Urinary delta aminolaevulinic acid and porphobilinogen in lead-exposed workers.

Of 100 workers exposed to lead in varying degrees, 34 had a urinary delta amino-laevulinic acid (ALA) concentration of above 0-6 mg./100 ml. and a further 35 had an ALA concentration of between 0 3 mg. and 0-6 mg./100 ml. In only 20 of the workers was the urinary porphobilinogen concentration above 0-1 mg./100 ml., two of these being above 0-2 mg./100 ml. No significant correlation was found between the urinary concentration of ALA and coproporphyrin, nor was there correlation between theALA and urinary lead levels, in fact the highest level of ALA was associated with a urinary lead of less than 200 ,ug./litre. A raised urinary lead was always associated with a raised ALA.