Dispersions health hazards

Numerous factors affect the spread of luizardous substances into tlie area surrounding a leaking/buming container or contaituuent vessel. Evacuation decision-makers must carefully consider each of tliese factors in order to determine the conditions created by the release, tlie areas tluit have been or will be affected, and the heiilth affects on people. The factors tliat affect evacuation include amount of released material(s), physical and cheniical properties of the released material(s), health hazards, dispersion pattern, rate of release, and potential duration of release. Each of these factors is explained below. 

Radon in indoor air arises primarily from radium in the soil. The radon in the soil gas flows under a pressure gradient from the soil into the building. In some cases building practices can lead to high radon levels in the living areas of the house. Radon is chemically quite inert and does not pose a significant radiation health hazard in itself because the retained fraction in the body is so low (Mays et al., 1958). It is, however, an excellent vehicle for the dispersion of its short-lived radioactive decay products. 

The response to a nuclear explosion differs dramatically from the response to an attack with conventional explosives. When conventional explosives such as dirty bombs disperse radiological materials, the health hazards from the radiation exposure are secondary to the explosion (flying shrapnel, debris, fire, and smoke). In the case of a nuclear explosion, the risks of death, serious short-term health effects, and serious long-term health effects are no longer secondary to the explosion. 

Although various restrictions have been placed on carbon particulate emissions from different types of power plants, these particles can play a beneficial, as well as a detrimental, role in the overall plant process. The detrimental effects are well known. The presence of particulates in gas turbines can severely affect the lifetime of the blades soot particulates in diesel engines absorb carcinogenic materials, thereby posing a health hazard. It has even been postulated that, after a nuclear blast, the subsequent fires would create enormous amounts of soot whose dispersal into the atmosphere would absorb enough of the sun s radiation to create a nuclear winter on Earth. Nevertheless, particulates can be useful. In many industrial furnaces, for example, the presence of carbon particulates increases the radiative power of the flame, and thus can increase appreciably the heat transfer rates. 

Delmelle P., Stix J., Baxter P. J., Garcia-Alvarez J., and Barquero J. (2002) Atmospheric dispersion, environmental effects and potential health hazard associated with the low-altitude gas plume of Masaya volcano, Nicaragua. Bull. Volcanol. 64, 423-434. 

Polytetrafluoroethylene dispersions may contain one or more surfactants (and other additives) such as perfluoroammoniumoctanoate, also known as C8 in parlance of the industry. There are health hazards associated with some of the surfactants such as C8. 

Alpha emitters such as polonium-210 and curium-242 are used to excite emission of low-energy x-rays. They offer the advantage of large signal-to-background ratio, but the thickness of sample analyzed is extremely small. The alpha emitters are health hazards and generally have very limited application in energy-dispersion analysis. 

As with all materials that have been recently developed, the health risks associated with SiC whiskers are not well known however, because their sizes and shapes are similar to that of asbestos, therefore they are considered hazardous. Airborne dispersion and subsequent inhalation are the most serious health hazards. However, with proper worl lace handling requirements and procedures, large quantities of SiC whiskers can be safely processed. No release of whiskers has been observed from dense ceramic matrix composites during fracture or wear processes. Material Safety Data Sheets (MSDS) are packaged with all products containing loose whiskers and the directions in the data sheets should be followed. At the present time, the American Society for Testing of Materials (ASTM) has developed procedures and handling practice standards for SiC whiskers [14]. 

According to a recent assumption, powdered SbgOa forms a health hazard. For this reason, manufacturers are attempting to market this agent in other forms, such as a dispersion, masterbatch, or granules, or by substituting it with alternative antimony compounds. 

An essential requirement for the use of polymeric barriers in food packaging is the absence of any additive or residual monomers which can transfer potentially toxic components in any way to the contents of the package and impart an off-flavor to the product or present a health hazard. They must have little or no extractives which is particularly important to avoid odor or taste being imparted to food in the coated container. A variety of special purpose additives, which must be acceptable for use in food-contact applications, are used in coating systems. These additives include pigment dispersants, suspension agents, defoamers, emulsifiers, and rust prevention concentrates. 

Two-phase systems of fine dispersed solids in a continuous gas stream are quite common in many processing industries dealing with dry solids operations. In diverse processes such as the dry milling of grains, some combustion reactions, or the grinding of raw materials in the cement industry, fine solids may be released to the surrounding air as part of their normal operation. Tiny solid particles (dust) produced in many processes may become airborne and carried out by air currents. There are many problems associated with dust emissions, such as health hazards, abrasion damage to equipment, impaired... 

Synergetic mixtures presenting no health hazard are worthy of mention. They are zinc-based compounds mixed mainly with calcium soaps. Since zinc-containing stabilizers function only at very low concentration in PVC (0.1-0.4% by weight), it is necessary to ensure a good dispersion of the stabilizer mixture in the polymer matrix to obtain the best stabilizing effect. Too high a concentration of zinc stabilizer decreases the heat stability of PVC appreciably [55]. To avoid this, epoxide compounds should be used as HCl acceptors in conjunction with the stabilizer mixture. 

Having obtained the magnitudes of the classes of radioactivity release, and their probabilities, the next step is to calculate the consequences, in terms of health hazard and property damage, of each release. This depends on the manner in which the radioactivity is dispersed and on the distribution of population around the reactor. The dispersion in turn depends on the type of release, on its duration and elevation above ground, for example, and on the weather prevailing at the time of the accident. 

Soot fmeparticles produced by a combustion processes are similar in structure to the carbonblack profile of Figure 1.1 (a). When one is looking at the dispersal dynamics of a smoke and/or the health hazards of the smoke fineparticles, one must use an operational diameter known as the aerodynamic diameter. The aerodynamic diameter is the size of the smooth dense sphere of unit density which has the same dynamic behavior as the soot particle. Several procedures for measuring the aerodynamic diameter of airborne fineparticles will be discussed in various chapters of this book. 

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