A composite index of lead effects. Comparative study of four occupational groups with different levels of lead absorption.

Biological indicators of lead effects on the central nervous system (CNS), hematogenous bone marrow, and kidney function as measured by performance tests, hemoglobin (Hgb) and BUN levels respectively were combined in an integrative index (INDEX). Such an index was calculated by removing age effects in measures of performance and kidney function and then transforming all the variables to Z (standard) units. The relationships between INDEX and biological indicators of lead exposure and absorption (Pb-B and ZPP) were studied in four groups: 191 non-lead exposed males (control group), 169 copper smelter workers, 133 autobody shop workers and 87 secondary lead smelter workers. We found that: 1) the magnitude of the correlation coefficient between INDEX and ZPP was much higher than were the correlations between the various single indicators of lead effects (performance test scores, Hgb, and BUN); and 2) the magnitude of the correlation coefficients was related to the degree of lead exposure and absorption (as reflected in distribution patterns of Pb-B and ZPP) in each group. The concept of an integrative index of biological effects of lead is important for the evaluation of early manifestations of lead toxicity and also for the correct assessment of adverse health effects of lesser intensity than those characteristic for the classic picture of overt lead poisoning.