The American Chemical Society published a new report yesterday, on September 11, about the pesticide concentration in natural freshwater bodies, such as rivers and streams. The good news is that drinking water has become much safer for humans in recent years. The bad news is that for marine life in urban areas, water is much less safe. For marine life in other areas, things have not improved.
The study spanned the past 20 years and compared urban rivers and streams to rural ones. The researchers found reduced use of chemicals that were harmful to humans in over 200 rivers at points all around the United States. In the first ten years of the study, from 1992 to 2001, 17% of all rivers tested had too-high levels of pesticides for humans, but from 2002 to 2011, only one river had too high of a level. The researchers attributed this to both an increased awareness and increased regulation of chemicals harmful to people, and manufacturers making insecticides and herbicides safer for people.
However, although pesticides seeping into rivers have become much safer for humans, they still pose a serious threat to animal life.
The research team found that overall, the rivers had pesticide concentrations much higher than suggested guidelines for marine life. From 1992-2001 and 2002-2011, the study found that pesticide levels for agricultural and mixed-land-use rivers stayed fairly constant. However, there was a marked increase in pesticides found in urban rivers and streams. From 1992-2001, the concentration of pesticides was about 53%. From 2002-2011, it was as high as 90%. Two chemicals that contributed the most to this jump are fipronil and dichlorvos, two insectides. Fipronil is a newer insecticide, and was not included in the first decade of this study. Fipronil became popular after use of other chemicals were restricted for environmental protection. It is commonly used in products like flea collars.
The decline in chemicals harmful to humans coupled with an increase or stagnation in chemicals harmful to other animals suggests that the federal government should impose stricter regulation on chemicals that are dangerous to fish and other marine life.
"It's very clear in the data that regulatory changes in use do affect what you see in the streams," said Wes Stone, the lead researcher on the study. "It's showing what you would expect, and that's good."
This study was conducted as part of the Geological Survey's National Water-Quality Assessment Program. The other two authors are Robert Gilliom and Karen Ryberg.
