While many have suspected that low dose environmental exposure to chemicals has a role to play in development of cancer risk, it has been very difficult prove. In light of this difficulty a meeting was convened by the non-profit Getting To Know Cancer in  Halifax in 2013 bringing together scientists, NGOs and progressive regulatory agencies to explore this area of science. This project was named The Halifax project and their investigation of the relationship between cancer and low-dose exposures to chemical mixtures could fundamentally shift the way we think about carcinogenesis.
The Halifax Project has just published a series of groundbreaking papers on cancer in a special issue of the scientific journal Carcinogenesis. The Halifax Project team examined toxicity data on 85 chemicals that can trigger cancer-related hallmark processes to see if they might pose a risk at exposure levels people typically encounter in day-to-day life. Among the substances were phthalates (common plasticizers), and several pesticides. What they found was that 59 percent of the chemicals studied do affect cancer hallmark processes at low doses.
Current cancer policy focuses on identifying complete carcinogens. Complete carcinogens are substances that can cause cancer in their own right. However new research suggests that cocktails of chemicals not thought to be carcinogens in their own right can affect normal cells and make them more susceptible to becoming cancerous.

“It is time to expand the definition of carcinogenesis beyond the idea of a single chemical acting alone. We must begin to consider how combinations of chemicals working in concert and affecting a cell’s functioning in disparate ways may result in cancer.”

The study was published in the peer-reviewed medical journal Carcinogenesis on an open access basis so it is free to read online or download as a PDF.