Studies suggest link between lead, violence

Experiment on rats indicates exposure hinders brain growth

Analysis tracks lead, crime

May 09, 2000|By Jim Haner | Jim Haner,SUN STAFF

Two new studies on the effects of lead exposure to be released this week suggest that the toxin commonly found in household paints made before 1960 may stunt normal brain growth and could contribute to patterns of violent crime.

The reports - to be published almost simultaneously in two leading research journals - are the first in an expected wave of new studies this year examining how lead exposure influences learning disabilities in children, violent behavior in teens and mental dysfunction in the elderly.

Researchers who have reviewed the two studies caution that they are both preliminary and do not establish a firm causal link between lead exposure and aberrant behavior.

But they say the results go to the heart of scientific research on the subject.

In one of the first experiments of its kind, Baltimore's Kennedy Krieger Institute for children found in a two-year study that relatively low levels of lead fed to a colony of nursing mother rats in their drinking water caused brain abnormalities in their offspring that stunted their sensory perception.

Experts say the research, which appears today in the Proceedings of the National Academy of Sciences, may have implications for human brain development, since lead tends to have similar effects in animals and young children.

"We know that kids can experience permanent reductions in IQ from lead exposure," said Mary E. Blue, a neuroscientist involved in the study.

"And that suggests there may be physical changes in actual brain structure - which is exactly what our research found."

In the second study, a private consulting group working under contract for the U.S. Department of Housing and Urban Development used computers to track lead consumption in paint and gasoline over the past century and uncovered a striking coincidence.

As the amount of lead released into the environment in paint and auto exhaust rose and fell through the decades, so did a broad range of reported violent crimes - including rape, robbery, assault and murder - a researcher at ICF Consulting in Fairfax, Va., found.

`Astonishing consistency'

"Historians have grappled with this question for years, trying to explain these huge arcs in the crime rate," said Rick Nevin, an economist who authored the report appearing later this week in the journal Environmental Research.

"But no one ever looked at the possible effects of lead exposure. When you put that data up on the chart, the consistency is quite astonishing."

Lead has been shown to increase aggressive behavior in humans in repeated studies since at least 1943, when doctors at Boston's Children's Hospital first noted a tendency toward "cruel impulsive behavior" and "irritability" in children exposed to lead.

But scientists have yet to establish precisely how lead fuels anger, except that it causes humans and animals alike to have difficulty learning and adapting to changes in the environment.

The quest for the exact mechanism - and the lowest dosage at which the toxin begins to cause mental problems - has been among the most controversial in the field over the past two decades.

"Both of these reports are striking in their general observations about the possible gross effects of lead exposure," said Dr. Ellen K. Silbergeld, a professor of toxicology at the University of Maryland and an authority on lead poisoning. "And they both fit rather nicely into the existing research.

"But they raise more questions than they answer. That said, it doesn't make the findings any less disturbing, especially for a city like Baltimore."

More than 7,000 children a year are exposed to highly toxic dust from disintegrating lead paint in Baltimore, and at least 1,200 are poisoned.

Mostly poor and disproportionately African-American, they live primarily in the dilapidated rental housing enclaves of Park Heights, Sandtown and Middle East.

These neighborhoods have been associated with high rates of childhood lead poisoning since at least the 1930s, according to historical health records at the Johns Hopkins University.

Paint in old houses

While lead levels in the blood of U.S. children have declined sharply nationwide since the 1970s - when the U.S. Congress banned lead in gasoline and paint - kids living in older, poorly maintained houses continue to be exposed nationwide.

In impoverished rural communities and cities such as Chicago; Milwaukee; Providence, R.I.; Newark, N.J.; and Philadelphia, lead paint exposure constitutes a con-tinuing public health crisis affecting more that a million children annually, according the U.S. Centers for Disease Control and Prevention.

In Baltimore, the Kennedy Krieger Institute on Broadway is the primary treatment facility for the hardest-hit kids, an oasis amid the city's worst slums.

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