Few residents of Spring Valley face risks from the soil and air contamination detected so far from World War I-era munitions buried in their neighborhood, a comprehensive health report has concluded 12 years after a utility contractor uncovered the hazardous material.

"Most people in Spring Valley have not and will not experience adverse health effects," the federal Agency for Toxic Substances and Disease Registry said, because exposure levels to the explosives, chemical agents or their residue "are not high enough."

Still, as that qualified wording indicates, the report does not give the Northwest Washington community of some 1,500 homes, 27 embassies, a university and a hospital a completely clean bill of health.

"Some uncertainties remain," the report acknowledges, a reference to the hundreds of chemical components the Army might have discarded decades ago at a research and testing site then known as the American University Experiment Station. The report recommends that additional environmental sampling be done in targeted locations and that residents remain vigilant to the possibility that more dangerous materials could be unearthed.

Though an epidemiological study failed to find an elevated incidence of cancer, one year's statistics showed the mortality rate from leukemia to be more than twice as high in Ward 3 as in the city as a whole. City health officials could evaluate the numbers by census tract to determine whether the incidence is localized to Spring Valley, the report suggests.

The conclusions await review by the panel of scientists and citizens charged with watching over the complex cleanup -- a $165 million effort, expected to last until 2010, that is one of the most costly projects of its kind in the country. General public comment is being solicited through late April.

If the March meeting of the Restoration Advisory Board is any reflection, the community is moving toward acceptance despite some families' suspicions about medical problems they or neighbors have suffered. The meeting included a presentation by the report's authors and discussion of what could be proved through further health investigations.

"We could always wait for the next perfect study," one board member said.

Spring Valley's days as a chemical weapons dump date to the late 1910s. The Army used the then-rural area, bounded mainly by Loughboro Road, Dalecarlia Parkway and Massachusetts Avenue, for trying out all sorts of noxious agents contemplated for use in World War I. When the Army abandoned the site in 1921, it haphazardly trashed or buried an assortment of materials.

This legacy was ignored or forgotten as an affluent neighborhood was built up -- until that contractor chanced upon the ordnance in 1993 while digging a utility trench.

The most prominent finding in the report focuses on arsenic because it is the "most persistent breakdown product" of chemical warfare and at certain doses of exposure can cause blood disorders, certain cancers, even death.

More than 120 of 1,602 pieces of property in Spring Valley have been found to have arsenic exceeding the cleanup threshold of 20 parts per million; so far, the Army Corps of Engineers, the lead agency on the project, has excavated and replaced 30 yards. None has contained arsenic levels high enough to cause harmful health effects, the report says. Excluding major disposal areas and burial pits, "the soil pathway . . . does not represent a public health hazard," it says.

The conclusion came as little surprise, according to several board members. "I believe we have turned the corner on the arsenic investigation," said toxicologist Gregory Beumel, who has lived in the area since 1992.

The advisory board's scientific consultant concurs, but with some reservation. Environmental biologist Peter deFur cautioned last week that excepting data on contaminated drinking water, the health risks of long-term, elevated exposure to arsenic through soil or soil gases remain an unknown.

"For most other exposure pathways, we have very, very limited information," he said.

Besides the yards targeted because of elevated arsenic levels, an even greater number potentially have buried ordnance that would need removing. The largest known disposal area is a debris field called Lot 18 on the southwestern edge of the American University campus.

The agency that conducted the study advised that soil gas sampling should continue to be done before any excavation. It also endorsed the corps' investigation of whether groundwater could be contaminated and possibly migrating toward the Dalecarlia Reservoir, a prime source of drinking water for much of the region. "The report is saying there are uncertainties. The Army must finish the job," stressed Scott C. Heuer, who grew up in the neighborhood and has raised concerns about the number of troubling health problems identified on certain streets.

The report does not address the surprise discovery late last year of perchlorate in the reservoir. The toxic chemical, which can cause an array of serious health problems, is often found in explosives and rocket propellants. The Corps of Engineers has argued that Spring Valley's contamination does not endanger Dalecarlia.

"We do not believe there's connectivity between groundwater and the reservoir," corps project manager Gary Schilling said Friday. "The perchlorate issue has forced us to prove that."

Last week, engineers began digging for the first of 30 wells -- six times what was planned before perchlorate was discovered -- that by late summer should start to provide answers.

The city will monitor the installation and move forward on the federal health recommendation. The D.C. Council has authorized $250,000 for its own Spring Valley health study, which could include door-to-door interviews, patient chart reviews and medical testing. Given the leukemia issue, "we're trying to optimize the amount of answers we could derive," said city Health Director Gregg A. Pane.