Monitoring of zinc protoporphyrin levels in blood following occupational lead exposure.

The value of measurements of zinc protoporphyrin in blood (ZPP) in the surveillance of workers occupationally exposed to lead has been studied. From a group of referents, consisting of 1,088 men and 511 women, it has been established that the normal mean ZPP is in the region of 25 micrograms/100 ml, and only rarely do values exceed 45 micrograms/100 ml. The higher ZPP values are frequently associated with low blood hemoglobin concentrations and appear to be manifestations of an iron-deficiency anemia. Women have higher ZPP values than men; smoking has no influence. Measurements of ZPP and blood lead concentration (PbB) have been made every other month for 2.5 years on a group of around 200 men and 40 women exposed to lead in a storage battery factory. The mean ZPP of the group throughout the period was 70.9 micrograms/100 ml blood, and a linear relation between log ZPP and PbB in the PbB range of 10-80 micrograms/100 ml has been established. ZPP thresholds in the control of excessive occupational lead exposure, and the economic advantage of ZPP measurements over PbB, are discussed.