Editor's note: The article "Exposures at the World Trade Center: Ten Years Later, What Have We Learned?" from the September 2011 issue of The Synergist has been republished in this issue from the archives.

The WTC Towers had been built in the 1960s and 1970s, a time when asbestos was being phased out of fireproofing materials. In the bottom third of 1 WTC (the North Tower), sprayed-on asbestos fireproofing was applied to the structural steel; in the rest of the North Tower, and for the entire structure of 2 WTC (the South Tower), an asbestos-free material consisting of mineral wool and binder was used. The use of non-asbestos formulations may have contributed to the collapse of the WTC Towers. 2 WTC fell first, shortly before 10:00 a.m., followed by 1 WTC around 30 minutes later. Among the approximately 2,600 killed on 9/11 were more than 300 firefighters and 70 police officers. Another 55 military personnel died at the Pentagon.

The cloud of debris swelled over lower Manhattan, enveloping all nearby properties. Outdoor air intakes for the buildings at World Financial Center as well as residential structures in Battery Park could not be closed in time and property managers were unaware of the damage or the loss of electrical power. Everyone knew that cement and other dust particles had entered the building tenant spaces but had little understanding of how and what toxic chemicals were present in the dust.

Perhaps not well publicized was the collateral damage to other buildings in proximity to the WTC. At least five other buildings sustained serious structural damage, including 3 and 5 World Financial Center and the Deutsche Bank building. As many as 45 additional buildings and residential structures in the vicinity suffered less serious structural damage but were contaminated by the dust cloud.

Following the attacks, cell phone service within New York City and along the U.S. East Coast became overloaded, leading to network crashes that inhibited communication. Firefighters and first responders used a different communication channel than police, further hindering the response. Confusion about regulatory oversight complicated recovery and cleanup in the first week. With EPA and OSHA not yet on site, no one was sure which agency had authority: the New York City Department of Environmental Protection, the New York State Department of Health, or the Port Authority? Mixed messages about where to sample and what to sample for were common. A heightened sense of national security also contributed to the confusion. Eventually, building owners, insurance companies, engineers, and other stakeholders started to communicate with each other and developed a plan for remediation and recovery.

CLEANUP AND RECOVERY The attacks on the WTC initiated two separate events: the demolition of the buildings, and the ignition of the largest industrial fire in North America. Fed by jet fuel, the fire that began on 9/11 continued to burn, pumping out contaminants, until December 19, 2001. Cleanup work at the WTC site proceeded around the clock, seven days a week, for nine months. Approximately 1.8 million tons of rubble were removed from the site.

The Fresh Kills landfill in Staten Island was reopened the day after the attacks to serve as a staging ground for efforts to retrieve victims’ remains. While New York City police and K-9 units sifted through the rubble, other building debris was stored for forensic analysis of the steel girders. Some police details used shotguns to keep seagulls searching for food away from the workers. Members of the various federal agencies wore their mechanical filter respirator and personal protective clothing, but most police officers were untroubled by the asbestos fibers and silica dust in the debris pile and failed to wear their respirators while working around the shaker tables. Only when a New York City police chaplain was conferenced for support did these officers take risks of exposure seriously.

Not everyone faithfully followed the requirements of the OSHA hazardous waste operations and emergency response (HAZWOPER) standard. The support zone, contamination reduction zone, and exclusion zone were not clearly delineated. Workers essentially put on their personal protective clothing, respirator, hard hat, and safety glasses in the parking lot with their construction boots and walked on site. None were provided boot covers or separate boots to prevent cross contamination of personal vehicles. Limited air monitoring was performed to comply with the OSHA asbestos standard, but few workers wore the devices for a full shift. Most workers had some understanding of the health concerns associated with exposure to asbestos fibers, but their exposure was not apparent to them.

In the weeks following 9/11, the pervasiveness of the dust generated an immediate need among property managers for cleanup services. Unfortunately, individuals who had little understanding of hazardous waste operations hired themselves out as cleanup contractors. In one case, a contractor quickly hired untrained staff to clean all the visible surfaces in a building—desks, chairs, file cabinets, and tables. Upon verification of the workmanship, it was determined that dust remained underneath the file cabinets, on the underside of the desks and the suspended floor in the computer room, inside the contractor utility chases, and inside the corrugated ductwork from the variable air volume (VAV) boxes into each office space. The damage was so significant that the project, which involved rebuilding and remediating the tenant space, was halted until further review with the property owner. Ultimately, the entire building had to be decontaminated because of the extent of the damage.

CHARACTERIZING THE DUST According to a geologist from the United States Geological Survey, who was quoted in a 2003 article in Chemical and Engineering News, the WTC towers contained 6 million square feet of masonry, 5 million square feet of paint, 7 million square feet of flooring, 600,000 square feet of glass, 200 elevators, and approximately 200 tons of spray-on asbestos insulation. In addition, the buildings had thermostats containing mercury, personal computers containing lead, mainframe computers and servers, and hundreds of thousands of fluorescent light bulbs. Polychlorinated dibenzo dioxins and furans were produced during combustion of PCB-containing materials and PVC plastics. The site also included a shooting range for the Secret Service with millions of rounds of lead ammunition and a laboratory for the U.S. Customs Service where toxic chemicals were stored. In a matter of minutes, these materials were converted to millions of tons of respirable dust.

On the day of the attacks, a Port Authority officer drove to the Mount Laurel, New Jersey, office of International Asbestos Testing Laboratories and handed over a #10 business envelope containing dust that he said was from the WTC site. He asked that the dust be tested; he did not say which analytes he wanted it tested for or specify a turnaround time. It was the first of many samples that iATL would receive. Samples would arrive nearly every day for the next four years. On some days, more than a hundred samples were delivered.

Detailed investigation of the asbestos commonly found in samples indicated that the force of the explosions and collapse apparently crushed the asbestos into fibers that could potentially evade EPA’s usual testing methods. Analysis with transmission electron microscopy (TEM) revealed that the surface of the asbestos fibers was pitted and that atomic fragments of sulfates seemed to have chemically bonded to the fibers. This unusual feature would become a signature of WTC asbestos and would help investigators determine whether the asbestos found in a building might have originated from the WTC. Further studies also concluded that the dust contained a large concentration of ultra-small asbestos fibers, which may be missed by standard microscopy techniques. A sample collected from the coating on a steel WTC beam indicated the presence of a significant amount of chrysotile asbestos—as much as 20 percent by volume. Thus, asbestos sample collection and analysis became a significant aspect of nearly all IEQ investigations initiated by the collapse of the WTC.

On October 12, 2001, a report that characterized WTC particulate deposited in residential structures with no visible signs of structural damage was submitted to Congressman Jerrold Nadler, chair of the “Ground Zero” Elected Officials Task Force. The report documented the presence of significantly elevated concentrations of asbestos in surface dust and air in the apartments evaluated. Surface concentrations of PCBs, PCDDs, PCDFs (expressed as 2,3,7,8-TCCD Equivalents), and inorganic metals were generally low or below comparative background levels. This report underscores the importance of acknowledging that sensitive residential populations, who may not be the focus of a disaster, can be significantly impacted by the fugitive airborne contamination released.

SAMPLING AND ANALYSIS The volume and variety of sample matrices spurred innovations in laboratory methods. Especially during the initial chaos, no precedents existed for the collection of air samples following an event such as 9/11. A team at the University of California-Davis invented the DELTA (Detection and Evaluation in Long-Range Transport of Aerosols) instrument for sampling particulate matter. Using DELTA, investigators could sample a month’s worth of data and characterize particulate across eight size ranges for any given day.

Several proprietary analytical methods were used. These methods built on work begun in the 1980s by organizations such as EPA, the National Institute of Standards and Technology, and the American Society for Testing and Materials, now known as ASTM International. EPA, NIOSH, OSHA, and others had already proposed methods for determining asbestos in bulk building materials and had validated methods for asbestos particles in air. Still in development were methods for analyzing asbestos in water and in settled dust. Further development followed the 1993 bombing of the WTC garage. By the time of the 9/11 attacks, work was under way on the following: • ASTM D5755, Standard Test Method for Microvacuum Sampling and Indirect Analysis of Dust by Transmission Electron Microscopy for Asbestos Structure Number Surface Loading • ASTM D5756, Standard Test Method for Microvacuum Sampling and Indirect Analysis of Dust by Transmission Electron Microscopy for Asbestos Mass Surface Loading • ASTM D6480, Standard Test Method for Wipe Sampling of Surfaces, Indirect Preparation, and Analysis for Asbestos Structure Number Surface Loading by Transmission Electron Microscopy • EPA 600/R-93/116, Method for the Determination of Asbestos in Bulk Building Materials • EPA 600/J93-167, Methods for the Analysis of Carpet Samples for Asbestos

Work on these methods helped define evaluation thresholds used during the post-9/11 cleanup to determine whether a building was safe for reoccupancy or for contractors to perform repairs. It also identified levels of cleanliness for accessible areas such as offices and inaccessible areas such as pipe chases and elevator shafts. These methods were helpful tools for investigators and insurance companies that sought to determine remediation responsibility and perhaps whether an illness was a preexisting condition or could be tied to exposures from 9/11.

The Zadroga Act also established the World Trade Center Health Program, which offers healthcare to those directly affected by the attacks. As of March 2021, the program had enrolled 80,745 responders, including recovery and cleanup workers as well as volunteers who helped at the WTC and the Pentagon, and 29,453 survivors—individuals who were present on the day of the attacks or who lived, worked, or went to school in the New York City disaster area. The most common health conditions of enrollees include chronic rhinosinusitis, gastroesophageal reflux disease, cancer, asthma, chronic respiratory disorder due to fumes and vapors, and WTC-exacerbated chronic obstructive pulmonary disease.

In 2009, EPA issued “Guidance for Catastrophic Emergency Situations Involving Asbestos,” which updated a document the agency originally issued in 1992. The 2009 update explains regulatory requirements related to asbestos; discusses how EPA has addressed asbestos following catastrophes, including the attacks on the WTC; and identifies exposure concerns for first responders, the cleanup and disposal of debris, the demolition and renovation of buildings during recovery, and the transport and disposal of materials that may contain asbestos.

Among the lessons learned from 9/11 is the importance of interagency preparation and coordination, particularly by harmonizing communication through the incident command structure. Preparing for an emergency such as 9/11 requires thinking through contingencies such as how to ensure people can communicate if electric power is unavailable or satellite linkages have been disabled.

Having a plan about what to sample for and what to test would have helped limit confusion in the first days following the attacks. In future emergencies, personnel in the field collecting samples should be given license to improvise and labs should be free to use whatever methods they deem to be reasonable and responsible given the circumstances.

Collaboration among a wide range of stakeholders is essential for successful recovery operations. After 9/11, months passed before tenant organizations, building owners, and insurers came together to discuss issues relating to the cleanup. This collaboration ideally would have begun much earlier.

Finally, the amount of work generated for laboratories by an event like 9/11 can be overwhelming. Lab managers should build in time to periodically assess their data so that important insights, such as the unique characteristics of WTC asbestos, are more likely to be discovered more quickly.

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