For Healthy Brains, Get the Lead Out

Recently I've been writing about various substances that seem to be either healthy (omega-3 fatty acids) or poisonous (mercury) to our brains. The metal lead definitely belongs in the latter category — its persistent toxic effects on the central nervous system have been known for decades. In spite of efforts to reduce the ways that lead can enter our bodies, the problem of lead exposure continues.

Over the past century, the most important sources of lead exposure have been through paint and gasoline. (The Australians first identified lead-based paint as a source of deadly childhood poisoning in 1904.) Laws now restrict lead in these products; however, many older houses still have lead paint that chips or disintegrates into dust and can be ingested or inhaled by people.

Lead has an especially detrimental effect on children. This is why the recent reports that certain toys produced in China had unacceptable lead levels sparked such an outpouring of concern and anger.

What's wrong with lead? In addition to causing many other toxic effects throughout the body, lead exposure, in the nervous systems of children, can permanently impair mental development by lowering intelligence and causing behavioral problems. Some recent research has suggested that exposure to lead during childhood can increase the risk of criminal behavior later in life.

Between 1979 and 1984, researchers in Cincinnati measured the lead levels of 376 pregnant women, as well as the lead levels of the children born from those pregnancies, up through the first 7 years of life.

In the intervening years, the researchers have been able to follow 250 of those original children into early adulthood. Now, a new study has assessed the criminal records of these 250 subjects. Perhaps not so surprisingly, the researchers found that 55 percent of these young adults had been arrested at least once.

The researchers then referred back to the group's lead-level measurements taken before birth and up to age 7. Sure enough, a direct relationship was found between the number of arrests a young adult had and his or her lead levels during childhood. In fact, the relationship was the strongest for violent crimes, including murder, rape, domestic violence, assault, robbery, and possession of weapons.

In a related research project, magnetic resonance imaging (MRI) studies were performed on 157 individuals from the Cincinnati lead study already cited above. It was found that higher lead levels were associated with reductions in the volume of adult-brain gray matter that was located in the specific areas associated with decision making and mood regulation. These findings were especially prominent among the males.

There is no way to reverse the detrimental effects of lead on the brain, but it may be possible to limit future damage in people who have elevated lead levels. A blood test can confirm whether the body's lead level is excessive and, when the levels are high, medications can help remove some of the lead.

Fortunately, the risk of lead exposure in our environment is much lower now than it was several decades ago, but it is important for our society to remain vigilant. The goal of the Childhood Lead Poisoning Prevention Program of the U.S. Centers for Disease Control and Prevention (CDC) is to eliminate elevated blood levels in children by the year 2010 — 106 years after the Australians first identified the problem.