This unit addresses the problem of air pollution. In lesson 1.1, the basic concepts necessary for the study of this discipline are introduced. Lessons 1.2, 1.3, and 1.4 are devoted to the description of the sources and removal mechanisms of major air pollutants. In lesson 1.5, the chemical reactions that produce secondary atmospheric pollutants are presented. Finally, lesson 1.6 analyzes the effects of air pollution on human health and the environment including the three major global problems: acid rain, climate change and the ozone layer hole.