Monday, September 14, 2015

Gauging the impacts of toxic chemicals may have gotten a little harder

What happens when a long-trusted canary in the coal mine can no longer do the job? The U.S. Environmental Protection Agency and other monitoring agencies may have to grapple with this question if new IWRC-supported research confirms that a small but critical crustacean is now resistant to one of the most toxic class of chemicals in our rivers and streams.

Michael Lydy, an environmental toxicologist at Southern Illinois University, will spend the next three years testing populations of the crustacean for resistance to pyrethroid insecticides. U.S. EPA and others rely on Hyalella azteca to determine the overall toxicity of water and sediment. If these guys are thriving, your local river habitat is relatively healthy. If they start to die off, you can expect to see other species decline as well.

At least, that's the theory. But the recent discovery of pyrethroid-resistant populations of Hyalella azteca in California casts doubts on the accuracy of biomonitoring programs that depend on the crustacean to sound the alarm. 

Lydy and his team want to know just how widespread this resistance is. What they find could have lasting impacts on environmental monitoring and regulations. 

At the same time, the study will also investigate whether a relatively-new testing method known as Tenax can help scientists and natural resources managers more accurately predict the threat pyrethroids pose to aquatic life. The new approach makes it possible to hone in on the level of insecticide aquatic animals are actually exposed to instead of just how much total chemical is in the waterway. This distinction is key for compounds like pyrethroids, which quickly bind to sediment and remain out of reach to some species. 

If it proves successful, Tenax could produce results at a fraction of the time and cost of more traditional monitoring methods.  

Funding for the project comes from a grant to IWRC from the U.S. Geological Survey in cooperation with the National Centers of Water Resources. It is one of four chosen for USGS's annual National Competitive Grants. 

***Photo from Kate Heddleston.