Biological aerosols have been recognized as indoor hazards for several hundred years. Pasteur demonstrated that infectious diseases are transmitted through indoor air. Dust has been a recognized allergen since the mid-19th century. Recently, however, the role of indoor air in transmission of infectious disease has been de-emphasized, and the problems associated with other kinds of indoor bioaerosols have received only minimal public health attention. This is in spite of the fact that we spend an average of 22 hours/day indoors. Influenza causes 10,000 deaths per year. The house dust mite is probably the single most important cause of asthma among children and young adults. Indoor allergens are thought to be responsible for as much as 50% of the incidence of acute asthma in adults under 50 years old. Microbial toxins are among the most toxic substances known to man with effects that include acute toxicity symptoms, birth defects, cancer, and in some cases, death. The concentrations and health effects of these toxins are completely unknown for the vast majority of indoor environments. Volatile organic compounds are produced by all microorganisms and accumulate in confined spaces, causing odors and possibly unknown health effects. The nature of these substances, their health effects, and concentrations in indoor environments is unknown.

"January 1992"