VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

IV.e. Asbestos

Asbestos is a term used to describe a family of hydrated metal silicate minerals. Asbestos exhibits some special properties, such as high tensile strength, the ability to be woven, heat stability, and resistance to attack by acid and alkali. Thus, it was widely used for building fireproofing insulation and other purposes during the 1960s and early 1970s. At the peak of its demand, about 3000 applications or types of products were listed for asbestos. In 1973, EPA prohibited the spraying of asbestos-containing material on buildings and structures for fireproofing and insulation purposes. The use of asbestos has been sharply declining for more than two decades. Sprayed on asbestos was used to fireproof approximately the lower half of one of the WTC towers, and may have been used in other places in the towers as well. One of the reasons that asbestos has been so useful is that it exists in long, thin fibers that can be sprayed, woven or mixed. The extremely light and aerodynamic asbestos fibers also lead to their ability to become and remain airborne. The fibrous nature also contributes to the health effects associated with asbestos exposure.

There are six minerals whose fibrous forms are characterized as asbestos and that are currently regulated. All the six minerals also occur in non-fibrous forms and these forms are not known to cause any health effects. The six regulated asbestos fibers include one from the serpentine family of minerals: chrysotile, and five from the amphibole family: fibrous reibeckite (crocidolite), fibrous grunerite (amosite), actinolite asbestos, anthophylite asbestos, and tremolite asbestos. Inhalation of these asbestos fibers has been linked to several adverse health effects including primarily fibrosis of the limgs (asbestosis), benign pleural plaques and thickening, lung cancer, and mesothelioma (a cancer of the thin membrane that surrounds the lungs and other internal organs). It also may increase the risk of cancer at other sites, but the evidence is not strong. Over the years the evidence has accumulated that longer thinner “asbestiform” fibers are of more concern for human health. The widely accepted definition of the asbestiform fiber is a particle having a length to diameter (aspect) ratio of ^3:1 and a length of at least ^5 pm. The evidence is overwhelming that both the mineral content and the size and shape of the fiber affects the severity of the disease. The respirable fibers are those with the diameter of <3 pm. Fibers exceeding the diameter of 3 pm are considered to be non-respirable.

Asbestosis, a chronic, degenerative lung disease, has been documented among asbestos workers from a wide variety of industries. The disease is generally expected to be associated only with the higher levels of exposure commonly found in workplace settings (Brown et al., 1994; Case and Dufresne, 1997). Several researchers have found that asbestosis and lung cancer are associated with cumulative exposure to asbestos. Benign pleural plaques and thickening also have been linked to higher cumulative exposure to asbestos (Albin et al., 1996; de Klerk et al., 1993). Both asbestosis and benign pleural plaques result in reduced breathing capacity and mortality. In a review of the epidemiologic evidence for asbestosis exposure- response relationship, the World Health Organization Task Group on Environmental Criteria for Chrysotile Asbestos (WHO, 1998) concluded that “asbestotic changes are common following prolonged exposures of 5 to 20 f/mL.” These prolonged exposures corresponded to cumulative exposure of 50 to 200 f/mL for a 10-year exposure period. They also concluded that “the risk at lower exposure levels is not known.”

DRAFT-DO NOT QUOTE OR CITE 86 October 2002

NYC-WTC_000149030