A study of asbestos emission from asbestos-containing products with particular regard to public schools in the Hobart area

OCCURRENCE OF ASBESTOS EMISSIONS AND HEALTH RISK IN THE GENERAL ENVIRONMENT For a long time, exposure to asbestos has been considered as an occupational health hazard for asbestos workers. Recently, research studies have shown that almost the entire community is exposed to low levels of airborne asbestos. According to Scientific Authorities (U.S.E.P.A. 1979) in cases where exposures are very low, it is not possible to establish a threshold level of exposure below which there is no evidence of some health risk. This statement has raised concern throughout the world regarding general public health because asbestos is ubiquitous and low levels of asbestos contamination can be demonstrated everywhere. Asbestos fibre emission causing risk for the general population might be associated with open-air construction activities such as where asbestos products are used for roofing, side cladding, guttering, and ducting for'ventilation systems as well as during the demolition or renovation of structures containing asbestos. Asbestos fibres released from automobile brake linings, or during the handling of asbestos waste, may also cause a health risk. Demolition processes may constitute the most significant source of short-term exposure to the general population living nearby. According to the Canadian Asbestos Information Centre (Candaian A.I.C. 1982), even high density products will liberate fibres as they are severely fragmented by explosive demolition. The same source provides data of measurements made in the Federal Republic of Germany during the demolition of an asbestos cement facade. It states that, in the breathing zone of the apparatus, a concentration level of 0.4 to 0.8 fibres per millilitre, with a fibre length longer than 5 micrometres, was measured. At 8 to 100 metres down-wind distance, the concentration was lower, but still significantly higher than the background concentration in that area. Generally, the hygiene standard at demolition sites is breached from time to time and the people living nearby such operations are exposed to elevated levels of asbestos fibres. Also, in areas directly neighbouring industrial users of asbestos, the levels of air population with asbestos fibres have been shown to be high. Such a situation is a direct result of difficulties encountered in reducing the emission of fine particles of asbestos during factory operations and asbestos transportation. Measurement studies of the air pollution of several cities have proved that, in some industrial countries, exposure to asbestos dust has extended from occupational to environmental situations. Monitoring programmes in European countries have determined the levels of asbestos fibres in samples from major city locations. Sampling locations have been designated to provide information on levels of asbestos in air in some typical urban sites such as crossroads with heavy traffic, areas with building construction or in the vicinity of a freeway. The assessment of environmental air pollution by asbestos has been accomplished with the transmission Electron Microscope or the SEM in a quantitative way chrysotile fibres were present in every sample analysed. Data on sampling and number of samples analysed in Paris and its suburbs are given in Table 1.1. As can be seen, analysis of samples yielded very similar results. Mean value derived from the analysis of samples taken in areas with buildings under construction was highest, but all results obtained were approximately more than 10 thousand times lower than hygienic standards for the occupational exposure (Sebastien et al. 1979).