Contamination control technology employed at Ground Zero
11/01/2001
Mark A. DeSorbo
NEW YORK—Shortly after rescue crews stormed Ground Zero, state, local and federal agencies deployed contamination control technology to monitor and clean up the disaster left in the wake of debris-filled leviathans that were unleashed by the collapsing of the World Trade Center towers.
"We're doing a lot of sampling," says Mary Helen Cervantes, a spokesperson for the U.S. Environmental Protection Agency (EPA).
In fact, 15 fixed air monitors, she says, have been installed at Ground Zero, around Manhattan and in New Jersey to detect asbestos, which was commonly used as a flame-retardant until the 1970s, when studies linked it to lung diseases and two varieties of cancer.
EPA and the Federal Emergency Management Agency (FEMA) indicated that low levels of asbestos in dust were still being detected within the restricted zone, within one block of the World Trade Center. At the Pentagon, EPA has found either no asbestos or levels "well below the level of concern."
The fixed air monitors the EPA is using might be considered scaled-down versions of what cleanroom end-users are accustomed to seeing. Most cleanroom monitoring equipment is more sophisticated, using electronics to warn of unsafe conditions or high particle concentrations. Fixed air monitors, however, are equipped with filtration cartridges that are manually collected and taken to a lab for analysis.
Meanwhile, EPA and officials from the Occupational Safety and Health Administration (OSHA) were advising rescue and clean-up workers on dust control measures, such as wetting down the debris to keep dust from getting into the air.
The EPA is also using 16 HEPA-vacuum trucks to remove dust and asbestos fibers in residential and business areas near the World Trade Center, Cervantes says. The trucks, which are essentially huge shop vacs on wheels, have 1,500-gallon tanks and 1,000-foot hoses that can reach inside buildings.
"We have been using them all over the city," Cervantes says. "We've used them in the parks, and we have brought them to anywhere there is elevated levels of asbestos or other forms of dust."
EPA Administrator Christine Todd Whitman deployed the trucks about a week after the attack. "Everything will be vacuumed that needs to be," she says. "We're not going to let anybody into a building that isn't safe. And these buildings will be safe. The President has made it clear that we are to spare no expense on this, and get this job done."
Household bleach is also being used for disinfecting and cleaning purposes. In fact, the Clorox Co. has donated more than 1000 cases of bleach to the rescue and clean up effort.
Perhaps the most sophisticated pieces of contamination control technology that are being used are TAGA units, short for trace atmospheric gas analyzers.
The Winnebago-like vessels are equipped with several kinds of air monitoring and analytical equipment. A two- to three-person staff drives through areas within Ground Zero and around Manhattan, capturing samples and doing spot analyses. TAGA units were also used in Kuwait during the Gulf War to measure toxins caused by burning oil wells.
"The TAGA unit looks like a small mobile home, and the lab equipment inside searches for volatile organic compounds (VOCs), poly-chlorinated biphenyls (PCBs) and dioxins," Cervantes says. "We are also using handheld instruments to take samples right from plumes in the debris in search of metals as well as VOCs, PCBs and dioxins."
Clean-up crews often don protective garments, resembling bunny suits, and masks while vacuuming or sampling slurry and dust. "The workers have the direct exposure while taking readings from plumes, so the EPA has also advised the workers in the restricted areas to wear respirators to protect themselves from the dust and any asbestos it may contain," Cervantes adds.
Another spokesperson for the EPA, who requested anonymity, indicated that of 24 samples the agency took in the first two days of chaos following the attack, many contained asbestos, but just one registered levels above acceptable limits. That sample, taken near the epicenter of the disaster in Manhattan's financial district, contained 4.5 percent asbestos fibers. It was taken as agents fled the collapsing buildings.
At press time, dust samples showed elevated levels of 2.1 to more than 3 percent. A level of 1 percent or less is considered safe. Asbestos exposure, however, is only dangerous when it is over continuous long periods of time.