NYC-WTC_000195164

NYC 9/11 Public Portal Document

. ASBESTOS REPROTEXT ® System Page 3 of 27

2.0 INTRODUCTION

A. Asbestos represents a group of naturally occurring impure magnesium silicate minerals (Clayton & Clayton, 1993; Lewis, 1997). On a macroscopic scale, asbestos occurs in white, gray, green, and brown fibrous forms (Lewis, 1997). B. The main forms are the serpentine subgroup, consisting of chrysotile (white), and a subgroup called amphiboles, which consists of actinolite, amosite (brown), anthophyllite, crocidolite (blue) and tremolite (Clayton & Clayton, 1993). Chrysotile represents 95 percent of natural mineral fiber asbestos used in the US and 99 percent of the world's production (Landrigan et al, 1999; ACGIH, 1991). C. Asbestos has been used for thermal insulation and resistance to high temperature or fire, saltwater, or corrosive chemicals (Lewis, 1998). Although the high-level exposures encountered by insulation workers and shipyard workers no longer occur, substantial exposures can occur today among PAINTERS (Selikoff, 1975) and DRYWALL INSTALLERS (Fischbein et al, 1979) who are renovating old buildings, as well as among asbestos-remediation workers. D. Commercial applications of asbestos are in the process of being phased out in the US, with the last group scheduled to be banned from distribution by 25 August 1997 (Clayton & Clayton, 1993). Because of widespread asbestos use in Europe, its proven role in human cancer and the inability to control its use, the Collegeum Ramazzini, a consortium of European health professionals, has called for an international ban on asbestos (Collegeum Ramazzini, 1999).

3.0 EFFECTS OF ACUTE EXPOSURE

A. There is no evidence of any acute systemic effect from exposure to asbestos (Clayton & Clayton, 1993). Nearly all of the toxicologic literature on asbestos is concerned with its activity as a human carcinogen with chronic exposure. B. Asbestos is not acutely toxic, except for possible irritation of the eyes, skin, and respiratory tract due to mechanical action of the fibers. Skin irritation with com formation can result from penetration of the skin by asbestos spicules (HSDB, 2000). C. The dose-response relationship for induction cancer from exposure to asbestos is not well understood for low-level exposures. It has been suggested that even a single, high- dose acute exposure might be sufficient to induce cancer (Stich, 1985). D. Asbestos fibers can stimulate the production of interleukin (IL)-8 in cultured lung cells. The mechanism of this induction involves redox changes and phosphorylation by means of staurosporine-sensitive and tyrosine kinase(s), activation of transcription factors that bind to the NF-kappaB/NF-IL-6 binding site of the IL-8 promoter, and upregulation of the IL-8 gene (Simeonova & Luster, 1996). E. Transforming growth factor (TGF)-alpha was also upregulated in the lungs of rats as a result of a single 5-hour exposure to asbestos. Increases in TGF-alpha mRNA and peptide were seen as early as 24 hours after the acute exposure and persisted for at least 2 weeks. These results support the idea that TGF-alpha is involved in the mechanism of asbestos-induced proliferation of epithelial and mesenchymal cells in the lung (Liu et al, 1996).

4.0 EFFECTS OF CHRONIC EXPOSURE

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