Chain of custody form for DEP environmental samples, 2001

NYC 9/11 Public Portal Document

5. Discussion

This project was an essential element of EPA's efforts in responding to concerns raised by residents of lower Manhattan regarding the presence of WTC dust in their homes. EPA endeavored to confirm that the cleaning methods that individuals were using, and that representatives of health and environmental agencies had recommended, were efiective in removing the dust generated by the unprecedented disaster.

Concurrent with this study, EPA conducted the Indoor Air Residential Assistance-WTC Dust Cleanup Program, cleaning residential spaces for residents of lower Manhattan who expressed interest. It was imperative to complete this study as quickly as possible to determine if the routine cleaning procedures being employed in the WTC Dust Cleanup Program required modification.

The study addressed cleaning of a complex mixture of contaminants, including construction debris and fire-related compounds. As noted in the Executive Summary, EPA was unaware of a precedent for an indoor environmental cleanup with such a diverse set of parameters. However, time pressure did not allow for conducting extensive research on potential cleaning techniques in a controlled setting. The urgent and real-time need to determine the effectiveness of the cleaning methods being used by residents and being employed in the WTC Dust Cleanup Program drove the decision to field test the effectiveness of the standard dust removal methods in a heavily- impacted unoccupied building.

Multiple endpoints were used in the study to ensure that the complexity of the dust was comprehensively considered. Sampling for a variety of compounds was conducted before and after cleaning. Clearance was determined by the removal of contaminants to the health-based benchmarks established in the COPC/Benchmark Report.

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

5.1 Data Sets

Many different samples from multiple media for specific compounds were collected over the course of the study which resulted in a variety of data sets being generated. Different data sets were used to evaluate the objectives listed above. Multiple data sets were used for determining the extent of contamination before any cleaning events occurred and for evaluating the effectiveness of various cleaning methods.

The most informative data sets included results from asbestos wipe sampling, lead wipe and micro vacuum sampling and MMVF wipe sampling events conducted before and after first cleaning of the residential units. The majority of results for other compounds for which wipe samples were collected before and after first cleaning (e.g., dioxin, PAH) were below the detection limits for both sampling events. Therefore, these data sets did not provide a useful basis for determining the extent of contamination prior to cleaning or for evaluating the effectiveness of the cleaning methods. Pre-cleaning air sampling was not conducted because of concerns that the presence of significant levels of dust accumulation might make overloading of filters more likely using the 103

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