This Halifax Project task force focused on "Assessing the Carcinogenic Potential of Low Dose Exposures to Chemical Mixtures in the Environment". 174 scientists from prominent institutions in 28 countries were formed into 12 teams (see below) and they focused on the possibility that complex mixtures of commonly encountered chemicals in the environment may be capable of carcinogenic effects that have yet to be fully appreciated. This project was initiated because we believe that the historical scientific and regulatory emphasis on “mutagens as carcinogens” and the ongoing search for individual chemicals and precisely defined mixtures that are “complete” carcinogens (i.e., can cause cancer on their own) is an incomplete approach that has serious limitations. The last few decades have shown us that cancer can be enabled by a series of key events, while chemical exposure research has shown us that many of these key events can be independently instigated. At the same time, we have discovered that many chemicals have low dose effects that have not been fully appreciated. So this task force looked at the possibility that exposures to mixtures of disruptive chemicals at low doses (in our day-to-day lives) might be contributing to the high rates of cancer incidence that society is currently facing.
From the thousands of chemicals to which the population is now routinely exposed, the scientists selected 85 prototypic chemicals that were not considered to be carcinogenic to humans and they reviewed their effects against a long list of mechanisms that are important for cancer development. Working in teams that focused on various hallmarks of cancer, the group found that 50 of those chemicals support key cancer-related mechanisms at environmentally-relevant levels of exposure. This supports the idea that chemicals may be capable of acting in concert with one another to cause cancer, even though low level exposures to these chemicals individually might not be carcinogenic. This is a paradigm shift in the field of toxicology and the research has now been published in Oxford's Carcinogenesis (click here to see the special issue).
The teams that worked on this effort are shown below.