Background: Analyses of mortality data for participants examined in 1976-1980 in the second National Health and Nutrition Examination Survey (NHANES II) suggested an increased risk of mortality at blood lead levels > 20 microg/dL. Blood lead levels have decreased markedly since the late 1970s. In NHANES III, conducted during 1988-1994, few adults had levels > 20 microg/dL.

Objective: Our objective in this study was to determine the risk of mortality in relation to lower blood lead levels observed for adult participants of NHANES III.

Methods: We analyzed mortality information for 9,757 participants who had a blood lead measurement and who were > or = 40 years of age at the baseline examination. Using blood lead levels categorized as < 5, 5 to < 10, and > or = 10 microg/dL, we determined the relative risk of mortality from all causes, cancer, and cardiovascular disease through Cox proportional hazard regression analysis.

Results: Using blood lead levels < 5 microg/dL as the referent, we determined that the relative risk of mortality from all causes was 1.24 [95% confidence interval (CI), 1.05-1.48] for those with blood levels of 5-9 microg/dL and 1.59 (95% CI, 1.28-1.98) for those with blood levels > or = 10 microg/dL (p for trend < 0.001). The magnitude of risk was similar for deaths due to cardiovascular disease and cancer, and tests for trend were statistically significant (p < 0.01) for both causes of death.

Conclusion: In a nationally representative sample of the U.S. population, blood lead levels as low as 5-9 mug/dL were associated with an increased risk of death from all causes, cardiovascular disease, and cancer.