Updated

More than half a million children in the United States have elevated levels of lead in their blood, according to a new report from the Centers for Disease Control and Prevention.

Surveys done between 2007 and 2010 show that about 535,000 children ages 1 to 5, or 2.6 percent of kids in this age group, had blood lead levels equal to or above the recommended 5 micrograms per deciliter (mg/dl), the report says.

That's down from the 8.6 percent seen in earlier surveys done between 1999 and 2002, but disparities remain among minority groups and those from low-income families.

In earlier years, the CDC had used a higher threshold —10 mg/dl or greater — to identify kids with concerning blood lead levels. But last year, the recommendations changed to say that kids with levels at or above 5 mg/dl should identified, because these levels are higher than normal.

The idea behind the change is to identify kids with high levels earlier, so that action can be taken to reduce their lead exposure. Kids need medical treatment (called chelation therapy) for lead exposure if their blood lead levels reach 45 mg/dl, the CDC says.

Even low levels of lead in the blood have been linked with lower IQs and attention problems, and there is no safe level of lead exposure, the CDC says.

The higher blood lead levels seen among minority groups and low-income families can be attributed to differences in housing, nutrition and other environmental factors, the report says.

Most homes made before 1978 have lead paint that can find its way into dust, and from there, into kids' mouths. While public health efforts, such as removing lead from paint, have dramatically reduced children's exposure to lead, continued efforts to increase awareness of lead hazards can further reduce exposures, the CDC says.

Increasing iron and calcium intake can also reduce the amount of lead absorbed by the body, the CDC says.

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