URINARY-EXCRETION OF HOMOVANILLIC-ACID IN WORKERS EXPOSED TO MANGANESE

Homovanillic acid, an end product of dopamine catabolism, and manganes e (Mn) were measured in the urine of 68 male workers exposed to Mn-con taining dust in a dry alkaline battery plant or an Mn oxide and salt p roducing plant, and in 35 control male subjects. The geometric mean of the airborne concentration of inhalable (total) dust amounted to 0.95 and 1.37 mg/m3 in the dry alkaline battery plant and the Mn oxide and salt producing plant, respectively. In the latter, a higher prevalenc e of increased values of urinary homovanillic acid concentration was f ound. In the total population, there was a low but statistically signi ficant positive correlation between the concentration of homovanillic acid and Mn in urine (r = 0.20, P = 0.04) but there was no significant correlation between the level of homovanillic acid in urine and Mn in airborne dust or duration of exposure. This observation might be comp atible with the stimulation of dopamine turnover in the brain, which h as been observed in the early phase of Mn intoxication in animals. How ever, the large variability in urinary homovanillic acid excretion in control subjects precludes the use of this biological indicator to det ect early interference of Mn with the dopaminergic system.