Lead poisoning is "the No. 1 environmental health hazard facing American children," according to the U.S. Department of Health and Human Services.
Public health agencies say even low-level lead exposure can cause mental retardation, learning disabilities, stunted growth, hearing loss and behavior problems that affect at least 1.7 million children nationwide.
About 9 percent of all American children under 6 years old, and about 22 percent of African-American children under that age, have elevated blood lead levels, according to the Centers for Disease Control and Prevention.
Experts say the biggest remaining source of lead poisoning is lead-based paint flaking off the walls and windowsills of aging, poorly maintained housing stock.
"We have huge stocks of older homes in poor condition," said Kim Dietrich, a developmental psychologist at the University of Cincinnati. "As these houses age, the lead in old paint gradually becomes part of the dust in the home, in the soil. We don't see as many kids with elevated blood lead levels as we used to, but we are still seeing them."
More than half of the entire U.S. housing stock - and more than 75 percent of the buildings built before 1978 - are thought to contain at least some lead paint. An estimated 5 million to 15 million units are in poor-enough shape to present lead "hazards," according to the National Lead Information Center.
The mission to create a lead-free America has spun an expanding web of federal, state and local regulations. It also has spawned a multibillion-dollar industry of lead-paint inspectors, licensed lead abatement contractors and companies making special equipment and products.
Now, critics are beginning to question the high costs and marginal health benefits of lead-paint abatement programs.
"This is what I call an epidemic by edict. Lead poisoning is a disappearing disease in this country. Yet here they are throwing all this money at it," said Dr. Edgar Schoen, a pediatrician and medical director of perinatal screening programs at Kaiser Permanente in Oakland, Calif. "I think the threat of lead poisoning has been blown way out of proportion."
Many other experts disagree.
"If you find a house with high lead content, it's a good bet that any young children in that house will have elevated blood lead levels," Dr. Dietrich said. "We see it in Cincinnati, in Boston, in Detroit and in Brisbane, Australia."
"Once lead gets in the blood, it can be hard to remove. And it is not clear whether the damage it does can be fully reversed," said Dr. Omer Berger, director of the lead screening program at Children's Hospital Medical Center.
The question isn't whether lead is toxic. At high levels, lead has been shown to cause brain damage, organ damage, even death. Generally, doctors start treating lead-poisoning once blood levels reach 45 micrograms per tenth of a liter.
What scientists disagree about are the health effects caused by low-level lead exposure - defined as 10 micrograms per tenth of a liter. At that level, studies have found lead can cause or aggravate developmental disabilities.
"We've been searching . . . but we haven't really found a firm, safe threshold of lead exposure," Dr. Berger said.
The public health implications of reducing the lead poisoning threshold are huge. In Hamilton County in 1996, lead screening programs reported 656 children above the 10-microgram standard. But just 74 children were above 20 micrograms per tenth of a liter.
What happens at 10 micrograms? "We're not talking about gross mental retardation," Dr. Dietrich said. "What we have here are subtle effects."
Critics say the effects are too subtle. They say there's no way to distinguish whether a child's developmental problems were caused by lead-paint exposure, pollution in general, genetic defects, diet, bad schools, abusive parents or other factors.
CITY LEAD CLEANUP STALLED
CLEANING UP A LEAD-TAINTED HOUSE
