Estrogen and Fish
The discharge of small concentrations of female sex hormones into lakes and rivers can completely decimate wild fish populations, according to a new study. Fisheries and Oceans Canada, found minnow populations in an experimental lake in Ontario began to collapse after prolonged exposure to small amounts of synthetic estrogen, similar to that found in birth control pills.
The study found male fish, including larger species like trout and suckers that have longer lifespan and feed on minnows, began producing egg proteins and that early stage eggs were even found in the testes of some of the fish. The hormones also impacted the potency of male sperm, while female fish were found to produce more egg proteins.
The seven-year study involved adding five to six nanograms of estrogen to the water, the equivalent of a few grains of sand in an Olympic size swimming pool. The ratio is based on what's been found in the natural environment. Estrogen is a chemical that will degrade within weeks of entering lakes and rivers, compared to stronger pollutants that can linger for decades, so fish populations can generally recover once the hormone is removed.
Secondary wastewater treatment can get rid up to 95 percent of the estrogens released by sewage plants, but a lot of waste receives only primary treatment or in some cases none at all. Many sewers contain both sanitary and storm waste, and it's not uncommon for effluent to be discharged untreated to avoid flooding in periods of severe wet weather.
May 23, 2007 6:55 AM | Category: Fish