Magnetic properties of asbestos fibers

It is now well known that inhalation of asbestos fibres can cause a number of severe health problems, including bronchial carcinoma and mesothelioma. Exposure of workers to contaminated atmospheres is strictly controlled and Control Limits have been published defining the maximum concentration of airborne fibres. The values have recently been revised and now depend on type of asbestos fibre as well as concentration. The current method of measuring fibre concentration involves examining an exposed filter pad with a high power optical microscope. This technique is extremely laborious, is of limited accuracy and cannot distinguish between different types of asbestos fibres. A recently developed method, which considerably improves the accuracy of analysis, involves orientation of fibres in a strong magnetic field. In the present work, the orientation of amosite fibres has been measured as a function of magnetic field strength. Results indicate that fibres in the range 5 μm to 20 μm have ferro - magnetic properties and the magnetic moment of individualfibres has been predicted. An analytical technique based on this work has recently been patented and should distinguish between fibre types as well as accurately predicting the airborne concentration of asbestos fibres.