group were higher than those in non-welders. There was a significant weak positive correlation between exposure level to ELF magnetic field and thyroid hormones level (r < 0.12; p> 0.05) and also, fatigue score increased with decreasing   T3 and T4 levels (p <0.05). A statistically significant direct relationship between level exposure to ELF –EMFs and fatigue score was found (r = 0.54; p <0.05). Conclusion: Exposure to ELF-EMFs may disrupt the thyroid hormone secretion such as T4 and TSH levels and may increase the fatigue level. This study is only a starting point for such researches, many issues need to be addressed for drawing the definite conclusions.