It was about 12 years ago that the first cry of "get the lead out" started a nationwide campaign that turned up thousands of children who were somehow injured, brain-damaged, poisoned by lead, often in their own homes. In 1970 half a million children throughout the country were estimated to have some degree of lead poisoning.

Small children are particularly susceptible to lead poisoning. In addition, studies over the past decade have built up a body of alarming evidence indicating that low levels of lead in a child's vulnerable, growing system can be as ominously destructive as more dramatic high levels can be life-threatening. Lead can cause damage ranging from behavior problems to intellectual impairment to retardation to blindness to death.

Progress in controlling sources of lead has been agonizingly slow over the years, but real progress has been made. Lead paint has been banned for use in interiors of houses and in some places it has been banned altogether. The switchover to unleaded gasoline already has dramatically lowered lead traces in the air, which some scientists have felt was, perhaps, the greatest source of poisoning.

Karen Ehrnman, public health research aide in the office of Child Health Advocacy in Children's Hospital, is the coordinator of the Committee for Lead Elimination in the District of Columbia.

Because of intense screening programs, she says the percentage of youngsters in Washington found to have elevated lead levels has dropped from about 30 percent in 1973 and 3.6 percent in 1979.

Better, she feels, but not good enough.

"It's the screening," she says. "We're finding the children earlier and we're not having the morbidity of 12 years ago, but it is still a problem. Because the incidence has decreased, it's easy to ignore the problem. There was 554 children with elevated leads last year in the District. And it is a totally preventable health problem."

Ehrnman and her committee believe that the major source of lead poisoning is still from "being around lead paint."

"Primarily," she says, "you think of children in old homes which have lead paint on the wall. We used to warn parents about children eating the chips off the wall -- and we still do, of course. It has a sweet taste, often, and as soon as you get one little break in the wall, they love to get at it and pick at it and get into it.

"Certainly that is still a problem. But now the message includes homes which had lead paint (where there is no more chipping), because as the paint disintegrates it gets into the dust and it's everywhere. And it's important for parents to know that it's a hazard. It helps to tell them to do good hand washing because, you know, we're talking about young children that always have their hands in their mouths, anyway . . ."

The lead committee is this week conducting a door-to-door screening program in Adams Morgan to try to pick up children who might not be coming under the District's regular screening program. Under a federal grant, there is free blood-level screening for children from 10 months to 6 years at all Department of Human Services clinics in the city. Hospitals like Children's and Howard do screening on a free-for-services basis.

Once a child is identified with a lead problem, a coordinated team effort goes into effect. First, of course, the child must be removed from the source of lead. If the levels are low enough, the lead will be eliminated naturally.

In cases of very high levels, hospitalization and a course of extremely painful injections, a procedure called chelation, must be undertaken. Last year, Ehrnman said, 31 children underwent chelation in the District. "They hate it."

Then, theoretically, the city sends inspectors to find the source of the lead -- whether paint, dust, comic books, sometimes, or children eating newsprint. If lead paint is found, as it usually is, the owner is notified and is required to make repairs. But, says Ehrnman, "It never goes quite that simply . . . The abatement process can take up to two years."

In the meantime, the lead committee has devised a series of adroit and resourceful measures to help lead-proof the area on a temporary basis. If costs are a problem, the committee organizes a block party.

Lead-poisoning symptoms can include behavioral changes, vomiting, stomach aches, or nothing. If you suspect there is lead or lead poisoning in your house, call the lead committee at 745-3029 right away.