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

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. 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.  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). 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.