The threshold of the delta-aminolevulinic acid dehydratase (ALAD) activities reduced by lead (Pb) exposure could be 10 μg/dL without modification of ALAD G177C genotypes in Chinese Han Taiwanese.

Background: Lead inhibits the enzymes in the heme biosynthesis, mainly the δ-aminolevulinic acid dehydratase (ALAD) activities. The aims of this study was to establish ALAD activity assay in Taiwan and analyzed the effects of lead exposure on hematological system and the ALAD activity with the modification of the ALAD genotypes. Methods: Among 121 lead workers and 117 non-exposed workers, the data were from health examination. ALAD activity was determined by the standardized method of the European Community. ALAD genotyping was using a method of PCR-RFLP. For finding a threshold effect, we used generalized additive models (GAM) and scatter plots with smoothing curve, in addition to multiple regression methods. Results: There were 229 ALAD1-1 homozygotes, 9 ALAD1-2 heterozygotes were identified, and none of ALAD2-2 homozygote. Lead workers had significantly lower ALAD activity than non-exposed group (41.6 ± 22.1 vs. 63.3 ± 14.0 U/L, p-value < 0.001). The results of multiple regressions showed the blood lead level (BLL) was profound factor associated with ALAD activity inversely. The possible threshold of BLL affecting ALAD activity was around 10 μg/dL. Conclusions: ALAD activity was inhibited by blood lead, which could be a threshold of 10 ug/dL, which ALAD activity may be adopted as a biomarker of health examination for lead workers.