高强度甚低频电磁辐射对外毛细胞影响的初步研究

Possible outer hair cells hazards from occupational exposure to very low frequency electric and magnetic fields:a pilot study

目的:了解高强度甚低频电磁辐射作业环境中作业人群的职业暴露现状及其内耳功能的变化。方法:以某高强度甚低频电磁辐射作业环境中作业人群为调研对象并将其分为长期暴露组(>5年)、短期暴露组(<5年)及对照组。应用电磁辐射场强仪和噪声分析仪对作业现场不同工作岗位的作业环境进行电磁辐射强度测试和噪声强度测试,观察作业环境的电磁污染和噪声污染现状。调研采取现场问卷调查的形式。所有调研对象均进行纯音测听(PTA)和DPOAE测试,对于PTA或DPOAE异常的研究对象进行ABR测试。结果:作业场所的电场频率为20kHz,电场强度在21～38kV/m,超出中国标准;噪声强度在52～65dBHL(安全范围)。问卷调查结果提示,长期暴露组中头痛、失眠、耳鸣的发生率明显升高;DPOAE检测结果显示,长期暴露组异常率高于其他2组;DPOAE检测结果显示,长期暴露组在676,933,3 616,5 130,7 253Hz频率的幅值低于短期暴露组和对照组,而短期组和对照组间无明显差别。对DPOAE异常的调研对象行ABR检测未发现异常。结论:该作业环境的电磁辐射强度已严重超出健康标准。DPOAE检测结果提示高强度甚低频电磁辐射的长期暴露可能会引起外毛细胞轻度、散在的改变,有必要及时采取有效地防护措施。

Objective： Our purpose was to investigate occupational high-strength very low frequency electric and magnetic fields（VLF EMFs） and assess changes of function of the inner ear. Method： The people exposed to high-strength VLF EMFs were divided into three groups： long term exposure group（〉5 years）, short-term ex- posure group（〈5 years）and the control group. The field intensity indicator and noise analyzer were employed for the examination of the electromagnetic energy intensity and noise value at the working sites. Self-administered questionnaire was adopted. Universal hearing screening by pure tone audiometry（PTA） and distortion product otoacoustic emission（DPOAE） were done. The subjects who failed the screening tests were confirmed with audito- ry brainstem response（ABR） test. Result.. The frequency of the electromagnetic field was 20 kHz, the average elec- tric power density in job locations was 21-38 kV/m, which was higher than national standard（〈5 kV/m）. Av- erage noise-level in job locations was 52-65 dBHL, which was within the standard. Questionnaire presented that VLF EMFs might increase the incidence of headache, insomnia and tinnitus in long-term exposure. The incidence of abnormal DPOAE was higher in the subjects of the long-term exposure group than the short-term exposure group and the control group（P〈0. 01）. At 676, 933, 3616, 5130, 7253 Hz, the DPOAE amplitudes of the long term exposure group workers were significantly lower than the short-term exposure group and the control group. There was no obvious difference of the incidence of abnormal DPOAE between the short-term exposure group and the control group. The result of ABR with those subjects with abnormal DPOAE were no significant abnormali- ties. Conclusion：The average electric power density in job locations was significant worse than health standards. The changes of DPOAE indicated that the exposure to high-strength VLF EMFs had a subtle, discreet and local- ized impairing effect on outer hair cells. Effective intervention measures should be taken.