The Committee focused its attention on the following pollutants: sulfur and nitrogen compounds, trace metals, and organic substances. The Committee noted that understanding of patterns of emission, transport, deposition, and biological effects of these pollutants is incomplete, and they provided a preliminary guideline for the sorts of integrated research needed. After discussing biogenic emissions of the substances of concern and the magnitude and form of anthropogenic emissions, the Committee described in detail atmospheric transport and deposition processes and biological accumulation. A guide was developed to predicting consequences of continued or accelerated pollution, and a case history was given of effects of acid rain. The conclusion was reached that increased scientific effort is needed in two critical areas: long-term monitoring and forecasting of future effects of these pollutants, and ecotoxicology. The Committee recommended that U.S. agencies provide funding for the needed scientific effort and in particular for the establishment of graduate training programs in ecotoxicology.