NIOSH, in collaboration with NIEHS, studied a comprehensive panel of clinical immunological outcomes in workers employed at a secondary lead smelter and in workers at a hardware manufacturing company without occupational lead exposure (unexposed). This study is by far the largest to date investigating the immunologic effects of lead among workers for workplaces that operate within the OSHA lead standard. All study participants were male. 145 exposed and 84 unexposed workers participated. Endpoints evaluated included: hematology, lymphocyte immunophenotyping, clinical chemistries including sera immuoglobulin levels, lymphocyte proliferation and natural killer cell cytolysis. The median blood lead level (exposed) was 39 ug/dl (range: 15-55 ug/dl) and <2 ug/dl (range: <2-12 ug/dl) among the unexposed group. The median zinc protoporyhrin (ZPP) was 48 ug/dl (range: 2-424 ug/dl) among the exposed and 17.5 ug/dl (range: 1-59 ug/dl) among the unexposed group. Analyses of raw data indicated statistically significant changes in selected parameters (when compared to the unexposed group) including changes in serum IgG and IgA levels, salivary IgA, percent of CD3 + cells and CD 19 + cells. Analyses of covariates (age, race, smoking, alcohol use, etc.) is ongoing; however, the relationship between the number of CD3 + /CD4 + T-cells and exposure varied by age. Among workers under 30 years of age, there was no difference in the number of CD3 + /CD4 + T-cells between the unexposed and exposed group. But among workers 30 years of age or older, exposed workers, on average, had fewer CD3 + /CD4 + T-cells. These results emphasize tile importance of covariate analyses in human clinical immunological studies.
The Toxicologist. Society of Toxicology 35th Annual Meeting, March 10-14,1996, Anaheim, California