VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

The majority of evidence indicates that lung cancer and mesothelioma are the most important risks associated with exposure to low levels of asbestos over a long period of time. There is ample evidence that all types of asbestos have been found to be associated with lung cancer. Several investigators have reported lung cancer mortality in workers exposed to chrysotile, amosite, crocidolite, anthophyllite, tremolite, and to multiple fiber types. The onset of exposure to time of occurrence of the disease is known as “latency period.” As with most carcinogens, asbestos-related cancers have a substantially long latency period. The latency period for lung cancer has been reported to be 10 to 40 years. Most researchers have found that occurrence of limg cancer depends on the cumulative dose as well as other underlying lung cancer risk factors (U.S. EPA, 1986c; Peto et al., 1985). Similarly, several investigators have found that all types of asbestos cause mesothelioma of either pleura or peritoneum in adults who had occupational exposure. This finding also pertains to individuals who had no occupational exposure but who lived with a parent, spouse, or sibling who was an asbestos worker and presumably carried asbestos home on work clothes. Mesothelioma has a latency period of about 30 to 40 years. Lanphear and Buncher (1992) reviewed 1,105 mesothelioma cases in workers occupationally exposed to asbestos. They reported that 99% had a latency period >15 years and calculated a median latent period of 32 years. Further details on the toxicology and epidemiology of asbestos exposure can be found in the recent ATSDR Toxicological Profile for asbestos (ATSDR, 2001).

This next section reviews the air monitoring data for asbestos and discusses how these data relate to human health benchmarks developed for asbestos. The following sections discuss the analytical methods for measuring asbestos in air, the health risk benchmarks that measured air concentrations will be compared to, the background concentration of asbestos that can be compared to the measured values, and then the actual air data.

IV.e.l. Analytical Methods for Asbestos Ambient Air Measurements The two analytical methods used in analyzing the WTC air samples for asbestos are phase contrast light microscopy (PCM) and transmission electron microscopy (TEM). PCM, although cheaper, is imable to distinguish between asbestos and nonasbestos fibers. It counts all fibrous structures with a minimum diameter of 0.3 pm and has a magnification range of 100 - 400X. Fibrous structures are defined as particles exhibiting a length of > 5 pm and an aspect ratio of length to width of 3:1. PCM cannot resolve internal structure or distinguish the mineralogy. PCM results are reported on a mass-per-volume basis, fiber per cubic centimeter (f/cc or fZcm^) or, equivalently, fiber per milliliter (f/mL). TEM, on the other hand, is more expensive, but it can count the fibrous structures with a diameter of < 0.01 pm, and it can resolve internal structure and distinguish mineralogy. It has a magnification range of 5,000 - 20,000X. TEM results may be reported as concentrations or, for comparison with EPA AHERA standards (see below), as structures per square millimeter (S/mm“) of filter in the ambient air monitor used. Details about the monitoring apparatus appropriate for measurement of asbestos using the TEM method and the appropriate ways to count and interpret the electron microscopy results are supplied in EPA (1987) and NIOSH (1994). Details about the PCM method for workplace measurements can be found in NIOSH (1994) and in OSHA (1994).

TEM data, expressed on a structures per filter unit area basis (as listed on the EPA web site), can be converted to a concentration in air in structures per cubic centimeter. This is

DRAFT-DO NOT QUOTE OR CITE 87 October 2002

NYC-WTC_000149031