MONDAY, April 23 (HealthDay News) -- Prolonged exposure to low levels of the heavy metal cadmium may fuel the growth of some breast cancer cells and encourage them to spread, preliminary research indicates.

Found in many farm fertilizers, cadmium can make its way into soil and water. Some other main sources of cadmium include cigarette smoke, rechargeable batteries, certain cosmetics, bread and other cereals, potatoes, root crops and vegetables. Once it enters the body, cadmium may mimic the effects of the female hormone estrogen.

Unlike previous research, this new analysis looks at lifetime exposure to cadmium, not acute bursts of high levels of the heavy metal.

This research is still in its infancy, explained study author Maggie Louie, an associate professor of biochemistry at the Dominican University of California, in San Rafael.

"We are trying to figure out if it is the cadmium causing cancer or the cancer attracting the cadmium," she said. "If it is chronic exposure to cadmium that increases breast cancer risk, being aware of other exposures to estrogen and taking steps to minimize these exposures may become important."

Her findings are to be presented Monday at the American Society for Biochemistry and Molecular Biology meeting, which is held in conjunction with the Experimental Biology 2012 meeting in San Diego. Research presented at meetings should be viewed as preliminary until published in a peer-reviewed medical journal.

According to the findings, breast cancer cells can pass through the outer barrier of the breast with prolonged cadmium exposure. Specifically, cells chronically exposed to cadmium express higher levels of SDF-1, a protein associated with tumor invasion and cancer spread, the study showed.

Dr. Stephanie Bernik, chief of surgical oncology at Lenox Hill Hospital in New York City, said the findings make sense.

"If cadmium acts like an estrogen in our bodies, it may contribute to the development of breast cancer," she said.

It is difficult to reduce exposure to cadmium, but there are other things women can do to lower their risk for breast cancer, Bernik said. "Eat a healthy diet, don't drink a lot of alcohol and maintain a normal body weight. Focus on what you can control, not what you can't," she stressed.

Another expert cautioned that the findings are very preliminary.

"This is an interesting study and it raises a lot of questions, but what happens in the lab is not always what happens in the real world," said Dr. Ken Spaeth, director of the Occupational and Environmental Medicine Center at the North Shore-LIJ Health System in Manhasset, N.Y. "Theoretically, cadmium exposure should not be an issue for most of us, most of the time."

But, "we know cadmium is toxic and should be avoided," he said. "More work needs to be done in terms of elucidating the relationship between cadmium and breast cancer in a real-world setting."

More information

Learn more about breast cancer risk from the U.S. National Cancer Institute.