The largest study yet to examine whether certain "environmental estrogens" - synthetic chemicals that can act like hormones in the body - could contribute to cancer breast cancer found no evidence of such a link. the research, to be published tomorrow in the New England Journal of Medicine , deals a blow to a popular theory to explain the recent increase breast cancer.
breast cancer rates are the highest in the developed countries, leading some researchers to believe that industrial pollution could be a major factor. the main suspects are two types 'environmental estrogens present in the adipose tissue of everybody. - polychlorinated biphenyls (PCBs) and DDE, a metabolic product of the pesticide DDT There are four years, a US study of 58 women with breast cancer patients seem to confirm the hypothesis: He suggested that women with high blood levels of DDE had a four times greater risk of breast cancer than women with normal levels. But a study over a year later found no link between breast cancer and DDE or PCBs.
Now a team led by epidemiologist David Hunter of the Harvard School of Public Health analyzed 240 cases of breast cancer occurring in a group of nearly 33,000 women after they gave samples blood in 1989 and 190 as part of the health study of nurses and nursing Harvard. Comparison of DDE and PCBs levels in the blood of 240 women with those of a control group of women without cancer, researchers found women with higher levels were at no greater risk for breast cancer. While "no epidemiological studies" can answer the question once and for all, Hunter said, "the weight of evidence is now strongly against the hypothesis" of a DDE or PCB-breast cancer link.
the Harvard findings and "other recent studies should reassure the public that weakly estrogenic organochlorine compounds such as PCBs, DDT and DDE are not a breast cancer cause," wrote Stephen Safe, a toxicologist at Texas a & M University, College station, an editorial in the same issue of NEJM . But all researchers are not willing to exempt the chemicals. Epidemiologist Devra Davis of the world resources Institute in Washington, DC, notes that older women tend to have higher levels of DDE as nurses, whose median age was 59. as a result, she said, the effects of chemical products may have been masked by stronger factors risk -. such as smoking and radiation nurses were exposed in their work
0 Komentar