Biological monitoring of lead effects in a smelter community before and after emission control.

Biological monitoring of lead effects in specific population groups living in the vicinity of a lead smelter has been followed up after effective emission control, in order to estimate the length of time necessary before the characteristic indicators of increased lead absorption normalize. The period established could be a realistic basis for predicting the time necessary to elapse before a lead contaminated area can be proclaimed as safe for normal living. Three groups of subjects were examined: preschool children, school children and mothers. The biological monitoring included the measurement of delta-aminolevulinic acid dehydratase activity (ALAD) and the concentration of zinc-protoporphyrin (ZPP), blood lead (Pb-B) and hemoglobin (Hb). The results obtained demonstrated a gradual normalization of the characteristic indicators of lead absorption, although they were still outside corresponding values in the control group even four years after the installation of effective emission control. These findings emphasize the advantages of biological monitoring over environmental for objective assessment of internal and external lead exposure following effective engineering control of the emission source.