Asbestos fibres in the air of towns

Methodologies for determining the sources, characteristics, distribution, and abundance of asbestiform and nonasbestiform amphibole and serpentine in ambient air and water

Anthropogenic and nonanthropogenic (erosion) processes contribute to the continuing presence of asbestos and nonasbestos elongated mineral particles (EMP) of amphibole and serpentine in air and water of urban, rural, and remote environments. The anthropogenic processes include disturbance and deterioration of asbestos-containing materials, mining of amphibole- and serpentine-bearing rock, and disturbance of soils containing amphibole and serpentine. Atmospheric dispersal processes can transport EMP on a global scale. There are many methods of establishing the abundance of EMP in air and water. EMP include cleavage fragments, fibers, asbestos, and other asbestiform minerals, and the methods employed do not critically distinguish among them. The results of most of the protocols are expressed in the common unit of fibers per square centimeter; however, seven different definitions for the term "fiber" are employed and the results are not comparable. The phase-contrast optical method used for occupational monitoring cannot identify particles being measured, and none of the methods distinguish amphibole asbestos from other EMP of amphibole. Measured ambient concentrations of airborne EMP are low, and variance may be high, even for similar environments, yielding data of questionable value for risk assessment. Calculations based on the abundance of amphibole-bearing rock and estimates of asbestos in the conterminous United States suggest that amphibole may be found in 6-10% of the land area; nonanthropogenic erosional processes might produce on the order of 400,000 tons or more of amphibole per year, and approximately 50 g asbestos/km(2)/yr; and the order of magnitude of the likelihood of encountering rock bearing any type of asbestos is approximately 0.0001.

Levels of asbestos air pollution in some environmental situations

Asbestos contamination of the outside aid in Paris and suburbs has been monitored in some environmental situations, namely, "typical" urban sites removed from known sources of asbestos emissions, crossroad locations, the vicinity of a freeway, areas with buildings under construction, and areas around asbestos factories. In the same manner, measurements have been performed inside buildings of various types: those sprayed with asbestos-containing materials, those fitted with asbestos products, and control buildings. Air has been sampled by use of 0.45 micrometer pore size Millipore filters. After low-temperature ashing, ultrasonicated ashes were transferred to carbon film on 200-mesh gold grids examined under an analytic transmission electron microscope. Levels of pollution were expressed in terms of gravimetric concentrations. Inside buildings, when the air was in contact with significant amounts of asbestos-containing materials (spray, sheets), the levels were in the range 0.1--1000 10(-9) g m-3. In the vicinities of asbestos plants, the concentrations were higher: 1000--3000 10(-9) g m-3. Under other circumstances, the levels were of the same order of magnitude: 99% of the values were below 7 X 10(-9) g m-3. The Conseil Supérieur d'Hygiène Publique de France proposed a numerical ambient air quality standard of 50 X 10(-9) g m-3 inside buildings sprayed with asbestos.