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Overhaul of CDC Panel Revives Lead Safety Debate

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Science  25 Oct 2002:
Vol. 298, Issue 5594, pp. 732
DOI: 10.1126/science.298.5594.732

Just as an advisory committee began looking at evidence for setting a stricter lead-exposure standard, it got reorganized

How far should society go in protecting children from exposure to low levels of lead? The question, hotly debated in decades past, is suddenly back on the front pages after public health advocates and a group of Democrats in Congress accused the Bush Administration of trying to load an influential advisory panel with friends of the lead industry. They suspect that the Administration wants to head off an effort to tighten the definition of lead poisoning. A government spokesperson acknowledges that a panel that advises the Centers for Disease Control and Prevention (CDC) in Atlanta is getting new members. But he denies that the Administration has any policy in mind and says that the new panelists are well qualified.

The changes to CDC's Advisory Committee on Childhood Lead Poisoning Prevention are the latest of several that have raised concerns about scientific advice (see Editorial, p. 703). This change comes at a critical time for the CDC committee: It is examining studies suggesting that lead is harmful below the allowable level of 10 micrograms per deciliter (μg/dl) of blood. If the panel decides that even this amount of lead is harmful, it could recommend lowering exposure. This would likely prompt tighter cleanup regulations, which would be expensive for the lead industry and owners of housing with lead-based paint to implement.

The CDC changes also come at a critical time in litigation over lead's toxic effects. Rhode Island, following the model of states that sued the tobacco industry, is suing lead-paint producers to recover the cost of treating lead-poisoned children and removing crumbling paint from old buildings. Some 38 million U.S. housing units still had lead-based paint in the late 1990s, according to a recent survey. Lowering the level deemed harmful would increase the number of children at risk and probably boost damage claims.

In the 1960s, doctors diagnosed lead poisoning if the blood level was above 60 μg/dl, exposure that can cause severe abdominal spasms, kidney injury, and brain damage. After the United States began phasing out leaded gasoline in 1976, average blood lead levels plummeted. But epidemiological studies in the 1980s and 1990s revealed that low levels still damaged children's ability to think, concentrate, and hear. CDC continued to reduce the allowable lead level—to 30 μg/dl in 1975, 25 in 1985, and 10 in 1991. The current level has been endorsed by the National Academy of Sciences, the American Academy of Pediatrics, and the World Health Organization. But about 900,000 U.S. children under age 6 still have blood lead levels of 10 μg/dl or more, according to CDC.

Subtle poison.

Bruce Lanphear found that even low-level exposure to lead—as from old paint—can affect children's test scores.

CREDIT: (TOP TO BOTTOM) CINCINNATI CHILDREN'S HOSPITAL MEDICAL CENTER

New studies in the past decade indicate that children's ability to think and learn might suffer at still lower levels. For example, in Public Health Reports in 2000, preventive medicine expert Bruce Lanphear of Cincinnati Children's Hospital Medical Center reported that data from a nationwide health study suggest that lead levels below 10 μg/dl lowered children's scores on reading and arithmetic tests. And there is no good treatment.

The CDC committee began evaluating the new research last year. Meanwhile, a group of senators, including Jean Carnahan (D-MO), began pressuring Secretary of Health and Human Services (HHS) Tommy Thompson to lower the standard from 10 to 5 μg/dl. CDC seemed agreeable: The St. Louis Post-Dispatch last summer quoted Richard Jackson, head of the CDC division that deals with childhood lead toxicity, as predicting that the committee would recommend lowering the lead standard and CDC “would go along.”

But Jackson isn't commenting now. And the Administration's critics see the latest committee changes as a reversal. The CDC's advisory panel overhaul was documented by an environmental group, the Natural Resources Defense Council, and a report released on 8 October by Representative Edward Markey (D-MA). The critics blasted Thompson for rejecting several qualified nominees to the panel, including Lanphear, who has publicly advocated halving the permissible level, and Michael Weitzman of the University of Rochester, New York, who had been on the committee since 1997. The Markey report also raised questions about some experts nominated to the panel, including Joyce Tsuji of Exponent, a California-based consulting firm whose clients include a major lead smelter; Sergio Piomelli of Columbia Presbyterian Medical Center in New York City, who in 1991 opposed lowering the lead standards; and pediatric toxicologist William Banner of the University of Oklahoma Health Sciences Center in Oklahoma City, who provided written testimony on behalf of lead-industry defendants in Rhode Island. Banner argued in that testimony that lead levels below 70 μg/dl do not injure the nervous system.

Public health advocates are worried about what will follow the panel overhaul. “I would be very concerned that these scientists were placed on this committee to represent the interest of their clients,” says pediatrician Susan Cummins of the National Academy of Sciences, who chaired the CDC panel in the mid-1990s. But Cummins adds that, although there's no evidence for a threshold below which lead is safe, “you reach a point where there really isn't much you can do beyond moving a family out of their home.”

The new CDC nominees defend their inclusion on the panel. Banner says that he has “an open mind” about lead poisoning and dismisses allegations in the Markey report as “absurd.” Tsuji declined the nomination because of perceptions that she might have a conflict of interest, she says. Piomelli says that in the past he frequently opposed the lead industry on gasoline standards and has testified for defendants and plaintiffs.

Summing up the Administration's view, HHS spokesperson Bill Pierce says that he thinks the new roster of members will improve the panel as a whole and that “the secretary wants to see a breadth and depth of opinion.”

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