The Diagnosis of Industrial Lead Poisoning

A series of IOO lead workers from different industries, 9I at work and nine admitted to hospital with lead poisoning, was studied in order to define more clearly the clinical and biochemical criteria of lead poisoning in three stages-(A) a presymptomatic state of lead exposure (37 men), (B) a state of mild symptoms or mild anaemia (45 men), and (C) frank lead poisoning with severe symptoms and signs (i8 men). The tests used were haemoglobin, reticulocyte count, and blood lead, and urinary lead, coproporphyrin, 8-aminolaevulinic acid (ALA), and porphobilinogen (PBG) estimations. Of these, the urinary lead was similar for all three groups and the blood lead estimation was of less value for determining the clinical group of the men than the haemoglobin and urinary coproporphyrin or ALA estimations, which correlated well with the clinical assessment and with each other but showed no correlation with the urinary and blood lead levels. PBG levels became raised only with the onset ofsymptoms oflead poisoning. A haemoglobin of I3 g. /100 ml. (90%) or less is'a cautionary sign. Urinary coproporphyrin above 80 K1g. IOO mg. creatinine (8oo Kg./litre), ALA above 2 0 mg./Ioo mg. creatinine (2z0 mg.%), and PBG above 0I5 mg./Ioo mg. creatinine (OI5 mg.%) were almost always associated with symptoms or signs and were therefore considered to be the upper safety limits. Although the blood lead level does not differentiate between lead toxicity and lead exposure, values above 6o Hg. lead/ioo g. blood should alert the physician t