This report deals with the less ubiquitous, but potentially harmful, contaminants that are in our atmosphere. Thirty such pollutants have been identified and available information has been summarized in a series of reports describing their sources, distribution, effects, and control technology for their abatement. A total of 27 reports have been prepared covering the 30 pollutants. These reports represent current state-of-the-art literature reviews supplemented by discussions with selected knowledgeable individuals both within and outside the Federal government. Among the pollutants covered are: aeroallergens, aldehydes, ammonia, arsenic, asbestos, barium, beryllium, biological aerosols, boron, cadmium, chromium, ethylene, hydrochloric acid, hydrogen sulfide, iron, manganese, mercury, nickel, odorous compounds, organic carcinogens, pesticides, phosphorous, radioactive substances, selenium, vanadium, and zinc. (BT)