Supplementary information files for Quantifying the impact of heat on human physical work capacity; part II: the observed interaction of air velocity with temperature, humidity, sweat rate, and clothing is not captured by most heat stress indices

Supplementary files for article Quantifying the impact of heat on human physical work capacity; part II: the observed interaction of air velocity with temperature, humidity, sweat rate, and clothing is not captured by most heat stress indices.Increasing air movement can alleviate or exacerbate occupational heat strain, but the impact is not well defined across a wide range of hot environments, with different clothing levels. Therefore, we combined a large empirical study with a physical model of human heat transfer to determine the climates where increased air movement (with electric fans) provides effective body cooling. The model allowed us to generate practical advice using a high-resolution matrix of temperature and humidity. The empirical study involved a total of 300 1-h work trials in a variety of environments (35, 40, 45, and 50 °C, with 20 up to 80% relative humidity) with and without simulated wind (3.5 vs 0.2 m∙s−1), and wearing either minimal clothing or a full body work coverall. Our data provides compelling evidence that the impact of fans is strongly determined by air temperature and humidity. When air temperature is ≥ 35 °C, fans are ineffective and potentially harmful when relative humidity is below 50%. Our simulated data also show the climates where high wind/fans are beneficial or harmful, considering heat acclimation, age, and wind speed. Using unified weather indices, the impact of air movement is well captured by the universal thermal climate index, but not by wet-bulb globe temperature and aspirated wet-bulb temperature. Overall, the data from this study can inform new guidance for major public and occupational health agencies, potentially maintaining health and productivity in a warming climate.

本文补充文件针对《量化热量对人体体力工作能力影响》一文的第二部分进行了研究，探讨了风速与温度、湿度、出汗率和衣物之间的交互作用，而这种交互作用并未被大多数热应激指数所捕捉。增加空气流动可以缓解或加剧职业热应激，但其影响在广泛的热环境中并不明确，且与不同的衣物水平相关。因此，本研究结合了一项大规模的实证研究与人体热传递的物理模型，以确定在哪些气候条件下增加空气流动（使用电风扇）能够有效降低体温。该模型允许我们利用高分辨率的温度和湿度矩阵生成实用的建议。实证研究包括在多种环境下（35°C、40°C、45°C和50°C，相对湿度从20%至80%），在有无模拟风（3.5 m∙s−1 vs 0.2 m∙s−1）的情况下，穿着最小限度的衣物或全身工作服的共计300次1小时的工作试验。我们的数据提供了强有力的证据，证明风扇的影响强烈取决于空气温度和湿度。当空气温度达到或超过35°C时，在相对湿度低于50%的情况下，风扇无效且可能有害。我们的模拟数据还显示了考虑热适应、年龄和风速时，高风速/风扇有益或有害的气候条件。使用统一的天气指数，空气流动的影响被普遍热气候指数所充分捕捉，但并非湿球温度和吸气湿球温度。总体而言，本研究的数据可以为主要的公共卫生和职业健康机构提供新的指导，有助于在变暖的气候中维持健康和生产力。