EPA interim final report on WTC background study, April 2003

NYC 9/11 Public Portal Document

4.1.1 Indoor Air Sample Collection Airborne fibers and particulate matter were collected by drawing a known volume of air through a filter membrane cassette following the procedures specified in Table 4-1. The equipment used for the collection of air samples is provided in Section 4.2 of this report.

When available and permitted by the resident or building manager, some of the air sampling was conducted employing the use of oscillating fans and/or operating the window air conditioning units. How the air conditioning units were utilized during sampling depended upon the unit’s features. For example, some units had the option to recirculate interior air or use outside air. When this option was available, the unit was set to recirculate interior room air. Other units did not have this option. The intended purpose for the use of fans or window air conditioners was to simulate typical household activity within each unit.

The collection of air samples did not employ the use of aggressive techniques due to the risk of dust exposure to the residents or persons in each unit during the sampling activities. Aggressive sampling techniques employ the use of electric leaf blowers with a maximum velocity ranging from 140 miles per hour (mph) to 225 mph, and maximum air volumes ranging from 78 cubic feet per minute (cfin) to 425 cfin in order to agitate dust into the air. The dust then remains suspended in air by using'fans. The aggressive techniques do not simulate “normal” household activity or living conditions. However, as the goal of the Study was to estimate background concentrations imder typical conditions, the use of non- aggressive sampling techniques is more representative of typical household activity and living conditions.

4.1.2 Microvacuum Sample Collection Samples of settled dust were collected from porous surfaces using microvacuum techniques and analyzed for asbestos and lead. Porous surfaces included carpet, area rugs, upholstered couches, chairs, ottomans and in some cases drapery when furniture and/or carpet were not available.

The standard test method used for the collection of asbestos microvacuum samplesis referenced in Table 4-1. This method describes the procedures for collecting non-airbome dust samples. It is stated in sub-section 1.2.1 of the ASTM Standard D 5755-95 that “The collection efBciency of this technique is unknown and will vary among substrates. Properties influencing collection efficiency include surface texture, adhesiveness, electrostatic properties and other factors.” Due to the limitation of the microvacuum sample collection method for asbestos, the intended use of the method was to determine only the presence or absence of asbestos contaminants.

For the purpose of this Study, lead dust samples were collected using microvacuum techniques for the determination of lead on a loading basis (microgram of lead per area sampled). As stated in section 1.3 of the ASTM Standard E 1973-99, “Due to a number of physical factors inherent in the vacuum WORLD TRADE CENTER BACKGROUND STUDY 12

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