Low-Level Environmental Exposure to Lead Unmasked as Silent Killer

Abstract

Since the dawn of human civilization, lead has been a ubiquitous environmental pollutant.1 In 370 BC, Hippocrates described colic in a lead worker.2 The industrial application of lead continues to the present day. Lead is a toxic metal that, during a lifetime, accumulates in the human body.1 Recent evidence3–6 suggests that lead affects human health at levels of exposure that, until now, were considered safe. The underlying premise is that a dose-related continuum of toxicity exists. Asymptomatic health effects may occur at even a very low dose and may evolve into clinically overt adverse effects if the exposure persists during a person’s lifetime or becomes more intense. The report published by Menke et al7 in this issue of Circulation breaks new ground by extending the dose–effect relation to considerably lower blood lead concentrations than reported in previous studies.3–6 Article p 1388 Menke et al7 analyzed the database of the Third National Health and Nutrition Examination Survey (NHANES III) to investigate the relation between total and cause-specific mortality and blood lead in a representative sample of the US population. All 13 946 participants (≥17 years of age) included in the analysis had a blood lead concentration <0.48 μmol/L (10 μg/dL). (To convert micromoles per liter of lead into micrograms per deciliter, multiply by 20.712.) Follow-up lasted until December 31, 2000. With adjustments applied for confounders, subjects in the highest third of the blood lead distribution (≥0.17 μmol/L), as compared with those in the lowest third (<0.09 μmol/L), experienced a significantly higher risk of death. Estimates of the excess risk amounted to 25% and 55% for total and cardiovascular mortality, respectively, and 89% and 151% for myocardial infarction and stroke.7 The blood lead concentration did not predict mortality from cancer. These risk estimates withstood …