Evaluation of zinc protoporphyrin in an occupational environment

Zinc protoporphyrin (ZnP) has been identified by several investigators as the predominant fluorescent porphyrin accumulating in erythrocytes as a result of chronic lead absorption or iron deficiency anemia. This report describes an evaluation of a new portable hematofluorometer for the determination of ZnP in finer puncture or venous blood samples. Samples were obtained from a number of employees in various job categories at steel operations throughout the United States to study the utility of ZnP as a biologic monitoring method in the occupational environment. Urinary lead, urinary aminolevulinic acid and blood lead were also determined on the same employees to examine any relationships among these measurers and to estimate a biologic threshold limit value for ZnP. The results of this investigation show that there is little elevation of the ZnP level with increasing blood level until the blood lead concentration reaches the area of 50--60 micrograms/dl. A biologic threshold level of 300 micrograms/dL, which correlates with a blood level of 60 micrograms/dL, is suggested as a guideline value for identifying workers requiring further investigation.