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CORVALLIS, Ore. - Silicone breast implants may absorb environmental pollutants from surrounding tissues and possibly reduce their concentrations within the body, according to a new study by Oregon State University.

OSU environmental chemist Kim Anderson and her colleagues found that silicone implants are a "sink" for environmental chemicals that build up in the fatty tissues of humans and animals. Over time they can become a long-term record of a person's exposure to environmental toxins.

The study, which appeared in the journal Environmental International, was partly inspired by recent studies showing that silicone implants may reduce risk of breast cancer by as much as 50 percent, Anderson said. "That research piqued our interest in looking at implants as a potential sink for contaminants," she said. She cautioned that her findings don't prove that breast implants protect against cancer or any other disease.

In a two-part experiment, Anderson, a professor in OSU's College of Agricultural Sciences, and her colleagues screened eight discarded silicone breast implants--surgically removed from women for medical or personal reasons--for some 1,400 environmental chemicals. For controls, they also screened unused silicone "sizers," used in fitting breast implants or prostheses.

The implants contained 14 common compounds used in foods and personal-care products, commercial and industrial products, and pesticides. The most common one detected was caffeine, found in all eight samples. Next was p,p'-DDE, a suspected cancer-causing agent that results from the breakdown of the now-banned insecticide DDT. It was found in five of the samples.

Nine of the chemicals showed up in only one sample. That was not surprising, said Anderson, because individual exposure to environmental chemicals varies widely depending on where a person lives and what kind of work he or she does. "People are exposed to different chemicals in Burns, Oregon, than in Portland," she said, "and there are differences even between neighborhoods in Portland."

In the second phase of the study, to determine how silicone implants respond to a known chemical exposure, the researchers surgically implanted tiny silicone disks into anesthetized laboratory mice. The mice received as much silicone, in proportion to their body mass, as would be used in a range of typical human breast implants or reconstructions.

The mice then were given injections of two compounds: p,p'-DDE and also PCB 118, which belongs to a class of once widely used industrial chemicals and is also a probable carcinogen. These two substances are known to accumulate in fatty tissues. A group of control mice received surgical implants but no chemicals; another control group received chemicals and surgery but no implants.

After nine days, the researchers analyzed the silicone that had been implanted in the mice along with the surrounding fatty tissue. They found that the silicon and the tissue contained both chemicals. This, said Anderson, indicated that the chemicals had passed from the tissue into the silicone until the concentrations may have reached a balance.

Silicone is known to absorb organic-based pollutants in much the same way human cells do. "Silicone is lipophilic--meaning it loves fat," Anderson explained. "Our bodies' cells are also lipophilic. In order for a chemical to do us harm, it has to cross our cell barriers. So silicone is a good surrogate for an organism's cell."

Anderson's lab pioneered the use of silicone wristbands as passive samplers of environmental pollution in air and water. "However, those environments are hydrophilic--water-loving--which is the opposite of lipophilic," she said. "We wanted to demonstrate that silicone would also pull contaminants out of a fat-rich environment."

Anderson added that discarded breast implants could be a gold mine for public-health researchers. "Tens of thousands of implants are removed from women every year, and they're typically burned as waste," she said. "Instead, they could be an important resource for quantifying the types and amounts of environmental chemicals absorbed by the human body and for assessing long-term toxic exposure."

The research was funded by the National Institute of Environmental Health Sciences and OSU's Food Safety and Environmental Stewardship Program.