Silent Spring Paves the Way in Redefining What Constitutes a Carcinogen

Silent Spring Institute
Photo Credit: National Cancer Institute

For years, Silent Spring Institute has warned policy-makers, scientists, and consumers that chronic exposure at low doses to multiple chemicals over a person’s lifetime could hasten the development of cancer. It seems the rest of the world is finally hearing our call. In June, a global task force comprised of more than 170 scientists from prominent research institutions in 28 countries released a landmark study affirming the relationship between cancer and environmental chemicals.

Called the Halifax Project, the international group reviewed a list of dozens of environmental chemicals that are traditionally not thought to be carcinogenic to see which ones might actually increase cancer risk. Of the 85 chemicals reviewed, 45 were found to trigger cancer pathways (molecular changes in the body that lead to cancer) at doses historically deemed safe. In other words, numerous chemicals that have been classified as “non-carcinogenic” may in fact play a role in cancer, and their role in the disease has been largely overlooked.

“Efforts like these are challenging us to rethink how we define a carcinogen,” says board member Margaret Kripke, who is chief scientific officer of the Cancer Prevention and Research Institute of Texas in Austin. “This also means we need to rethink how we regulate environmental chemicals.”

We’ve seen this happen already—chemicals in products are originally dismissed as harmless, then later found to increase cancer risk because regulators relied on the wrong tests to screen them. For instance, our recent study on parabens, a common ingredient in lotions and other personal care products, suggests that parabens might increase breast cancer risk at doses much lower than previously thought. In the study, we found that when tested in combination with a growth factor naturally present in breast tissue, parabens are 100 times more potent at stimulating the growth of HER2- positive breast cancer cells than parabens on their own.

To help develop new tests that do a better job at identifying which chemicals and mixtures of chemicals might cause cancer, Silent Spring is working on an international effort to map the molecular pathways that lead to breast cancer. The project will fill an important gap in the Adverse Outcome Pathways (AOPs) project— an effort launched by the Organization for Economic Cooperation and Development to learn how chemicals affect human biology. Because the AOPs project does not include breast cancer and women’s health, many top scientists worldwide have asked us to lead in this area and we are glad to take up the challenge.

And our ongoing work developing BCScreen—a new ultra-fast chemical screening tool—will enable us to quickly test a variety of chemicals and chemical mixtures to see their effects on hundreds of genes associated with important breast cancer pathways. These efforts combined mark the next critical chapter in the history of breast cancer.

Contributed by Silent Spring Institute