"Who's peeing in the water?" Unlikely as it may seem, there is a great deal of science behind this question. Determining the source of fecal contamination—an important public health issue—requires years of research. Doctoral student Rose Ragot and Professor Richard Villemur of the Institut national de la recherche scientifique (INRS) are working on genetic primers, a short DNA sequence that serves as a starting point for sequencing. Primers make it possible to identify potential sources of fecal contamination, particularly in water that flows through urban and agricultural environments. Their work has been published in the journal Environmental Monitoring and Assessment.