A Westchester lawyer is suing New York City on behalf of rescue workers who became sick after working at Ground Zero. Nearly 3,000 people died when the World Trade Center collapsed. Now David Worby, of White Plains, says even more people may be killed by the lasting health effects of the toxic air. Recent studies suggest that combinations of chemicals are to blame for a host of serious illnesses, like cancer and at least one police officer's death. About 8,000 people who responded to Ground Zero have decided to sue the city, the state and the federal government claiming their safety was not assured. The city, however, is trying to have the lawsuit thrown out claiming immunity under a state emergency act.