Breast Cancer and smoking

I just watched a program featuring Stanton Glanz, PhD. from the University of California in San Fransisco. He is one of my heroes. He has been a leading force in California's smoke free laws since 1978. He was talking on the relationship between smoking and breast cancer. Another subject dear to my heart since I am a breast cancer survivor. I was diagnosed when I was 32.
Glanz presents a very compelling argument linking not only smoking but exposure to secondhand smoke to breast cancer. He points out that research in the past would compare women who smoked with women who didn't smoke and there was a relative risk of 1.2, not a large difference. However, what these studies fail to look at was the percentage of non-smoking women that were exposed to secondhand smoke, either at home with a smoking husband or at work. When these same studies took this into consideration, the rates of breast cancer went up, but only in pre-menopausal women and the risks were similar. Smoking women have a double risk (or 2 times that of a non-smoking, non-secondhand smoke exposed woman), while a non-smoking woman that is exposed to secondhand smoke has a 1.7 times risk.
Animal studies have shown that about 20 of the harmful chemicals in smoke, are found in breast tissue and in breast milk. So it would only make sense that this could lead to breast cancer.
There are many known risk factors for breast cancer having to due with the exposure to estrogen: the age of puberty, age of having a child, age of menopause. Smoking lowers estrogen in a woman's body which increases the risk for osteoprosis and a lwer age for menopause. But this might also explain why the relative risk is similar between smoking and smoking exposed women. Secondhand smoke might not have the same effect of lowering estrogen but still leave chemicals in breast tissue.
A woman's breast goes through different stages from when she is born, to puberty, to full development to lacation after having a child. It appears that the effect of smoking and smoke exposure is higher for women before having a child.

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