Study on exposure assessment of heat stress and the combined effects of heat stress and noise exposure
Date Issued
2007
Date
2007
Author(s)
Juang, Yow-Jer
DOI
zh-TW
Abstract
The heat stress is one of major occupational and environmental health issues for workers and residents in the tropical and subtropical areas. The prevention of heat-related illness caused by heat stress is always the important topic for occupational hygiene practitioners, especially in Taiwan with hot and humid climate. The aims of this study are to develop the assessment techniques for thermal exposure of and health effects with simultaneous exposure to heat and noise. A climate chamber made of steel plate packed with polyurethane foam was optimized and used for the experiment.
For the thermal exposure assessment technique, we first developed 81 experimental conditions of different environmental parameters to evaluate effects of natural wet bulb temperature and globe temperature. Second, 131 sets of experimental data including air temperatures, relative humidities, globe temperatures, air velocities and natural wet bulb temperatures were generated with the prediction model of natural wet bulb temperature and analyzed using multiple regression analysis. Designed thermal and noise exposure conditions were simulated in the chamber to study the combined effects among volunteers who had received medical examination before the experiment. The L9 orthogonal array of different levels of wet bulb globe temperature, noise intensity, exposure duration and workload was determined by adopting Taguchi’s method.
It was found that globe temperature increases with the size of globe and radiant temperature when radiant heat appears, but decreases with the increasing air velocity. However, the change of relative humidity has no effect on the measurement of globe temperature. In addition, the increasing response time of globe temperature is observed for greater globe size. For air velocity smaller than 2.60 m/s, natural wet bulb temperature was found to be greater than psychrometric temperature. And measurement of natural wet bulb temperature will increase with air temperature, relative humidity and radiant temperature, but the trend is reversed when air velocity increases. Therefore, greater air velocity will result in smaller natural wet bulb temperature, globe temperature and wet bulb globe temperature, which leads to the misjudgment on heat stress. According to multiple regression analysis, it was found that natural wet bulb temperature is highly correlated with the environmental parameters. The prediction model is expressed as Tnwb = 0.81×Ta + 0.05×Tg + 0.15×RH - 0.35×Va - 9.98 (R=0.996), and the error is within 1 ℃. From the investigation of combined effects of heat and noise and workload exposure, it was observed that the temporary threshold shift driven by noise exposure is enhanced by heat and workload. The recovery time of temporary threshold shift is determined by the degree of hearing loss after noise exposure.
In conclusion, this study proposed wet bulb globe temperature obtained by prediction model as a heat stress index for the prevention of heat-related illness. Further research on health effect induced by combined exposure of chemical and physical agents are suggested to meet the problem of global warming.
Subjects
熱暴露艙
綜合溫度熱指數
自然濕球溫度
黑球溫度
噪音
複合效應
Thermal exposure chamber
wet bulb globe temperature
natural wet bulb temperature
globe temperature
noise
combined effects
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-96-D87844001-1.pdf
Size
23.31 KB
Format
Adobe PDF
Checksum
(MD5):3dc09cf9cda24271f56216eeaaeeab08