THURSDAY, Nov. 11, 2004 (HealthDayNews) -- Long-term exposure to the synthetic estrogen ethynylestradiol can shrink fish populations, says a study in the December issue of Environmental Health Perspectives.
The study found that, even at levels below those currently found in the environment, the synthetic hormone can damage the ability of male fish to fertilize eggs. Ethynylestradiol is a form of estrogen used in oral contraceptives.
The researchers exposed three generations of zebrafish to low concentrations of the hormone. After 210 days (a full zebrafish lifetime) of exposure to the hormone, second-generation zebrafish showed reduced fertility. Out of nearly 12,000 eggs spawned, none were viable.
Further study revealed the second-generation male zebrafish had normal testes but did not produce expressible semen. But they still displayed normal reproductive behavior patterns and competed with healthy male zebrafish for mates.
The findings suggest that ethynylestradiol has more of an effect on the development of the testes in male fish than it does on their reproductive behavior. This could have serious consequences for fish populations because infertile males could interfere with successful breeding by healthy males.
"Previous studies in fish have shown that endocrine disruptors can reduce sperm counts and induce female-specific proteins in males," Environmental Health Perspectives science editor Dr. Jim Burkhart said in a prepared statement.
"But until now little evidence existed to show that environmentally relevant concentrations of endocrine disruptors could induce such changes and actually reduce fertility," Burkhart said.
More information
The Nemours Foundation has information about the birth control pill.
