On November 15th, the Kentucky Division of Water received notice that the EPA approved part of the proposed water quality standards for selenium put forth in May 2013. The EPA approved Kentucky’s chronic water criteria and the practice of fish tissue sampling to determine compliance. However, Kentucky’s acute water criteria was rejected by the EPA, which means that Kentucky’s previous acute water quality criterion of 20 ug/l will continue to be used to implement the Clean Water Act. In rejecting Kentucky’s acute water quality criteria, the EPA indicated a shift in their view of what constitutes acute toxicity. While acute toxicity (lethality) is typically the driver for acute water criteria, the EPA indicated a desire to see chronic toxicity drive the acute water quality criteria. In the end, EPA’s ruling raises new questions on how it intends to pursue acute water quality criteria in relation to selenium concentration in water bodies.
