Objective To assess the factors influencing blood lead levels of workers occupationally exposed to lead, and the association between zinc protoporphyrin (ZPP) and blood lead.
Methods A total of 454 workers (300 males and 154 females) in a lead battery factory located in Jiangsu Province were recruited in the study. Lead concentrations in workplace air were measured. All the subjects underwent structured questionnaire survey on lifestyle and measurement of blood lead and ZPP. Workers with blood lead >400 μg/L, 100-400 μg/L, and < 100 μg/L were stratified into high, medium, and low blood lead groups for statistical analysis respectively. Benchmark dose calculation software (BMDS 2.6.1) was used to calculate blood lead benchmark dose and the 95% lower confidence limit of benchmark dose (BMDL) by applying blood lead as the exposure marker and ZPP as the effect marker.
Results Statistical differences among the three groups were observed in blood lead, age, educational level, type of work, job seniority, lead-exposed seniority, smoking, and drinking in univariate analysis. Low educational level, operation worker, drinking, and short lead-exposed seniority were the risk factors of high blood lead in logistic regression analysis. There was a positive linear correlation between ZPP and blood lead (100-400 μg/L) (P < 0.001). The blood lead benchmark dose and the related BMDL were 562.23 μg/L and 441.13 μg/L, respectively (P=0.78).
Conclusion High-level blood lead and ZPP are positively correlated, and ZPP is a sensitive indicator of lead exposure. In practical work, other indicators should be combined with ZPP when screening workers with low blood lead level ( < 100 μg/L).
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