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Low Levels of Lead Damage Children

16-April-2003

By Ed Edelson, HealthScoutNews Reporter

Two studies offer more worrisome news about the harm done to children by lead exposure.
One study says IQs are lowered significantly by levels of lead in the blood below those now regarded as acceptable by U.S. health officials.

The other finds delayed puberty in girls with elevated levels of the metal in their blood.

The first study, of 172 children in the Rochester, N.Y., area, found lower IQs in those with blood lead levels of 10 micrograms per deciliter, which the U.S. Centers for Disease Control and Prevention (CDC) lists as acceptable.

Previous studies had found an IQ reduction of seven points for a blood level of 10 micrograms, with IQ declining by another two to three points as levels rose to 30 micrograms.

The new study determined the greatest damage is done as blood levels increase from 1 microgram to 10 micrograms, indicating that levels now regarded as safe are, in fact, damaging.

The study, published in the April 17 issue of The New England Journal of Medicine [requires registration to read the full text], was done by a team led by Richard Canfield, director of the cognitive development and neurotoxicology laboratory at Cornell University.

"We were very surprised because it is counterintuitive to think that the amount of damage done to mental function per increment in blood level is greater at lower levels than at higher levels," he says.

There was another surprise: "We obtained these findings when we tested children at the age of 3," Canfield says. "It is counterintuitive to find damage at so young an age."

The study suggests current estimates of a safe lead level may have to be revised, Canfield says: "Our research does not allow you to set a safe level."

But, he adds, more research into acceptable blood lead levels in children is needed. "It is necessary to replicate these findings in other samples," Canfield says. "We need more children at more than one testing site around the country."

The children were first tested at 6 months of age, with additional tests at one year, 18 months, and then yearly up to age 5. The relationship between blood lead levels and intelligence held true up to age 5, Canfield says.

Using the CDC numbers as a gauge, he makes a "very approximate" estimate that 1 million to 2 million children in the United States have lead blood levels in the 5 microgram to 10 microgram range. The CDC says one in 10 children has a blood lead level of 10 micrograms or higher.

The puberty study, which also appears in this week's issue of The New England Journal of Medicine, was done by a group headed by Sherry G. Selevan, an epidemiologist at the U.S. Environmental Protection Agency. It draws on data from 2,500 of the 40,000 girls studied for the third National Health and Nutrition Survey (NHANES), conducted from 1988 to 1994.

"Significant delays in breast and pubic hair development" were found in black and Hispanic girls with blood levels as low as 3 micrograms, the study says. Breast development was delayed anywhere from to two to five months, while pubic hair development was delayed from two to six months.

There were "non-significant" delays in white girls with the same lead blood levels. But this failure to find a cause-and-effect relationship may be due to the relatively small number of white girls in the study, Selevan says.

It isn't possible to say whether the delay is harmful, Selevan says. "You're talking about a basic developmental alteration, and you don't yet know how it will play out in the long run."
 
The EPA team is now looking at NHANES data for boys to see if the same effect occurs in them. Results might be available "in a year or so," Selevan says.

There is some good news behind this bad news about lead's effect on childhood development, says James H. Ware, dean for academic affairs at the Harvard School of Public Health and co-author of an accompanying editorial in the journal.

"It wasn't so long ago when the mean blood level in this country was high," he writes. "It's now below 3. We were burning leaded gasoline and using leaded paint. This is arguably one of the most successful things the EPA has done. Exposure to lead keeps falling."

The main exposure to lead now occurs in housing built before 1950, where paints with high levels of lead are more common, Canfield says. Lead particles can fall on the floor and be picked up by children, and toys can be contaminated.

More information

Learn about the damage done by lead and ways to prevent it from:

Copyright 2003. HealthScoutNews. All Rights Reserved.

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Study: Lead Paint Affects Child IQ

AP 30-April-2001

By JEANNE A. NAUJECK, Associated Press Writer

BALTIMORE (AP) – Children exposed to lead at levels now considered safe scored substantially lower on intelligence tests, according to researchers who suggest one in every 30 children in the United States suffers harmful effects from the metal.

Children with a lead concentration of less than 10 micrograms per deciliter of blood scored an average of 11.1 points lower on the Stanford-Binet IQ test than the mean of children with a lead concentration of 1 microgram or less, the researchers found. The mean is the intermediate value between the lowest and highest scores.

"There is no safe level of blood lead," said Dr. Bruce Lanphear, lead author of the lead study presented Monday at the Pediatric Academic Societies annual meeting.

Lanphear said newborns have lead in their blood because of its presence in their mothers, but children are most commonly exposed to lead by inhaling lead-paint dust or eating paint flakes. Lead-based paint was widely used in homes throughout the 1950s and 1960s until it was banned in 1978.

At high levels, lead can cause kidney damage, seizures, coma and death.

Before 1970, scientists believed lead poisoning took effect at 60 micrograms per deciliter. But the toxicity standard has been lowered over the years to the point where a concentration of 10 micrograms or less now is considered safe.

The researchers said their work suggests that lead is a potent toxin at levels previously thought to be harmless.

Experts predicted the study would prompt federal regulators to lower the acceptable blood-lead standard.

"This is a wonderful study that has very serious implications for public health in the United States and the rest of the world," said Dr. Daniel Courey, a pediatrics and developmental behavior professor at Columbus Children's Hospital in Columbus, Ohio.

Lanphear's team tracked 276 children in Rochester, N.Y., from ages 6 months to 5 years, measuring blood lead levels every six months and administering the IQ test at age 5.

The study also found an average 5.5-point decline in IQ for every additional 10-microgram increase in blood-lead concentration, said Lanphear, a physician at Children's Hospital Medical Center in Cincinnati.

The study adjusted for other predictors of lowered IQ such as the mother's IQ, tobacco exposure and intellectual environment in the home, Lanphear said.

Lanphear's findings confirm what those who work with "lead kids" already know, said Ruth Ann Norton, executive director of the Baltimore-based Coalition to End Childhood Lead Poisoning.

"There are kids who are disruptive, then there are 'lead kids' - very disruptive, very low levels of concentration," Norton said.

Besides affecting reading and reasoning abilities, lead also is linked to hearing loss, speech delay, balance difficulties and violent tendencies, Norton said.

Copyright 2001. The Associated Press. All Rights Reserved.

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Lead Levels Up in Overseas Children

AP 10-Feb-2000

WASHINGTON (AP) – An estimated 400,000 poor children with elevated lead levels in their blood were not screened under Medicaid and other federal health programs despite federal law that requires such testing, congressional investigators say.

Nationally, about 890,000 children have elevated lead levels, and most do not know it, the General Accounting Office concluded in a report Tuesday. "This is a health tragedy. Lead poisoning is a preventable disease," said Rep. Henry Waxman, D-Calif., who requested the report.

It found that 82 percent of children ages 1 to 5 in federal programs were not screened for lead. And high blood levels were five times as common for children served by Medicaid, federally supported health centers and the Women, Infants and Children program. Lower-income children have a greater risk of lead poisoning.

The report from the research arm of Congress echoes a similar GAO study a year ago. At high levels, lead can cause a variety of debilitating health problems, including seizure, coma and even death. At lower levels, lead can affect a child's intelligence and ability to learn.

Screening is a critical element in eliminating childhood lead poisoning because in most cases there are no obvious symptoms. Screening rates ranged from less than 1 percent of Medicaid children in Washington state to about 46 percent in Alabama. In 1989, Congress passed legislation requiring lead screening as part of Medicaid's special preventive health program for poor children.

Sen. Robert Torricelli, D-N.J., said Tuesday he would reintroduce legislation requiring states to provide a minimum number of screenings and establishing penalties for failure.

Copyright 2000. The Associated Press. All Rights Reserved.

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Poor Children Not Screened for Lead

AP 26-Jan-1999

WASHINGTON (AP) – An estimated 400,000 poor children with elevated lead levels in their blood were not screened under Medicaid and other federal health programs despite federal law that requires such testing, congressional investigators say.

Nationally, about 890,000 children have elevated lead levels, and most do not know it, the General Accounting Office concluded in a report Tuesday. "This is a health tragedy. Lead poisoning is a preventable disease," said Rep. Henry Waxman, D-Calif., who requested the report.

It found that 82 percent of children ages 1 to 5 in federal programs were not screened for lead. And high blood levels were five times as common for children served by Medicaid, federally supported health centers and the Women, Infants and Children program. Lower-income children have a greater risk of lead poisoning.

The report from the research arm of Congress echoes a similar GAO study a year ago. At high levels, lead can cause a variety of debilitating health problems, including seizure, coma and even death. At lower levels, lead can affect a child's intelligence and ability to learn.

Screening is a critical element in eliminating childhood lead poisoning because in most cases there are no obvious symptoms. Screening rates ranged from less than 1 percent of Medicaid children in Washington state to about 46 percent in Alabama. In 1989, Congress passed legislation requiring lead screening as part of Medicaid's special preventive health program for poor children.

Sen. Robert Torricelli, D-N.J., said Tuesday he would reintroduce legislation requiring states to provide a minimum number of screenings and establishing penalties for failure.

Copyright 1999. The Associated Press. All Rights Reserved.

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