Researchers have long known that repeated exposure to lead-containing substances can have deleterious effects on the body. But a study reported today in the journal Neurology reveals the substance's long-lasting effects, indicating that exposure to lead can cause progressive declines in brain function even two decades after exposure has ceased. The results call into question the factors contributing to so-called "normal aging."
Brian S. Schwartz of Johns Hopkins University and his colleagues followed 535 former manufacturing workers who had worked with lead for an average of eight years but who had not been exposed to the substance for the past 16 years. They contrasted this set of people with a control group of 118 unexposed individuals from the same neighborhood. After studying the lead levels in the blood and bones of the participants over a four-year period and conducting neurobehavioral tests, the researchers arrived at a surprising conclusion. "The effects of the average level of bone lead found in former lead workers was like five more years of aging on the brain," Schwartz says. "Since these declines were seen long after exposure to lead had stopped, it suggests that the effect of lead on the brain is progressive." Differences concerning memory and learning abilities were noted between the two groups.
Schwartz further notes that previous research focused on how chemicals like lead affect children. This study, he says, is the first to investigate long-term problems caused by adult exposure to such chemicals. Furthermore, "Some of what we have been calling 'normal aging' may in fact be due to past exposures to chemicals or other agents that can affect the nervous system," he observes. "This is potentially a very important health problem."
In related news, scientists at the Health Research Institute in Naperville, Ill., recently announced that analyses of eight strands of Ludwig von Beethoven's hair reveal extremely high levels of lead. The composer spent a good deal of his life in search of a cure for his many ailments, including abdominal pain, depression and irritability--all of which are characteristic of lead poisoning. The new study also failed to find evidence to support the possibility that Beethoven had syphilis, which had been proposed by some scholars to be the cause of his illness.