海口市公交司机全身振动暴露特征与健康风险评价方法比较研究
Whole-body vibration exposure characterization in bus drivers of Haikou City: A comparison between two health risk assessment methods
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摘要:
背景 长期暴露于全身振动（WBV）影响职业司机身体健康，对城市公交司机暴露的WBV特征与健康风险的研究尚不充分。
目的 分析海口市公交集团3家分公司31条线路的公交车司机驾驶过程中的WBV暴露特征，探索公交车司机WBV相关的职业健康风险评估方法。
方法 从海口市公交集团3家分公司运营的142条线路中按比例共抽取31条线路，监测31位公交车司机在驾驶过程中的WBV暴露情况。在公交司机驾驶座椅位置安装六通道人体全身振动测量仪，测量司机驾驶时长内的x、y、z三轴向的频率计权加速度（
a wx、a wy、a wz）与三轴向波峰因数（CFx、CFy、CFz）数据。应用基于a w的8 h频率计权加速度的均方根值A(8)与基于振动剂量（VDV）的日暴露振动剂量VDV(8)两种方法，参考ISO 2631-1:1997标准对A(8)与VDV(8)推荐的行动限值与暴露限值，将WBV的健康风险分级为高、中、低三个水平，对3家分公司的公交线路的WBV健康风险进行分级评价；并采用Fisher's精确法，分析A(8)与VDV(8)两种评价方法的差异性。结果 研究对象的WBV合成加速度（
a v）范围为0.321~0.680 m·s−2，监测区间VDV与VDV(8)的范围分别为3.824~10.174 m·s−1.75与6.039~13.505 m·s−1.75。a v的均数加减标准差为（0.480±0.100）m·s−2 ，监测区间的VDV为（6.987±2.737）m·s−1.75，VDV(8)为（9.773±4.540）m·s−1.75。aw x与aw z，a v与aw z存在较强的正相关，CFx与CFy，CFy与CFz存在较强的正相关。分别采用A(8)与VDV(8)两种评价方法对公交线路WBV健康风险进行评价，未呈现“高健康风险”水平。采用A(8)评价“低健康风险”水平的线路数为26条，而采用VDV(8)评价“低健康风险”水平的线路数为12条。3家分公司采用两种方法评价的风险等级结果一致的线路数分别为6、6、5条，一致率分别为66.7%（6/9）、54.6%（6/11）和45.5%（5/11）。两种评价方法对WBV健康风险评价的差异不具有统计学意义。结论 三轴向加速度间和三轴向波峰因数间存在正相关。在城市铺装路面条件下，使用A(8)与VDV(8)两种方法对公交线路进行健康风险等级评价结果无差异。
Abstract:Background Long-term exposure to whole-body vibration (WBV) will affect the health of occupational drivers. However, research on the characteristics of WBV exposure by urban bus drivers and health risk evaluation is still insufficient.
Objective To identify the characteristics of occupational WBV exposure of bus drivers serving 31 bus routes provided by three branches of Haikou Public Transport Group, and to evaluate their occupational health risks related to WBV.
Methods A total of 31 out of 142 bus routes run by three branches of Haikou Public Transport Group were selected to monitor WBV exposure of 31 bus drivers during driving. WBV parameters such as triaxial frequency weighted acceleration (
a wx,a wy,a wz) and triaxial crest factor (CFx, CFy, CFz) of the drivers were determined with a six-channel human vibration meter. Two methods, 8-hour daily value of the weighted root mean square average weighted vibration A(8) based ona w and 8-hour daily value of vibration dose VDV(8) based on vibration dose value (VDV), were used for health risk assessment and classified WBV health risk results into three levels (high, medium, and low) by the exposure action value (EAV) and exposure limit values (ELV) for A(8) and VDV(8) recommended by ISO 2631-1:1997. The two evaluation methods, A(8) and VDV(8), were compared by Fisher's exact test.Results Regarding the WBV parameters, the vector sum of acceleration (
a v) was 0.321-0.680 m·s−2, the VDV of monitoring interval was 3.824-10.174 m·s−1.75, and the VDV(8) was 6.039-13.505 m·s−1.75; their values in mean ± standard deviation were (0.480±0.100) m·s−2, (6.987±2.737) m·s−1.75, and (9.773±4.540) m·s−1.75, respectively. Positive correlations were found betweenaw x andaw z,a v andaw z, CFx and CFy, CFy and CFz. No bus route's WBV exposure level was graded as high health risk by either A(8) or VDV(8). The number of routes graded as low health risk by A(8) was 26, while the number by VDV(8) was 12. The consistency rates of health risk levels evaluated by the two methods were 66.7% (6/9), 54.6% (6/11), and 45.5% (5/11) for the three bus group branches, respectively. The difference in WBV health risk assessment results between the two evaluation methods was not statistically significant.Conclusion Positive correlations are found between triaxial acceleration and triaxial crest factor. There is no difference in the results of using A(8) and VDV(8) to evaluate health risks of WBV in urban bus routes.
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