NYC-WTC_000195194

NYC 9/11 Public Portal Document

w COPC included: asbestos, lead, dioxin, polycyclic aromatic hydrocarbons (PAH), fibrous glass and crystalline silica (alpha-quartz, cristobalite, tridymite.)

The study used a combination of data sets to determine the extent of contamination, the w effectiveness of cleaning methods, and the differences of sampling and analytical methods.

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.

Conclusions Regarding Contamination of the Building: • The study found that the observation of WTC dust is an indicator that WTC contaminants may be present and that the amount of WTC dust correlates with the level of contamination.

The study found that concentrations of some contaminants in the WTC dust were elevated above health-based benchmarks.

Conclusions Regarding Cleaning Ejfectiveness: • The study demonstrated that 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.

The study found that one to three cleanings were necessary to reduce contamination levels to below health-based benchmarks, and the number of cleanings required generally correlated with the levels of contamination initially identified in the units.

The study found that standard Heating, Ventilation and Air Conditioning (HVAC) cleaning methods reduced the concentrations of WTC contaminants in HVAC systems. «r The study found that conducting asbestos air sampling was a conservative method for determining if additional cleaning was needed.

The study successfully demonstrated that standard cleaning practices are effective in removing the complex mixture of WTC dust, thereby reducing individual exposure to WTC-related contaminants. Therefore, EPA’s recommendation continues to be that individuals concerned about the presence of WTC dust use HEPA vacuums and wet wiping to remove the dust from their dwellings. Depending on the amount of dust deposited, repeated cleanings may be necessary.

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NYC-WTC_000195199