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Study Suggests DDT-Breast Cancer Link
NEW YORK (Reuters Health) -
Women with
breast cancer may be more likely to have pesticide residues in their
blood, a new study from Belgium suggests.In the study, women with breast cancer were more likely to have
residues of the chemicals DDT and HCB in their blood than women who
did not have cancer. "These results add to the growing evidence that certain
persistent pollutants may occur in higher concentrations in blood
samples from breast cancer patients than controls," writes a team
led by Dr. Charles Charlier of Sart Tilman Hospital in Liege,
Belgium. Nonetheless, the findings do not prove that exposure to the
chemicals causes breast cancer. In fact, a 2001 analysis of five studies involving more than
1,400 people with breast cancer and more than 1,600 people without
cancer living in New York, Maryland and Connecticut found no
association between DDT and chemicals called PCBs and breast cancer. Charlier's team calls for more research on the topic, noting that
the development of cancer "is a multifactorial event, and it is
important to try to clarify the role of chemicals in cancer
development." These chemicals, which can build up in fatty tissue and blood,
were used in the U.S. until the 1970s. DDT, a pesticide, was banned
in 1972 after it was found to cause egg shell thinning in wild
birds, and HCB was widely used as a pesticide to protect the seeds
of agricultural plants against fungus until 1965. Currently, HCB is
not used commercially in the United States. Studies have shown that these and other environmental pollutants
mimic the effects of estrogen by stimulating the growth of
precancerous and cancerous breast cells in test tubes. But the effects of exposure to the chemicals in humans have
remained unclear, with some studies finding an association among
women with breast cancer, while others have not. Charlier's group tested for the presence of DDT and HCB in blood
samples from 159 women with breast cancer and 250 healthy women. The study, reported in the journal Occupational and Environmental
Medicine, found that women with breast cancer were more likely to
show signs of pesticide exposure. Twenty-four percent of the healthy
women had no detectable levels of the pesticides in their blood
compared to only 2.5 percent of the women who had breast cancer. Specifically, women with breast cancer had concentrations of DDT
and HCB in their blood that were more than twice as high as those
measured in healthy women. Although some breast tumors are sensitive to the effects of
estrogen and others are not, DDT and HCB levels were not related to
estrogen sensitivity. The authors conclude that more research is needed, including how
women might be exposed to these chemicals. SOURCE: Occupational and Environmental Medicine 2003;60:348-351.
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