Asbestos, effects

Moisture plays an important rble in many eases of oxidation. Its presence is necessary, for example, to effect the spontaneous combustion of pyrophoric metals. At ordinary temperatures, also, the majority of metals are stable m dry oxygen, although readily attacked by the moist gas. Small quantities of many foreign substances arc capable of catalytically assisting the rate of oxidation of certain substances. Thus a trace of platinum black introduced into electrolytic gas causes the gases to instantly unite with explosive violence and the passage of a mixture of sulphur dioxide and oxygen over platinised asbestos effects their union to form sulphur trioxide. 

Case BW, Ip MPC, Padilla M, et al. 1986. Asbestos effects on superoxide production An in vitro study of hamster alveolar macrophages. Environ Res 39 299-306. 

Doll R, Peto J. 1985. Asbestos Effects on health of exposure to asbestos. A report to the Health and Safety Commission. London, England, Her Majesty s Stationery Office. 

Jones RN, Diem JE, Ziskand MM, et al. 1984. Radiographic evidence of asbestos effects in American marine engineers. J Occup Med 26(4) 281-284. 

In conclusion, there are numerous examples showing that imaging by thin-section CT scan is more sensitive than the chest radiograph for asbestos effects. However, this advantage has not clearly been shown for other dusts. Furthermore, there may well be substantial variability among thin-section CT scan interpretation even by experienced readers, particularly in the interpretation of pleural abnormalities among asbestos workers. There is no standardized protocol for the interpretation of the thin-section CT when addressing potential dust-induced effects. 

Jones RN, Diem JE, Hughes JM, Hammad YY, Glindmeyer HW, Weill H. Progression of asbestos effects a prospective longitudinal study of chest radiographs and lung function. Br J Ind Med 1989 46 97 105. 

The advantages of the above air bath are (1) simplicity and cheapness of construction (2)ease of temperature control (3) rapidity of cooling of the contents of the flask effected either by removing the asbestos covers or by completely removing the air bath and (4) the contents of the flask may be inspected by removing the asbestos covers. 

Broadly speaking, the differences in effectiveness of palladium and platinum catalysts are very small the choice will generally be made on the basis of availability and current price of the two metals. Charcoal is a somewhat more efficient carrier than asbestos. 

Lipoproteins may denature on heating and if present during pasteurization can result in the formation of haze or turbidity in the final product. This material was removed traditionally by filtration through asbestos (qv) sheets (6) however, health hazards associated with asbestos have led to its replacement by alternative filter materials (23,37,193). These media have been less effective than asbestos and further measures have been required to ensure the visual clarity of albumin products, eg, further filtration developments for Hpid removal (194), preferential denaturation of contaminants using in-process heat treatment, and anion-exchange chromatography (49). 

The primary environmental concern for the coating plant is actually the residual material on the anode stmctures being returned for recoating. Therefore the anode user must enact effective cleaning procedures prior to shipment. For example, anodes in chlorine use must be cleaned of all traces of mercury and asbestos (qv). Anodes used in electrogalvanizing or in copper-foil production must similarly be cleaned to remove all traces of process materials. If cleaning at the user s plant is not done effectively, the anode may well be shipped back to the user for appropriate action before it is considered for recoating. 

Finally, the combined reinforcing effect and high absorption capacity of asbestos fibers have been exploited in a variety of appHcations to increase dimensional stabiHty, typically in vinyl or asphalt tiles and asphalt toad surfacing. Figure 9 summarizes, as of 1984, the various classes of application for asbestos fibers in combination with other materials. The diagram shows that in recent years, most industrial appHcations have evolved towards composite materials where the fibers are bonded within an organic or inorganic matrix. 

After the mid-1970s, the downsizing of North American vehicles and the introduction of front wheel drive vehicles brought about the widespread usage of a new class of friction materials (4) called semimetallics, also called semimets and carbon—metaUics. Because of the allegedly adverse health effects associated with asbestos [1332-21 -4] (qv) fibers, a second new class of friction materials called nonasbestos organics (NAOs) came about (5). Such materials are called either asbestos-free or nonasbestos friction materials (2). 

A. E. Anderson, "Brake Systems Performance—Effects of Eiber Types and Concentrations", Proceedings from Fibers in Friction Materials Symposium, Asbestos Institute, Atiantic City, N.J., Oct. 1987. 

For electrical insulation china clay is commonly employed whilst various calcium carbonates (whiting, ground limestone, precipitated calcium carbonate, and coated calcium carbonate) are used for general purpose work. Also occasionally employed are talc, light magnesium carbonate, barytes (barium sulphate) and the silicas and silicates. For flooring applications asbestos has been an important filler. The effect of fillers on some properties of plasticised PVC are shown in Figure 12.21 (a-d). 

In 1968 the Monsanto Company announced the availability of novel soluble low molecular weight polyphenylene resins. These may be used to impregnate asbestos or carbon fibre and then cross-linked to produce heat-resistant laminates. The basic patent (BP 1037111) indicates that these resins are prepared by heating aromatic sulphonyl halides (e.g. benzene-1,3-disulphonyl dichloride) with aromatic compounds having replaceable nuclear hydrogen (e.g. bisphenoxy-benzenes, sexiphenyl and diphenyl ether). Copper halides are effective catalysts. The molecular weight is limited initially by a deficiency in one component. This is added later with further catalyst to cure the polymer. 

Figure 24.9. Effect of cure time on some properties of M-F mouldings. Cure temperature cellulose filled 295-308°F mineral filled 300-320°F O glass-filled material, asbestos-filled material, A cellulose-filled material (a) Cross-breaking strength (b) tensile strength (c) impact strength (d) impact strength (e) water absorption (rag), boiling water 30 min (f) cold water 24 h, 23°C ...

Total frequencies of environmental illness are difficult to measure. When causes can be identified, however, scientists observe that frequencies of occurrence of a particular illness vary directly with the severity and extent of exposure. Particularly frequent in the workplace are skin lesions from many different causes and pulmonary diseases related to the inhalation of various dusts, such as coal dust (black lung), cotton dust (brown lung), asbestos fibers (asbestosis), and silica dust (silicosis). Environmental agents can also cause biological effects without overt clinical illness (for example, chromosome damage from irradiation). 

Applicability Most hazardous waste slurried in water can be mixed directly with cement, and the suspended solids will be incorporated into the rigid matrices of the hardened concrete. This process is especially effective for waste with high levels of toxic metals since at the pH of the cement mixture, most multivalent cations are converted into insoluble hydroxides or carbonates. Metal ions also may be incorporated into the crystalline structure of the cement minerals that form. Materials in the waste (such as sulfides, asbestos, latex and solid plastic wastes) may actually increase the strength and stability of the waste concrete. It is also effective for high-volume, low-toxic, radioactive wastes. 

Deactivation and D D actions can range from stabilization of multiple hazards at a single site or facilities containing chemical or radioactive contamination, or both, to routine asbestos and lead abatement in a nonindustrial structure. Strategies include programs that meet compliance objectives, protect workers, and make certain that productivity and cost-effectiveness are maintained. The content and extent of health and safety-related programs should be proportionate to the types and degrees of hazards and risks associated with specific operations. 

Specialty duties are assigned to teams formed for specific tasks or responding to unusual circumstances (e.g., waste characterization, confined-space rescue, asbestos, lead abatement, etc.). These teams are formed, as necessary, on a permanent or temporary basis. In many cases, special training, drills and exercises, and development of safe work plans are needed to prepare team members to conduct work safely and effectively. 

Nitric oxide may induce deleterious effects when airway epithelial or immunological cells are exposed to mineral particles (asbestos, quartz). These particles also stimulate cells to produce NO in large quantities, but pulmonary cells are unable to destroy these particles, and a non-physiologically excess production of NO results, perhaps causing tissue damage due to a reaction of NO with cellular macromolecules. 

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