New Orleans asthma : IV. Semiquantitative airborne spore sampling, 1967 and 1968

A semiquantitative survey of atmospheric spore concentrations in the city of New Orleans with the use of automatic intermittent rotoslide samplers was performed during the years 1967 and 1968. In comparison with our previous rotoslide pollen survey, spores were invariably detected in excess of pollen grains by a factor of 10 to 100. Relatively large spores of the deuteromycetes (fungi imperfecti) were easily identified morphologically. Identification of small spores was uncertain because of considerable group overlap and interspecies variation. Spores in this category were detected in highest quantity. Spores resembling large basidiospores were included in a third general category. Many myxomycete spores were also likely included in this category because of similar morphology. In all morphological categories, semiquantitative atmospheric spore counts were comparatively low in January and February. Counts increased sharply in March and April and increased variably throughout the summer and late fall months. Noticeable decreases were recorded in late November at or near the usual onset of local killing frosts. Petri plate colony identification, although performed only sporadically, was not as helpful as anticipated. Analysis of one typical large asthma epidemic (December, 1968) revealed high rotoslide catches in all major spore categories but no sharp increase in total cultural colony count or obvious change in colony composition.