To determine the impact of estrogens in municipal wastewater, Kidd and coworkers seeded a Canadian lake with a synthetic estrogen commonly found in birth-control pills at low concentrations (5 parts per trillion) and studied the effect on fathead minnows. They found that the chemical was concentrated in the fish at 10000 times normal levels, leading to significant feminization of males and altered egg production in females, ultimately leading to the near extinction of the species from the lake in just under three years. More →