The purpose of this chapter is to familiarize the reader with the negative impacts of air pollution on climate and aquatic and terrestrial ecosystems. This chapter provides knowledge of the major phytotoxic air pollutants and their effects on plants; the concept of forest decline and how atmospheric pollutants may contribute to forest decline; understanding of potential pollutant exposures to livestock and other animals; description of the effects of acidic deposition on aquatic and terrestrial ecosystems; understanding of potential threats to forest and estuarine ecosystems posed by nitrogen deposition; acquaintance of the environmental concern associated with mercury deposition in the Great Lakes and other regions; recognition that other persistent chemicals, e.g. organochlorine compounds, are a significant component of atmospheric deposition; understanding of potential ecosystem effects of increasing UV radiation associated with stratospheric O3 depletion; awareness of biological changes occurring as a result of global warming and what changes may occur in the future; awareness of the effects of pollutants on materials such as metals, building stone, paper, leather, fabrics, rubber, and glass; understanding of olfactory mechanisms by which many chemicals can be sensed; understanding of variables associated with odor detection and measurement; and understanding of the nature of odor pollution problems.