Lead poisoning remains a major health hazard for
Excerpted fron U.S. News & World Report, Dec. 20, 1999
By Amanda Spake And Jennifer Couzin
When Karen and Bob Brantley found the lovely old Baltimore County, Md., farmhouse for rent in 1992, it seemed like a dream come true. The 25-acre property had woods, a pond nearby, and room for a dog and their kids, Tommy, Kaitey, and Bobby, who was born shortly after they moved in.
Christian, their fourth child, came along in 1996. He was a calm and happy kid at first. But last year, when Christian was about 18 months.. Testing revealed that his blood lead level was 19 micrograms per deciliter, nearly twice the level at which a child is considered at risk.
Karen Brantley was shocked. "I'm a stay at-home mom," she says. "I watch my children." Like many middle-class parents, the Brantleys did not know that lead poisoning remains the most significant environmental health hazard for U.S. children. An estimated 1.7 million children are already affected by lead from old paint, water pipes, soil, and other sources, according to the Environmental Protection Agency. This breaks down to 4.4 percent of all children and a full 22 percent of African-American kids who live in older homes.
Some 890,000 of all children affected are under age 6, when the brain and central nervous system are most vulnerable. At the same time, scientists have determined that lead levels once considered safe can actually dampen IQ scores and cause lifelong learning disabilities, hyperactivity, attention-deficit disorders, and aggressive behavior. "I don't know of any other disease as disabling as lead poisoning that strikes 1 in 25 children that people wouldn't be screaming about," says Herbert Needleman, pediatric psychiatrist and lead expert at the University of Pittsburgh.
Doctors have known of lead's toxic effects since the turn of the century. In 1904, the first article about childhood lead poisoning from paint appeared in an Australian medical journal. France and Austria banned the interior use of lead paint in 1909, but a U.S. ban on residential use didn't come until 1978. At that time, studies showed that 88 percent of U.S. children had elevated lead levels.
While children on Medicaid are supposed to be screened for lead at the age of 1 or 2, fewer than 20 percent nationwide have been tested. (The state of Missouri filed suit last month against Healthcare USA of Missouri LLC and Prudential Health Care Plan Inc., two Medicaid providers, charging that the plans failed to screen their St. Louis pediatric patients for lead as federal law requires. Other states are considering similar action.) Children from well-off families are rarely checked as toddlers, though some school systems require screening. "But if you screen at school entry, it's too late," says Katherine Farrell of the Anne Arundel County (Md.) Health Department. "The damage is done between 9 and 18 months."
At the same time, the amount of lead regarded as hazardous has dropped steadily over the past three decades, from 60 micrograms per deciliter of blood to 10. And doctors are finding that even levels below 10 can be harmful. A Boston study of 148 children-many of them from relatively affluent families-showed that those with low lead levels at age 2 had decreased intellectual performance at age 10.
Links to crime. Children with elevated lead levels, Pittsburgh's Needleman has found, were seven times as likely to drop out of high school as other children, and six times as likely to have a reading disability. "We estimate that 20 to 30 percent of the special education caseload in urban centers results from lead poisoning," says Ruth Ann Norton, executive director of the Coalition to End Childhood Lead Poisoning. For decades, teachers and parents have reported disruptive behavior in lead-poisoned kids. In 1996, Needleman published the first rigorous study demonstrating that boys with elevated lead levels were more likely to engage in bullying, vandalism, arson, shoplifting, and other delinquent behaviors. Needleman is now trying to assess what portion of the juvenile criminal population suffered elevated lead levels as children; his theory is that a reduction in lead poisoning would result in less crime.
The precise mechanism by which lead affects behavior and damages the brain is not clear. Because lead is chemically similar to calcium, it can disrupt brain mechanisms that depend on calcium, like neurotransmitters that play a role in mediating responses to stimuli. The lead may also disrupt a process called neural pruning, in which the maturing brain weeds out some of a child's neural circuits, the connections between brain cells. Inadequate neural pruning may cause impulsiveness, hyperactivity, and diminished attention span. "Lead is potentially one preventable cause associated with the rise in attention-deficit disorders or ADD," says David Bellinger, a lead expert at Children's Hospital in Boston. Poor nutrition, particularly calcium and iron deficiencies, contributes to lead uptake. So does hunger. "If people are exposed to lead on an empty stomach, they absorb much more lead," says Kathryn Mahaffey, a scientist at the EPA.
Once ingested, lead, like calcium, is stored in the bones. During pregnancy, when the bones release calcium into blood, the lead is released with it, sometimes affecting the baby's brain development. And new research released last month by Ellen Silbergeld, a University of Maryland scientist, shows that blood lead levels rise at menopause; as a result, some women experience hypertension and cognitive dysfunction.
Today, the Brantley family lives in a lead-free home in a Baltimore suburb. Christian's blood lead levels have dropped, but the symptoms remain. "He attacks his brother Bobby until he draws blood," his father says. "He tries to gouge out his eyes." The Brantleys worry every day about Christian's future, not only whether he will have a lower IQ or cognitive impairment resulting from his lead poisoning but how he will learn to control his behavior. "Christian," his father says, "is violent way beyond what a normal 3-year-old should be. What will he be like at 12? At 15?"
copyright U.S. News & World Report 1999