Why talk about risks?

Risk factors are conditions or environmental exposures that increase the probability that a disease will occur. However, having a risk or being exposed to a risk factor does not necessarily mean a person will develop the disease. For example, sex and age are considered risk factors for breast cancer because women, and especially older women, have an increased incidence of the disease. But being female and being older are not necessarily causes of breast cancer; most older women do not develop it. However, aging and being female are causally related to the processes of developing cancer in some women.

Individuals may be exposed to many factors that are risks for complex diseases like breast cancer. It is therefore often difficult to determine the precise cause or causes of the disease, when so many common risk factors appear to be important. Only very rarely (as with smoking and lung cancer) do they give us a good indication of why a particular individual actually develops a disease. More generally, risks tell us about how factors may change the likelihood across large groups of people, for an increase in the rate of a disease.

So why talk about risks? Although risk information doesn't usually help us define exactly why any particular person develops a disease, it does tell us a lot about reasons that large groups of people may be more or less likely to become ill. We know that women who have never had children, on average, are more likely to develop breast cancer than those who have delivered children after full-term pregnancies. We understand that this is related to changes in breast tissue that accompany pregnancy and breastfeeding. Similarly, we have growing evidence that women who are exposed to certain toxic chemicals have an increased incidence of breast cancer. We are learning a lot about the mechanisms by which some of these environmental chemicals mimic our body’s natural hormones to alter the rate of breast cancer. Environmental chemicals may also have effects on cancer rates through other influences on breast cell activity. However, just as not all women who have never had a child get breast cancer, not all women who live in polluted areas get cancer, although many (more than expected by chance) do.

The point is that breast cancer is a very complicated disease. An individual's likelihood of developing the disease is probably influenced by a number of factors: for example inherited factors, reproductive history, lifestyle, and chemical exposures within the home, school and workplace. The interaction of many of these risks may ultimately play an important role in determining whether or not any individual will develop breast cancer.

The goal of this project is to explore some of the important, and potentially controllable, risks in our environment that have been implicated in increasing the rate of breast cancer. By understanding these risks better, we can make personal and community choices that will decrease our exposures to these substances and may therefore decrease the likelihood of women and men developing breast cancer in the future.