Different effects of serum iron status on the relationship between blood lead and zinc protoporphyrin in lead workers in Korea

This study was conducted to determine whether there was a different toxic effect of lead on heme synthesis by serum iron status in 360 lead workers in Korea. We examined the association between blood lead (PbB) and zinc protoporphyrin (ZPP) in whole blood according to the level of serum iron in low to moderate lead-exposed workers in 1997-1998. Serum iron levels (FeS) were divided into two groups: iron-deficient group (serum iron < 80 μg/dl, 57 subjects) and iron-sufficient group (serum iron ≥ 80 μg/dl, 303 subjects). Blood lead corrected by the standard value for hemoglobin (15 g/dl) as an explanatory variable was assessed to explain the variance of ZPP. After adjusting for possible confounders, such as age, body mass index (BMI), cigarette smoking, alcohol drinking, and size of factory, the linear slope of corrected PbB on ZPP in the iron-deficient group was statistically higher than that of the iron-sufficient group. The interaction term between corrected PbB and ZPP with the modification of the serum iron status was statistically significant in the regression model (p=0.0053). The result suggests that the relationship between corrected PbB and ZPP may be modified by the serum iron status in male lead-exposed workers.