Occupational lead poisoning in the United States: Clinical and biochemical findings related to blood lead levels

Abstract

Dose-response relationships between blood lead levels and toxic effects have been evaluated in 160 lead workers in two smelters and a chemicals plant. Blood lead levels ranged from 0.77 to 13.51 μmol/l (16-280 μg/dl). Clinical evidence of toxic exposure was found in 70 workers (44%), including colic in 33, wrist or ankle extensor muscle weakness in 12, anaemia (Hgb < 8.69 μmol/l (Hb/4) or 14.0 gm/dl) in 27, elevated blood urea nitrogen (≥7.14 mmol/l or 20 mg/dl) in 28, and possible encephalopathy in 2. No toxicity was detected at blood lead levels below 1.93 μmol/l (40 μg/ml). However, 13% of workers with blood lead levels of 1.93 to 3.81 μmol/l (40-79 μg/dl) had extensor muscle weakness or gastrointestinal symptoms. Anaemia was found in 5% of workers with lead levels of 1.93-2.85 μmol/l (40-59 μmol/l (80 μg/dl). Elevated blood urea nitrogen had at least 4 yr occupational lead exposure, and 9 had received oral chelation; 8 of this group had reduced creatinine clearance, and 8 had decreased renal concentrating ability. These data support the establishment of a permissible biological limit for blood lead at a level between 1.93 and 2.90 μmol/l (40-60 μg/dl).