Thursday marked two years since the terrorist attacks on the World Trade Center and elsewhere, but health problems continue to plague cleanup, rescue and recovery workers.

Many of the heroes of Sept. 11, 2001, now live with lasting physical reminders of their bravery.

"Among the most serious problems we're seeing are upper and lower respiratory disorders, including things like sinusitis, persistent laryngitis and new onset asthma because of chemical burns people suffered in their airways," said Stephen Levin, a physician at Mt. Sinai Center for Occupational and Environmental Medicine (search) in New York.

Since April 2002, Levin, director of the federally-funded World Trade Center Worker and Volunteer Medical Screening Program (search), has conducted free and confidential screenings of about 6,000 workers to check for Sept. 11-related illnesses.

Levin said many continue to suffer very high rates of mental health problems, including severe post-traumatic stress disorder and depression.

Doctors say a lot of the physical illnesses have resulted from exposure to toxic soot, including asbestos and pulverized concrete.

"When plastic burns, especially PVC (search) plastic, which coats every bit of wire in a tower like the World Trade Center towers, it releases hydrochloric acid mist, so people were inhaling this mix," Levin said.

At New York University Hospital, just three blocks from where the towers stood, doctors say serious respiratory problems still linger.

What used to come in to the emergency room as just a bronchitis, now frequently comes in as a pneumonia. The conditions are much more serious, said Dr. David Goldschmidt, director of emergency service at the hospital.

Sen. Hillary Clinton (search), D-N.Y., has struck out at the Bush administration, saying the White House misled the public about the air quality in the city when it helped edit press releases by the Environmental Protection Agency. She and Sen. Joe Lieberman (search), D-Conn., had written a letter to President Bush last month asking for explanations about the EPA's statements shortly after Sept. 11, 2001.

Last week, acting EPA administrator Marianne Horinko (search) responded to the senators' letters, quoting that agency's inspector general's report.

The report does not conclude whether the outdoor air around the World Trade Center after Sept. 11 was safe to breathe, but said, "the EPA staff did a commendable job reacting to this unprecedented disaster."

The response prompted a critical response and another letter to the president in which the senators said Horinko was trying again to deceive them.

"The [EPA] inspector general's findings were that, in the absence of adequate monitoring data, the EPA made deceptively reassuring statements," the two senators wrote. "[Horinko] clearly chose to selectively excerpt the most favorable quotes from a 155-page report and claim that the remainder of the report is similarly supportive of the conduct of the White House and the EPA."

The two continued that while they hope no long-term health effects will result from the tragedy, that answer won't be known for years, and "does not excuse the White House's misleading statements that were inserted into the EPA press releases." Clinton has said she will block Bush's nominee to head the EPA until she gets some answers.

Physicians say the ailments they are seeing now may be just the beginning. In five or 10 years from now, workers could contract rare cancers, chronic mental illness and diseases like rheumatoid arthritis and lupus.

Medical screening runs through next March and psychological screening will continue until June.

By that time, about 12,000 of the estimated 30,000 people who worked at the site will have been screened at a cost of $12 million. The database may be used to extrapolate attack-related illnesses that may not appear for years.