LA CROSSE, Wis. -

More than half a million kids nationwide are now believed to have lead poisoning.

That's about twice as high as the last estimate, but that doesn't necessarily mean lead poisoning is becoming more common.

The increase can be chalked up to a change in the way the U.S. Centers for Disease Control and Prevention has decided to classify risk for lead poisoning.

Last year, the CDC lowered the threshold for lead poisoning by half, so now many children are considered at risk when they weren't before.

Still, public health experts said 1 in 38 children is something to take seriously, especially in La Crosse, where the older housing stock means many kids could find themselves exposed to lead-based paint.

It’s a concern for La Crosse mother Deborah Nerud, whose family has been living in a 1920s-era house for six years.

But just the other night, she noticed something strange -- paint chips at the top of the stairs.

“I thought, 'Not a big deal.' We cleaned them up. But then they kept reappearing," said Nerud.

That's when she realized her 3-year-old daughter, Beatrice, had been peeling paint chips off the wall.

"Like most 3-to-almost-4-year-olds, they come up with new and interesting ways to avoid bed time,” said Nerud. “After she was put to bed, she'd get out of bed. And I found little paint chips on the stairs.”

She leaned down to Beatrice, who was sitting in her lap.

“And who was that, was that you? Yeah, that was you,” said Nerud.

"In 2012, we followed up on 21 children who were potentially lead-poisoned, and where the public health nurses had to do follow-up services for them," said La Crosse County Public Health nurse Charity Kocinski.

That was when the CDC's standard for risk was a level of 10 or more micrograms of lead per deciliter of blood. Now that the threshold has been lowered to 5 micrograms, Kocinski said it's likely many more La Crosse kids would test positive.

"All kids are different, so it's really hard to say at what level each child is going to have problems at," said Gundersen Lutheran pediatrician Dr. Casandra Grube.

Grube said the symptoms can be hard to notice, but can have a lasting impact.

"It can actually decrease kids' IQ level, their ability to develop at appropriate steps, attention problems, learning problems, those sorts of things," said Grube.

That’s why Nerud said it's time to get Beatrice checked out soon.

"I have to take her in again and make sure that she gets tested because I don't want to take any risks with this house," said Nerud.

These new changes to how the CDC measures lead-poisoning come at a time when the federal government is making large cuts to local public health departments’ budgets. Kocinski said she's not sure how it will affect the county's lead testing program, but the department may have to look for other sources of funding.

The state still only requires local health departments to follow up on children who test at a level of 15 or above, but many Wisconsin county health departments choose to lower that level.