Abstract
The activity of 5-aminolevulinate hydro-lyase (ALAD) in blood decreases in lead-exposed subjects. The activity of the hemolysed blood is restored by heat treatment (60°C, for 5 min) almost completely. A parameter of "activity ratio", dividing the enzyme activity before heat treatment by that after heat treatment, is proposed for evaluation of lead exposure, and this ratio was calculated in 167 human subjects, including those exposed to lead in work, lead concentration in their blood ranging 3.5 to 82μg/100 g blood. Correlation of the ratio against blood lead concentration was higher than that of the ALAD activity itself. As there are, in addition, subjects with lower-than-normal ALAD activity values regardless of lead exposure, the ratio is available as an index to evaluate the extent of lead exposure.
