High lead levels are still a concern for children living in Vieques, Puerto Rico, according to Primera Hora, a daily newspaper in the island.

The School of Medical Technologies of Puerto Rico tested 98 children in Vieques, and 24 children came back with high levels of lead in their blood. Childhood lead poisoning, which has no obvious symptoms, can lead to learning disabilities, behavioral problems and, in worst cases, death, according to the Center for Disease Control.

The results of the test were an average of five micrograms of lead per deciliter of blood, not an alarming figure but still a cause for concern. The CDC says blood levels above 10 micrograms of lead per deciliter of blood are considered a public health emergency.

The study found that more than half of the children, about 51 of 98, have less than 3.3 in their blood. The rest had between 3.3 to 27.6 micrograms of lead in their blood, the newspaper said. About 24 people, or 25 percent of those tested, had lead levels over five.

The study did not look into what caused the high lead levels in Vieques, but for four decades Vieques was used by the U.S. Navy as a training ground for exercises and munitions testing. Over the years, it dropped millions of pounds of ordnance on the area – including bombs, artillery shells and rockets – until the training range was closed in 2003 after years of protest.

The long-term impact of the military activities there has long been a matter of debate.

The U.S. Agency for Toxic Substances and Disease Registry tested the site in 2003 and concluded there were no lasting health effects from the military exercises. But 7,000 current and past residents of Vieques have filed a federal lawsuit seeking billions for illnesses they say were caused by decades of weapons testing.

Lead contamination is usually caused by lead-tainted paint, dust or soil. Public awareness campaigns to use products with no lead prompted a decrease of lead poisoned children, the CDC said. In 1978 there were 14.8 million poisoned children in the U.S., in the 1990s that number dropped to 890,000.

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