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TUESDAY, July 15, 2003 (HealthDayNews) -- New research shows the heavy metal cadmium might increase the risk of breast cancer for pregnant women and their female offspring.
Found in soil, rocks and water, cadmium mimics the effects of the female hormone estrogen, say scientists at Georgetown University Medical Center, and that could trigger the development of breast cancer. Their report appears in the July 13 online issue of Nature Medicine.
Few studies have examined the impact of lower doses of cadmium, instead focusing on the impact of large, toxic doses. The authors examined how the heavy metal might act in the body at doses similar to what humans are typically exposed to through their diet or environment.
Using rats as a model, they injected the animals with the equivalent of what a human might be exposed to -- and found it caused significant changes in responses normally regulated by estrogen.
Specifically, exposure induced an increase in uterine weight, changes in the lining of the uterus and an increase in the density of epithelial cells in the mammary glands, all of which are early signs of breast cancer. There was also an earlier onset of puberty in the female offspring of pregnant rats who were exposed to cadmium; early puberty increases a woman's chances of getting breast cancer by 50 percent.
Cadmium is generally ingested through contaminated foods such as shellfish, liver and kidney meats or inhaled through cigarette smoke, municipal waste or metal smoldering fumes. It's known to damage the lungs and kidneys, and it can also cause bone loss. This latest study indicates the heavy metal may wreak havoc on hormones.
"The ability of environmentally relevant amounts of cadmium to mimic the effects of estradiol [estrogen] suggests the metal may represent a new class of endocrine disrupters," the authors write.
Study author Mary Beth Martin, an associate professor of oncology at Georgetown University, says this "means that cadmium might be a risk factor for breast cancer."
The findings build on intriguing results from a 1994 National Cancer Institute epidemiological study that found that women with occupational exposure to cadmium had a one to two times greater risk of developing breast cancer than women with no occupational exposure.
Taken together, these preliminary studies suggest further research on the health link between exposure to cadmium and breast cancer risk is warranted, Martin says.
"These studies are causing us increasing concern about heavy metals like cadmium and the role they play in breast cancer," says Janice Barlow, executive director of Marin Breast Cancer Watch, a California non-profit group that conducts research aimed at uncovering the underlying causes of Marin County's breast cancer rate -- currently one of the highest in the world.
The Marin County group and the International Breast Cancer Research Foundation plan further studies on the link between cadmium exposure and breast cancer risk.