An elevated zinc protoporphyrin (ZPP) indicates impairment of the heme biosynthetic pathway.
In children, a blood lead level of >20 ug/dL and an ZPP level of >70 mcmol ZPP/mol heme are indicative of lead toxicity.(1)
Elevated ZPP levels in adults may indicate long-term (chronic) lead exposure or may be indicative of iron deficiency anemia or anemia of chronic disease.