May 2010, Vol. 22, No.5

Research Notes

Insecticide Threatens Life in California Waterways

Concentrations of pyrethroids, a chemical compound commonly found in home insecticides, have made their way into California rivers at levels toxic to some stream dwellers, according to a University of California–Berkeley news release.

Pyrethroids, used to control a variety of pest insects, including mosquitoes, ants, and termites, are washed into sewers or directly into local waterways, explained Aundrea Asbell, university staff research associate. The insecticide, found in runoff and wastewater treatment plant effluent in the Sacramento, Calif., area, ended up in two urban creeks, the San Joaquin River, and a 32-km (20-mi) stretch of the American River, the news release says.

A research report on the study, “Urban and Agricultural Sources of Pyrethroid Insecticides to the Sacramento–San Joaquin Delta of California,” was published in Environmental Science & Technology. The study is the first to document toxic levels of the chemical in the water columns and sediments of both streams, according to the news release. Researchers at Berkeley and at Southern Illinois University (Carbondale) found that even though pyrethroid levels were low — about 10 to 20 parts per trillion (ppt) — they were high enough to kill Hyalella azteca, an indicator species used to assess water safety.

Hyalella azteca is an amphipod — a freshwater crustacean like a tiny shrimp — that is found throughout U.S. waters in submerged, decomposing materials, Asbell said. The amphipod is food for larger fish and is sensitive to toxins.

Hyalella azteca is very sensitive to pyrethroids,” Asbell said. “If you measured the pyrethroid sensitivity of 100 species, Hyalella would certainly be in the top five.”

Although the levels of pyrethroids detected in the streams are low, several groups of aquatic insects in these streams are sensitive to such environmental changes, Asbell said. These insects form the prey base for fish, and if pyrethroids reduce either the abundance or diversity of these insects, there may be a scarcity of food resources for fish. “This has implications at the fisheries level,” Asbell said.

Pyrethroids are hydrophobic, binding to sediment more readily than they stay dissolved in water, Asbell explained. In sediment, the insecticide is frequently detected in the ppb range, while in water it’s found in the ppt range. Even though the concentrations in water are lower, the chemical is more toxic in that matrix, Asbell said.

Toxicity depends on both concentration and duration of exposure. The tests exposed the aquatic creatures in a 96-hour test to detect effects from chronic toxicity or more subtle developmental effects after long-term exposure to other species. A concentration of 2 ppt causes 50% mortality of Hyalella azteca during the 96-hour exposure.

Pyrethroids also were found in effluent from wastewater treatment plants at concentrations just high enough to be toxic to the test organism but well below levels in urban runoff, the news release says. “Concentrations in wastewater treatment plant effluents are low, but it takes very little to cause toxicity,” Asbell said. Mortality for the test organisms begins at about 1 ppt.

Pyrethroids have been around for decades but were seldom used until organophosphates, such as chlorpyrifos and diazinon, were banned for homeowner use in 2001 and 2004, respectively. Since then, use of pyrethroids increased dramatically, the news release says. Because it is used around the nation, the insecticide could be a threat to other aquatic habitats.

“Given the variety of applications, it is certainly possible that other aquatic habitats are at risk,” Asbell said.  

Water Environment Research Foundation Issues Report on Climate Change

In February 2010, the Water Environment Research Foundation (WERF; Alexandria, Va.) released a report on the implications of climate change on the wastewater and stormwater sectors. The report, Implications of Climate Change for Adaptation by Wastewater and Stormwater Agencies (CC2R08), is part of a 5-year WERF program on the potential effects of climate change on wastewater and stormwater utilities.

The report says four major types of local climate change have the potential to affect wastewater and stormwater sectors. They are

·          sea-level rise,

·          warmer and shorter winters,

·          warmer and drier summers, and

·          more-intense rainfall.

These types of changes have many implications, such as an increased risk of storm and flood damage to facilities and frequently altered biology and chemistry of receiving waters.

If sea levels rise, there is a risk of increased intensity of coastal erosion and coastal storms. Sea-level rise may alter the biology and chemistry of brackish waters and increase the salinity and acidity of coastal waters.

Warmer and shorter winters increase the risk for earlier spring melt of snow and runoff. Warmer temperatures and fewer extreme cold days can alter the biology and chemistry of receiving waters.

Warmer and drier summers, which are expected over most of North America, could lead to more hot-weather operating challenges, increased water temperatures, and lower dissolved-oxygen concentrations.

Finally, warming is expected to lead to more-intense rainfall, with an increased risk of flooding, sedimentation, bacterial contamination, and more-frequent wet weather operating challenges, among other things.

These are only potential risks, and their magnitude and timing are uncertain, the report says. Nevertheless, it notes, adaptation planning is an important approach to use to identify the risk of the events and to plan accordingly.

The WERF research team identified future research needs for the wastewater and stormwater sector to pursue to adapt to climate change. To approach adaptation planning, the team recommended a risk-management framework based on the familiar steps of risk identification, risk assessment and characterization, and risk management (adaptation). In the climate arena, this is referred to as a “bottom up,” or threshold, approach to adaptation planning.

While some of the identified risks imply that wastewater and stormwater agencies already should be implementing some types of adaptive strategies, other types of risks may not require significant changes in facilities or operations for decades, according to the report.

Before implementing adaptation strategies, it is prudent first to undertake a vulnerability analysis to assess how soon the effects may materialize at a level that represents a meaningful threat to existing or planned facilities and operations, according to the report. This analysis will help define the most appropriate adaptive responses, the report says.

Since greater uncertainty will exist for planning long-term infrastructure projects, adaptation planning may be a cross-generational strategy, the report says. The sustainable path for infrastructure planning means that current managers will lay the foundation for future generations to re-evaluate the presumed useful lives of wastewater and stormwater assets.

The report states that wastewater infrastructure planners will need to assess how things are changing, as well as assess how practices can best be adapted to meet these changes. Although adaptation planning includes elements of a long-term strategy, utilities are recommended to begin moving on these items in the near term, the report says.

The report, written by John Cromwell of Stratus Consulting (Boulder Colo.), can be obtained from WERF’s Web site, It is free to WERF subscribers and costs $50 for nonsubscribers.


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