The Weight of Lead: Effects Add Up In Adults

Abstract

Lead toxicity is not a problem of the past, nor is it the exclusive domain of children. In fact, lead continues today to pose a serious threat to the health of many U.S. adults. It’s true that in the United States, environmental lead levels are much lower than before the toxic metal was removed from gasoline, food cans, and other products in the 1970s and early 1980s. The National Health and Nutrition Examination Surveys have shown that average adult blood lead levels have declined from about 15 μg/dL in the 1970s to today’s 1–2 μg/dL. But there are still pockets of high exposures, such as among workers in certain industries. Despite reductions in exposure following OSHA’s 1978 publication of lead standards for general industry, more than 80% of elevated lead levels in adults come from workplace exposures. Industries most affected include lead mining, refining, and smelting; construction work involving paint removal, demolition, and maintenance of outdoor metal structures such as bridges and water towers; auto repair; and battery manufacturing and recycling. When workplaces adhere to the OSHA standard, occupational exposures are usually reduced below levels that cause symptomatic lead poisoning. But as far back as 1990, studies have suggested that significant health effects happen at levels below those allowed by OSHA. “Historically people had huge lead exposures, so the OSHA standard, when it was originally established, was protective. But right now nobody thinks that that’s a protective standard,” says Rosemary Sokas, director of the Division of Environmental and Occupational Health Sciences at the University of Illinois at Chicago School of Public Health. Now scientists say the evidence is overwhelming that action needs to be taken to further reduce lead exposures in both the workplace and the general environment. “What’s driving concern over the need to reduce permissible levels of exposure in the workplace are . . . more subtle or chronic problems such as hypertension, and contributions to cognitive dysfunction,” says Michael Kosnett, an associate clinical professor of clinical pharmacology and toxicology at the University of Colorado Health Sciences Center. With the lower levels of lead found in the general population in the United States, much of the worry is about lead’s health effects over the long haul. The most recent evidence from epidemiological and toxicological studies suggests that low levels of exposure can, over time, damage the heart, kidneys, and brain. Some of these health effects, such as a 1-mm rise in blood pressure or a slight cognitive decline, seem small when expressed as the average impact to the entire population. In one individual, they may not even be noticed. But the overall impact on public health nevertheless worries scientists.