Academic journal article Environmental Health Perspectives

Analysis of the Biological and Chemical Reactivity of Zeolite-Based Aluminosilicate Fibers and Particulates. (Articles)

Academic journal article Environmental Health Perspectives

Analysis of the Biological and Chemical Reactivity of Zeolite-Based Aluminosilicate Fibers and Particulates. (Articles)

Article excerpt

Environmental and/or occupational exposure to minerals, metals, and fibers can cause lung diseases that may develop years after exposure to the agents. The presence of toxic fibers such as asbestos in the environment plus the continuing development of new mineral or vitreous fibers requires a better understanding of the specific physical and chemical features of fibers/particles responsible for bioactivity. Toward that goal, we have tested aluminosilicate zeolites to establish biological and chemical structure-function correlations. Zeolites have known crystal structure, are subject to experimental manipulation, and can be synthesized and controlled to produce particles of selected size and shape. Naturally occurring zeolites include forms whose biological activity is reported to range from highly pathogenic (erionite) to essentially benign (mordenite). Thus, we used naturally occurring erionite and mordenite as well as an extensively studied synthetic zeolite based on faujasite (zeolite Y). Bioactivity was evaluated using lung macrophages of rat origin (cell line NR8383). Our obxive was to quantitatively determine the biological response upon interaction of the test particulates/fibers with lung macrophages and to evaluate the efficacy of surface iron on the zeolites to promote the Fenton reaction. The biological assessment included measurement of the reactive oxygen species by flow cytometry and chemiluminescence techniques upon phagocytosis of the minerals. The chemical assessment included measuring the hydroxyl radicals generated from hydrogen peroxide by iron bound to the zeolite particles and fibers (Fenton reaction). Chromatography as well as absorption spectroscopy were used to quantitate the hydroxyl radicals. We found that upon exposure to the same mass of a specific type of particulate, the oxidative burst increased with decreasing particle size, but remained relatively independent of zeolite composition. On the other hand, the Fenton reaction depended on the type of zeolite, suggesting that the surface structure of the zeolite plays an important role. Key words: erionite, faujasite, Fenton reaction, fiber toxicity, mordenite, zeolites. Environ Health Perspect 110:1087-1096 (2002). [Online 12 September 2002]

http://ehpnet1.nihs.nih.gov/docs/2002/110p1087-1096fach/abstract.html

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Epidemiologic data suggest that environmental and/or occupational exposure to minerals, metals, and fibers can cause lung disease (1-3). These diseases typically develop over many years after exposure to the agents. The most studied fiber is asbestos (1-3). Man-made mineral or vitreous fibers can also be bioactive, though their role in respiratory disease in humans is not yet well established and is an active area of study (4,5). There are more than 70 varieties of synthetic inorganic fibers, covering over 35,000 applications, with different physicochemical and morphological characteristics. These include insulation materials (glass wool, rock wool, slag wool), glass filaments and microfibers, and refractory ceramic fibers (4). As a consequence of the extensive applications of these fibers, a significant fraction of the population is exposed. Thus it is essential to understand the basis of toxicity of respirable fibers. In this study, we focused on developing a better understanding of the biological and chemical reactivity of aluminosilicate fibers and particles.

Epidemiologic and experimental data have demonstrated that exposure to asbestos can induce pulmonary inflammation, fibrosis of the lower respiratory tract (asbestosis)(1-3,6) and is a risk factor for developing bronchiogenic carcinoma and mesothelioma (7). Numerous studies have been performed over the past 30 years to determine the mechanism(s) by which asbestos causes disease, and several hypotheses have been generated (8). Activation of macrophages by phagocytosis of the fibers results in the formation of reactive oxygen species (ROS) (1-3,6,9,10), where ROS is a collective term that includes radicals (superoxide anion, hydroxyl, peroxyl, and alkoxyl radicals), and hydrogen peroxide ([H. …

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