World Trade Center asbestos situation memorandum, December 2001

NYC 9/11 Public Portal Document

V

REGION 1's BENCHMARK FOR SETTLED ASBESTOS DUST

EPA Region 1 derived a benchmark, or a safe level, for asbestos in settled dust in order to justify asbestos levels found in the Brookfield, Connecticut school system.^* A level of 45,000 structures asbestos per square centimeters (s/cm^) was derived as the benchmark. This is remarkably high considering the universally accepted level of 1000 s/cm^ as low. (See Table 2.)

As discussed later, the Brookfield School System has roundly rejected EPA Region I's unsafe level of45,000 s/cm^ asbestos dust, and has instead chosen a tentative cleanup level of5000 s/cm^ for the schools to be occupied by its children.

Description of Region 2's risk assessment for settled asbestos dust: Use of a “K-factor” to back-calculate dust levels from background air levels

EPA Region 1 calculated its benchmark by first assigning a level for background ambient outside air. Then, it used a stud/’ which found different ratios between the amount of dust on surfaces with the amount of asbestos in the air, depending on the activities going on in a room that would stir up dusts. The ratios of dust levels to air levels are called “K-factors.”

For its calculations, Region 1 assigned a false value of 0.045 structures per milliliter (s/mL) as the supposed background ambient outside air level. Then, then chose an incorrect K-factor of 0.000001 (which is the same as 10"* if expressed as an exponential) as the ratio between air levels and dusts. The result was 45,000 structures per square centimeter (s/cm^) dust on surfaces, using the following formula.

Benchmark for x K-Factor [K-Factor Air Level, structures per milliliter asbestos in expressed (s/mL) Dust, structures as per square exponential

45,000 X 0.000001 [ 10 (-6) ] 0.045 This is the level This is the K-factor, or multiplier, This is the alleged background outdoor air derived from the chosen by Region 1 level put into the formula by Region 1. This formula by Region 1 value is the one highest outlier measurement found in an early 1983 study.

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