Changes in Urinary Biochemistry in Machinists Exposed to a Hot Environment

Lee, Jong Min; Lee, Nam Kyu; Park, Young Ho

Abstract

PURPOSES: To demonstrate changes in urinary biochemistry that lead to a supersaturation of some salt, which makes a higher prevalence of urinary stone in workers chronically exposed to a hot environment and massive sweating.
MATERIALS AND METHODS
The study was performed at a metal plant and exposure to heat stress was estimated by the Wet Bulb Globe Temperature climatic index. Stone risk profile from our laboratory included volume, specific gravity, creatinine, sodium, potassium, calcium, magnesium, chloride, uric acid, phosphorus and pH. On a randomly selected sample of 19 workers exposed and 19 workers not exposed to heat stress without any evidence of stone disease, and family history of nephrolithiasis or predisposing factors such as gout, we performed a stone risk profile by collecting the urine during the 8-hour work shift for 1 consecutive days. The independent student t-test was used to compare each parameter between the different groups.
RESULTS
Among a randomly selected urine sample of 19 workers exposed and 19 workers not exposed to heat stress without any evidence of stone disease, significant differences were found in fluid intake (2816.0+/-1981.0 ml. versus 1200.0+/-4147.0), and concentration of creatinine (1481.0+/-691.0 ml./l. versus 1032.0+/-574.0), sodium (201.0+/-55.0 mg./l. versus 147.4+/-58.0), calcium (202.0+/-76.0 mg./l. versus 132.0+/-71.0), uric acid (475.0+/-138.0 mg./l. versus 359.0+/-196.0), phosphorus (638.0+/-283.0 mg./l. versus 328.0+/-196.0), pH(6.05+/-0.61 versus 6.72+/-0.92), specific gravity(1.029+/-0.005 versus 1.014+/-0.006) respectively.
CONCLUSIONS
This study confirms the concept that heat stress represents a real lithogenic risk factors. Therefore, we recommend adequate fluid intake during hot occupations.