In 2001, scientists began adding tiny amounts of synthetic estrogen to an Ontario lake; within the next two years, its fathead minnow population collapsed

Environmental changes in freshwater can affect aquatic life in ways that become visible only after prolonged exposure. A seven-year whole-lake experiment in northwestern Ontario examined whether chronic exposure to a synthetic estrogen could affect the reproductive health and population sustainability of fathead minnows.

A Long-Term Experiment in Lake 260