Cocktail of chemicals may trigger cancer

Fifty chemicals the public is exposed to on a daily basis may trigger cancer when combined, according to new research by global task force of 174 scientists
June 23, 2015

Disruptive potential of environmental exposures to mixtures of chemicals (credit: William H.Goodson III et al./Carcinogenesis)

A global task force of 174 scientists from leading research centers in 28 countries has studied the link between mixtures of commonly encountered chemicals and the development of cancer. The open-access study selected 85 chemicals not considered carcinogenic to humans and found 50 of them actually supported key cancer-related mechanisms at exposures found in the environment today.

According to co-author cancer Biologist Hemad Yasaei from Brunel University London, “This research backs up the idea that chemicals not considered harmful by themselves are combining and accumulating in our bodies to trigger cancer and might lie behind the global cancer epidemic we are witnessing. We urgently need to focus more resources to research the effect of low dose exposure to mixtures of chemicals in the food we eat, air we breathe, and water we drink.”

Professor Andrew Ward from the Department of Biology and Biochemistry at the University of Bath, who contributed in the area of cancer epigenetics and the environment, said: “A review on this scale, looking at environmental chemicals from the perspective of all the major hallmarks of cancer, is unprecedented”.

Professor Francis Martin from Lancaster University who contributed to an examination of how such typical environmental exposures influence dysfunctional metabolism, pointed out that despite a rising incidence of many cancers, “far too little research has been invested into examining the pivotal role of environmental causative agents. This worldwide team of researchers refocuses our attention on this under-researched area.”

In light of the compelling evidence, the taskforce is calling for an increased emphasis on and support for research into low dose exposures to mixtures of environmental chemicals. Current research estimates chemicals could be responsible for as many as one in five cancers. With the human population routinely exposed to thousands of chemicals, the effects need to be better understood to reduce the incidence of cancer globally, the scientist say.

The research was published in Oxford University Publishing’s Carcinogenesis journal today (June 23).

William Goodson III, a senior scientist at the California Pacific Medical Center in San Francisco and lead author of the synthesis said: “Since so many chemicals that are unavoidable in the environment can produce low dose effects that are directly related to carcinogenesis, the way we’ve been testing chemicals (one at a time) is really quite out of date.  Every day we are exposed to an environmental ‘chemical soup’, so we need testing that evaluates the effects of our ongoing exposure to these chemical mixtures.”

Abstract of Assessing the carcinogenic potential of low-dose exposures to chemical mixtures in the environment: the challenge ahead

Lifestyle factors are responsible for a considerable portion of cancer incidence worldwide, but credible estimates from the World Health Organization and the International Agency for Research on Cancer (IARC) suggest that the fraction of cancers attributable to toxic environmental exposures is between 7% and 19%. To explore the hypothesis that low-dose exposures to mixtures of chemicals in the environment may be combining to contribute to environmental carcinogenesis, we reviewed 11 hallmark phenotypes of cancer, multiple priority target sites for disruption in each area and prototypical chemical disruptors for all targets, this included dose-response characterizations, evidence of low-dose effects and cross-hallmark effects for all targets and chemicals. In total, 85 examples of chemicals were reviewed for actions on key pathways/mechanisms related to carcinogenesis. Only 15% (13/85) were found to have evidence of a dose-response threshold, whereas 59% (50/85) exerted low-dose effects. No dose-response information was found for the remaining 26% (22/85). Our analysis suggests that the cumulative effects of individual (non-carcinogenic) chemicals acting on different pathways, and a variety of related systems, organs, tissues and cells could plausibly conspire to produce carcinogenic synergies. Additional basic research on carcinogenesis and research focused on low-dose effects of chemical mixtures needs to be rigorously pursued before the merits of this hypothesis can be further advanced. However, the structure of the World Health Organization International Programme on Chemical Safety ‘Mode of Action’ framework should be revisited as it has inherent weaknesses that are not fully aligned with our current understanding of cancer biology.