Ever since 9/11, when terrorists in hijacked jets smashed into the World Trade Center's twin towers and sent the country into high alert, the health and safety of millions of Americans on the East Coast has depended in large part on dedicated personnel in the city's Department of Health and Mental Hygiene.

This dependence became even more acute a month after the toppling of the towers when officials were alerted to a bio-terrorist attack in which deadly anthrax spores were discovered in envelopes mailed from many locations to targets that included members of Congress.

"Many of those letters ended up here," said Sgt. Jorge Fernandez, a Local 237 member and one of three supervising special officers at the city's Public Health Laboratory on First Ave. and East 26th St. in Manhattan. Fernandez said that when the bio-terrorists struck, the Manhattan lab was the only one in the tri-state area capable of handling the deadly letters and the local cases in which the victims died from the infected mail.

Since Oct. 12, 2001, the date when the envelopes were discovered, the lab has processed about 3,000 specimens for examination, the sergeant said. Before this date, the lab had been processing only one or two bio-terrorism environmental samples a month.

Within a week of the anthrax attack, the Public Health Laboratory had a fully functional bio-terrorism response laboratory set up and operating 24-hours a day, seven days a week.

The cadre of special officers at the lab are supervised by Chief Thomas Breuers and Deputy Chief Sol Berger, both long-time veterans of the system. The work of his officers has been recognized publicly by the federal Center for Disease Control (CDC), the White House, and the mayor's office.

Their work also has been commended by Dr. Sara Beatrice, the assistant commissioner of bio-terrorism for the Public Health Lab.

When the anti-bio-terror program was first initiated in 2001, Detective Sgt. Harold Smalls, now retired, was a vital cog in its formation, as were Officers Princess Pascall and Lester Lloyd, who were instrumental in compiling the manner of documentation submission.

Others who played important roles in the lab's operations but who were subsequently transferred are Detective Rolando Rivera, Sgt. Fernando Rivera and Officer Regina Nealy.

Because of the importance of the operations in the lab, there was a great need for its expansion and extensive improvements in security. Detective Sgt. Cecilio Gonzalez was given the job of overseeing the safety of those entering and leaving the building and of everything that was brought to the facility for examination.

"Specimens brought to the lab are potential criminal evidence and must be treated as such," Gonzalez pointed out. "We must ensure the integrity of the 'chain of custody' of all these samples and make sure they are sequestered in a safe and secure area."

Gonzalez also noted that the facility contains special chemicals used in analysis of the various samples that must be protected. "Some are explosive in nature and some are radioactive," he said.

The physical security specialist called his job stressful. "You never know what biological agent is coming in, and it's our job to make sure it comes safely into the building," he said.

Everything brought to the lab must be examined by the Department of Health and Mental Hygiene police officers using standardized procedures, which are enforced by the third supervisory officer, Sgt. William Hayward. The procedures are the same as those followed by the New York City Police Department and Fire Department Hazardous Material units, Gonzalez noted.

In addition to screening all incoming packages, the DOH Police initiated special procedures that included in-depth background investigation of all personnel, the use of personnel identification badges, special badges for restricted areas, and a sign-in logbook.

Only one entrance is available to the public and there is a special entrance by which potential bio-terrorism samples are brought into the building. All areas in the building - entrances, elevators, laboratories and emergency exits - are continually monitored by closed circuit television.

Fernandez said the agency provides the officers with training "sufficient for the work that we do," Gonzalez said. "We are probably the only agency and probably the only department that is always in the same state of readiness as the NYPD. If they're in red alert, we're in red alert; if they're in orange, we're in orange."

Noting that they are the first step in the "chain of evidence," Fernandez said that since 9/11, "we've become quasi-experts in fields we thought we'd never be in. I never thought I'd see this, but it is interesting. We are the initiating agent in an actual investigation of a possible bio-terrorism incident."

Fernandez said the importance of the labs has had a gratifying effect among the officers. "There is a distinct knowledge now that the job is vital and you are performing a service that shows an end result," he asserted. "They come to work now with a sense they are providing a service to the city, the state and the country."

He added that when the officers now read the papers about possible bio-terror incidents, they can pinpoint it and say, "I may not have been there, but I was a part of that. From the officer who maintains the post right down to the officer that initiates the paperwork, it's a one-whole-team effort to make sure that the agency can provide the service that the city needs."

Officer Sharon Halloway, who transferred to the lab from the Morrisania Health Station in the Bronx just after the attack on the twin towers, said that her work at the lab is a wonderful learning experience. She said it provides her with a great opportunity to interact and learn from a great many experts in the Police and Fire Departments and the science and health fields.