Propellants environmental actions

Particles with diameters between 1 and 5 pm are deposited in the tracheobronchial region as a result of either inertial impaction at airway bifurcations or gravitational sedimentation onto other airway surfaces. Undissolved particles may then be removed by the action of the mucociliary defense system working as an escalator particles trapped in the mucus are propelled toward the pharynx by the action of thin cilia located on the surface membrane of specialized cells. Once in the pharynx, the particles may be swallowed. The efficiency of the escalator defense system may be greatly impaired by various environmental contaminants, like sulfur dioxide, ozone, and cigarette smoke that are known to paralyze the activity of the ciliated cells and consequently the upward movement of the mucus. 

Nevertheless, the Environmental Protection Agency recently announced that it plans to propose limiting U.S. production of CFCs for nonaerosol uses. However, no other major industrialized nation followed the EPA s lead in banning CFCs as aerosol propellants in 1978. Since ozone depletion, should it occur, would be a global problem, it would seem to make sense to obtain international agreement rather than rushing off to establish another regulatory action which would place added economic burden on the U.S. industry and consumer. 

CFCs are just one of many examples of the trade-offs between beneficial and possible harmful effects of a new research product. During World War II, the use of CFCs as propellants for the insecticide DDT saved the lives of many troops in the Pacific zone who were suffering more casualties from malaria than from enemy action. But later, indiscriminate use of CFCs as propellants for all sorts of trivial purposes led to problems with their environmental accumulation. Chemicals (in this case, CFCs) are neither good nor evil, but we must exercise good judgment in how we use them. 

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