Effects of air pollution on asthma: A review

Interest in air pollution and its effects on health and disease has been increasing steadily. A majority of physicians and scientists have been impressed that air pollution cannot help but aggravate diseases of the upper anal lower respiratory tracts, although it has been questioned whether t,hcrc is firm evidence that this is an established fact; some have called air pollution “a cause in search of a disease.“l The intent of this review is to describe concisely the current state of knowledge about the effects of air pollution on asthma, with the understanding that the primary etiologic factors in the asthmatic response are generally not characterizetl for the stutly populat,ions in the reports to be reviewed. Good reviews of other various asp&s of air pollution effects on health have been published in recent sears.l-’ For the purpose of this discussion, a modifiecl definition of air pollution has been adapted from that of the Air Clonservat,ion Commission”: “that state resulting from the production of man-m& wastes p~otluccd so rapidly that they accumulate in concentrations which cannot be dispersed by the normal scllfcleansing propensities of the atmosphere.” This definition excludes naturally appearing materials such as pollens, molds, and infectious agents. Loca,li& air pollutants such as cigarette smoke and occupational exposures will also 1~ OSeluded, although they are important factors in selected cases. The major components of “air pollution” will be described with the underst,anding that (3) they exist to varying degrees in tlifferent communities anti atmospheric conditions, (2) air pollutants do not o~ur as individual cntitirs hut in combination, frequently with synergistic effects, and (3) there may bc other pollutants or atljunctivc factors equally important whose role is not yet appreciated. The U.S. Air Pollution Control Administration (a division ol the Environmental Protection Agency) is currently investigating 12 types of atmospheric pollutants, only a few of which artl collsidcrcd here. The majo known pollutants are particulate matter, oxides of sulfur, I~llotochemical COW stituent,s, carbon monoxide, and metals.