AIRBORNE BIOLOGICAL MATERIALS 



the possibility that aeroallergens may 

 exert such a selective influence. 



An additional aspect of aerobio- 

 logical health effects that seems to 

 warrant study relates to possible 

 (nonspecific) irritant effects of bio- 

 logical particulates due to vasoactive 

 materials carried by them. Cultures 

 of certain hyphomycetes (molds that 

 produce conidia on loose, cottony 

 hyphae) do synthesize such agents, 

 and it would be useful to know 

 whether airborne spores could do so 

 in the concentrations encountered in 

 nature. Many "allergic" persons re- 

 port "irritation," hoarseness, and mu- 

 cous membrane burning following 

 massive exposure to fragments of 

 fungi (e.g., while raking leaves), sug- 

 gesting the possible action of chemical 

 irritants. Possible direct interactions 

 of eluted materials with the human 

 respiratory flora might also be ques- 

 tioned, since purulent bacterial infec- 

 tion often follows rapidly on such 

 exposures. 



Present Urgency — The recognition 

 that precipitating antibody-mediated 

 reactions to biological agents can pro- 

 duce systematic effects and granulo- 

 matous lung disease (i.e., farmer's 

 lung, bagassosis, maple-bark disease) 

 provides new incentives for exploring 

 and characterizing the breadth of bi- 

 ological materials in free air. The 

 dearth of even preliminary informa- 

 tion regarding incidence and variety 

 of bacteria in free air (apart from hos- 

 pital wards and operating rooms) is 

 distressing. Similarly, background 

 knowledge and general techniques are 

 at hand for making studies of algal, 

 actinomycete, and protozoan bodies 

 in the "aerial plankton," but scarcely 

 a beginning has been made. Study of 

 algal, insect, and acarid material in 

 air will require development of meth- 

 ods for identifying these components 

 either as individual particulates or as 

 components of bulk samples. 



Aerobiology of Urban and 

 Indoor Environments 



Assemblages of species and mate- 

 rials in the atmosphere of the urban 



environment are markedly different 

 from rural and wild landscape as- 

 semblages. 



Outdoor Environment — One com- 

 ponent in urban air has been derived 

 from the local region or from even 

 wider areas, depending on the char- 

 acteristics of the particles for remain- 

 ing airborne. Atmospheric concen- 

 trations of rust and smut spores from 

 agricultural lands come into urban 

 areas in only slightly reduced num- 

 bers. In addition, the urban pollen 

 spectrum is dominated by street and 

 park trees (elm, oak, ash, pine, birch, 

 mulberry) and weeds of alleys and 

 vacant lots (grasses, lambs-quarters 

 and pigweeds, and the ragweed 

 group). There are greatly increased 

 local concentrations of mold spores 

 (conidiospores, conidia, etc.), frag- 

 ments of algal colonies, and "organic 

 trash" that tends to accumulate in 

 nooks and crannies in masonry and 

 asphalt where normal processes of 

 humification and recycling are ineffec- 

 tive in disposing of it. Soil surfaces, 

 even in the heart of a city, are prob- 

 ably helpful in taking some of these 

 offensive dust components out of the 

 air and converting them into an in- 

 nocuous humus component of the soil. 

 However, there are only limited soil 

 surfaces in the hearts of cities. 



Indoor Environments — Inside 

 dwellings and industrial buildings 

 there are entirely unique and ex- 

 tremely varied assemblages of air- 

 borne materials, as one would expect. 

 Old wooden buildings accumulate 

 wood-rotting fungi, molds, and in- 

 sect and mite populations that make 

 up "house dust," to which certain 

 persons are very sensitive. It was 

 recently reported that North Ameri- 

 can and European house-dust mites 

 (Dermatophagoides spp.) were found 

 in dusts used for commercial extracts 

 in treatment of allergies. Masonry 

 buildings, especially in damp climates, 

 develop mold fungus and algal col- 

 onies that populate moving air with 

 spores and fragments. In these struc- 

 tures, parts of dead spiders, mites, 

 insects, and other organic matter 



become mixed with fungus n 

 to form various substrates for bac- 

 terial decay or, in larger masses, site 

 for insect, mite, or milliped colonies. 



Very little specific attention has 

 been given to the airborne plant and 

 animal material of indoor environ- 

 ments. Questions arise with regard 

 to saprophytic, or at least non- 

 invasive, organisms, since reactions 

 to these involving skin sensitizing 

 and precipitating antibodies or de- 

 layed (cell-mediated) hypersensitivity 

 may be involved etiologically in dis- 

 eases presently of unknown origin. 

 Evidence from sampling strongly sug- 

 gests that domestic humidifiers pose 

 a real hazard for fungus-sensitive 

 patients; careful investigations of in- 

 door allergens is warranted. Forced 

 ventilation through ducts that are not 

 periodically cleaned is a potential 

 source of continuous dispersal of 

 spores, mycelia, and dust. The longer 

 the occupancy, the greater the accu- 

 mulation of offending materials. Al- 

 lergists in the United States and 

 Europe are increasingly interested in 

 these aspects of indoor environments. 

 Recent reports of a small epidemic 

 of severe lung disease due to thermo- 

 philic antinomycetes (probably Mi- 

 cromonospora sp.) contaminating a 

 commercial air-conditioning system 

 underscore the potential value of 

 work in this area. 



Atmospheric Dispersal of Insects 

 and Other Microfauna 



Transport of insects and other very 

 small animals by wind is proving 

 worthy of special study, not alone 

 for the biogeographical implications 

 but because of the inherent potential- 

 ity of pest epidemics and vectoring of 

 diseases. In regions where alfalfa 

 and mixed hay crops are grown, sum- 

 mer winds and disturbance by mow- 

 ing usually launch great numbers of 

 leaf hoppers, spittle bugs, and other 

 small sucking insects into the air. 

 Once airborne, these insects are car- 

 ried as much as 100 miles downwind, 

 where they settle down on new crops, 



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