EPA's WTC Residential Confirmation Cleaning Study

• Summary
  • Background
  • Conclusions
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• Background Study
• Selecting Contaminants of Potential Concern and Setting Health-Based Benchmarks

Summary

The U.S. Environmental Protection Agency (EPA) began its response minutes after the first plane hit the north tower of the World Trade Center (WTC). The Federal Emergency Management Agency (FEMA), as the federal coordinating agency in disasters, issued mission assignments to EPA. The Agency cleaned dust/debris from the streets of lower Manhattan, sampled the air and dust, provided respiratory equipment and worker and truck washing stations to personnel working at ground zero and the landfill on Staten Island, and removed more than 650,000 gallons of oily water and more than 4,000 drums and containers from the WTC site..

Shortly after the collapse, the New York City Department of Health and Mental Hygiene (NYCDOHMH), provided the residents of lower Manhattan with recommendations on cleaning methods through the media, fact sheets and community meetings. These recommendations were based on previously established cleaning procedures that were proven to be effective in removing layered particulate matter and debris with minimal dust generation.

Residents of lower Manhattan expressed concerns about the safety and reliability of cleaning methods to remove dust and debris from residential units and building facades. To address these concerns, EPA conducted a study of residential cleaning techniques in an effort to evaluate and compare the effectiveness of the recommended cleaning methods. A summary of this study, the WTC Residential Confirmation Cleaning Study, is presented below.

Background
Some residential living spaces located in the immediate vicinity of the WTC complex were impacted with dust and debris following the attack. Samples taken by EPA of dust and debris from streets of lower Manhattan contained asbestos at levels greater than 1% in approximately 35 % of the 160 samples taken between September 11, 2001 and October 10, 2001. This is a regulatory standard used to determine if material is asbestos containing. FEMA funded a study conducted by the Agency of Toxic Substances and Disease Registry (ATSDR) and NYCDOHMH of residential interior spaces around the WTC site. This study showed the benchmarks for asbestos in air were not exceeded. There was asbestos in some residual dust found in some of the homes. Preliminary results of this study were provided to the public early in 2002. The final study was issued in September 2002.

In an effort to confirm that the cleaning methods recommended to the public were effective in reducing contaminants from dust generated from the WTC collapse and recovery efforts, EPA, with support from FEMA and the City, studied cleaning methods in a highly impacted building on Liberty Street, just south of the WTC site. The cleaning confirmation study examined various cleaning and vacuuming methods that were likely to be used by residents and professional cleaning companies to clean dust and debris from residential living areas in the aftermath of the attacks.

EPA contractors cleaned homes and a few commercial spaces in the building that contained a complex mixture of contaminants, including construction debris and fire-related compounds. Eleven cleaning methods were selected and assigned to the residential units within the building according to the levels of observed dust. Each cleaning method was tested in both units with significant and minimal levels of dust. The following cleaning methods were used:

• Residential quality upright vacuums and shop vacuums
• Residential quality upright vacuums with the addition of an AFD
• HEPA-filtered upright and shop vacuums
• HEPA-filtered upright and shop vacuums with the addition of an AFD
• Industrial quality HEPA-filtered vacuums
• Industrial quality HEPA-filtered vacuums with the addition of an AFD
• Wet wiping of all horizontal and/or vertical surfaces with soap and water
• Carpet cleaning
• Standard cleaning procedures used by professional duct cleaning companies for the cleaning of air conditioning (A/C) systems, ducts and related equipment
• Use of water only for wet wipe of horizontal and/or vertical surfaces
• Scope A cleaning procedures developed by EPA and New York City for the cleaning of residential units in lower Manhattan

Results were compared to health-based benchmarks for contaminants of potential concern (COPCs) to determine if the cleaning was successful. The COPCs are asbestos, lead, dioxin, polycyclic aromatic hydrocarbons (PAHs), fibrous glass and crystalline silica (alpha quartz, cristobalite, tridymite).

A summary of the significant conclusions of the study are provided below. These include observations about the extent of WTC-related contamination within the building and the effectiveness of the cleaning methods tested in the study.

• The observation of WTC dust is good indicator that WTC contaminants may be present and that the amount of WTC dust correlates with the level of contamination.

• Concentrations of some contaminants in the WTC dust were elevated above health-based benchmarks.

• The use of a standard cleaning method of vacuuming and wet wiping significantly reduced levels of WTC-related contamination with each cleaning event and was successful in reducing concentrations to levels below health based benchmarks.

• In some cases, multiple cleaning sessions (2 or 3) were necessary to reduce contamination. The methods were highly effective in reducing all COPCs below health based benchmarks.

• Asbestos in air is a good indicator of whether additional cleaning is needed. Based on the compounds and testing methods chosen, the data suggests that using asbestos air samples as an indicator for additional cleaning is the most sensitive of the testing methods, as it resulted in the largest percentage of additional cleanings.

• Standard HVAC cleaning methods reduced the concentrations of WTC contaminants in HVAC systems.

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