Law Department notice on WTC document preservation, Oct 2001

NYC 9/11 Public Portal Document

Table 2-2: Outdoor Sampling Timeline for Pollutants of Concern

Pollutant Sampling Source Sampling Results Availafalell] Started Lead Dust September 11 September 12 Asbestos Bulk Dust September 11 September 12 Ambient Air September 12 September 13 Benzene [2] Air Grab Samples September 16 September 17 Mercury Ambient Air September 16 September 18 Dust September 16 September 20 Lead Ambient Air September 16 September 20 [3] PAHs Ambient Air September 16 September 20 Cadmium Chromium Manganese PAHs Dust September 16 September 22 Dioxin Dust September 16 September 24 [4] Ambient Air September 16 September 28 RGBs Ambient Air September 16 September 28

PMxs Ambient Air September 21 October 4 PM,o[5]

TSP [5] Ambient Air No Monitoring No Monitoring Notes: [1]= Based on Daily Summaries of monitoring results prepared by Region 2 staff in Edison, New Jersey, which were used to brief management on data results. [2] = EPA sampled for additional VOCs on this date as well. [3] = EPA’s Health Risk Evaluation reported lead results were known on September 18. [4} = EPA’s Health Risk Evaluation reported dioxin results were known on September 23. [5] = “PM" stands for “Particulate Matter. ” PM^^ represents “Une"particulate matter less than or equal to 2.5 micrometers in diameter. PM^^ refers to particulate matter less than or equal to 10 micrometers, with the fraction between 2.5 and 10 micrometers known as “coarse." “TSP" stands for “Total Suspended Particutates," and includes all sizes of particles.

Health-based benchmarks for short-term and acute exposures did not exist for pollutants of concern resulting from the collapse of the WTC. For asbestos, EPA used benchmarks originally designed for other purposes to assess potential health risks from breathing the air following the WTC collapse. Because health-based benchmarks for short-term exposures did not exist for most of the other pollutants, EPA revised benchmarks for lifetime (30-year) exposures to develop screening levels for short-term (1-year) exposures. Further, health-based benchmarks did not exist for assessing the risk to human health from exposure to the combination of air pollutants that were emitted.

11 Report No. 2003-P-00012

NYC-WTC_000145531