Common chemicals are linked to breast cancer

The LA Times features a study arising from the Silent Spring institute.

Common chemicals are linked to breast cancer – Los Angeles Times

More than 200 chemicals — many found in urban air and everyday consumer products — cause breast cancer in animal tests, according to a compilation of scientific reports published today.

Writing in a publication of the American Cancer Society, researchers concluded that reducing exposure to the compounds could prevent many women from developing the disease.

The research team from five institutions analyzed a growing body of evidence linking environmental contaminants to breast cancer, the leading killer of U.S. women in their late 30s to early 50s.

Experts say that family history and genes are responsible for a small percentage of breast cancer cases but that environmental or lifestyle factors such as diet are probably involved in the vast majority.

“Overall, exposure to mammary gland carcinogens is widespread,” the researchers wrote in a special supplement to the journal Cancer. “These compounds are widely detected in human tissues and in environments, such as homes, where women spend time.”

The scientists said data were too incomplete to estimate how many breast cancer cases might be linked to chemical exposures.

The resources to come out of this study include two databases, one that summarizes animal mechanistic studies, and one that summarizes human epidemiological studies. It’s a good start and I hope these databases are continually expanded. The study was essentially a big lit review and data organization project.

There are two major issues with the way carcinogenicity is studied. Firstly, animals other than humans are dosed at high levels to test for possible cancer outcomes. This leaves most researchers vulnerable to the charge that these high dose studies do not translate well to humans because the dose-response relationship at ambient levels is not well studied. So, the obvious criticism is that just because cancer endpoints were seen at high levels does not mean that the same thing will happen at low levels. This cuts both ways, though. We’re seeing with bisphenol A that low doses can cause more harm than intermediate doses. Another issue is the additivity of the interactions. Does 1 “dose” of PAH + 1 “dose” of PCB = 2 “doses” of PAH? We’re exposed to a whole host of chemicals all our lives, who knows which ones add, which ones subtract, which ones multiply, etc.

Of course, as with most diseases, some macro variables dominate. For instance, the US has seen 8-9% decline in breast cancer incidence recently due to a decreased use of hormone replacement therapy. So, as with all diseases, taking care of some of these big ticket items is very important. One discouraging story I read today reported on a four percentage point decline in mammograms (70 to 66%) in women age 40 and older. Why? decreased access to health insurance and dropping the ball on promotion.

The depressing fact of the matter is that the boring basics of good preventative healthcare, screening, good lifestyle and diet are the most important factors, and if we take care of these factors, we will make most health issues easier to deal with.

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  1. Thank you for this post and great comments about studies. Knowing that only roughly 10 percent of breast cancer is genetic, leaving 90 percent related to environmental causes, it is disheartening to see my medical journal filled with articles on genetic testing and chemotherapy modalities, with little on how to encourage lifestyle changes in patients. Prior to researching cancer prevention I felt like we were more protected from dangerous chemicals in our environment. This study raised information on chemicals we should try to avoid, but still only 2 percent of chemical used in commerce have been tested for carcinogenicity. Should we panic? No. Practicing common sense can make a big difference. Switching to environmentally friendly products, or old-fashioned choices, using gloves since we know chemicals can be absorbed through the skin, and having an awareness of chemicals in our environment can go a long way. I evaluate all products in our home using the Household Products Database. http://www.householdproducts.nlm.nih.gov/products.htm.
    Taking time to do a little research about the factors that can lower cancer risk, and making a few simple changes in our lifestyles, is much less expensive than investigating a new chemotherapy drug.

    Lynne Eldridge M.D.
    Author, “Avoiding Cancer One Day At A Time”

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