Document kDbQy85dwB6oxwMYMbEwDgye0

INDUSTRIAL HYGIENE viewed ) Detergent-aiid-water cleaning so lutions can be considered for use in place of organic solvents Benzene can be replaced by toluene in most lacquers, synthetic-rub ber solutions, and paint removers Natural rubber cements with aliphatic hydrocarbon solvents can perform virtually the same function as benzene cements The felt-hat industry has controlled the hazard of mercunalism by substituting mercury-free carroting materials Foundries using parting compounds that contain free silica can mini mize the silicons hazard by substituting relatively harmless powders Sandstone grinding wheels have been largely replaced by artificial abrasive wheels usually made of aluminum oxide. Changing the process In some cases, a process can be modified to reduce the exposure to a dust or fume and thus markedly reduce the hazard In the automobile industry, the amount of lead dust created by grinding solder seams with small high-speed sanding disks was greatly reduced by changing to hand filing Brushpainting or dipping instead of spray paint ing will minimize the concentration of air borne contaminants from toxic pigments Other examples of change of process are arc welding m place of nvebng, vapor de greasing to replace hand-washing of parts, airless spraying techniques and electrostatic devices to minimize overspray as replace, ments for hand-spraying, and machine appli cation of lead oxide to battery grids which reduced lead exposure in making storage batteries However, mechanization may aggravate rather than decrease hazardous conditions m some instances, so process changes must be considered carefully Isolation or enclosure Isolation is particularly useful for limited operations requiring relatively few workers or where control by any other method is too difficult or too expensive The ]ob is iso lated from the rest of the operation and thus the majority of the workers are not ex posed to the hazard The workers actually concerned with the operation can then be protected by installing a ventilation system which probably would not have been satis factory if the operation had not been iso lated and thus able to be enclosed Enclosing the process or equipment is a desirable method of control since the en closure will prevent or minimize the escape of solvent vapor mto the workroom atmos phere Where some of the more highly toxic solvents are used, enclosure should be one of the first measures attempted, after con sidering substitution In most instances, the enclosure should also be exhausted to avoid buildup of solvent vapors Additional pre cautions must be taken when cleaning en closed equipment or during start up or shut down in older to avoid high concentrations of solvent vapors Enclosure of an operation effectively pre vents the dispersal of contaminants En closed equipment is usually run tightly closed and is only opened dunng cleaning or filling operations Further examples of where this type of control is effective are radium dial painting, glove booths, wheelabrators or shot blast machines for cleaning tastings, and abrasive blasting cabinets In the chemical industry, the isolation of hazardous processes in closed systems is a widespread practice, which is one reason why die manufacture of toxic substances is often less hazardous than their use In the mechanical industries, complete enclosure is frequently the best solution of severe dust or fume hazards, such as those from sand blasting or metal spraying operations Wet methods Dust hazards can frequently be'minimized or greatly reduced by application of water or other suitable hquid at the source of dust, a method often used for silica and loose dusts Wetting of floors before sweep ing to keep down the dispersion of harmful dust is advisable when better methods, such as vacuum cleaning, cannot be applied "Wetting down" is one of the oldest, sim plest, and when properly used, most effec tive methods for the dust control. Its effec tiveness, however, depends upon proper wetting of the dust This may require the addition of a wetting agent to the water and proper disposal of the wetted dust before it dnes out and is ledispersed. Tremendous reductions in dust concentrations have been achieved by the use of water forced through the drill hits used in rock drilling opera tions Many foundries successfully use wa ter under high pressure for cleaning cast ings in place of sandblasting. Airborne dust 39-37