Fluorometric HPLC determination of Delta-aminolevulinic acid (ALA) in the plasma and urine of lead workers: Biological indicators of lead exposure

A fluorometric high-performance liquid chromatographic (HPLC) method was developed for the highly sensitive measurement of Δ-aminolevulinic acid (ALA) in biological materials. By using this method, we determined ALA in the plasma and urine of 418 workers occupationally exposed to lead and in the plasma and urine of 227 controls. The concentrations of ALA in the plasma and urine of lead workers were significantly elevated as compared with those of the controls. The concentration of ALA in plasma and urine was highly correlated with that of lead in blood in lead workers. It was found that the correlation (r = 0.742) between log of plasma ALA concentrations and blood lead concentrations in lead workers was similar to that (r = 0.711) between log of urine ALA concentrations and blood lead concentrations. These results demonstrated that the measurement of ALA in plasma or in urine using a fluorometric HPLC method was useful for the biological monitoring of lead workers.