Behind the headlines about the crisis in the Persian Gulf was another crisis of sorts last week in the White House: The nation's First Dog, Millie, was sick -- a victim of one of civilization's oldest health hazards.

"Lead poisoning. It's a terrible thing," the President explained. "Flaking the paint, licking her toes . . . they're redoing the White House, and she's licking her feet and she's ingested lead." The ancient metal has long been known to damage the central nervous system, and Millie apparently has not been quite herself for the last three months.

Of much greater concern to health officials is the fact that the Bushes' English springer spaniel is not the only one exposed to lead in the United States. It is estimated that 10 percent of all American children -- and more than half of poor black children -- have levels of lead in their blood that scientists believe can cause neurological damage.

The major source of lead exposure in the U.S. is old housing, where lead-based paint is slowly crumbling off the walls -- the kind of housing found in inner cities and poor rural areas. "It's potentially devastating the segment of our population that lives in housing with high lead levels," says David Rall, director of the National Institute of Environmental Health Sciences. "That's typically in lower-income areas."

The White House was quick to say that Millie is now okay -- "back to performing her functions as First Dog," as White House spokesman Marlin Fitzwater put it. In fact, her condition was downgraded from lead poisoning to "acute lead exposure, much less serious," according to a White House spokesman.

But such official optimism over the Bushes' dog contradicts growing scientific evidence that exposure to even low levels of lead can lead to subtle but significant brain impairment, including reduced I.Q. and a higher rate of learning disabilities. "People don't worry about a dog or cat developing symptoms," says J. Routt Reigart, associate professor of pediatrics at the Medical University of South Carolina in Charleston. "We can accept a little brain damage in a dog or cat. We can't accept that for our children."

Two studies published earlier this year suggest that the dangers of lead exposure in infancy and childhood are greater and the effects more permanent than previously realized. In one study, a group of first- and second-graders from Chelsea and Somerville, Mass., were tracked into adulthood. The children had no symptoms of lead exposure but measurements of lead residue in their teeth indicated that some of them were indeed exposed to the metal.

A decade later, researchers tracked down about half of the students and tested them again. The results, published in the New England Journal of Medicine, showed that students who had been exposed to low levels of lead as children had seven times the high-school dropout rate and six times the rate of learning disabilities as children not exposed.

A second study published in the Journal of the American Medical Association concluded that the damaging effects of lead could be traced to levels once considered harmless. "There is no evidence of any safe level of lead," says Herbert L. Needleman of the University of Pittsburgh School of Medicine, author of the JAMA report as well as the Massachusetts study.

What's more, the social consequences of lead exposure are profound. "We think this disease is at the center of the problems of poverty," says Needleman. "If you don't graduate from high school and you can't read, there's no question about what your earning ability will be."

The past 20 years have seen some progress. Removing lead from gasoline has reduced the amount of lead in the atmosphere. Screening programs have virtually eliminated cases of acute lead poisoning that used to send children into convulsions, coma and death.

But the legacy of exposure to low levels of lead is just beginning to be addressed. Only last month, a meeting was held at the Centers for Disease Control in Atlanta on the problem, and scientists expect the CDC to lower the limit of what is considered an acceptable level of lead exposure.

The problem is enormous because lead-based paint was used in almost all houses until the 1950s, and the product was not banned until 1977. It is estimated that 30 million dwellings in the United States have lead-based paint and that more than 2 million children are living in run-down housing where lead paint chips are flaking off walls and empty lots are filled with lead-laden dust.

Now with the gentrification boom, doctors are seeing a rise in what some call Yuppie lead poisoning as the children -- and pets -- of affluent families are exposed to lead in houses that are being restored. As in the White House, old layers of lead-based paint are sanded or stripped away, releasing toxic flakes and dust into the environment.

Like Millie, children lick their toes and fingers because lead has a sweet taste. Yet a chip the size of a thumbnail has about 250 times the amount of lead federal officials consider safe.

At last report, Millie is still lethargic -- all right for a dog, but the symptom could signify tragedy for a child.

"I feel sorry for Millie," says Charleston pediatrician Reigart, "but maybe it will help people realize that this is happening everywhere."