Blood Tests

As mentioned, initial medical surveillance consists of two blood tests: one for lead levels, and one for zinc protoporphyrin.

Zinc protoporphyrin is a substance found in small amounts in red blood cells. Normally, protoporphyrin combines with iron to form heme, the part of red blood cells that carries oxygen to the brain. If lead is present, however, it blocks the formation of heme, and the protoporphyrin instead bonds with zinc. High levels of ZPP can therefore indicate high lead exposure. It takes time for ZPP to accumulate in and disperse from the blood. For that reason, ZPP tests are not useful for judging recent exposure, but are very useful for determining average exposure over the past three to four months.

Blood lead level testing, on the other hand, is more useful to determine recent exposure, but not so useful for chronic exposure. Lead gets absorbed by bones and organs as it circulates through the body, so measuring blood lead levels does not paint the whole picture.

To learn more about Construction Lead Exposure visit our Cal/OSHA Construction Lead Exposure Online Training web page.