Sweat- and urine-related water and mineral metabolism among workers with occupational heat exposure

  Objective  To examine water and mineral metabolism related to sweatiness and urination among workers under various levels of occupational heat exposure.

  Methods  Sweat and urine samples were collected among 226 workers engaged in operations in heat environment in an iron steel company in Tangshan city between June and July 2014. The amount of sweat and urine were measured and mineral elements in sweat and urine samples were detected. Sweat amount of the workers was estimated by measuring body weight before and after working.

  Results  The total sweat and urine excretion for all the participants was 3 560 ± 550 ml and 86.5 % of the excretion was via sweating during a work shift under the workplace temperature of 30 – 43 ℃ measured with the wet bulb globe temperature (WBGT). In sweat excretion, the concentration was 174.4 ± 39.6 mg/L for potassium (K), 1 229.2 ± 264.2 mg/L for sodium (Na), 33.4 ± 6.6 mg/L for calcium (Ca), 6.0 ± 1.11 mg/L for magnesium (Mg), 310.0 ± 60.8 μg/L for iron (Fe), 290.2 ± 68.4 μg/L for zinc (Zn), 29.9 ± 6.2 μg/L for copper (Cu), and 6.3 ± 1.5 μg/L for selenium (Se). The total mineral excretion via sweat and urine for a participant during a work shift was 586.5 ± 136.9 mg for K, 3 982.1 ± 831.0 mg for Na, 164.9 ± 25.4 mg for Ca, 61.2 ± 12.7 mg Mg, 962.9 ± 210.8 μg for Fe, 1 046.7 ± 269.6 μg for Zn, 112.4 ± 26.3 μg for Cu, and 38.0 ± 10.5 μg for Se, respectively. The excretions of K, Na, Ca, Fe, Zn, and Cu were mainly via sweat (81 % – 96 % of total excretion) and did not varied with the change of workplace temperature, but the excretion of Mg was mainly via urine (70 % of total excretion). The excertion of Se via sweat differed by the change of workplace temperature, with the proportions for total excretion of 36.5 %, 58.9 %, and 67.0 % under the workplace temperature of 30 – 34 ℃, 35 – 39 ℃, and 40 – 43 ℃, respectively.

  Conclusion  During working under high temperature, the excretion of sweat and mineral elements increase with the rise of workplace temperature but the urine discharge decreases, and excretions of body fluid, minerals such as K, Na, Ca, Fe, Zn, and Cu, and Se (under the workplace temperature of > 35 ℃) are mainly via sweating.