Bernard Thomas E, Iheanacho Ivory
a College of Public Health , University of South Florida , Tampa Florida.
J Occup Environ Hyg. 2015;12(5):323-33. doi: 10.1080/15459624.2014.989365.
Ambient temperature and relative humidity are readily ava-ilable and thus tempting metrics for heat stress assessment. Two methods of using air temperature and relative humidity to create an index are Heat Index and Adjusted Temperature. The purposes of this article are: (1) to examine how well Heat Index and Adjusted Temperature estimated the wet bulb globe temperature (WBGT) index, and (2) to suggest how Heat Index and Adjusted Temperature can be used to screen for heat stress level. Psychrometric relationships were used to estimate values of actual WBGT for conditions of air temperature, relative humidity, and radiant heat at an air speed of 0.5 m/s. A relationship between Heat Index [°F] and WBGT [°C] was described by WBGT = -0.0034 HI(2) + 0.96 HI - 34. At lower Heat Index values, the equation estimated WBGTs that were ± 2 °C-WBGT around the actual value, and to about ± 0.5 °C-WBGT for Heat Index values > 100 °F. A relationship between Adjusted Temperature [°F] and WBGT [°C] was described by WBGT = 0.45 Tadj - 16. The actual WBGT was between 1 °C-WBGT below the estimated value and 1.4 °C-WBGT above. That is, there was a slight bias toward overestimating WBGT from Adjusted Temperature. Heat stress screening tables were constructed for metabolic rates of 180, 300, and 450 W. The screening decisions were divided into four categories: (1) < alert limit, (2) < exposure limit, (3) hourly time-weighted averages (TWAs) of work and recovery, and (4) a caution zone for an exposure > exposure limit at rest. The authors do not recommend using Heat Index or Adjusted Temperature instead of WBGT, but they may be used to screen for circumstances when a more detailed analysis using WBGT is appropriate. A particular weakness is accounting for radiant heat; and neither air speed nor clothing was considered.
环境温度和相对湿度易于获取，因此是用于热应激评估颇具吸引力的指标。利用气温和相对湿度创建指数的两种方法是热指数和校正温度。本文的目的是：（1）研究热指数和校正温度对湿球黑球温度（WBGT）指数的估计效果如何，以及（2）建议如何利用热指数和校正温度来筛查热应激水平。利用心理测量关系来估计在风速为0.5米/秒时气温、相对湿度和辐射热条件下的实际WBGT值。热指数[°F]与WBGT[°C]之间的关系由WBGT = -0.0034HI² + 0.96HI - 34描述。在较低的热指数值时，该方程估计的WBGT值在实际值上下±2°C - WBGT范围内，对于热指数值>100°F的情况，约为±0.5°C - WBGT。校正温度[°F]与WBGT[°C]之间的关系由WBGT = 0.45Tadj - 1十六描述。实际WBGT在估计值以下1°C - WBGT到以上;1.4°C - WBGT之间。也就是说，校正温度对WBGT的估计存在轻微高估偏差。针对180、300和450瓦的代谢率构建了热应激筛查表。筛查决策分为四类：（1）<警戒限值，（2）<暴露限值，（3）工作和恢复的每小时时间加权平均值（TWA），以及（4）休息时暴露>暴露限值的警戒区。作者不建议用热指数或校正温度代替WBGT，但在适合使用WBGT进行更详细分析的情况下，它们可用于筛查相关情况。一个特别的不足是未考虑辐射热；且未考虑风速和衣物因素。
