a Centers for Disease Control and Prevention , National Institute for Occupational Safety and Health, National Personal Protective Technology Laboratory , Pittsburgh , Pennsylvania.
b Human and Environmental Physiological Research Unit, Faculty of Health Sciences , University of Ottawa , Ottawa , Ontario , Canada.
J Occup Environ Hyg. 2019 Jul;16(7):467-476. doi: 10.1080/15459624.2019.1612523. Epub 2019 May 20.
This study examined whether different combinations of ambient temperature and relative humidity for the effective wet bulb globe temperature, in conjunction with two different levels of clothing adjustment factors, elicit a similar level of heat strain consistent with the current threshold limit value guidelines. Twelve healthy, physically active men performed four 15-min sessions of cycling at a fixed rate of metabolic heat production of 350 watts. Each trial was separated by a 15-min recovery period under four conditions: (1) Cotton coveralls + dry condition (WD 45.5 °C dry-bulb, 15% relative humidity); (2) Cotton coveralls + humid condition (WH: 31 °C dry-bulb, 84% relative humidity); (3) Protective clothing + dry condition (PD 30 °C dry-bulb, 15% relative humidity); and (4) Protective clothing + humid condition (PH 20 °C dry-bulb, 80% relative humidity). Gloves (mining or chemical) and headgear (helmet or powered air-purifying respirator) were removed during recovery with hydration . Rectal temperature (Tre), skin temperature (Tsk), physiological heat strain (PSI), perceptual heat strain (PeSI), and body heat content were calculated. At the end of the 2-hr trials, Tre remained below 38 °C and the magnitude of Tre elevation was not greater than 1 °C in all conditions (WD: 0.9, WH: 0.8, WH: 0.7, and PD: 0.6 °C). However, Tsk was significantly increased by approximately 2.1 ± 0.8 °C across all conditions (all p ≤ 0.001). The increase in Tsk was the highest in WD followed by PD, WH, and PH conditions (all p ≤ 0.001). Although PSI and PeSI did not indicate severe heat strain during the 2-hr intermittent work period, PSI and PeSI were significantly increased over time (p ≤ 0.001). This study showed that core temperature and heat strain indices (PSI and PeSI) increased similarly across the four conditions. However, given that core temperature increased continuously during the work session, it is likely that the American Conference of Governmental Industrial Hygienist's TLV upper limit core temperature of 38.0 °C may be surpassed during extended work periods under all conditions.
本研究旨在探讨不同的环境温度和有效湿球温度的相对湿度组合，结合两种不同水平的服装调节因素，是否会产生与当前阈限值指南一致的相似水平的热应激。12 名健康、体力活跃的男性在固定的 350 瓦代谢产热率下进行了 4 次 15 分钟的骑行。每个试验之间间隔 15 分钟恢复期，在以下四种条件下进行：（1）棉工作服+干燥条件（WD，45.5°C 干球温度，15%相对湿度）；（2）棉工作服+潮湿条件（WH，31°C 干球温度，84%相对湿度）；（3）防护服+干燥条件（PD，30°C 干球温度，15%相对湿度）；（4）防护服+潮湿条件（PH，20°C 干球温度，80%相对湿度）。在恢复期内，脱下手套（采矿或化学）和头饰（头盔或动力空气净化呼吸器）并补水。计算直肠温度（Tre）、皮肤温度（Tsk）、生理热应激（PSI）、感知热应激（PeSI）和体热含量。在 2 小时试验结束时，Tre 仍低于 38°C，所有条件下 Tre 升高幅度均不超过 1°C（WD：0.9，WH：0.8，WH：0.7，PD：0.6°C）。然而，所有条件下 Tsk 均显著升高约 2.1±0.8°C（所有 p≤0.001）。WD 条件下 Tsk 升高最高，其次是 PD、WH 和 PH 条件（所有 p≤0.001）。尽管 PSI 和 PeSI 在 2 小时间歇性工作期间没有表明严重的热应激，但 PSI 和 PeSI 随时间显著增加（p≤0.001）。本研究表明，在四个条件下，核心温度和热应激指数（PSI 和 PeSI）的增加相似。然而，由于在工作期间核心温度持续升高，在所有条件下，美国政府工业卫生学家会议 TLV 上限核心温度 38.0°C 可能会在延长的工作期间内超过。
