EXPOSURE TO METALLIC MERCURY IN WORKERS IN A TROPICAL CHLORALKALI PLANT EVALUATED THROUGH URINE ANALYSIS, RIO-DE-JANEIRO, BRAZIL

Occupational exposure to Hg vapour was investigated in 78 workers duri ng three periods with different temperatures: August 1991, December 19 91, and February 1992. Each individual was sampled twice in each perio d; before and after a six working days period (with a two free days in terval). As an attempt to normalise Hg excretion urine was sampled alw ays after a normal 8 hours night sleeping and immediately frozen. Mine ralisation was done with acid and oxidant mixture and determination by cold vapour Atomic Absorption Spectrophotometry (Varian VGA-76 and AA -1475). Analytical accuracy was controlled by routine analysis of cert ified reference material (Seronorm TM trace elements, Nycome As diagno stics Olso - Norway) and all samples were analysed in triplicates. Of a total of 355 samples analysed 13% were over the maximum limit for oc cupational exposure (50 mu g . l(-1) or ppb). From the 78 individuals investigated 13% presented average value smaller than 10 ppb; just 8% had the average over 50 ppb; 64% showed averages smaller than 30 ppb; and 28% were between 30 and 50 ppb. Seasonal variation was observed wi th the highest values in the hottest periods. High variability was obs erved in the same individual even within an interval of just few days (seven days). No increase of Hg in urine after the six days of exposur e was observed when compared with the values after the two free days i nterval.