Lead poisoning remains a threat for kids

Washington -- Phone calls from concerned Washington, D.C., parents kept physicians busy earlier this year as news broke that high levels of lead were leaching from the city's aging water lines and posing a health risk to vulnerable families.

Children's National Medical Center in Washington actually sponsored a phone bank to respond to queries from area residents and "the phones rang off the hook for two hours," said attending physician Dana Best, MD, MPH. Parents wondered whether to boil the water. The answer was no. Adults wondered if there was any risk to them. The answer was that the damage had probably already occurred.

Those considered most at risk for lead poisoning are children younger than 6 and women who are pregnant or nursing. For those groups the Washington Public Health Dept. advised not to drink the tap water unless it is filtered or to drink bottled water.

At times, the D.C. water situation seemed to reach almost crisis proportions. But concerns about lead poisoning should constantly rank high on everyone's list. Any source of lead is bad news, especially for rapidly growing children, as it affects nearly every system in the body. Once the damage is done, there is no way to reverse it. And lead in water isn't generally the largest lead poisoning threat. Lead-based paint holds that title.

Lead poisoning was recognized as a health threat decades ago, and it remains an issue today. The Centers for Disease Control and Prevention estimates that approximately 434,000 children in the nation already have lead levels greater than 10 μg/dL of blood, the agency's threshold for concern.

The CDC recommends testing children for lead exposure at ages 1 or 2, and the American Academy of Pediatrics also urges physicians to provide advice to parents that could prevent lead exposure in the first place.

For example, physicians could caution the many families who embark on renovation projects of older homes when a new child is expected that they run the risk of exposing a vulnerable fetus and any other young child in the home to lead from paint chips and dust.

When Anne Evens, director of the Chicago Public Health Dept.'s Childhood Lead Poisoning Prevention Program, was pregnant she was surprised to find that she was only one of many expectant parents at her local home improvement store. This prompted the launch of a citywide educational campaign aimed at do-it-yourselfers and local hardware stores.

For physicians, knowledge of their patients' home or child care environment becomes crucial information. "The dilemma is that most of our efforts happen inside the clinic walls," said Bruce Lanphear, MD, MPH, director of the Cincinnati Children's Hospital's Environmental Health Center. "But since every disease and condition has an environmental component, to truly protect individuals from harm we are going to have to think about that environmental component."

Danger levels

The CDC established its current lead exposure standard of 10 μg/dL of blood in 1991, and many believe that the level should be lower still.

Telling parents whose children have blood lead levels below 10 that all is well is overly simplistic, said Dr. Lanphear.

"We know that blood lead levels can change very quickly in the first two years of life," he said.

A very young child with an already elevated level of 9 μg/dL of blood, for example, should prompt concern that his or her lead levels will likely surpass the danger point.

Recent research has also found that blood lead levels lower than 10 pose a risk. "Even within the zero to 10 range, there is still a relation between exposure to lead and children's IQ scores," said Richard Canfield, PhD, senior research associate in Cornell University's Division of Nutritional Sciences in New York.

Dr. Canfield led a five-year-study that found intellectual impairments in children whose blood lead levels were below the CDC's threshold.

The study followed 172 children in the Rochester, N.Y., area whose blood lead level was assessed at ages 6, 12, 18, 24, 36, 48 and 60 months. Their IQs were tested when they were 3 and 5 years old.

"We estimated that, after controlling for a large number of factors, the children would be expected to lose about seven points of IQ over the first 10 μg/dL of blood, which is a lot," said Dr. Canfield.

The study was published in the April 17, 2003, issue of The New England Journal of Medicine.

"If it were my decision to make, I think it would be prudent at this time to reduce the lead level to 5 μg/dL and to continue to carry out more research on children at that level," he said.

Dr. Canfield and his colleagues also found that the first low exposures to lead did more damage to the children studied than did the same exposures at higher levels.

"It was sort of like the first hit is the worst," he said. "We don't have a good biological mechanism to explain that but it seems a reasonably consistent finding across studies. We believe it is a real pattern."

Another study, this one carried out by the National Institute of Environmental Health Sciences, found that treating children with elevated lead levels with succimer did not improve the children's scores on IQ tests.

"We concluded that if what you want to do is improve these neurocognitive outcomes, then chelation therapy won't do it for you," said Walter Rogan, MD, an epidemiologist at NIEHS.

Despite the dire consequences of lead exposure, Dr. Canfield offers some reassurance. He points out that although earlier generations were likely exposed to even higher levels of lead, many members went on to accomplish great things. "So lead is not the sole determinate and probably not even the major determinant at these low levels of the eventual life outcome of the child."

Nonetheless, all agree that the best route is to ensure that homes are free of lead paint and that lead levels in drinking water are acceptably low.

Meanwhile, the widely publicized Washington, D.C. public health controversy not surprisingly drew the attention of Congress and prompted Sen. James Jeffords, (I, Vt.), to introduce the Lead-Free Drinking Water Act.

"Safe drinking water is not a privilege; it is a right -- whether you live in Washington, D.C., or Washington state or Washington County, Vermont," he said.