(Beyond Pesticides, March 20, 2008) A 2000-2005 U.S. Geological Survey (USGS) study, Pesticide Occurrence and Distribution in the Lower Clackamas River Basin, Oregon, 2000-2005, finds a variety of pesticides in river and tributary samples, along with trace-level detections of pesticides in treated drinking-water samples collected from a drinking-water treatment plant that uses the Clackamas River as a raw-water source. While the federal government is quick to point out that detections in drinking water are below existing Environmental Protection Agency (EPA) drinking-water standards and most river samples are below the agency’s aquatic life benchmarks, studies show hazardous endocrine-disrupting and immunosuppressive effects at extremely low levels — far below EPA standards.
A total of 63 pesticide compounds were detected in 119 water samples collected during storm and non-storm conditions using low-level detection methods. More pesticides were detected in the tributaries than in the Clackamas River mainstem. One or more of 15 pesticides were detected in nine of 15 samples of drinking water. Environmental and public health advocates are concerned that these results add to a pattern of contamination across the country. USGS data released in 2008, shows widespread pesticide contamination in the Chesapeake Bay watershed, and a 2004 USGS report of nationwide data, shows similar contamination.
Pesticides were detected in all eight of the lower-basin tributaries after heavy rainfall, with the largest pesticide contributions coming from Deep and Rock Creeks. The herbicides atrazine and simazine were the most common, detected in half of the samples. High-use herbicides such as glyphosate, triclopyr and 2,4-D also were frequently detected.
Concentrations of four insecticides-diazinon, chlorpyrifos, azinphos-methyl, and p,p’-DDE-exceeded USEPA aquatic-life benchmarks during storms in seven streams, and concentrations of several other pesticides exceeded other, non-USEPA benchmarks, including chlorpyrifos in the Clackamas River mainstem. Nearly one-quarter of the tributary samples had at least one pesticide that exceeded an aquatic-life benchmark. Further, “Benchmarks have not been established for many of the pesticides detected, and current regulations do not yet account for multiple compounds that often occur in a single sample,” noted Kurt Carpenter, USGS Hydrologist and lead scientist for the study.
Although most of the samples were detected at low-levels, scientists are increasingly finding serious health and developmental effects, well below EPA drinking water standards and levels of concern. Chlorpyrifos, for example, is linked to learning disabilities at extremely low levels. Edward Levin, Ph.D., a professor at the University of North Carolina, shows in his research that rats are slower to find food in a maze when exposed to low-levels of chlorpyrifos. The research suggests an inverse dose response, meaning the effect is most pronounced at the lowest doses. Additionally, atrazine is linked to endocrine-disrupting effects at levels below EPA’s drinking water standard. Research by UC Berkeley professor, Tyrone Hayes, Ph.D., has demonstrates that exposure to doses of atrazine as small as 0.1 parts per billion, turns tadpoles into hermaphrodites – creatures with both male and female sexual characteristics.
According to USGS, the individual sources of pesticide contamination in the Clackamas River basin are difficult to identify because of the diverse land use in the basin and the multiple-use nature of most of the pesticides detected. More than 90 percent of the 51 current-use pesticides can be used on nursery or other agricultural crops; about one-half are commonly used on lawns and landscaping in urban areas, on golf courses, or along roads and right-of-ways; and some can be used on forestland. “Because pesticide-use data currently are reported only for the Willamette River basin as a whole, not for individual subbasins, watershed managers could benefit from more detailed reports of which pesticides are being used and where,” Mr. Carpenter observed.
The Clackamas River Water Providers, a coalition of municipal drinking water providers, and the Clackamas County Department of Water Environment Services cooperated with the USGS in the study. Andrew Swanson, Water Quality Analyst with Clackamas County Water Environment Services Department (WES) said, “Even though pesticides were typically detected at low levels during this study, the data collected will prove valuable in increasing public awareness of this important issue. WES is concerned about the numerous pesticides, regardless of the detected level, in water flowing from and through North Clackamas County’s urban area. As a result, WES is working in a cooperative manner with other watershed partners to develop and implement a public awareness and educational campaign regarding pesticides. We appreciate the USGS’ efforts in bringing this subject to the forefront of the environmental challenges we’re all facing today in the Clackamas River watershed.”
Results of the lower Clackamas River pesticide study are available in USGS Scientific Investigations Report 2008-5027, Pesticide Occurrence and Distribution in the Lower Clackamas River Basin, Oregon, 2000-2005.