"Trace levels of pharmaceuticals and other chemicals may be harming fish in Minnesota rivers and lakes, according to a study released Thursday by the Minnesota Pollution Control Agency (MPCA)," reports Minnesota Public Radio. The new study confirms that such chemicals as antidepressants, insect repellent and the X-ray contrast agent iopamidol are commonly found in the state's rivers. MPCA lead scientist Mark Ferrey asserts, "Chemicals, even at those concentrations, can cause adverse effects in fish and wildlife that we're really just starting now to be able to understand." New developments in genetics allow scientists to examine the effects of this pollution. Prof. Dalma Martinovic-Weigelt of the University of St. Thomas is doing such a study, exposing fathead minnows to contaminated water and tracking the genetic response. Her research has the goal of pinpointing "what you should be worried about. Because there's so much information about these chemicals and their effect." Her study shows changes in minnow genes related to reproduction, growth and tumor formation among fish exposed to the contaminants. The entire MPR article can be found here.