Physiological monitoring of heat stress in UK coal mines

Heat stress is a potential problem in UK coal mines due to high temperatures and humidities, and high metabolic rates. Hanson and Graveling (1997) produced a Code of Practice on reducing the risk of heat strain in UK coal mines; this study measured the physiological response of miners at work to identify the extent of heat strain and determine the appropriateness of the environmentaltemperature levels outlined in the Code of Practice above which action should be taken to reduce the risk of heat strain.Miners at three hot and humid UK coal mines were studied; Basic Effective Temperatures (BETs)were mostly in the range 26-32�C. Data were collected on 30 miners working in a total of 155 shifts.The miners’ auditory canal temperatures (tac) and related work activity were recorded at regular intervals during the shift. Environmental temperatures were also recorded for each shift. Over 1100Uc data points were obtained. Readable heart rate recordings were made for 44 shifts.Auditory canal temperatures (tac) in excess of 38.0�C were recorded in 9% of the measurements and those in excess of 38.5�C were recorded in 3%. tac increased with increasing BET, with an increase of 10�C BET associated with an increase in tac of 0.4�C. tac values in excess of 38.5�C were unlikely at BETs of less than 27�C. tac also increased with increasingly heavy workload.Symptoms of heat related ill health were reported for 15% of the shifts for which self-reported data were available (129 shifts). Fluid replacement was estimated to be an average of 0.45 Ih-1, which appears to be inadequate.