Lead-based paint may not be the major cause of lead poisoning in children, according to federal researchers involved in the government's program to eliminate the use of lead paint in housing.

During the past seven years, the government has spent more than $51 million to study the problem of lead poisoning, and eliminate the lead-paint hazard from urban housing.

But according to a report prepared by Irwin H. Billick, the man who heads the Department of Housing and Urban Development's lead elimination research program, "although lead-based paint is a prime source of environmental exposure, it is not the only source."

"Further," the report asserted, "the relative contribution of lead-based paint to children's lead levels is unknown, as is the relative importance of other sources, such as lead from food, dust or the ambient air."

According to the study, there was been a marked decline in the number of deaths attributed to lead poisoning and acute lead poisoning.

"Currently, anecdotal information from screening programs indicates that the very high lead levels experienced in the early days of the programs are less prevalent," it went on to say. "Deaths due to lead poisoning seem to be rare.

"Children with slightly to moderately elevated blood-lead levels have replaced children as the major concern," the report continued." In addition, field personnel also indicate they frequently cannot identify even possible lead-based paint hazards in the dwelling units of children found with elevated blood levels."

No one is suggesting that lead paint does not constitute a health hazard, particularly to children who may eat chips of it as the paint peels from the walls of older houses. Most of these are in inner-city neighborhoods.

In fact, Donna Shalala, HUD's assistant secretary for policy and research, stressed that the report is only a staff document and emphasized that "we don't want to let lead paint off the hook; it's clear that lead paint is a hazard."

What is not clear, however, is the relative importance of paint as a hazard compared to, for example, air-borne lead particles.

According to a New York City study conducted between 1970 and 1976 and cited in Billick's report blood-lead levels in children dropped significantly while little was being done to remove lead paint from housing in the city.

According to the Billick report, the New York data did show "a reduction in the air-lead levels in the New York area as measured at a single area sampling station."

When the federal programs were conceived, lead poisoning and death caused by high blood-levels were the major concern.

Today, however, some researchers are worried about long-term effects of minimal blood-lead levels in children. There has been some research to indicate that even very low levels of lead may cause mental retardation and various learning disabilities.

Also lead-related problems in children were thought to be a problem of the inner city. But two recent studies in Northwest Washington in the Georgetown, Glover Park and Cleveland Park areas have thrown that theory into doubt.

The first study, conducted by Dr. Bailus Walker, chief of the city's Department of Environmental Services, found that 42 percent of 500 children sampled had slightly elevated lead levels in their blood.

A second study, conducted in the same area of the city by the Department of Human Resources, found that only 4 per cent of the children had elevated lead levels.

However, the DHR survey was conducted in the late fall, while the Walker study was done during the summer. There is a sharp seasonal variation in blood-lead levels, with the highest levels being found in the summer.

Billick's report concludes that the government needs to radically improve its data collection and analysis in lead poisoning study, must look for other sources of lead in the environment and has to improve cooperation among government agencies responsible for elimination of the lead hazard.