The uses of asbestos

If the gap between the two pieces is too large for the above method to be attempted it may be possible to fit a sleeve of wider tubing over the two tubes and fuse its ends down on to them. This method inevitably leads to a very thick-walled joint, but the excess glass can be pulled off with forceps or by fusing a glass rod on to the thick part and pulling it out. 

All joints, no matter how they are made, shoidd be annealed with a relatively cool flame (p. 170). 

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During the late 1960s and 1970s, the finding of health problems associated with heavy exposure to airborne asbestos fibers led to a strong reduction (or ban) in the use of asbestos fibers for thermal insulation. In most of the current applications, asbestos fibers are contained within a matrix, typically cement or organic resins. 

Keport of the Kojal Commission on Matters ofiHealth and Safety Arising from the Use of Asbestos in Ontario, ]. S. Duprn, chairman, Vol. 1, Ontario Government Book-Store, Toronto, Ontario, Canada, 1984, pp. 87, 89—93. 

Another problem is the extent of regulative measures. On the one hand, the use of asbestos is now almost completely banned in the European Union and in many other industrialised and economically thriving countries. On the other hand, more than 2 milhon tons of asbestos are extracted and consumed globally every year. A uniform global hazardous substances pohcy evidently does not exist yet. 

The use of asbestos is being curbed because it has been shown to cause lung cancer if inhaled. A simple explanation for this is that the straight molecules in asbestos cleave easily. The asbestos dust consists of small sized fibrous particles... 

Although the use of asbestos has been greatly reduced and the disease asbestosis has declined, the incidence of mesothelioma has increased threefold since 1990. ... 

If groups of children exposed to known levels of asbestos could be identified, the lifetime studies could be designed to assess long-term effects of childhood exposure to asbestos. Respiratory effect end points could be compared to those in occupationally-exposed adults in an effort to assess susceptibility in children relative to adults. However, due to changes in the use of asbestos during the past several decades, it may be difficult to identify such groups of children. 

Asbestos may also be released to indoor air from the use of asbestos-contaminated household water (Hardy et al. 1992 Webber et al. 1988). Limited studies indicate that both amphibole and chrysotile... 

The use of asbestos filters in food or pharmaceutical preparation has been discontinued in the United States, and intake of asbestos through foods or drugs is now unlikely. 

Some people may also be exposed to elevated levels of asbestos in drinking water, particularly where there are widespread natural deposits of asbestos (e.g., San Francisco Bay area), disposal of asbestos-containing ore tailings (e.g., Duluth, Minnesota), or the use of asbestos-containing cement pipes in drinking water distribution systems with low pH and low hardness (Craun et al. 1977 Kanarek et al. 1981 Webber et al. 1989). 

Dupre JS, Mustard JF, Uffen RJ, et al. 1984. Report of the Royal Commission on matters of health and safety arising from the use of asbestos in Ontario. Ontario, Canada Ontario Ministry of the Attorney General, Pubk, 73-112. 

Hardy RJ, Highsmith VR, Costa DL, et al. 1992. Indoor asbestos concentrations associated with the use of asbestos-contaminated tap water in portable home humidifiers. Environ Sci Technol 26 680-689. 

Harrington JM, Craim GF, Meigs JW, et al. 1978. An investigation of the use of asbestos cement pipe for public water supply and the incidence of gastrointestinal cancer in Connecticut, 1935-1973. Am J Epidemiol 107 96-103. 

Millette JR, Craun GF, Stober JA, et al. 1983b. Epidemiology study of the use of asbestos-cement pipe for the distribution of drinking water in Escambia County, Florida. Environ Health Perspect 53 91-98. 

US Food and Drug Administration currently regulates the use of asbestos in preparation of drugs and restricts the use of asbestos in food-packaging materials. 

The use of asbestos has been greatly diminished because of its identification with health hazards. There have been proposed replacement materials such as the Zeta Plus filter media from the AMF Cuno Division, consisting of a composite of cellulose and inorganic filter aids that have a positive charge and provide an electrokinetic attraction to hold colloids (usually negatively charged). These media therefore provide both mechanical straining and electrokinetic adsorption. 

Filters that shed fibres should not be used. The use of asbestos-containing filters should be absolutely excluded. 

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