NEW ORLEANS -- EPA research on three high-profile pollutants -- dioxin, atrazine and perfluorooctanoic acid (PFOA) -- suggests a link to the trend of early puberty among U.S. girls, and one agency scientist involved in the studies says the findings may also shed light on breast cancer risk factors.

The findings could result in the compounds being given a high priority in the agency’s Endocrine Disruptor Screening Program (EDSP), for which the agency is still developing a research strategy. In the studies, carried out by the Office of Research and Development (ORD), female mice subjected to prenatal exposure to each of the substances demonstrated an effect on mammary gland development, said ORD researcher Suzanne Fenton in a presentation of the findings at the Society of Toxicology’s annual meeting March 7.

PFOA is used to manufacture various non-stick consumer products, such as Teflon cookware and Gore-Tex clothing, and has been detected in the blood levels of the general population. Dioxin is a byproduct of combustion and industrial process, such as paper manufacturing. Atrazine is a widely used agricultural pesticide. All three substances are suspected endocrine disruptors that pose developmental and other health risks.

One of the scientific questions driving the studies involved the growing trend of what is known as "precocious puberty," or the onset of puberty before the age of 8, in U.S. girls, Fenton said. While just 2.5 percent of U.S. girls reported the condition in 1969, the figure had risen to 10 percent in the 1990s.

Though they start puberty earlier, "precocious" girls actually take longer to progress through the developmental stage. The suspicion is that the delay shown in the test animals’ mammary development may reflect this delayed development in U.S. girls, Fenton said.

The real danger in delayed mammary development lies in the fact that it creates a greater opportunity for cancer to develop, according to Fenton. "These delays mean a longer window for cancer susceptibility," she said.

Another concern is that the relevant exposures come very early after conception -- 12 to 14 days into gestation for the test subjects, which would translate into the first trimester for women, "when many women aren’t even aware they’re pregnant," Fenton said.

The potential tie to breast cancer "raises the stakes for [the three chemicals] as endocrine disruptors," one environmentalist says. "These are already pretty controversial" substances, according to an agency source. But if they weren’t on the list before, EDSP "may find the evidence of mammary gland impairment, not to mention relevance to breast cancer, hard to ignore," the source says.

Among EDSP’s tasks is selecting a group of 50 to 100 chemicals for its initial round of screening, with testing on those flagged as significant endocrine disruptors. EPA also is conducting studies to validate its screening and testing methods. A new EPA panel charged with advising the agency on validation, the Endocrine Disruptor Methods Validation Advisory Committee, meets next month for the first time.

While the ORD research on dioxin has been completed, the findings from the other two are only preliminary at this point. The study on PFOA, which is also the subject of a class-action lawsuit against its manufacturer, should be finished within a year, and the findings on atrazine, which is a herbicide applied mainly to corn and soybean crops, should be out very soon, Fenton said. "We always make our studies available" to EDSP organizers, she said.