Scientists from the National Marine Fisheries Service (NMFS) also found that dangerous oil pollutants linger years longer than had been believed.

The results come from a study started in 1993 following the spill in Prince William Sound, Alaska, in 1989.

Biologists wanted to find out why pink salmon spawned in streams oiled by the Exxon Valdez disaster were still suffering years after the event.

Retarded development

Scientists in the NMFS laboratory in Auke Bay, Alaska, simulated the salmon's spawning conditions. They raised salmon in the laboratory in old, weathered oil like that persisting on many beaches along Prince William Sound.

They found that the fish developed gross deformities such as extra fins, or suffered from retarded development and other problems.

NMFS Toxicologist Stanley Rice said the results contradict previous assumptions that the light elements of oil, which cause acute effects on marine life but evaporate within days, are the most toxic.

"Back in the '70s we were thinking mostly of the short-term toxicity. We really didn't think there would be that many long-term effects," he said.

Rice said the studies have caused scientists to rethink water-quality standards. Even Alaska's standards, which are the nation's toughest and restrict hydrocarbon pollution to 15 parts per billion, may not be strict enough, he said.

Eventual recovery

Exxon scientists dispute the findings. The company has long maintained that Prince William Sound was full of hydrocarbons even before the 1989 disaster, the result of natural oil seeps, and marine life there was accustomed to oil exposure.

But the Auke Bay scientists and researchers from the US Geological Survey have concluded that any background, non-spill hydrocarbons in the sound came from coal, which sinks to the sound's bottom and is locked in a crystalline structure unavailable to marine life.

Rice said the scenic area, with only a few thousand residents, will eventually heal from the 1989 disaster. "Unless it has another Exxon Valdez, Prince William Sound is going to do well from a wildlife perspective," he said.

But the outlook is much gloomier for marine life in waterways near major cities like New York, San Francisco and Philadelphia, where a constant flow of spilled oil and other pollution is washed from streets and parking lots, he said.