Relationship Between Blood Lead Level and Urinary ALA Level in Workers Exposed to Very Low Levels of Lead

The relationship between blood lead (PbB) level and urinary delta-aminolevulinic acid (ALAU) level was examined in a total of 3, 636 lead-exposed workers in a periodic medical examination in 1992, in accordance with the Ordinance on Prevention of Lead Poisoning. The results were consistent with previously reported results2, 4) in that ALAU level was found to increase with an increase in PbB level above 22.4 μg/dl (1.35 as a logarithmic value) and to rise markedly above 35.5 μg/dl (1.55). On the contrary, the geometric means of ALAU levels appeared to decrease with an increase in PbB levels within a range between a logarithmic value of 0.15 (1.4 μg/dl) and 1.25 (17.8 μg/dl). Because the earliest sign of the adverse health effects of lead is reported to occur at a PbB level of 20 μg/dl, the relationship between PbB level and ALAU level was examined at PbB levels below 20 μg/dl. A regression formula was obtained, Y (log ALAU (mg/l)) = 0.0570X (log PbB (μg/dl)) + 0.4099. This result indicates that ALAU level decreases with a concomitant increase in PbB level lower than 20 μg/dl.