Normal levels of delta-aminolevulinic acid in the spot urines of adult men, as measured by a simplified method (author's transl)

Abstract

Increased urinary excretion of delta-aminolevulinic acid (ALA) is an early biological sign of toxic lead absorption. Therefore, its determination is a very useful screening test for the periodical examination of workers exposed to lead. Previously, we developed a simplified method for determining urinary ALA without ion-exchange column. This method is based on two findings: (a) ALA-pyrrole is extractable with ethyl acetate to be separated from other Ehrlich-positive substances such as urea, and (b) the ALA-pyrrole can form a complex with the modified Ehrlich's reagent in ethyl acetate. In the present study, using this method, we determined urinary ALA of healthy adult men and estimated the normal levels for ALA. The results are as follows: (1) The urinary ALA concentration obtained from the spot urine samples of 299 workers (age: mean=37.1 years range=20-56 years) with no history of occupational lead exposure was 2.39 +/- 0.87 mg/liter (mean and standard deviation), with upper limit of 4.10 mg/liter for 95%-confidence interval. (2) The distribution of ALA in the normal spot urine was not log-normal, but normal. (3) No significant difference between the excretion level of urinary ALA and the age was observed.