A Northwest Washington family yesterday became the first to sue concerning toxic munitions from World War I left beneath a large swath of their Spring Valley neighborhood.

The suit, on behalf of Thomas and Kathi Loughlin and their children, Nora, 7, and Hannah, 5, claims that the family was exposed to toxic chemicals for several years without warning. Kathi Loughlin developed a brain tumor in 1997, and doctors said they could not rule out a connection. Although the tumor was removed, apparently successfully, the family's pediatrician warned that the children should not return to the house, said the family's attorney, Patrick M. Regan.

The civil suit for $32 million, filed in U.S. District Court, alleges that the U.S. government, American University, the U.S. Army and four developers were aware of highly toxic substances under the house at 4825 Glenbrook Rd. and failed to tell the family about it.

Other Spring Valley residents say they think they may have been exposed to high levels of toxic substances, such as arsenic.

The Loughlins lived in the house for six years after purchasing it in 1994. It sits atop a site, once owned by the university, that the Army used to test chemical weapons during World War I, the suit says. Since March of last year, the Army has recovered more than 200 chemical weapons and related items, including several corroded 55-gallon drums -- empty but having signs of leakage -- on the Loughlins' property, Regan said.

Numerous Spring Valley residents have said they worry there might be a link between illnesses in their families and the presence of high levels of arsenic.

"Before the litigation is concluded, it will involve hundreds of homeowners," Regan said.

This month, an analysis by the D.C. Department of Health said that the Spring Valley neighborhood has not experienced an abnormal number of deaths from cancer.

Using 10 years of data for a demographically similar neighborhood -- Potomac in Montgomery County -- the study found "no substantial difference in the cancer mortality rate," officials said.

Regan questions the study. "They never contacted my clients," he said. "Whatever methodology they used was fatally flawed."

In July, American University filed an $86.6 million claim against the Army for damages from use of the campus as a chemical testing ground and for cleanup costs. That claim is pending, university spokesman Todd Sedmak said. He would not comment on the Loughlins' suit.

A spokesman for the Army Corps of Engineers and others involved in the suit were unavailable or could not be reached to comment last night.

The Loughlins, who now live in the 4800 block of Foxhall Crescent NW, also could not be reached.

Arsenic contamination was found in some soil on campus last year. The Corps of Engineers announced in 1995 that it had cleaned up the problem, but under pressure from residents and city officials, its teams returned to sample the soil of every property in a 661-acre area. As of Dec. 11, it had tested 1,194 of the 1,525 properties and had found that 140 had arsenic levels greater than the threshold set by officials for conducting additional tests.

The Loughlins were not told about the contamination until 1999 and were reassured that the levels were not dangerous, Kathi Loughlin has said. The family first filed a claim with the Army last year, seeking more than $2 million. The Army did not act on it, and the family sued to force a response.

In about 1990, the university sold the property to four developers, Limited Partnership, Brandt Inc., Lawrence Brandt and Robert Brandt, the suit says. In 1992, five construction workers at the Loughlins' homesite were overcome by toxic fumes and required medical care, the suit says.

Two years later, when the Loughlins moved in, the Corps of Engineers tested the soil on the property. "And although these soil samples revealed dangerous levels of arsenic . . . the Army did not disclose this information," the suit states.