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Proceedings Paper

Measurements Of Scattered Light From Asbestos Particulate
Author(s): P. Riis; E. A. Ballik
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Paper Abstract

Light-scattering techniques are potentially very important for the low-level detection and identification of particulate species such as asbestos in aerosol and liquid suspensions. Low-level detection is essential because asbestos is a known carcinogen, even at very-low exposure levels. At present, most asbestos particulate monitoring is used on optical microscopy. If detailed analysis is required, then electron microscopy is employed. Both of these methods are labour intensive. Furthermore, the optical microscopy method is not very reliable. Although the light-scattering techniques described here have general applicability, the emphasis is on asbestos measurements. Ordinary measurements of Mie scattering from asbestos suspensions can provide only limited information on asbestos content. owever, a more sophisticated technique can be employed which relies on the fact that asbestos particulate is fibrous rather than spherical in shape, and that the fibres align in a strong magnetic field (approximately 0.5 T). Particulate other than asbestos is generally non-fibrous in shape. Measurements have been carried out on liquid suspensions of asbestos contained in a small cell placed between the poles of a rotating magnet. The aligned fibres, which rotate about their centre of mass as they follow the field, are illuminated using a laser source. The Mie-scattering intensity is measured as a function of rotation angle, and the resulting data is then analysed with the aid of a microcomputer. Intensity maxima and minima provide reliable information on asbestos concentration, even in the presence of strong scattering from other particulate. In addition, the angular location of the intensity peaks provides information on the type of asbestos present. Each type has a characteristic alignment behaviour in a strong magnetic field. Using relatively-simple equipment, chrysotile asbestos (the most commonly-used type) has been detected at levels below 30 ng/l.

Paper Details

Date Published: 10 September 1987
PDF: 7 pages
Proc. SPIE 0808, Inverse Problems in Optics, (10 September 1987); doi: 10.1117/12.941471
Show Author Affiliations
P. Riis, McMaster University (Canada)
E. A. Ballik, McMaster University (Canada)

Published in SPIE Proceedings Vol. 0808:
Inverse Problems in Optics
Edward Roy Pike, Editor(s)

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