Most ground zero workers still suffer from health problems two years after Sept. 11, and many do not have health insurance or job security, doctors told a congressional panel.

Robin Herbert and Stephen Levin, the co-directors of a federal screening program at New York City's Mount Sinai Medical Center for ground zero workers, said they had examined 8,000 workers, with 75 percent experiencing persistent respiratory problems. Forty percent of the workers suffer from mental health problems after the 2001 terror attack.

Herbert and Levin, who said the workers are at risk for developing cancer in the next decade, sought funding to screen more than 10,000 workers a year for the next 20 years.

Lawmakers also questioned federal officials about how much they knew about the health risks at ground zero in the days after the attack and about how many workers were told of the danger.

OSHA regional administrator Patricia Clark said that the agency handed out more than 100,000 dust masks. Clark said OSHA inspectors strongly urged workers to keep their respirators on, but many did not because the masks were uncomfortable, or believed to be unnecessary.

"Clearly they did not wear them all the time," Clark said. "That's very unfortunate, and I regret that very much."