ABSTRACT
Bioaerosols include viruses, bacteria and their relatives, fungal spores, pol-
len and other plant particles, and many fragments released from living organisms. Bioaerosols have long been considered to be ‘‘natural’’ and
therefore not pollutants. For the most part, this is true. The organisms that
are part of or produce the aerosol are a natural part of the earth’s environ-
ment, and most are probably essential to the functioning of the earth’s
ecosystem. Humans have evolved in the presence of bioaerosols, and also
have evolved to withstand their onslaught. It is probably true that some
bioaerosol exposure is essential to the proper functioning of the human
immune system and fungal exposure may have other protective effects (1). These natural components of the earth’s environment do become pol-
lutants when, by human action, exposure patterns are modified so that
excess disease results. Human disturbance that has led to detrimental
changes in exposure include changing plant ecosystems resulting in mono-
cultures of aerosol-producing organisms, and the development of built envir-
onments that foster the development of communities of aerosol-producing
organisms leading to unusual human exposure. In addition, human travel
has allowed broad distribution of organisms that can have devastating effects
in new environments.
