Web Date: November 14, 2011
Androgen Blockers Appear In Effluent
Scientists have long blamed environmental estrogens in wastewater for feminizing male fish downstream of sewage plants. Instead of estrogens, however, a new study of treated wastewater identifies a wide range of antiandrogens--compounds that block male hormones--that can accumulate in fish (Environ. Sci. Technol., DOI: 10.1021/es202966c).
“About 90% of the studies on endocrine disruption focus on environmental estrogens,” says Helmut Segner, a toxicologist at the University of Bern, in Switzerland, who was not involved in the study. These studies show that compounds in sewage effluent behave like estrogen and lead to low sperm counts and the genesis of eggs in the testes of male fish.
However, recent surveys have found that sewage effluent can also block testosterone. The same surveys linked the effluent to feminized male fish. Some scientists think they could affect human reproductive health, as well. But the surveys of antiandrogens didn’t nail down the identity of the compounds. Elizabeth Hill, an analytical chemist at the University of Sussex, wanted to know which compounds posed a threat to fish.
Hill and her team took advantage of the fact that bile ducts in fish livers concentrate environmental contaminants. The scientists exposed trout for 10 days to effluent from a domestic sewage plant in the U.K. They then extracted the bile and separated it into fractions, using reversed phase-high performance liquid chromatography.
Using recombinant yeast containing a human androgen receptor, the researchers tested whether each fraction contained antiandrogens. The yeast also contained a reporter gene that produced a color change when the scientists exposed the yeast to androgens. If the researchers added a bile fraction to the yeast and saw no color change, they reasoned that it contained androgen blockers. Team member Pawel Rostkowski then analyzed the chemicals in the fraction using gas chromatography/mass spectrometry. He identified each chemical by comparing its spectrum to those of known compounds. He then purchased commercially available standards for compounds he had found and confirmed that they blocked androgens using the yeast screen.
The research revealed 14 antiandrogenic compounds, and Hill thinks there were dozens more in the samples. The study is the first to show that fish take up antiandrogens from among the thousands of organic compounds in sewage effluents, Hill says.
“What’s surprising and shocking is how many compounds in effluent could be antiandrogenic,” says Louis Guillette Jr., an environmental toxicologist at the Medical University of South Carolina, who was not involved in the study. “If you combine such a large number of antiandrogens with estrogenic compounds, then you have a milieu that generates a more feminizing signal,” he says. “Researchers have to start thinking about the total hormonal signal arising from exposure to multiple compounds.”
Based on the concentrations of antiandrogenic compounds in the bile combined with their potency in the yeast screen, the researchers estimated that over half of the androgen blocking activity in fish bile came from chlorophene and triclosan, two germicides popular in consumer products like soap. This study is the first to show that chlorophene is antiandrogenic, Hill says.
Hill cautions that the study did not show that antiandrogens affect fish health. Her collaborators at the University of Exeter are currently testing these compounds to see if they feminize male fish.
This story was updated on Nov. 11, 2011, to correct the spelling of Pawel Rostkowski’s name
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