skip to main content

→ Top Stories:
Clean Power plan
Safe Chemicals

Sarah Janssen’s Blog

Breast Cancer and the Environment - a new report on Prevention.

Sarah Janssen

Posted October 19, 2010

, , ,
Share | | |

It’s Breast Cancer Awareness month. It seems everywhere I turn, there is a pink reminder of the disease that is the leading cause of death for women on the late 30s to early 50s.  

With one in eight women diagnosed at some point in their lifetime, most everyone knows someone who has been diagnosed with this disease and doesn’t need to be reminded of the devastation this diagnosis leaves in its path.

Most of us already know about breast cancer and the importance of early detection, but what we are at a loss for is how to prevent this disease from happening in the first place.

Most breast cancer is not linked to a genetic cause, which suggests that environmental links are important. Lifetime estrogen exposure is a risk factor for the disease - so entering puberty early, delaying childbirth and going through menopause “late” are all risk factors. Women no longer routinely take hormone replacement therapy when they enter menopause and breast cancer rates have fallen – we have eliminated one risk factor. But that doesn’t explain the rising incidence of pre-menopausal breast cancers and it certainly doesn’t explain the cause of all breast cancers.

What about environmental chemicals that mimic estrogen, shouldn’t they be avoided too? What about other chemicals? What do we know about their links to breast cancer? The answer is that we really don’t know, because most chemicals have never been tested for the toxic effects, including breast cancer.  In fact, even the relatively few chemicals that do undergone safety testing, are not routinely examined for their impacts on breast tissue.

Now there exists a way for our government to address this problem. The University of California, Berkeley School of Public Health and the Natural Resources Defense Council (NRDC) are pleased to present a new report, Pathways to Breast Cancer: A Case Study for Innovation in Chemical Safety Evaluation. The report is the product of the Breast Cancer and Chemicals Policy project, funded by the California Breast Cancer Research Program. An expert panel of 20 scientists and policy experts investigated the biological mechanisms associated with breast cancer and developed a testing strategy for screening and identifying chemicals that could increase the risk of the disease. I was a co-director of this project and have blogged before about the genesis of the report and our methodology.  

In the final report, we have proposed a toxicity testing strategy for prioritizing and testing chemicals for their links to breast cancer based on currently available scientific knowledge. We have recommended that the mammary (breast) tissue be routinely included in toxicity testing of any chemical and identified early indicators of disease that should be tested for, rather than waiting for a tumor to develop. For example, if a chemical is shown to cause DNA damage, mimic estrogen or alter the development of the mammary gland, it could be considered an “upstream” indicator for increasing breast cancer risk.

The methodology used by the expert panel is unique because it worked backwards from a disease to identify early indicators of disease as endpoints that could be used in toxicity testing of chemicals. This approach was recommended by the National Academy of Sciences in their 2007 report “Toxicity Testing in the 21st Century”. The Breast Cancer and Chemicals Policy Project is the first time these recommendations have been implemented for any disease, including breast cancer.  By identifying environmental chemical hazards, the approach developed by the Panel could contribute significantly to breast cancer prevention and could also promote the use of safer alternatives.  

So while all of us are surrounded by “pink” this month, let’s use this opportunity to remember that the foundation of medicine is prevention. And that the true cure for breast cancer lies in preventing it from happening in the first place. 

We plan on taking this new report to our government agencies and asking them to consider implementing our recommendations as new chemicals policies are implemented. We also hope to create lay documents to accompany this report and are working on scientific manuscripts to validate our methodology. Your comments on the report are welcomed and I’ll keep you posted as we continue to work on this project.


Share | | |


Switchboard is the staff blog of the Natural Resources Defense Council, the nation’s most effective environmental group. For more about our work, including in-depth policy documents, action alerts and ways you can contribute, visit

Feeds: Stay Plugged In