The effects of electromagnetic fields on living organisms at different frequencies have long been studied by researchers and in numerous cases. Moreover, the long duration of studies and the slow impact of fields on life cycle processes prevent making a definite statement. Accordingly, the judgment was based only on laboratory findings on animal samples. However, there exists a consensus on the adverse effects of too much exposure to a magnetic field. Necessary information about the level of melatonin in the employees of power substations in Iran is scarce. Besides, exposure to electromagnetic waves is harmful. Thus, this study aimed to determine the relationship between electromagnetic waves and serum melatonin levels in the employees of 230 kV substations in Golestan Province, Iran.

This descriptive study was performed on male employees of 230 kV substations in Golestan Province, Iran, in 2016. The intensity of electric and magnetic fields in five 230 kV substations in Golestan Province was determined and the relevant serum melatonin levels were measured. Demographic information was collected by a questionnaire. Changes in melatonin hormone levels of 44 employees were studied as the target group and compared with the control group (23 guards working in healthcare centers).
 The obtained data were analyzed in Spss v. 22. Quantitative variables were reported as mean and standard deviation and qualitative variables as a percentage. The Kolmogorov-Smirnov test was used to establish the normality of the data at a significance level of 0.05. Based on the collected results, parametric and non-parametric tests were selected. Independent Samples t-test, Mann-Whitney U test, one-way Analysis of Variance (ANOVA), as well as Kendall and Pearson correlation coefficient tests were used to compare melatonin levels in the case (operator, substation guards) and control (healthcare center staff) groups.

The mean electric field strength measured at substations was equal to 5.91 V/m in the range of 7.55-5.44; the average magnetic flux density was 5.08 mG in the range of 6.54-0.25. These values fell in the permissible range of occupational exposure. The Mean±SD level of melatonin hormone was calculated to be 25.44 60±1.60 and 24.58±2.45 in the case and control groups, respectively. Independent Samples t-test data revealed no significant difference in the mean level of melatonin between the case and control groups (P=0.761). One-Way ANOVA data indicated no significant difference between the age groups of subjects in mean melatonin levels (P=0.381). In the control group, there was no significant difference between the mean melatonin levels (P=0.551) and age groups. Kendall correlation coefficient data suggested no significant relationship in melatonin levels and age groups between the case and control groups (P<0.05). One-Way ANOVA data presented no significant difference between the research groups in the mean level of melatonin (P=0.213). In the control group, there was no significant difference between the mean melatonin levels based on work experience (P=0.383). Kendall correlation coefficient results suggested no significant relationship in melatonin levels and different groups of work experience between the case and control groups (P <0.05). One-Way ANOVA findings signified no significant difference in the mean level of melatonin hormone in the place of activity of employees (P=0.482) and the occupation of individuals (P=0.515) between the case and control groups. Pearson correlation coefficient data revealed no significant relationship between melatonin hormone levels in the case group with the values ​​of electric field intensity (P=0.851) and magnetic flux density (P=0.132).

All explored electrical and magnetic field measurements were within national and international standards. The measurement results of this study were consistent with those of Hosseini et al. [18], Mohamadyan et al. [17], and Ghorbani et al. [20] in Iran. In their study, all measurements were within the allowable range of occupational exposure. In this study, the mean level of melatonin in the case group was slightly higher than that in the control group; no significant difference was observed between the research groups in this regard. This result was consistent with those of Juutilainen (2006) [8] and El-Hellali [9]. They also observed no significant difference in the level of melatonin in their study. However, the results of this study were inconsistent with those of Dyche [24]. The mean level of melatonin in different age groups presented no significant difference in the case-control group. A slight decrease in melatonin was observed in the control group with age; however, no decrease was observed in the case group [22]. The obtained results signified that employees who are in authorized contact with electromagnetic waves and work in a safe environment, will not be affected by these waves concerning the amount of melatonin hormone under different age conditions, exposure history, and so on. We found no association between electromagnetic waves and the hormone melatonin.

This study was approved by the Ethics Committee of the University of Shahid Beheshty Medical Science (Code: IR.SBMU.THNS.REC.1395.9). 

The study was extracted from the MSc. thesis of the first author at the Department of Occupatonal Health and Safety Engineering, School of Public Health and Safety, Shahid Beheshti University of Medical Science, Tehran.

Conceptualization: Mohammad Ranjbarian and Kourosh Etemad; Data analysis: Fatemeh Zarei; Research and sampling method: Jalaluddin Saadi and Rozita Farhadi; Text writing and review: All Authors.

The authors declared no conflicts of interest.

 

Reference

1. Brzezinski A. Melatonin in humans. N Engl J Med. 1997; 336(3):186-95. [DOI:10.1056/NEJM199701163360306] [PMID]

2. Sokolovic D, Djordjevic B, Kocic G, Stoimenov TJ, Stanojkovic Z, Sokolovic DM, et al. The effects of melatonin on oxidative stress parameters and DNA fragmentation in testicular tissue of rats exposed to microwave radiation. Adv Clin Exp Med. 2015; 24(3):429-36. [DOI:10.17219/acem/43888] [PMID]

3. Michaelson SM. Health implications of exposure to radiofrequency/microwave energies. Br J Ind Med. 1982; 39(2):105-19. [DOI:10.1136/oem.39.2.105] [PMID] [PMCID]

4. Ohayon MM, Stolc V, Freund FT, Milesi C, Sullivan SS. The potential for impact of man-made super low and extremely low frequency electromagnetic fields on sleep. Sleep Med Rev. 2019; 47:28-38. [DOI:10.1016/j.smrv.2019.06.001] [PMID]

5. Ahlbom A. Neurodegenerative diseases,suicide and depressive symptoms in relation to EMF. Bioelectromagnetics. 2001; (S5):S132-43. [DOI:10.1002/1521-186X(2001)22:5+3.0.CO;2-V]

6. Carpenter DO. Human disease resulting from exposure to electromagnetic fields. Rev Environ Health. 2013; 28(4):159-72. [DOI:10.1515/reveh-2013-0016]

7. Sahraei H. [Induction of anger in rhesus monkeys using ELF waves at a frequency of 30 Hz (Persian)]. Paramed Sci Mil Health. 2019; 14(3):5-5. https://jps.ajaums.ac.ir/article-1-200-fa.html

8. Juutilainen J, Kumlin T. Occupational magnetic fieldexposure and melatonin: interaction with light-at-night. Bioelectromagnetics. 2006; 27(5):423-6. [DOI:10.1002/bem.20231] [PMID]

9. El-Helaly M, Abu-Hashem E. Oxidative stress, melatoninlevel, and sleep insufficiency among electronic equipmentrepairers. Indian J Occup Environ Med. 2010; 14(3):66-70. [DOI:10.4103/0019-5278.75692] [PMID] [PMCID]

10. Yousefi HA, Nasiri P. Psychological effect of occupational exposure to electromagnetic fields. J Res Health Sci. 2006; 6(1):18-21. http://journals.umsha.ac.ir/index.php/JRHS/article/view/303

11. Bagheri Hosseinabadi M, Khanjani N, Ebrahimi MH, Haji B, Abdolahfard M. The effect of chronic exposure to extremely low-frequency electromagnetic fields on sleep quality, stress, depression and anxiety. Electromagn Biol Med. 2019; 38(1):96-101. [DOI:10.1080/15368378.2018.1545665] [PMID]

12. Daryabari H, Bahramifar A, Morshedi M, Lotfi B. [Investigation of the relationship between exposures to electromagnetic waves with some clinical disorders in radar device users (Persian)]. J Mar Med. 2019; 1(1):18-23. [DOI:10.30491/1.1.18]

13. Bowman JD, Kelsh MA, Kaune WT. Manual for measuring occupational electric and magnetic fields exposures. U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Division of Biomedical and Behavioral Sciences; 1998.

14. Ministry of Health and Medical Education.Electronic forms [Internet]. 2017 [Updated 2017]. Available from: http://thc.qums.ac.ir/Portal/home/?177041/%D9%81%D8%B1%D9%85-%D9%87%D8%A7%DB%8C-%D8%A7%D9%84%DA%A9%D8%AA%D8%B1%D9%88%D9%86%DB%8C%DA%A9%DB%8C

15. ACGIH. TLVs and BEIs based on the documentation of the threshold limit values for chemical substances and physical agents and biological exposure indices. Cincinnati: ACGIH Publication; 2007. https://www.amazon.com/TLVs-BEIs-2007-Documentation-Substances/dp/1882417690

16. International Commission on Non-Ionizing Radiation Protection. ICNIRP statement on the guidelines for limiting exposure to time-varying electric, magnetic and electromagnetic fields (up to 300 GHz). Health Phys. 2009; 97(3):257-8. [DOI:10.1097/HP.0b013e3181aff9db] [PMID]

17. Mohammadyan M, Alizadeh Larimi A, Gorgani M, Taghavi Soghondikolaei F. [measurment of electromagnetic field of minitors and electric posts in one of the oil product distribution company in mazandaran province (Persian)]. J res Environ Health. 2017; 3(2):150-7. [DOI: 10.22038/JREH.2017.25132.1166]

18. Hosseini SZ, Jalili Jahromi A, Malakootian MA. [Investigation and measurement of electric and magnetic fields In the vicinity of Tehran’s metropolitan high-power lines and substations (persian)]. Twenty-seventh International Conference on Electricity, 2012, Tehran, Iran. https://civilica.com/doc/178257/

19. Eskandari M.H., et al. [Examination of 380 and 800 microtesla electromagnetic fields effect on plasma cortisol hormone level and humural immunity in Balb/c mice (persian)]. Biol J. 2009; 4(2):9-18. https://www.sid.ir/en/journal/ViewPaper.aspx?ID=193443

20. Ghorbani F, Eshaghi M, Dehghanpor T, Karami Z. [Assessment of Extremely Low Frequency (ELF) electric and magnetic felds in Hamedan high electrical power stations and their effects on workers (persian)]. Iran J Med Phys. 2011; 8(3):61-71. https://www.sid.ir/fa/journal/ViewPaper.aspx?ID=149146

21. Mazurek PA, Naumchuk OM, Kot K, Wdowiak A, Zybała M. Exposure of high frequency electromagnetic fields in the living environment. EJMT. 2018; 4(21):33-9. http://www.medical-technologies.eu/upload/exposure_of_high_frequency_electromagnetic_fields_-_mazurek.pdf

22. Brainard GC, Kavet R, Kheifets LI. The relationship between electromagnetic field and light exposures to melatonin and breast cancer risk: A review of the relevant literature. J Pineal Res. 1999; 26(2):65-100. [DOI:10.1111/j.1600-079X.1999.tb00568.x] [PMID]

23. Dyche J, Anch AM, Fogler KA, Barnett DW, Thomas C. Effects of power frequency electromagnetic fields on melatonin and sleep in the rat. Emerg Health Threats J. 2012; 5(1):10904. [DOI:10.3402/ehtj.v5i0.10904] [PMID] [PMCID]

24. Manikonda PK, JagotaA A. Melatonin administration differentially affects age-induced alterations in daily rhythms of lipid peroxidation and antioxidant enzymes in male rat liver. Biogerontology. 2012; 13(5):511-24. [DOI:10.1007/s10522-012-9396-1] [PMID]

25. Farhud D ,Tahavorgar A. [Melatonin Hormone, Metabolism and its clinical effects: A review (Persian)]. Iran J Endocrinol Metab. 2013; 15(2):211-23. https://www.sid.ir/en/journal/ViewPaper.aspx?ID=339250