Evaluation of increased proportion of cells with unusually high sister chromatid exchange counts as a cytogenetic biomarker for lead exposure.

Sister chromatid exchange (SCE) frequency and high-frequency cells (HFCs) were analyzed in 50 storage battery plant workers with mean blood lead level (BLL) of 40.14 +/- 9.99 microg/dL. The mean BLL in the control group (n=30) was 9.77 +/-1.67 microg/dL. This difference in mean BLLs between control and exposed group was statistically significant (p<0.05) and reflects clearly the lead exposure in the workers. Urinary aminolevulinic acid (U-ALA) was also determined in both control (3.37+/- 0.89 mg ALA/g creatinine) and exposed groups (12.39+/- 6.18 mg ALA/g creatinine) and U-ALA excretion was statistically higher (p<0.05) in lead-exposed workers. The relationship between biomarkers of lead exposure/effect and HFC percentage was higher than the relationship between biomarkers of lead exposure/effect and SCE frequency. Accordingly, HFC analysis seemed to be more sensitive than the SCE analysis as a cytogenetic biomarker for lead exposure. Additionally, the statistically significant correlation (r2=0.880, p<0.01) between U-ALA excretion and HFC percentage in lead-exposed workers supported the probability of ALA mediated indirect mechanism for lead genotoxicity.