Urinary 5-aminolevulinic acid in lead-exposed children

Lead intoxication can interfere with haem synthesis and alter the concentra tion of haem precursors, such as the neurotoxin 5-aminolevulinic acid, in p lasma and urine. The relationship between blood lead concentration (PbB), a biomarker of lead exposure, and 5-aminolevulinic acid concentration iii ur ine (ALAU), a biomarker of the early biological effect of lead, was examine d in lead-exposed children. ALAU was assayed by chemical derivatization and high performance liquid chromatography with fluorescence detection. The st udy subjects were 79 children with moderate to high lead exposure recruited from a lead-poisoning prevention clinic. Their urine had been previously a nalysed for creatinine (CR) concentration and the benzene metabolite trans, trans-muconic acid, and their blood had been analysed for lead. We found th at ALAU was not correlated with PbB (Spearman r=0.088, P =0.44), but the ra tio ALAU/CR was correlated with PbB (Spearman r=0.22, P = 0.054). Creatinin e and ALAU concentrations were higher in urine samples collected in the aft ernoon than those collected in the morning, a finding that is consistent wi th known diurnal variation. However the ratio ALAU/CR was not different in morning and afternoon urines, supporting the use of creatinine adjustment o f ALAU analysis of spot urine samples. In view of the neurotoxic properties of ALA, future validation studies of biomarkers of lead exposure and effec t in children should include ALAU or ALAU/CR as potential markers of lead e ffect.