To evaluate the effect of ALAD polymorphism on the relationship of blood and bone lead with hematologic biomarkers in lead exposed workers, 450 lead exposed workers and 85 non-lead exposed workers were selected.

Blood lead and tibia bone lead were selected as parameters of lead exposure and blood ZPP, urinary ALA (ALAU), hemoglobin (Hb) and hematocrit (Hct) were chosen as parameters of hematologic effect of lead exposure. Genotype of each subject was assayed and expressed as ALAD1 and ALAD2. Demographic information such as sex, age and personal habit of smoking and drinking were collected. Job duration of lead exposed workers was also obtained.

The overall prevalence of the variant allele, ALAD2 in lead exposed workers was 9.6 %(43 out of 450 lead workers) which was not differed from control workers (9.4 % : 8 out of 85). The means of tibial lead and blood ZPP in lead workers with ALAD2 were lower than those of lead workers with ALAD1, but the differences were not statistically significant. After adjusting for possible confounders (sex, job duration, BMI, drinking and smoking status) only blood lead and bone lead contributed negatively to the level of hemoglobin with statistical significance without any contribution of ALAD genotype. On the other hand, no significant effect of blood lead, bone lead and ALAD genotype were observed on the level of hematocrit after controlling possible confounder. ALAD genotype in the multiple regression analysis of blood lead and bone lead with log transformed urinary ALA (LogALAU) after adjusting for possible confounders showed significant main and interaction effect on LogALAU simultaneously, which resulted lower LogALAU in lead exposed workers of ALAD2 than ALAD1. It was also observed only main effect of ALAD gene type on blood ZPP after adjusting possible confounder resulting lower ZPP in lead workers of ALAD2 than ALAD1.

With above results, it was found that ALAD polymorphism did not affect on the level of hemoglobin and hematocrit, but ALAD polymorphism made significant effect on the association of blood and bone lead with urinary ALA and blood ZPP. The lower urinary ALA and blood ZPP in ALAD2 lead workers suggested that ALAD2 genotype may be supportive for the protective effect of lead.