Chelatable lead (Pb U-EDTA) is the best indicator of lead concentration at the critical organ level (indicator of dose) However, since this test is not easily applicable for the biological monitoring of lead-exposed subjects, the current practice is to determine lead in blood (Pb B) and/or in urine (Pb U). But these tests are indicators of exposure and not of dose To analyze the reliability of Pb B and Pb U in estimating lead dose, the relationships between Pb U-EDTA and Pb B and between Pb U-EDTA and Pb U were studied in two groups of male lead workers: 48 currently exposed and 45 with past exposure to lead.
In currently exposed workers the correlation between Pb U-EDTA and Pb B and between Pb U-EDTA and Pb U was very close (r = 0 85, r = 0 74, respectively); in past exposed workers the correlation with Pb U-EDTA was decidedly lower for Pb B (r = 0 54) and not significant for Pb U (r = 0 29) In both cases the relationship between the variables was linear In the previously exposed men, Pb B displayed lower values than those found in currently exposed men.
These results indicate that both Pb B and Pb U allow an indirect estimation to be made of the internal dose in currently exposed subjects, whereas the tests cannot be used for this purpose in subjects who have long since ceased to be exposed In these cases chelatable lead must be determined.