Subjective symptoms and exposure to lead

Health effects of low level occupational exposure to lead: the trail, British Columbia study

Blood lead (PbB) was measured in a sample of 245 lead smelter employees and their wives in Trail, B.C. and 144 controls in Nelson, B.C. Smelter workers were divided into three groups according to lead exposure: (1) directly-exposed, (2) indirectly-exposed, and (3) office workers. The average PbB values found (41, 33, and 16 micrograms/dl, respectively) reflected exposure level. In the highest exposure group, male smokers had significantly higher PbB concentrations than nonsmokers (44 vs. 37 micrograms/dl). For exposed males, average number of "days off work ill" increased with increasing PbB range and significant correlations were found between PbB values and five biologically plausible health symptoms. None of those symptoms planted to detect response bias correlated. Because of a 4-month strike, PbB values were measured in a sub-sample from each exposure group before and 1, 2, and 4 months after smelter operation resumed. Exposed workers' PbB levels stabilized after 1 month's operation.

Relationships between three indicators of lead exposure in workers: blood lead, delta-aminolevulinic acid and free erythrocyte protoporphyrin

Whole blood lead (Pb-B), urinary delta-aminolevulinic acid (ALA-U) and free erythrocyte protoporphyrin (FEP) were measured in three groups of workers (n = 196) with different degrees of exposure to lead, and one group of men with no previous exposure to the metal (n = 48). Inter-group comparison showed a correlation of r = 0.73 between Pb-B and log of ALA-U, and r = 0.91 between Pb-B and log of FEP. ALA-U and FEP values rose sharply after Pb-B values reached 450-500 micrograms/l.

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

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 mumol/litre (16-280 microgram/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 less than 8.69 mumol/litre (Hb/4) or 14.0 gm/dl) in 27, elevated blood urea nitrogen (greater than or equal to 7.14 mmol/litre or 20 mg/dl) in 28, and possible encephalopathy in two. No toxicity was detected at blood lead levels below 1.93 mumol/litre (40 microgram/dl). However, 13% of workers with blood lead levels of 1.93 to 3.81 mumol/litre (40-79 microgram/dl) had extensor muscle weakness or gastrointestinal symptoms. Anaemia was found in 5% of workers with lead levels of 1.93-2.85 mumol/litre (40-59 microgram/dl), in 14% with levels of 2.90 to 3.81 mumol/litre (60-79 microgram/dl), and in 36% with levels greater than or equal to 3.86 mumol/litre (80 microgram/dl). Elevated blood urea nitrogen occurred in long-term lead workers. All but three workers with increased blood urea nitrogen had at least four years occupational lead exposure, and nine had received oral chelation; eight of this group had reduced creatinine clearance, and eight 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 mumol/litre (40-60 microgram/dl).

Lead and morbidity: A dose-response relationship

Many laboratory tests have been recommended for monitoring factory workers exposed to lead. To select the most useful test the best predictor of selected measures of morbidity was sought. 639 lead-exposed workers in several factories were questioned about abdominal ache, constipation, and fatigue and were examined for hand tremot. Packed-cell volume, blood-lead, urinary lead, and delta-aminolaevulinic acid were estimated in 489 workers. About half of the values for the latter three tests fell into the "excessive" or "dangerous" category of lead absorption. Blood-lead was a better predictor of morbidity than any other laboratory test, and further information did not add appreciably to morbidity prediction. The findings suggest that blood-lead measurement is the most meaningful test for monitoring workers exposed to lead. The effect of lead on morbidity does not appear to depend on its action on the porphyrin metabolic pathway.