On the day of the terrorist attacks on the World Trade Center, the President’s declaration of a major disaster under the Stafford Act activated the Federal Response Plan (superseded by and incorporated into the National Response Plan). The Federal Response Plan established the process and structure for the federal government to provide assistance to state and local governments when responding to major disasters and emergencies declared under the Stafford Act. Under the Federal Response Plan, FEMA coordinated this assistance through mission assignments and interagency agreements, which assigned specific tasks to federal agencies with the expertise necessary to complete them. The Congress authorized $20 billion to respond to the attacks, of which $8.8 billion was provided through FEMA, for the New York City area. Under the Federal Response Plan (and the National Response Plan today), EPA served as coordinator during large-scale disasters for 1 of 15 emergency support functions (ESF)—ESF 10, which addresses oil and hazardous material releases. ESF 10 encompasses various phases of hazardous material response, including assessment and cleanup. In the first 6 months after the WTC disaster, EPA responded to FEMA mission assignments to assist with the response efforts and, among other tasks, provided wash stations for responders and disposed of waste from the WTC site. There are an estimated 330 office buildings in Lower Manhattan below Canal Street and roughly 900 residential buildings with approximately 20,000 apartments. In 2002, after initial efforts by the city of New York to advise New York residents how to clean the World Trade Center dust in their homes, FEMA and EPA entered into an interagency agreement to address indoor spaces affected by the disaster. While EPA has responded to hazardous material releases for decades, the WTC disaster was the first large-scale emergency for which EPA provided testing and cleanup in indoor spaces. WTC dust is a fine mixture of materials that resulted from the collapse and subsequent burning of the twin towers and includes pulverized concrete, asbestos, and glass fibers. WTC dust entered homes and offices through open windows, was tracked in, or was picked up by air-conditioning system intakes. Figures 1 and 2 show the dust generated by the WTC disaster. The amount of dust in indoor spaces in and around Lower Manhattan varied due to a variety of factors, including distance from the WTC site; weather conditions, such as wind; and damage to individual buildings. In the years since the disaster, the level of WTC dust in indoor spaces has varied, depending upon the cleaning performed by residents and other groups, including EPA and professional cleaning companies. In May 2002, EPA, New York City, and FEMA officials announced a program, to be overseen by EPA, offering a cleanup of residences in Lower Manhattan. Between September 2002 and May 2003, residences were cleaned and tested, or tested only, for airborne asbestos. EPA analyzed samples from 4,167 apartments in 453 buildings and 793 common areas in 144 buildings. This program cost $37.9 million—$30.4 million for indoor cleaning and testing by the New York City Department of Environmental Protection and $7.5 million for EPA oversight and sample analysis. Figure 3 shows the area in Lower Manhattan eligible for participation in EPA’s program. Residents could choose either an aggressive or modified aggressive testing method for providing samples of indoor air to EPA. For the modified aggressive method, the contractor ran a 20-inch fan for the duration of testing. For the aggressive method, a leaf blower was used, in addition to the 20-inch fan, to direct a jet of air toward corners, walls, fabric surfaces, and the ceiling to dislodge and resuspend dust. The contractors HEPA vacuumed and wet-wiped hard surfaces, including floors, ceilings, ledges, trims, furnishings, appliances, and equipment; and they HEPA vacuumed soft surfaces, such as curtains, two times. In addition, in cases where there were still significant amounts of WTC dust and debris, contractors used asbestos abatement procedures such as the use of personal protective equipment, including respirators and a properly enclosed decontamination system; posting of warning signs; isolation barriers to seal off openings; and disposal of all waste generated during the cleaning in accordance with applicable rules and regulations for asbestos-containing waste. The New York City Department of Health and Mental Hygiene and the U.S. Department of Health and Human Services’ Agency for Toxic Substances and Disease Registry (ATSDR) collected samples from in and around 30 buildings in Lower Manhattan from November though December 2001. In September 2002, these agencies released their assessment of the public’s exposure to contaminants in air and dust, recommended additional monitoring of residential spaces in Lower Manhattan, and referred residents to EPA’s program. Before EPA finalized its second indoor program plan, several assessments related to indoor contamination were conducted: an August 2003 EPA Inspector General report; an expert technical review panel that EPA conducted from March 2004 through December 2005; and three EPA studies. The studies identified background levels of contamination in New York City (“background study”); the WTC-related contaminants of potential concern, and associated cleanup benchmarks (“COPC study”); and the efficacy of various cleaning methods in eliminating WTC-related contaminants of concern (“cleaning study”). During the time EPA met with the WTC Expert Technical Review Panel, some expert panel members encouraged EPA to develop a method for differentiating between contaminants found in the New York City urban environment and those found in WTC dust. This method would have served as the basis for determining the extent of WTC-related contamination, and EPA officials believed it would have enabled the agency to limit its focus to contamination specific to the WTC disaster. Early in the panel process, EPA formed a subpanel of these experts to assist EPA’s Office of Research and Development in developing such a methodology. In August 2005, EPA released its final report describing its methodology, which was peer reviewed. In their October 2005 final report, the peer reviewers criticized the reliability of EPA’s method and provided suggestions on improving EPA’s approach. In a November 2005 letter, EPA officials told expert panel members that in the absence of a valid method, EPA could not definitively distinguish between WTC contaminants in dust and levels of the same contaminants found in an urban environment. At the same time, 2 weeks before the final panel meeting, the EPA chairman informed the panel that it would be disbanded as of the final meeting and that EPA would not be implementing a plan that included determining the extent of WTC contamination. Experts that were a part of the subpanel addressing this method reported that the peer-review comments could be addressed and that EPA should perform additional sampling. Nonetheless, EPA ultimately decided not to pursue developing this methodology. Figure 4 shows the chronology of events preceding the second program. In January 2006, EPA formally requested funds from FEMA. EPA and FEMA signed an interagency agreement to conduct EPA’s second program in July 2006, and EPA announced the agency’s second program to test indoor spaces in Lower Manhattan in December 2006. Appendix III provides information regarding EPA’s first and second indoor programs. In response to recommendations and additional input from the Inspector General and expert panel members, EPA’s second program incorporates some additional testing elements. However, EPA’s second program does not incorporate other items. Figure 5 shows the key recommendations and additional input the EPA Inspector General and expert panel members provided to EPA. While EPA tested solely for airborne asbestos in order to trigger cleanup in the first program, it agreed to test for three additional contaminants in its second program—man-made vitreous fibers, polycyclic aromatic hydrocarbons, and lead. These contaminants, as well as two additional ones—dioxin and silica, were identified as WTC contaminants of potential concern in a May 2003 report issued by EPA and other federal, New York City, and New York state agencies. EPA did not include dioxin and silica in the second program for several reasons. Regarding dioxin, EPA noted that concentrations were elevated in the weeks following the disaster when fires were still burning, but concentrations returned to predisaster levels by December 2001. Furthermore, because “only eight” of 1,500 dioxin samples exceeded cleanup benchmarks during tests in 2002 and 2003, EPA decided not to sample for this contaminant in its second program. Regarding silica, EPA noted that in 2002 an ATSDR/New York City Department of Health and Mental Hygiene report stated that short- term exposure to silica is unlikely to cause adverse health effects and that adverse health effects from chronic exposure are possible but unlikely if recommended cleaning is conducted. EPA also explained that levels of silica are likely to have been reduced by cleaning activities over the past 3 years. EPA also agreed to test for contaminants in dust. To do so, EPA developed site-specific cleanup benchmarks for asbestos and man-made vitreous fibers in dust over the course of nearly a year. In its second program plan, EPA explains that these benchmarks are not risk based but rather are based on, among other things, work by experts in the field as to what constitutes contamination and how it compares with site-specific background levels, and the benchmarks employed for cleanup at a Superfund site with asbestos-contaminated residences. Though EPA expanded the number of contaminants tested for in its second program, it did not adopt recommendations and additional input from the EPA Inspector General or the expert panel that addressed the following issues: Evaluating risks in geographic areas north of Canal Street and in Brooklyn. EPA did not expand the scope of testing north of Canal Street, or to Brooklyn, as advisory groups had advised. EPA reported it did not expand the scope of testing because it could not differentiate between normal urban dust and WTC dust; differentiating between the two would have enabled EPA to determine the geographic extent of WTC contamination. Some expert panel members had suggested that EPA investigate whether it was feasible to develop a method for distinguishing between normal urban dust and WTC dust. EPA initially agreed to do so.