Organochlorine pesticides are "complete" carcinogens, which both initiate and promote tumor growth, and whose presence (or absence) can change cancer statistics quite rapidly.
Actually, animal experiments conducted back in the 1960's proved that organochlorine pesticides caused breast cancer in rats. Like so many other animal studies, however, the results and their suggested human parallel were totally ignored when they proved inconvenient to the international chemical industrial machine. Other research conducted nearly thirty years ago demonstrated that organochlorine pesticides concentrate in animal and human fat tissue.
Unfortunately, organochlorines are merely one type of a current flood of xenoestrogens recently introduced into our environment. The synthetic hormone Diethylstilbestrol (DES), given to women in the 50's and 60's to (ineffectively) prevent miscarriage, with cancerous results for both the women and their children, is still widely used in the meat industry as a feed supplement to put weight on animals scheduled for slaughter; the hormone is, of course, passed on to people in the meat.
The dairy industry is currently awash in rBGH, a artificial hormone developed to stimulate dairy cows into producing more milk for an already glutted market, with dire results for the cows and as yet unknown effects on human consumers.
Xenoestrogenic material leaches out of polycarbonate plastics, often used in food and cosmetic packaging - even tin cans thinly lined with polycarbonate plastic leak estrogen into their contents.
Light pollution, the global trend toward filling the environment with artificial illumination, also seems to be compounding the problem; melatonin, a natural hormone secreted at night by the pineal gland, has anti-estrogenic properties and may inhibit the development of cancer, but is suppressed by the presence of artificial light. The production of melatonin is also reduced by the presence of even very weak electromagnetic fields, such as those associated with radio waves and household microwave ovens.