Use of zinc protoporphyrin in screening individuals for exposure to lead.

We studied the relation between the concentrations of lead in blood (PbB) and zinc protoporphyrin in blood (ZPP) in a group of 801 men occupationally exposed for more than one year to lead or inorganic lead compounds. Linear regression of PbB on log ZPP provided 95% tolerance intervals for PbB values for a given ZPP value. The intervals we found are too large to warrant the estimation of PbB on the basis of ZPP measurements in health surveillance of lead workers. Instead we propose a procedure in which ZPP can be used as an indicator to decide which individuals exposed to lead need further investigation of PbB in light of existing limit values for PbB. The procedure is applicable only for PbB values of 2.4 mumol/L or more but may reduce considerably the costs for screening individuals or groups of people exposed to lead.