Dr Linda Gulliver, from the University of Otago's Faculty of Medicine, was the only New Zealand scientist selected to join an 'Environmental Mixtures' task force, one of two task forces assembled by an NGO called "Getting to Know Cancer" in Halifax Nova Scotia in July 2013.
Amid worldwide concern on high rates of cancer, the task force brought together 174 scientists from prominent institutions in 28 countries to tackle longstanding concerns that there are linkages between mixtures of commonly encountered chemicals and the development of cancer. The synthesis of the findings is today published (along with a seminal series of supporting reviews authored by each of the teams) in a special issue of the top-tier journalCarcinogenesis.
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 (shared characteristics) of cancer, the group found that 50 of those chemicals examined supported key cancer-related mechanisms at environmentally relevant levels of exposure (i.e. levels at which humans are routinely exposed).
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.
"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that are directly related to carcinogenesis, the way we've been testing chemicals (one at a time) is really quite out of date.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," says William Goodson III, a senior scientist at the California Pacific Medical Center in San Francisco. Goodson is the lead author of this synthesis of the findings published today in the journal Carcinogenesis.
Their published report says: "Cumulative risk assessment methods that are based on 'common mechanisms of toxicity' or common 'modes of action' may be underestimating cancer-related risks….
"And current regulations in many countries (that consider only the cumulative effects of exposures to individual carcinogens that act via a common sequence of key events and processes on a common target/tissue to produce cancer) should be revisited."
In light of this evidence, the task force is calling for an increased emphasis and support for research on low-dose exposures to mixtures of environmental chemicals.
This was the first time this large-scale problem has ever been considered by interdisciplinary teams that could fully interpret the full spectrum of cancer biology and incorporate what is now known about low-dose chemical effects.
Dr Linda Gulliver is a senior lecturer and reproductive biologist with an interest in oestrogen-related cancer causation. She was recruited into the "The Halifax Project" initiative in late December 2012.
Dr Gulliver was a member of the 'Sustained Proliferative Signalling' team, which looked at one of the ten established hallmarks of cancer cells; their ability to grow and multiply in an uncontrolled manner that is prevented in normally functioning cells.
She says her own team found that chemicals that act as environmental oestrogens and androgens play important roles in the activation of the cancer hallmark of "Sustained Proliferative Signalling," as well as the cross-activation of several of the other cancer hallmarks.
And Dr Gulliver agrees with her colleague Dr David Carpenter, project contributor and Director of the Institute for Health and the Environment of the University at Albany in New York, that research into the area of how low-dose mixtures of environmental chemicals may facilitate cancer causation "merits considerable attention where interdisciplinary and international collaboration is needed."
Dr. Carpenter adds: "The science in this field is changing rapidly. Although we know a lot about the individual effects of chemicals, we know very little about the combined and additive effects of the many chemicals that we encounter every day in the air, in our water and in our food."
Current estimates suggest that as many as one in five cancers may be due to chemical exposures in the environment that are not related to personal lifestyle choices. So the effects of exposures to mixtures of commonly encountered chemicals needs to be better understood to try and reduce the incidence of cancer.