Abstract

This report summarizes a comprehensive analysis of existing information on national and regional patterns of pesticides in the atmosphere and major influences on their sources and transport. It is one of a four-part series that synthesizes current knowledge and understanding of pesticides in water resources of the nation as part of the National Water-Quality Assessment.

Highlights
• Existing data, gleaned from 132 studies, are unevenly distributed, with most in the Great Lakes region and California.
• Most of the pesticides studied have been detected in rain or air, but many that are used have never been studied.
• Pesticides have been detected in the atmosphere in all areas of the nation sampled.
• Concentrations of a pesticide in air and rain are most affected by its use and resistance to environmental degradation.
• The highest atmospheric concentrations of pesticides occur seasonally in high-use areas when applications are greatest.
• Low levels of long-lived pesticides are present in the atmosphere throughout the year.
• Atmospheric deposition of pesticides is most likely to affect stream water quality during runoff events when precipitation and direct surface runoff are the major sources of streamflow, but the full significance to water quality is largely unknown.