This book covers the proceedings of a study week held to bring together the most varied experiences in the many disciplines which form the background of ecology. The purpose of the meeting was to examine the present state of knowledge and the need for research in order to gather the information necessary for action to protect the environment and biosphere. Many aspects of the anthropogenic effects on the atmosphere have been studied. However more research is needed to quantify the impact of the various chemicals on the changes occurring in the atmosphere. Acid rain formation mechanisms, although investigated, are not yet fully understood. It is thus necessary to program carefully our future, after further interdisciplinary research, in order to avoid irreversible damage to our environment. The guidelines of this action, as a result of the presentations and discussions, are reported in the conclusions. The main points stressed are: tropospheric chemistry, the problem of the conservation of the ozone layer, the growth of carbon dioxide and climate changes, atmospheric acidity, the effects of changes on water, soils and biota as well as the particular problems of the tropical world. The book will be ideal for postgraduates studying atmospheric chemistry and for environmental protection agencies.