Work Physiological Study on Thermal Loads Caused by Body cooling during Intermittent and Repeated cold exposure

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The purpose of this research was to elucidate the characteristics of cold defense response and associated thermal loads caused by such intermittent and repeated cold exposure as observed in daily cold work. To achieve this, we carried out both the experimental studies in an artificial climatic chamber and the surveys in some cold work places.The main results obtained were as follows :1. The intermittent finger cooling experiment revealed that subjective judgment such as cold pain and cold sensation is not always a reliable and sensitive index for monitoring the risk of excessive peripheral cooling and frostbite formation.2. The whole body cold exposure experiment found that repeated cold exposure, even interposed with warm rest, caused successive body core cooling, increased cardiovascular load and decreased manual performance. The subjective thermal comfort and warm sensation at each warm rest were found to be not reliable indices for monitoring hypothermic state and increased thermal … More loads at the time. This phenomenon could be explained by a multiplicative interaction between skin surface and body core temperatures in the generation of thermoregulatory effector responses.3. The field surveys in refrigerated warehouse industry, outdoor work in winter and food industry found that many workers had excessive cooling of the peripheral part and whole body without noticing them. The surveys supported our experimental finding mentioned above and also showed that thermal insulation of cold protective clothing the workers chose by their self-judgment was insufficient for their cold work.4. These results suggested that planning work-rest schedule and using cold protective equipment (CPE) at cold work based on workers' subjective judgment are liable to cause them excessive body cooling and increased thermal loads without noticing.5. To prevent these health risks, we need to establish a rational management system for cold work. As one of our approaches for achieving this, we plan to standardize a test method for evaluating thermal protective performance of CPE and to propose a cold exposure limit based on the test results. Less