Occupational heat strain in a hot underground metal mine

Objective: In a hot underground metal mine, this study evaluated the relationship between job task, physical body type, work shift, and heat strain. Methods: Thirty-one miners were evaluated during 98 shifts while performing deep shaft-sinking tasks. Continuous core body temperature, heart rate, pre-and postshift urine specific gravity (USG), and body mass index were measured. Results: Cutting and welding tasks were associated with significantly (P < 0.05) increased core body temperature, maximum heart rate, and increased postshift urine specific gravity. Miners in the obese level II and III body mass index categories, as well as those working night shift, had lower core body temperatures (P < 0.05). Conclusions: This study confirms that job task, body type, and shift are risk factors for heat strain.