A new EPA report has found “compelling evidence” that certain chemicals are affecting the hormonal systems of a variety of fish and animals, resulting in developmental, reproductive and other problems.

At the same time, the report found no clear link between the chemicals, known as “endocrine disrupters,” and impacts on humans, though it called for more research.

Interest has been rising in recent years that a variety of pollutants — including PCBs, DDT-breakdown products, dioxins, herbicides and certain plasticizers — can mimic or block endocrine system processes that help to guide development, growth, reproduction, behavior and other bodily functions.

A team of researchers hopes to soon begin investigating whether endocrine disrupters are having an effect on fish in the Chesapeake.

Last month, after examining nearly 300 peer-reviewed studies, the EPA concluded that numerous studies had found impacts in animals, while information regarding human impacts were limited. But the potential risks to humans, particularly young children, warrants additional research, according to the study, titled “Special Report on Environmental Endocrine Disruption: An Effects Assessment and Analysis.”

“The findings contained in our assessment send a strong signal for more research on the effects of endocrine-disrupting chemicals, particularly into their possible effects on humans, where we currently do not have enough information to conclusively determine the potential risks of existing exposures,” said Robert Huggett, EPA Assistant Administrator for the Office of Research and Development.

“At the EPA, we have already begun to prioritize our research efforts so as to build on our knowledge of these effects and to improve our understanding of potential implications for our children and our future.”

Endocrine disrupters have not been a major focus of research in the Bay, but Mary Haasch, a researcher at the University of Maryland’s Chesapeake Biological Laboratory who is about to begin looking at their effect in catfish outside the Bay, said several projects in the Chesapeake put forward by a team of scientists are “in the wings.”

Haasch, for example, hopes to examine killifish, a relatively common species in the Bay and along the East coast. “It’s a fairly hardy species, so if we see problems with the killifish, you can expect that other species that are a little bit more sensitive to many things will probably be seeing greater effects,” she said.

The project would likely expose the fish to sediments and water taken from the harbor to see if contaminants are present at levels that would cause an impact. “Certainly, the kinds of chemicals that are known to cause those problems are here,” Haasch said. “But whether we’ll actually see the problems or not is another story.”

Other investigators are expected to look at other sites in the Bay.

Concern about endocrine disrupters gained widespread attention a year ago with the release of a book by zoologist Theo Colborn of the World Wildlife Fund and two other authors titled “Our Stolen Future; Are We Threatening Our Fertility, Intelligence and Survival?”

The book suggests that there is growing evidence that a broad range of synthetic chemicals are disrupting human hormonal systems, leading to increased cancers, infertility, reduced sperm counts and neurological disorders.

The issue has stirred debate in the scientific community as some scientists have disputed Colborn's conclusions, arguing there is no research that actually supports conclusions in the book.

Traditionally, researchers have looked for catastrophic outcomes for chemical exposures, such as cancer or death. By disrupting the endocrine system, chemicals could wreak havoc with a variety of other bodily functions. The endocrine glands include the pituitary, thyroid, pancreas, adrenal, and the male and female reproductive organs, all of which produce hormones.

In animals, observed effects have included the disruption of female and male reproductive functions, and disruptions to the thyroid gland, which helps maintain a normal metabolism.

The EPA review, which was begun before Colborn's book surfaced, found that while endocrine-disrupter effects have been seen in numerous animal studies, evidence of such effects in humans is limited.

“Conclusive evidence linking environmental exposure to endocrine disrupters with infertility or cancers of the breast or prostate is not available at this time,” the EPA review concluded. It said more research was needed to determine if such effects exist. Exceptions mentioned in the report include incidents of occupational exposure and the exposure of pregnant women to the drug DES (diethylstilbestrol).

But the report highlights the need for more information on the intensity, frequency and duration of human exposure to chemicals that have been demonstrated to disrupt the endocrine systems of animals.

The report notes the need for more research on the effects of chemical mixtures with endocrine-disrupting potential, and calls for a strengthening of specific cause-and-effect data. In the wildlife studies reviewed, the report concludes that it should be determined whether the adverse effects seen in animals at various sites are confined to isolated areas or are representative of more widespread conditions.

The EPA’s report represents an interim assessment of the issue, pending a more extensive review expected to be issued by the National Academy of Sciences later this year.

Copies of EPA's interim assessment may be ordered from the EPA’s Office of Research and Development at (513) 569-7562. It is also available on the Internet at: http://www.epa.gov/ORD/whatsnew.htm