A critical interpretation of data on the incidence of air-borne allergens

Abstract

0 NE of the unsolved problems of inhalant allergy is that of accurate measurement of the varying amounts of antigenic material in the air. The answer to this question is of basic importance in the interpretation and evaluation of skin reactions and in the effective employment of air-borne allergens in treatment. The object of this paper is to appraise the accumulated results of atmospheric pollen and fungus spore research, to scrutinize the recently suggested methods for interpreting these findings and, if possible, to introduce simpler and more accurate concepts. Seventy-five years ago Blackleyl sensed the need of quantitative information on aerial pollen incidence. He sought diligently for a met,hod of determining the number of pollen grains in a given volume of outdoor air. But after several fruitless experiments with various types of sampling apparatus, he discarded the volumetric method for the gravity slide method which has been widely used during the past two decades. All agree that the data which may be obtained from uniformly exposed gravity slides by counting the particles caught on a unit slide area are highly satisfactory when dealing with the pollen of a single botanical species-common ragweed, for example. In an investigation covering species other than ragweed, the unit area figures would still be significant, provided all pollen particles under investigation were approximately the same size and had the same rate of fall. But since the widely differing size and surface characters of the various air-borne pollens cause appreciable differences in their rate of fall, it has long been believed that figures obtained by this method give a very inaccurate idea of the relative atmospheric contamination by pollens of various sizes. With this concept has come the assumption that all inaccuracies of statement can be avoided by determining the actual number of each kind of particle suspended in a given volume of outdoor air, as Blackley attempted to do. Using Stokes’ law, Scheppegrell* derived a formula and worked out tables for direct conversion of gravity slide figures into volumetric figures, i.e., the number of pollen grains of any species per cubic yard