Evaluation of physical/chemical synergistic influence of the working environmental factor on hearing, and the application to the comfortable environment.

为了阐明工作环境因素对听力的物理/化学协同影响的评价，并在舒适环境中应用，进行了动物实验，并对男性工人进行了检查。实验对象是雄性豚鼠。采用听觉脑干反应测定听阈。第一个实验仅针对甲醇暴露，甲醇吸入水平为500 ppm、900 ppm、1500 ppm、1900 ppm、2400 ppm和3000 ppm。第一个实验的结果表明，甲醇吸入超过1900ppm的剂量依赖性地增加了听力阈值。第二个实验仅针对噪声暴露，噪声暴露水平为90、100和105 dB SPL。105 dB组的检测阈值显著升高。在第三个实验中，豚鼠暴露于1500 ppm或1900 ppm的甲醇作为亚耳毒性浓度，并在100 dB SPL白噪声的亚耳毒性水平下暴露。在联合组…More中，检测阈值明显增加。1900 ppm甲醇加噪声组的检测阈值增幅最大。本文测定了职业性有机溶剂和噪声环境下93名男性工人的听力水平和听力上限。进行了环境监测、生物监测和工作场所噪声水平测量。大多数有机溶剂和/或噪音的暴露水平都在职业暴露限度之内。听力上限低于75百分位曲线的患病率在接触有机溶剂和噪声的工人中较高，而接触5年及以上的工人听力上限降低。这种减少是剂量依赖性的，与呼吸区空气中的苯乙烯浓度和尿液中的扁桃酸浓度有关。结果表明，即使暴露在职业暴露限值内，也应考虑有机溶剂和噪声对听力的可能协同效应。少

To clarify of evaluation of physical/chemical synergistic influence of the working environmental factor on hearing, and the application to the comfortable environment, animal experiments were carried out, and the male workers were examined.The subjects were male guinea pigs. Hearing threshold was measured by auditory brainstem response. The first experiment was only for methanol exposure, and methanol inhalation levels were 500 ppm, 900 ppm, 1500 ppm, 1900 ppm, 2400 ppm and 3000 ppm. The results of the first experiment demonstrated that methanol inhalation more than 1900ppm dose-dependently increased the hearing threshold. The second experiment was only for noise exposure, and noise exposure levels were 90, 100 and 105 dB SPL. The detection threshold in the 105 dB group was significantly increased. In the third experiment, guinea pigs were exposed to 1500 ppm or 1900 ppm methanol as sub-ototoxic concentration following 100 dB SPL white noise as sub-ototoxic level. In the combined group … More , the marked increase in the detection threshold was observed. The increase detection threshold was the greatest in the group of 1900 ppm methanol combined with noise.We measured hearing level and upper limit of hearing in 93 male workers occupationally exposed to organic solvents and noise. Environmental monitoring, biological monitoring and noise level measurement in workplaces were done. Most exposure level of organic solvents and/or noise were within the occupational exposure limits. The prevalence rate of upper limit of hearing below 75th percentile curve was higher in workers exposed to organic solvents and noise, and the upper limit of hearing was reduced in workers who were exposed for 5 years or more. This reduction was dose-dependent and was related to styrene concentrations in breathing-zone air and mandelic acid concentrations in urine. The results suggest that the probable synergistic effect of organic solvents and noise on hearing should be considered even when the exposures are within the occupational exposure limits. Less