Groundwater & Pesticides -- Section 4.1 The Interaction of Many Factors

By the early 80s, the image of groundwater as a vast and largely invulnerable resource had been turned on its head. As the public and policy makers began to consider the impacts of a wide range of human activities that threatened the nation's underground water supply, however, the notion of contamination from the normal application of legally registered pesticides was still strongly resisted.

Although the federal program for registering or licensing pesticides had never been specifically crafted to consider groundwater impacts, many people made the assumption that the regulatory system's "conservatism" must be adequately protective of groundwater. It took the collected weight of numerous investigations to make it clear that the regulatory program was deficient in this regard.

In looking at what makes a given area vulnerable to contamination from agricultural chemicals, the relevant factors can be grouped simply as

the natural environment;
the pesticide, including the type and amount of pesticide; and
the methods and timing of application.

Pesticide contamination of groundwater represents a unique problem, not only because these chemicals are specifically manufactured to be highly toxic to specific organisms, but also because they are deliberately and widely introduced into our environment in massive quantities.... Further, most pesticide usage occurs in agricultural areas where the vast majority of rural residents obtain their drinking water from wells....

A.S. Crowe and P.M Milburn ¹

As researchers have learned over time, the multiple factors in these three general areas interact in a complex matrix that varies from location to location and from time to time.

A brief introduction to the key elements in this complex puzzle can help the informed layperson to participate in a debate about the programs and policies to protect groundwater. It won't allow an individual to make solid pronouncements about vulnerability but -- as this discussion will show -- that task is a difficult one even for the "experts."

1. Crowe, A.S. and P.M Milburn, The Contamination of Groundwater in Canada from Pesticides, Water Quality Research Journal of Canada, vol 30, no 3, 1995 available at <http://gwrp.cciw.ca/gwrp/abstracts/crowe-044.html>.

A Closer Look at Why Pesticides Threaten Groundwater

The Interaction of Many Factors