Pesticides in Drinking Water

Pesticides in drinking water are a growing cause for concern for people that live in agricultural regions where most people get their water from private wells. These man-made organic contaminants are found in underground water sources across the U.S., and Science is just beginning to fully understand the impact that these chemicals have on humans and the environment. Farmers apply pesticides to their fields each year in an effort to control the insects that can affect crop yields. The Environmental Protection Agency estimates that at least 200 and perhaps as much as 250 million pounds of pesticides are applied each year in the U.S. alone.

How do Pesticides get into Groundwater?

Pesticides that are not absorbed by crops or broken down by sunlight either:

The speed at which pesticides pass through soil is determined by the nature of the soil itself. Sandy soil tends to be more porous and regions like the Salinas Valley in California (America�s Salad Bowl) are at a significantly greater risk for water contamination as the soil does not have the time to filter and biodegrade pesticides through natural processes.

Types of Pesticides

Before 1940, most pesticides were made from arsenic, mercury, copper, or lead, and their effectiveness at controlling crop damage was a much larger concern than what they might do to the environment. A new class of synthetic organic pesticides was introduced during World War II that was initially thought to be much safer and effective.

Probably the most notorious of these was DDT. At first, DDT was hailed as a major breakthrough as it was very effective at controlling mosquitoes which infected millions each year with malaria. However, over time it became clear that DDT was building up in toxic concentrations all across the food web. Since the use of DDT was banned in the U.S. in 1973, a new group of organophosporous compounds such as malathion and diazinon have been widely used. Although highly toxic to humans, they were thought to be much safer because they rapidly biodegrade.

Health Effects of Pesticides

Pesticides enter our bodies not only through drinking water but also through our skin and lungs. Health officials tend to categorize the effects of pesticides into two groups:

How to Find Out if there are Pesticides in Your Drinking Water

If you get your water from a private well, it is recommended that you have your water screened for contaminants at least once every two years. You can contact your county water commission or health department for a list of local certified labs that will test your water for a spectrum of contaminants for a very reasonable fee.


About 50,000 different pesticides are applied each year in the U.S. The EPA is struggling to determine what the acceptable levels for each of these are, and the process is often very slow. Legislation such as the Clean Water Act which was enacted in the 1970�s has made a significant impact on the amount of contaminants in our drinking water. However, there is still much to be done. Raising your own awareness and lobbying your local politicians for stricter controls on pesticides may be the best ways to protect your own health and that of future generations.