Department of Electrical Engineering and Automation, Aalto University, Espoo, Finland.
Phys Med Biol. 2020 Oct 22;65(21):215006. doi: 10.1088/1361-6560/aba21e.
The International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines and the Institute of Electrical and Electronics Engineers (IEEE) standard establish safety limits for human exposure to electromagnetic fields. At low frequencies, only a limited number of computational body models or simplified geometrical shapes are used to relate the internal induced electric fields and the external magnetic fields. As a consequence, both standard/guidelines derive the exposure reference levels for the external magnetic field without considering the variability between individuals. Here we provide quantitative data on the variation of the maximum electric field strengths induced in the brain of 118 individuals when exposed to uniform magnetic fields at 50 Hz. We found that individual characteristics, such as age and skull volume, as well as incident magnetic field direction, have a systematic effect on the peak electric field values. Older individuals show higher induced electric field strengths, possibly due to age-related anatomical changes in brain. Peak electric field strengths are found to increase for larger skull volumes, as well as for incident magnetic fields directed along the lateral direction. Moreover, the maximum electric fields provided by the anatomical models used by ICNIRP for deriving exposure limits are considerably higher than those obtained here. On the contrary, the IEEE elliptical exposure model produces a weaker peak electric field strength. Our findings are useful for the revision and harmonization of the current exposure standard and guidelines. The present investigation reduces the dosimetric uncertainty of the induced electric field among different anatomical induction models. The obtained results can be used as a basis for the selection of appropriate reduction factors when deriving exposure reference levels for human protection to low-frequency electromagnetic exposure.
国际非电离辐射防护委员会 (ICNIRP) 指南和电气和电子工程师协会 (IEEE) 标准为人体暴露于电磁场制定了安全限值。在低频下，仅使用少数计算体模型或简化的几何形状来将内部感应电场与外部磁场联系起来。因此，标准/准则都没有考虑个体之间的差异，而是根据外部磁场推导了暴露参考水平。在这里，我们提供了 118 个人在 50Hz 均匀磁场下暴露时大脑中感应的最大电场强度变化的定量数据。我们发现，个体特征，如年龄和颅骨体积，以及入射磁场方向，对峰值电场值有系统影响。年龄较大的个体显示出更高的感应电场强度，这可能是由于大脑与年龄相关的解剖变化所致。对于较大的颅骨体积以及沿横向方向的入射磁场，峰值电场强度会增加。此外，ICNIRP 用于推导暴露限值的解剖模型提供的最大电场强度明显高于此处获得的值。相反，IEEE 椭圆暴露模型产生的峰值电场强度较弱。我们的研究结果有助于修订和协调当前的暴露标准和准则。本研究降低了不同解剖感应模型中感应电场的剂量不确定性。获得的结果可以用作在推导低频电磁暴露的人体保护暴露参考水平时选择适当的降低因子的基础。
