Work in the cold. Review of methods for assessment of cold exposure.

The obvious hazard of a cold exposure under natural as well as artificial conditions is tissue cooling and the associated sequel of more or less harmful effects from cold injury to discomfort. The nature, risk and magnitude of effects depend largely on the cooling effect, which results from the interaction of climatic factors (air temperature, mean radiant temperature, humidity and wind), protection (clothing) and metabolic heat production (activity). Assessment of cold stress should be based on methods which measure or predict this cooling effect in a relevant and reliable way. The nature of cooling encompasses (1) whole-body cooling, (2) extremity cooling, (3) convective cooling (wind chill), (4) conductive cooling (contact) and (5) airway cooling. The review contains a description of methods for evaluation of the various types of cold stress, as well as a discussion of their capacity and limitations. On the basis of selected methods, recommendations related to lowest permissible temperatures and other measures are discussed and compared with published data. Apparently, local cooling in most cases produces discomfort and harmful effects, before more significant whole-body cooling develops. With strong wind or movement at very low temperature, frostnip of unprotected skin may quickly develop. For most other conditions extremity (digit) cooling determines duration of exposure. However, as digit cooling largely depends on whole-body heat balance, it is important to control body cooling by selection and use of appropriate protective clothing.