Pesticides Still Flow Throughout Our Water Supplies, But at Safer Levels

We live in a radically different time for pesticides. It's easy to forget, collectively, that there was whole different era of pesticide use in the United States comprising all of the many, many years in which chemicals could be thrown around more or less freely and without significant regulation. These were the pre- Silent Spring years, before the Clean Water Act and before even the existence of the Environmental Protection Agency.

The CWA and the EPA were tremendous milestones in the creation of our current, vastly more safe chemical reality. Yet pesticides persist, running off of the fields of Midwestern growers into waterways and drinking supplies. A far-reaching study conducted by the US Geological Survey and published last week in the journal Environmental Science and Technology outlines the results of water samples taken regularly between 1992 and 2011 at over 200 points along rivers and streams across the US. Insecticides and herbicides were everywhere.

The good news is that the potentially harmful levels of these chemicals are far lower now, thanks to both newer, safer pesticides and increased regulation. "Human-health benchmarks were much less frequently exceeded," the study reports, "and during 2002−2011, only one agricultural stream and no urban or mixed-land-use streams exceeded human-health benchmarks for any of the measured pesticides."

The downside is that pesticide pollutants in urban streams went up during the same period (from 53 percent of waterways to 90 percent), largely the result of two pesticides: fipronil (used to kill cockroaches and ants) and dichlorvos (kills other household pests, including aphids and mites). Both of these chemicals—and their byproducts in particular—are harmful to aquatic life at the levels detected. Worth noting is that the study didn't monitor for some popular pesticides, including Roundup, mainly due to testing costs.

"There are constantly new pesticides coming out," Karen Ryberg, one of the study co-authors, told the New York Times, "and there's a lag time between deciding a pesticide will be around for a while, then developing a lab test to detect it, and then having enough data to analyze it. In science, that's a concern: How do you stay on top of it?"