Document k6po23Qjq2dR6JjqpryZne6pJ

Mining Industry (b) toxic dusts, which arc poisonous to body organs and body tissues (beryllium, organic, lend, mercury, radon, thorium, and othoni); (c) radio-active dusts, which am injurious because of thoir radiations (ores of uranium, thorium, etc.); (d) oxplosivo dusts, which aro combustlblo in nlrbomo suspension (coal dusts, sulphide dusts, and the liko); and (o) Inert dusts, which allegedly have no harmful effects. Somo dusts have multiple ratings and, ns our experience grows, more and moro dusts oro being added to tho harmful lists; there is, in fact, increasing reason to doubt whether any dust is really inert or pathologically harmless. Dusts can vary in their injuriousness when associated with gaseous contaminants which, in their own field can have adverse physio logical effects through asphyxiation, toxicity, or radio-activity. As with oxygen depletion, the physiological effect of a gas varies with the exposure time and the individual. Radon, because of its decay products, gives rise to particular problems of surveying and assess ment. A vast amount of work has yet to bo done on the sources of radon, its migration in mine waters, and tho mechanisms of its release into the working atmosphere. Can its solubility differential in water and oily liq uids bo put to beneficial control use? Its dis astrous assimilation in the blood stream is based upon this marked solubility differen tial. Generally, in our assessment of the harmfulness of industrial dusts, several factors emerge os important. Mineral composition is probably moro important than chemical composition, and the physio-chemical prop erties aro probably moro important than the physical properties. The surface activity of particles is important. Permissible concentra tions vary from dust to dust Radio-active and other toxic dusts can bo harmful at con centrations less than one-fifth that of a tradi tionally accepted harmful dust, such as sil ica. Exposure times are found to vary enor mously. In somo cases, silicosis has been diagnosed after less than one year of expo sure; in other cases, only after 15 or 20 years or even longer. Radiation damage generally does not make itself obvious until after sev eral years. Even in a single mine, are there variations in the silicosis-producing proper ties of quartz at various depths? This would appear to be so. For example, at Kolar in India, with shallow depths, classical silicosis was rare even in miners with a lifetime of underground employment; ns depths in creased, silicosis began to appear after 15-20 years and now, with depths of tho order of 11,000 feet, silicosis is reported to bo a seri ous hazard after less than fivo years of un derground working exposure. Tho behavior of particles, whose surfaces havo been coated with highly active films of parasitic dusts, has yet to be fully investigated. In any case, the mere presence of dust nnd/or radiations has an adverse psychologi cal effect upon miners. From this viewpoint alone, their abatement is important All dusts have nuisance value, in that they dccrcaso visibility, create uncomfortable environmen tal conditions, and result in labor inefficiency and dissatisfaction. Tho subject of abatement still remains in adequately studied. Water has been the uni versally applied medium, but its efficiency is open to question and it has limitations; for example, in certain winter-time open cut ac tivities, wet drilling is virtually impossible. Newer methods of abatement must bo inves tigated. Efforts have been made to apply electrostatic concentration to airborne dusts, but with only partial success. Somo are of the opinion that other meth ods should be investigated. Should wo be applying to airborne mlnerallic-particlo sus pensions the some sort of principles that we apply to water-bomo suspensions in oro dressing processes? Is it possible to introduce dust surface activators which would render tho dust particles more amenable to collec tion and, therefore, abatement, by the use of froths and foams? This is ono field of mlncrallic surface chemistry that could be impor tant. It might offer new solutions to this ago-old problem. Mine Illumination. Inadequate attention has been given to mino lighting. Although spectacular ad vances have been made in illumination engi neering, our industry has been slow to take advantage of the new developments. In al most any handbook on illumination it is pos sible to find tables which list optimum illu minating conditions for every form of indus trial activity, with the single exception of mining. To say that lighting has always been a problem underground, where illumination leaves much to be desired, is a serious un derstatement. A new approach is necessary. Any new application must take into account 7