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In our technological and highly industrialized society, we are exposed to hundreds of synthetic chemicals every day. Some of these chemicals are critical to so much of what we value in making our lives easier, more comfortable and more productive. Unfortunately, the manufacturing, use and disposal of many of these products lead to contamination of our environment with mixtures of chemicals that we breath in, eat and drink, and absorb through our skin.
Increasing scientific evidence suggests that many synthetic chemicals may interfere with cellular pathways that may be involved in the development of cancer, including breast cancer. To be honest, it is very difficult to draw conclusions about exposures to particular chemicals and individual cases of cancer. Often scientific studies explore the effects of single chemicals on (for example) breast cancer development, looking at levels in women at the time when they have been diagnosed with the disease. Unfortunately there are many problems with interpreting these kinds of data:
- Cancer develops over many years as the result of multiple changes in cellular activity. It is very difficult to accurately determine ordinary levels of exposure to common environmental chemicals ten to thirty years after what might have been a critical period of exposure.
- Chemicals don’t occur in the environment in isolation. We are exposed regularly to scores of chemicals, and most of us have many chemicals – pesticides, plastic residues, etc. in our bodies throughout our lifetime.
Understanding how these substances might interact to alter breast cancer risk is an important goal of scientific research in the field. And understanding who might be most susceptible to the carcinogenic effects of these chemicals is also important. It is clear that low levels of many environmental chemicals can interact to have larger than expected (based on individual contributions) effects on human health, including breast cancer risk. It is also increasingly clear that there are times in life, called critical periods of susceptibility, when a girl’s breast tissue may be more vulnerable to the cancer causing effects of exposures to environmental influences. Exposures during the periods between conception and adolescence may have more impact on later likelihood that a woman will develop breast cancer than exposures as an adult.
The information we present in the pamphlets in this section highlights both some of the controversies in the field, but also some of the most important evidence suggesting that individual chemicals of various sorts, and combinations of those substances, might be important risk factors for breast cancer.