MILWAUKEE — The house is not the biggest on the block, but Blanca de la Cruz's bungalow is swept and tidy, and she keeps a close watch on her two boys, 9-year-old Saul and 3-year-old Miguel.

So she was puzzled in February when, over the course of only a few days, Miguel began acting oddly: He was clumsy, irritable and high-strung. She took him for a checkup and four days later got a bold-faced letter from the city health department saying Miguel was "probably lead-poisoned."

Pediatricians ring alarm bells when a child's blood tests show lead levels above 10 ug/dL (micrograms per deciliter) of blood. A microgram is a millionth of a gram. A deciliter is one-tenth of a liter.

A blood test put Miguel's blood lead level at 33 ug/dL. A few more points and he would have been hospitalized. A city inspector visited the house, wipe-tested surfaces throughout and found what he expected: The lead was coming from the windows.

Massive recalls of lead-painted toys from China are making news these days. Mattel last month recalled 675,000 Barbie toys, including Barbie's Dream Puppy House and Kitty Condo. But for the thousands of kids sickened by lead each year, it's not Barbie's Dream House that makes them sick — it's their own house.

Americans could be excused for assuming that lead poisoning went away long ago. The government banned lead paint in 1978, and oil companies began phasing out leaded gasoline in 1975. But 30 years later, hundreds of thousands of children — most of under age 6 — show signs of lead exposure. The American Academy of Pediatrics estimates that one in four children live in housing with deteriorated lead paint.

Eliminating lead from gasoline, paint and other products has paid off. Lead concentrations in the air have declined dramatically, about 96 percent, from 1980 to 2005. Only two U.S. counties — Jefferson County, Mo., and Lewis and Clark County in Montana — now have lead levels that exceed federal air-quality standards.

But lead still harms an estimated 310,000 American kids, the Centers for Disease Control and Prevention reports.

A potent neurotoxin, lead affects the brain, kidneys and nervous system — often irreversibly. Even exposure to a small amount of dust can raise a toddler's blood lead to dangerous levels, scientists say.

Studies have linked lead to lower IQs, learning difficulties, behavioral problems and even death. Researchers also have found that children exposed to lead are more likely to end up with criminal records.

Poor and minority kids in big cities are among those hit hardest, according to the CDC — and many researchers say that has kept the nation's lingering lead problem from generating more public outrage. But lead also remains in older homes owned by middle-class families.

Lead paint in walls or windows chips or rubs off as a house ages. In most houses, such as Miguel's, paint dust settles near the windows, after years of opening and closing. The simple act of letting in fresh air grinds the old paint in the cracks to a powder. Miguel touched the dust and, as 3-year-olds do, put his fingers in his mouth.

De la Cruz and her husband bought the house in 2002, but for decades, the windows apparently had been painted with lead-based paint. Owners would have switched to safer stuff only after the 1978 government ban.

"That storehouse of lead that exists in the older housing in this country is enormous," says Philip Landrigan of Mount Sinai School of Medicine in New York. "It's going to be there for decades and decades."

BLOOD TESTING

For many kids, a routine blood lead test uncovers dangerous lead levels in their homes. Jamia Handy, her husband Thaddeus Chatman and four kids were living in a rental house in Baltimore for four months before a well-baby check in August for her daughter Jaiah Chatman, who is nearly 2, came back with a lead level of 84 — eight times the "action level."

The culprit: lead dust in and around the home's windows.

The Baltimore-based Coalition to End Childhood Lead Poisoning, which since 2000 has been pushing for a window-replacement program, moved in to renovate the home and replace the windows. The family is staying in a hotel while the work proceeds.

Doctors admitted Jaiah immediately to intensive care, where she began oral chelation therapy: one dose every eight hours of a concoction containing a chemical that binds to lead in the blood so she can get rid of it through her urine.

Jamia Handy, who attends nursing school, says her training has not covered how to prevent lead poisoning. Jaiah had the symptoms — loss of appetite, irritability — but Jamia says they were unusual only in hindsight.

"She's always irritable," Handy said. "She's the baby. She's got brothers."

Three weeks of chelation got Jaiah's lead level down to 44. But if it goes up, she'll have to be readmitted to the hospital.

It's unclear whether Jaiah will have developmental issues. If she does, they won't show up for another two to four years, doctors say.

In 2005, only 1.6 percent of children ages 1 to 5 had elevated blood lead, considerably fewer than in the 1970s, when 88 percent did. It's "one of the great triumphs in public health in this country over the last 20 to 25 years," says Landrigan, a pediatrician.

FIGHTING THE PROBLEM

Some cities have moved aggressively to curb the lead problem in older homes.

Health officials in Milwaukee, for example, pioneered a program in the early 1990s that pays homeowners $160 to repair or replace each lead-painted window.

By all indications, the program has been a success. In 1995, 39 percent of city kids had elevated blood lead. By 2006, it was down to 6.6 percent. Total cost: $53.5 million — about two-thirds of it from federal grants.

Rick Nevin, a Fairfax, Va., economist, and David Jacobs, a former U.S. Housing and Urban Development Department housing research director, are proposing a massive public-private effort to replace windows in the nation's aging housing stock.

They say the money spent — $22 billion, less than the federal government spends on education in a year — would yield $67 billion in benefits, including lower rates of special-education enrollment, Attention Deficit Hyperactivity Disorder, juvenile delinquency and crime — and lower heating costs.

It has been nearly eight months since Miguel's blood test. In that time, workers installed new windows in his house. That and a low-fat diet high in calcium and iron have cut his blood lead level nearly in half, from 33 to 17. But he's still in danger.

"It's real stressful," says de la Cruz, who keeps a detailed file of her son's blood tests — eight in all since February — in a zippered Mickey Mouse tote bag.

"I don't want anybody to face the experience I had," she says.

Contact Greg Toppo at gtoppo@gns.gannett.com.