NYC-WTC_000195194

NYC 9/11 Public Portal Document

5.5 Cleaning Effectiveness w Cleaning effectiveness was determined using two endpoints. One endpoint was the reduction in «ir contaminant concentration between the pre-cleaning and post-cleaning event concentrations in each unit. The other endpoint was the ability to meet health-based benchmarks. The evaluation of both endpoints proved that cleaning indoor environments using standard cleaning techniques (vacuuming and wet wiping techniques) succeeded in reducing contaminant concentrations below health-based benchmarks. This is evidenced by the fact that all residential units, commercial units, and common areas had marked reductions in contaminant concentrations between cleaning events. In addition, all of the residential units, commercial units, and common areas exhibited concentrations that were below health-based benchmarks at the conclusion of the study.

The comparison of pre-cleaning and post-first cleaning concentrations for asbestos wipe and air samples, lead wipe and micro vacuum samples, MMVF wipe samples, and asbestos air samples from post-second and third cleaning events is presented in Table 11.1. This table shows the average concentration of the pre-cleaning samples in comparison with post-cleaning events, with the difference presented in the last column on the right. Exceedances of COPC by cleaning event are presented in Table 11.2. Note: Due to the quantity of information presented, Table J J. J and Table J T2 are presented at the conclusion of this discussion.

The aggregate removal efficiencies for the nine apartments that were identified as being the most heavily contaminated, based on pre-cleaning results, are presented in Figure 1.0. This figure shows that with the exception of two apartments, there was a net decrease for each contaminant regardless of sampling media or test methods. Asbestos wipe samples for one apartment and MMVF wipe samples for another apartment were the two exceptions. The reason for this is unknown.

As indicated in Section 2.4, a total of eleven cleaning methods were tested in the study. These eleven methods were distributed among 25 spaces, although one of the methods, 4A, was used in <• all of the common spaces and commercial spaces. Because the different test methods that were evaluated were similar in nature, and the number of apartments that were available for testing the methods was limited, all of the test methods were identified as being able to reduce contaminant concentrations and no specific test method was identified as being more effective. Therefore, the central theme of these methods, specifically vacuuming and using wet wiping techniques, was * demonstrated to be effective for reducing contaminant concentrations.

109

CITY_21MC100_011105339

NYC-WTC_000195305