A 10-year study by the U.S. Geological
Survey’s (USGS’s) National Water-Quality Assessment (NAWQA) Program provides a national-scale view of pesticide
occurrence in streams and groundwater. The 1992-2001 study builds upon a preliminary
analysis from NAWQA’s first phase of studies during
1992-1996 (1, 2). Pesticide data available from various studies prior to 1992 did not allow national assessment because of limited and variable geographic
coverage (usually focusing on individual states or
regions), sparse and inconsistent inclusion of pesticides in use, and variable sampling designs (3-5).
The expanded geographic coverage and improved
data following 10 years of study (Figure 1) confirm
and reinforce previously reported findings and
enable more detailed analyses of each topic. This
article summarizes selected findings from a comprehensive report (6), with a focus on the nature of
pesticide occurrence and potential significance to
human health and stream ecosystems. Information
on study design and methods as well as additional
analysis of geographic patterns and trends in relation to use and management practices are available
in the full report (6).
