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PEDIATRIC PERSPECTIVE

Lead may be even more dangerous than we thought

On Friday mornings at Children's Hospital, a group of doctors and nurses reviews the week's most serious lead poisoning cases. When I attended the discussion a few weeks ago, there was talk of a 4-year-old boy who recently emigrated from Asia with his family, a 2-year-old girl from an affluent Boston suburb, another toddler whose father was in jail, then a 15-month-old whose family owned a construction business. The children shared one thing: Their caretakers all thought they were fine, until a blood test showed high levels of lead.

Thanks to tough laws in Massachusetts, the number of children with lead poisoning is falling: In 2003, only 242 Bay State children developed lead levels of more than 20 micrograms per deciliter of blood, down from 1,634 six years earlier.

But here's the frightening part: Tens of thousands of children in Massachusetts alone could still be at risk for lead poisoning. Long known to cause seizures and brain damage in children, lead poisoning, research suggests, may start at much lower levels than previously thought -- and below the level the federal government considers safe.

Research published last year in the New England Journal of Medicine by Dr. Bruce P. Lanphear, director of the Environmental Health Center at Cincinnati Children's Hospital Medical Center, and his colleagues, found that lead levels below 10 mcg/dl were associated with a decline in IQ of more than seven points. While the exact amount of IQ decline that can be blamed on lead poisoning has been debated, the trend has been confirmed by a separate analysis from Dr. Herbert Needleman of the University of Pittsburgh and David Bellinger of Harvard. Today, nearly 38,000 children in Massachusetts -- where we test a respectable 75 percent of all children under 6 for lead -- have levels of 5 to 10 mcg/dl, according to Paul Hunter, who heads the state lead prevention program. Because current Centers for Disease Control and Prevention guidelines don't yet consider levels below 10 mcg/dl toxic, their families probably were told that everything was fine.

Unfortunately, once lead enters a child's body, no medicine has been proved to reverse the damage to IQ. According to a 2001 New England Journal of Medicine article, when children with high levels (20-44 mcg/dl) were treated with medicine to lower lead, their IQ scores didn't recover. Furthermore, it's not clear if the medicines can reduce lead levels below 20 mcg/dl. Thus, a parent can't really do much to treat low-level lead poisoning, other than prevent further exposure. (For information on lead control in your home, go to www.mass.gov/dph/clppp/clppp.htm or call 1-800-532-9571.) Lead gets to kids from two main sources -- paint and the atmosphere. Lead's chemical durability once made it an attractive paint additive. Unfortunately, toddlers found lead paint chips tempting for their sugary taste; in fact, ancient Romans had used lead powder to sweeten wine. And, in 1922, a General Motors scientist developed a lead-based gasoline additive that prevented auto "knocking." Thus, more than 250,000 tons of lead entered American air every year.

By 1980, more than a half-million American children -- 4 percent of all toddlers -- had blood lead levels of more than 30 mcg/dl, a level today considered quite toxic.

Though lead paint was successfully banned in 1978, four years later pro-lead lobbyists almost convinced then-vice president George Bush to recommend removing limitations on leaded gasoline. Under heavy public pressure, the phase-out continued, and leaded gasoline was banned in the United States.

By then, doctors had proved that lead hurts kids even in small amounts. In 1979, Needleman reported in the New England Journal of Medicine that lead levels considered safe by the CDC -- at that time, 30 mcg/dl -- nevertheless correlated with lower IQs in children.

Nationwide, the eventual bans on leaded gasoline and paint caused median childhood lead levels to fall from 15 mcg/dl in 1978 to 2 mcg/dl in 1999. Massachusetts was a leader in lead control. Thanks to aggressive anti-lead housing laws, landlords in the state must de-lead all properties housing children under 6. Landlords cannot ask tenants to sign waivers of lead liability, nor can they refuse families with children.

While this is impressive, we're still far from eliminating low-level toxicity that lowers IQ. Dr. Michael Shannon, a former member of the CDC's lead advisory committee and a prominent toxicologist at Children's, paints the dilemma we face: Nationwide, health officials pursue "secondary prevention," where we screen children for high lead, then act if we find too much. By that time, though, we've already missed the boat. Shannon argues for "primary prevention."

The problem is expense, since de-leading a single dwelling can cost tens of thousands of dollars.

And politics, it seems, continues to shape lead policy. According to the Union of Concerned Scientists, a nonprofit group of 100,000 citizens and scientists, the CDC's lead advisory committee was on the verge of recommending tougher lead standards in 2002,when the administration got involved. Health and Human Services Secretary Tommy G. Thompson took the unusual steps of firing a respected committee member, trying to add five scientists who downplay the dangers of lead, and rejecting the suggested appointments of Lanphear and Susan Klitzman, of the Hunter College School of Health Sciences, who had both found lead toxic at low levels. To date, the CDC hasn't lowered the allowable lead level below 10 mcg/dl despite the recent research.

Few people argue getting the lead out will be easy, but we deserve honesty about what's known. Somehow, I have the feeling that the Friday discussions at Children's Hospital will continue for years to come.

Dr. Darshak Sanghavi is a clinical fellow at Children's Hospital and Harvard Medical School. His e-mail address is sanghavi@post.harvard.edu. 

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