Urinary excretion of mercury, copper and zinc in subjects exposed to mercury vapour.

The excretion of mercury, copper and zinc in urine, and mercury in whole blood and plasma, was determined in 40 chloralkali workers exposed to mercury vapour and 40 age-matched referents. The Hg concentrations in whole blood, plasma and urine were higher in the exposed group (35 nmol l-1, 30 nmol l-1, and 11.5 nmol mmol-1 creatinine, respectively) in comparison with the reference group (15 nmol l-1, 6.3 nmol l-1, and 1.8 nmol mmol-1 creatinine, respectively). The urinary copper excretion was similar in the two groups, while U-Zn excretion was significantly higher (P = 0.04) in the exposed group, median 0.83 mumol mmol-1 creatinine versus 0.76 munmol mmol-1 creatinine in the reference group. In a subgroup of exposed workers with current U-Hg above 11.5 nmol l-1 mmol-1 creatinine (20 micrograms g-1 creatinine) the median U-Zn was 1.1 mumol mmol-1 creatinine. In both groups smokers had high U-Zn levels than non smokers. When both U-Hg and smoking were taken into account in a linear regression model, there was a significant association between U-Hg and U-Zn in the combined group of exposed and referents (P = 0.002). This study indicates that mercury exposure in humans, as in animals, causes increased urinary excretion of zinc. The mechanisms may be induced synthesis of metallothionein in the kidneys, displacement of Zn from preexisting metallothionein by Hg, or a decreased reabsorption of zinc in the kidneys owing to a slight tubular dysfunction.