Inert dusts

Intrinsic asthma, also called idiopathic asthma, usually develops in adulthood. In intrinsic asthma allergic factors are not demonstrable. Episodes of intrinsic asthma may be triggered by a variety of stimuli, eg, emotional state, exposure to cold air, or inert dusts. Both intrinsic and extrinsic asthmatics can be prone to exercise-induced attacks. Individuals who experience a combination of extrinsic and intrinsic asthmatic reactions have mixed asthma. Status asthmaticus refers to an especially acute life-threatening asthma attack which is resistant to normal treatments and which may require hospitalization in order to stabilize the patient. 

Explosible dusts can also be changed into mixtures which are no longer explosible by the addition of inert dusts (e.g., rock salt, sodium sulrate). In general, inert dust additions of more than 50 wt % are necessary here. It is also possible to replace flammable solvents and cleaning agents by nonflammable halogenated hydrocarbons or water, or flammable pressure transmission fluids by halocarbon oils. 

Still another requirement is that the concentrated form of the insecticide readily combines with various types of vehicles. At the present time, pure DDT can be dissolved only in organic solvents, and it has been necessary to provide a 50% water-dispersible DDT powder when wrater was to be used as the vehicle. With the advent of 90% water-dispersible DDT, it may be possible to utilize this material in the preparation of both water suspensions and organic solutions of the chemical. The ideal chemical in this respect would be one that could be shipped as 100% dust, and could be readily diluted with inert dust, water, and organic solvents in the field. 

Replacing the atmospheric oxygen by inert gas, working in a vacuum, or using inert dust... 

Golob, P. 1997. Current status and future perspectives for inert dusts for control of stored product insects. J. Stored Prod. Res. 33, 69-79. 

Three classes of dust can exist in the workplace, namely, toxic dusts, inert dusts, and proliferative dusts. We have already seen the effects of some of the toxic dusts, such as lead. The other two groups are considered below. 

In a similar 11-month study in which animals were exposed to undoped bismuth telluride dust of 0.04-p,m diameter at 15mg/m no adverse responses of any type were observed other than the pulmonary responses to the inhalation of an inert dust. 

Synthetic graphite injected peritoneally in mice produces a reaction characteristic of an inert material. On the basis of experimental evidence, and the rarity of reports of adverse effects of exposure in humans, it is concluded that pure synthetic graphite acts only as an inert dust. 

Particulate Matter Other Than Systemic Poisons. Silica and asbestos dust produce fibrosis. Silicon carbide, carbon (other than exhaust emissions), and emery are inert dusts. Many organic dusts, eg, pollen, wood, and resins, cause allergic reactions. Acids, alkalies, fluorides, and chromates are irritants. 

Plutonium is so toxic that processing and fabrication are always done in sealed cells or glove boxes, but accidental dispersions of aerosol occur from time to time. Following combustion of Pu metal chips in a production area at Rocky Flats, Colorado, in 1964, airborne contamination was widespread. Alpha tracks from individual particles caught on membrane filters were detected on nuclear film, and the Pu content, and hence the particle size, was deduced (Fig. 5.2, curve E). The activity median diameter was 0.3 /urn (Mann Kirchner, 1967). The same method, used during normal operations in a production area at Los Alamos, gave activity median diameters in the range 0.15 to 0.65 /urn (Moss et al., 1961). However, when a spill occurred, followed by clean-up operations, the Pu particles were found to be associated with inert dust particles of mass median diameter 7 /urn. 

Wheeler (1936) uses a different method of determining inflammability. Having determined whether a given dust is explosive, he next proceeds to add known percentages of inert dust such as fuller s earth (200 I.M.M.-mesh) until the dust is no longer explosive. This critical point is called the index of inflammability." If the amount of fuller s earth used is denoted by / (in percent), the index of inflammability I may be written... 

Stalder, K. and Stober, W., Haemolytic activity of suspensions of different silica modifications and inert dusts, Nature, 207, 874, 1965. 

Inert dusts have been used traditionally as stored grain protectants, and there is increasing interest in their use as alternatives to chemical control measures. A number of studies demonstrating the efficacy of inert dusts as grain protectants have been reported (Desmarchelier and Dines, 1987), as structural treatments in empty stores (Bridgeman, 1994) and as surface treatments in conjunction with aeration (Nickson et al., 1994). Diatomaceous earths (DEs) have been registered for storage use in USA, Canada, Australia, Japan, Indonesia and Saudi Arabia. 

The products are based on inert materials such as silica gel or diatomaceous earth (DE) and contain no insecticides or knockdown agents. They are effective against species resistant to pesticides, and are stable at high and low temperatures (McLaughlin, 1994). In contrast to chemical insecticides, which induce rapid immobilisation and kill, the action of inert dusts is slow, and extended exposure periods of 20 days or more may be required to eliminate an insect population. Most products, at the appropriate concentration, provide protection for at least 12 months (McLaughlin, 1994). 

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