The purpose of this project is to develop an analytical method for detecting the influence of pharmaceutical residues in running water downstream of sewage treatment plants. This should be seen as a complement to costly chemical analysis. The goal is to set up experimental aquaria to test how web-weaving caddis larvae are affected by various chemicals. The ultimate goal is to be able to detect the presence of drug residues in the nature, by gathering nets from larvae upstream and downstream of sewage treatment plants.