The leak began slowly, just a trickle of chemical mist wafting from the top of a tower at an oil refinery near San Francisco Bay.

There was an initial flurry of concern. An emergency was declared, and the county health department was notified. But bad decisions and missed chances allowed 100 tons of toxic chemicals to leak for 16 days last summer.Hundreds of residents in the blue collar San Francisco suburb and dozens of Unocal Corp. employees suffered nausea, nosebleeds and headaches.

Nearly a year later, some still have eye problems they blame on the leak. Others have suffered miscarriages, stillbirths, rashes and fainting spells.

Even pets and farm animals are sick or dying, they say.

"We're worried," said Jody Mechling, 32, a dog groomer who suffers from migraine headaches and vomiting. "We want to know, when are we going to start feeling better? What will happen in the future? I worry about my two small kids. Who's to say they're not going to be sterile because of this? Who's to know?"

More than 1,000 people have filed lawsuits claiming the leak made them sick, said Scott Cole, a lawyer for a group of plaintiffs.

Unocal took responsibility for some of the illnesses and funded a clinic to treat those affected.

The company also could face millions of dollars in fines from regional environmental officials and a criminal investigation from the Contra Costa County prosecutor.

The company admits it made a mistake not shutting the plant down sooner, according to spokesman Lon Carlston.

The leak started Aug. 22, when steam, carbon dioxide and traces of a solution called Catacarb began escaping from a small hole near the top of the 180-foot hydrogen processing tower. The solution is used to remove carbon dioxide from hydrogen, which in turn is used to remove sulfur from gasoline.

Unocal notified the county health department as required, but said the leak didn't pose a public threat.

The company decided the release was too small to warrant a shutdown.

Various components of the solution, in their most pure form, can cause blindness and death. But spokeswoman Karen Rodgers said the company believed the release was not dangerous because the chemicals were heavily diluted.

Company managers sent memos to employees seven days into the release, saying the solution was not harmful.