Lead poisoning affects hundreds of thousands of U.S. youngsters, but most get it from paint chips and dust in deteriorating buildings — not recalled toys, U.S. health officials say.

Mattel Inc. issued a recall Tuesday for Chinese-made toys that could have lead paint. It was the toy maker's second recall involving lead paint in two weeks.

No children have been reported harmed by the lead paint in the toys, which were sold at retail stores between May and August. But lead poisoning's effects are cumulative so it's important to remove tainted toys from children, Nancy A. Nord, acting Consumer Product Safety Commission chairman, said at a Washington news conference.

Often, lead poisoning occurs with no obvious symptoms and frequently goes unrecognized. But it can cause irreversible learning disabilities and behavioral problems and, at very high levels, seizures, coma, and even death.

Federal guidelines define lead poisoning as occurring at a measurement of 10 micrograms of lead per deciliter of blood, but health officials in some states define lead poisoning at even lower limits.

But state and federal officials agree there are no safe levels of childhood exposure to lead. Dr. John Rosen, a lead poisoning specialist at the Children's Hospital at Montefiore in New York City, said he recommends that if a child has been playing with a recalled toy for a month or more, parents should consider bringing the child in for a blood test.

"My suggestion to parents is be safe and not sorry," he said.

There is no medicinal treatment for lower levels of blood poisoning, but recognizing the condition can help guide nutritional and educational measures, Rosen said.

About 310,000 U.S. children ages 1 to 5 have blood lead levels that require treatment or other measures, according to the U.S. Centers for Disease Control and Prevention.

Lead-based paint was banned from use in housing in 1978, but young children are living in more than 4 million U.S. homes that have deteriorated leaded paint and elevated levels of lead-contaminated house dust, health officials estimate.

Tiny leaded dust particles get on children's hands and feet, and the kids ingest then by sucking on their fingers, explained Rosen.

If parents are worried about lead in their homes or products, Nord recommended using professional testing services. She said home testing kits are not reliable.

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