Chemical contamination may be damaging one in five national wildlife refuges, but only 10 of the nation's 431 refuges have problems severe enough to require immediate attention, the Interior Department said yesterday.

"By and large, we have a healthy wildlife refuge system, with a few problems," said William P. Horn, assistant secretary for fish and wildlife and parks, who called the situation "manageable."

The department launched the study of refuge contamination last year, more than three years after refuge managers identified possible pollution problems, ranging from industrial waste to agricultural runoff, at more than one-third of the nation's wildlife sanctuaries.

"We'd heard horror stories about how widespread the problem was," Horn said. "The fact that we came up with only 10 out of 431 leads me to believe this may be a manageable problem."

Horn acknowledged, however, that the department has "reason for concern" at 74 additional refuges. Thirty of those showed evidence of contamination and will be studied in more detail.

At the remaining sites, investigators reported no direct evidence of contamination but considered pollution possible because of heavy pesticide use or industrial waste-dumping on adjacent property.

The most serious conditions were found at the Kesterson refuge in California's San Joaquin Valley, where agricultural drainage has concentrated naturally occurring selenium at levels that are toxic to migratory birds. The department has been shooing birds away from the refuge for more than a year, and farmers in the area are under orders to stop the flow of drainage.

Other refuges, including two in Virginia, were cited for contamination problems ranging from mustard gas, plutonium and dioxin left over from military activities to asbestos insulation in buildings in the refuges.

Industrial and municipal waste may pose the biggest threat to wildlife refuges with agricultural drainage running a close second, according to the study.

Horn said that 45 percent of refuges with known or suspected contamination were threatened by industrial or municipal discharges and 42 percent by pesticides, tainted irrigation drainage or other farm-related pollution.

High levels of DDT were found at Fisherman Island beneath the Chesapeake Bay Bridge and Tunnel, where the Defense Department once operated a radio station. At the Eastern Shore of Virginia refuge, a Delmarva Peninsula sanctuary once operated as the Cape Charles Air Force Base, the survey found asbestos pipe wrapping in 13 buildings and on steam lines.

Other refuges with problems requiring immediate attention are Wheeler in Alabama, Kenai in Alaska, Seal Beach in California, Johnston Atoll in Hawaii, Crab Orchard in Illinois, Great Swamp in New Jersey and Ninigret in Rhode Island.