Mortazavi S M J, Vazife-Doost S, Yaghooti M, Mehdizadeh S, Rajaie-Far A
Medical Physics & Medical Engineering Department, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.
J Nat Sci Biol Med. 2012 Jan;3(1):60-4. doi: 10.4103/0976-9668.95958.
Some studies indicate that dentistry is one of the job categories with high potential exposure to elevated levels of extremely low frequency magnetic fields. In spite of this, information on occupational exposure of dentists to these fields is scarce. Studies on other common sources of electromagnetic fields (EMFs) such as mobile base stations have shown alterations in the cortisol level following exposure of humans to these sources. The aim of this study is to compare the level of cortisol among dentists and dentistry students who are being occupationally exposed to EMFs emitted by magnetostrictive cavitrons (case group) and among their counterparts who are not being exposed to these fields (control group).
In this case-control study, blood samples were collected from 41 dentists and dentistry students, 21 of whom were exposed to EMFs emitted by cavitrons as the case group and 20 who were not exposed as the control group, twice; i.e. before work (at 8:30-9:30 a.m.) and after work (11:30-12:30 a.m.). The samples were coded and the serum cortisol level was investigated using the ELISA method (Cortisol AccuBind ELISA Kits).
The serum cortisol level of dentists and dental students in the morning (before starting the work) in the control group was 189.15 ± 110.70 (mean ± SD) whereas it was 157.77 ± 112.03 in those who were occupationally exposed to EMFs produced by the use of cavitrons. This difference was not statistically significant (P = 0.373). In contrast, the serum cortisol level of the participants in the noon (after stopping the work) in the control group was 136.25 ± 67.91 (mean ± SD) while it was 88.58 ± 52.83 in those who were occupationally exposed to EMFs produced by the use of cavitrons. This time, the observed difference was statistically significant (P = 0.016). In this light, while the difference between serum cortisol levels of dentists and dental students in the morning and after stopping the work was not statistically significant (P = 0.06), in the EMF-exposed group the cortisol level decreased significantly from 157.77 ± 112.03 in the morning to 88.58 ± 52.83 in the noon (P = 0.001).
As far as we know, this is the first study that evaluated the effect of occupational exposure of dentists to EMFs on their serum cortisol level. The EMFs produced by magnetostrictive cavitrons can decrease the serum cortisol level in dentists. As cortisol plays an important role in blood pressure regulation, cardiovascular, and immune system function, a low cortisol level may threaten health. More studies are needed to clearly understand the effects of EMFs emitted by magnetostrictive cavitron on the level of stress hormones. As some studies have shown that exposure to EMFs has no effect on the cortisol level, whereas other studies reported either an increase or a decrease in the cortisol level, it can be concluded that the effects of exposure to EMFs may occur only at specific absorbed energies or energy absorption rates (usually known as window) similar to that exists in the case of exposure to the low doses of ionizing radiations.
一些研究表明，牙科是潜在暴露于高水平极低频磁场的工作类别之一。尽管如此，关于牙医职业暴露于这些磁场的信息却很匮乏。对其他常见电磁场源（如移动基站）的研究表明，人类暴露于这些源后，皮质醇水平会发生变化。本研究的目的是比较职业暴露于磁致伸缩超声治疗仪发出的电磁场的牙医和牙科专业学生（病例组）与未暴露于这些磁场的同行（对照组）的皮质醇水平。
在这项病例对照研究中，从41名牙医和牙科专业学生中采集血样，其中21人作为病例组暴露于超声治疗仪发出的电磁场，20人作为对照组未暴露于这些磁场，采集两次血样；即在工作前（上午8:30 - 9:30）和工作后（上午11:30 - 12:30）。对样本进行编码，并使用酶联免疫吸附测定法（皮质醇AccuBind酶联免疫吸附测定试剂盒）检测血清皮质醇水平。
对照组牙医和牙科专业学生上午（工作开始前）的血清皮质醇水平为189.15±110.70（均值±标准差），而职业暴露于使用超声治疗仪产生的电磁场的人员该水平为157.77±112.03。这种差异无统计学意义（P = 0.373）。相比之下，对照组参与者中午（工作结束后）的血清皮质醇水平为136.25±67.91（均值±标准差），而职业暴露于使用超声治疗仪产生的电磁场的人员该水平为88.58±52.83。此次观察到的差异具有统计学意义（P = 0.016）。据此，虽然牙医和牙科专业学生上午和工作结束后的血清皮质醇水平差异无统计学意义（P = 0.06），但在电磁场暴露组中，皮质醇水平从上午的157.77±112.03显著降至中午的88.58±52.83（P = 0.001）。
据我们所知，这是第一项评估牙医职业暴露于电磁场对其血清皮质醇水平影响的研究。磁致伸缩超声治疗仪产生的电磁场可降低牙医的血清皮质醇水平。由于皮质醇在血压调节、心血管和免疫系统功能中起重要作用，低皮质醇水平可能威胁健康。需要更多研究来清楚了解磁致伸缩超声治疗仪发出的电磁场对应激激素水平的影响。由于一些研究表明暴露于电磁场对皮质醇水平无影响，而其他研究报告皮质醇水平要么升高要么降低，因此可以得出结论，暴露于电磁场的影响可能仅在特定的吸收能量或能量吸收率（通常称为窗口）下发生，类似于低剂量电离辐射暴露的情况。
