Introduction

The atmosphere is an important component of the hydrologic cycle to consider in assessing the effect of pesticides in the environment. Pesticides have been recognized as potential air pollutants since 1946. Long-range movement of pesticides was thought to be minimal, if any, because of their physical and chemical properties. A national perspective on the occurrence and geographical distribution of pesticides in the atmosphere is developed from the observations reported in the reviewed studies, with particular emphasis on the large-scale studies. Water is one of the primary mechanisms by which pesticides are transported from targeted application areas to other parts of the environment and, thus, there is potential for movement into and through all components of the hydrologic cycle. The atmosphere is recognized as a major pathway by which pesticides and other organic and inorganic compounds are transported and deposited in areas sometimes far removed from their sources.