Some male fish have such mixed-up hormones that they are born with ovaries and eggs instead of sperm ducts. Hormonal havoc, however, has previously been reported in alligators, birds, river otters, carp and other U.S. wildlife in isolated locations from the Channel Islands to Lake Mead to the Great Lakes. Mothers pass the excessive amounts of estrogen to their embryos or fetuses, which cannot distinguish between fake estrogens and real ones. When this estrogen boost comes during a critical phase of sexual development, genetic signals go haywire and males are born with feminized genitalia or other reproductive problems. No one knows what threat, if any, these artificial estrogens pose to human health and fertility.
Hormones play the same vital sexual role in humans as they do in fish and other animals.
Although people are exposed through food and water to the same pollutants as water-inhabiting animals, they encounter much lower doses, so any human effects may be subtle. One of the most surprising aspects of the British findings is that fish are suffering so many sexual defects in a part of the world with sophisticated environmental laws and technologies. The scientists do not know which chemicals are to blame, because sewage is a mix of wastes from homes and industries - everything that is washed down drains The culprits could be anything from the urine of women excreting artificial hormones from birth control pills, to pesticides or plastics. Shrugging Off Evidence Pesticide manufacturers and other industry groups are skeptical that hormone problems occur at the low amounts of pollution that animals and people routinely encounter today. Now, though, as research spreads, evidence is emerging that wildlife is being feminized in waters where modern environmental practices and laws are followed and the ecosystem appears outwardly healthy.