Animals' Sexual Changes Linked to Waste, Chemicals

James Owen
for National Geographic News
March 1, 2004

Animals throughout the world are undergoing unnatural sexual changes in response to environmental pollution, according to a group of scientists. The scientists warn that the gender-bending effects of certain man-made substances and human sewage seriously threaten polar bears, alligators, frogs, mollusks, and other wildlife.

The group's concerns are set out in a new report compiled by an international research team for the Paris-based Scientific Committee on Problems in the Environment (SCOPE) and the North Carolina-based International Union of Pure and Applied Chemistry (IUPAC). The scientists say the report represents the first major global investigation into body-altering chemicals known as endocrine active substances, or EASs.

"Understanding the scientific issues surrounding endocrine active substances is an international priority," the report states. "Endocrine disruptors affect not only humans, but also other living organisms. They affect not only our own generation, but also future generations."

The report suggests endocrine disruptors are now widespread in many animals and can seriously harm populations. The authors call for international authorities take urgent action to address the threat.

Endocrine disruptors interfere with animals' endocrine systems, leading to adverse health effects that can be passed to offspring. EASs mimic naturally produced hormones, setting off chemical reactions in the body. Endocrine disruptors can also block the action of hormones and alter their concentrations.

According to the Brussels, Belgium-based European Commission, endocrine active substances include the naturally-occurring hormones estrogen and testosterone. Other EASs are man-made substances like the synthetic hormones used in oral contraceptives and hormone-replacement therapies as well as chemicals used in industry and agriculture (such as pesticides).

Scientists first realized the scale of endocrine disruptors' gender-bending potential in the 1990s. According to Joanna Burger, studies have shown over 200 animal species around the world are known or are suspected to have been affected by EASs. Burger is co-chair of the SCOPE/IUPAC project and professor of cell biology and neuroscience at Rutgers University in New Jersey.

Sex-Change Pollution

The masculization of female polar bears in the Norwegian Arctic was linked to polychlorinated biphenyls (PCBs), an industrial pollutant that accumulates along food chains, according to a study published in 1998 in the Journal of Wildlife Diseases. The following year, a WWF report associated spontaneous abortions and declining seal populations along the Wadden Sea coast of the Neatherlands, Germany, and Denmark with low female hormone levels due to PCB contamination.

Studies undertaken in Lake Apopka, Florida, blame pesticide pollution for sex-organ abnormalities in Florida alligators, which researchers say have resulted in significant population losses. Females were having difficulty creating viable eggs, while males experienced premature sperm production and reductions in penis size, among other effects.

In Britain studies commissioned by the government's main environment agency found that sewage effluents caused egg development in male freshwater fish.

More recent studies published in the Proceedings of the National Academy of Sciences and Environmental Health Perspectives research journals also linked endocrine disruptors to limb deformities and feminization in frogs as well as masculization in many species of marine mollusks.

Continued on Next Page >>


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