Benchmark dose of lead inducing neuromotor dysfunction and potential health adverse effects.

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ObjectivesThis study was carried out to estimate the critical dose of lead to influence the hematological indicators and to cause neuromotor dysfunction in workers by using the benchmark dose (BMD) method of a hybrid approach.MethodsThe effects of lead on hemoglobin (Hb) and hematocrit (Hct) levels, and red blood cell (RBC) count were examined in 388 male lead-exposed workers with blood lead (BPb) levels of 1〜115 μg/dl (0.05〜5.5 μmol/L). In addition, postural sway parameters with spectral analysis were compared between 121 lead workers and 60 unexposed controls.ResultsThe blood lead (BPb) level was associated with Hb (r=-0.240), RBC (r=-0.237), and Hct (r=-0.201) among the workers with BPb levels of 1〜115 (median 22) μg/dl ; these linear relations were statistically significant (p<0.001) even after controlling for age and working status. The lower 95% confidence limits of BMD (BMDL) of BPb were estimated to be 19.5 μg/dl (0.94 μmol/L) for Hb, 19.4 μg/dl (0.94 μmol/L) for RBC, and 29.6 μg/dl (1.43 μmol/L) for Hct.All sway parameters, except for sagittal sways with eyes open, were significantly larger in the lead workers than in the controls. The BPb level was significantly related to sagittal sways at 1-2 Hz and 2-4 Hz with eyes open, and sagittal and transversal sways at 1-2Ha and 2-4 Hz with eyes closed. The mean BMDL of BPb for postural sway were estimated to be 14.4 μg/dl (range 0.58〜0.83, mean 0.69 μmol/L).ConclusionsThe reduction in hematopoietic indicators and postural instability in lead workers may be initiated at BPbs below the level currently considered no effect.