Workers Health & Safety Centre

Chronic exposures to common chemicals increase cancer risk, researchers find

A recent symposium adds to growing research evidence which suggests low dose environmental exposures to multiple chemicals can contribute to the development of cancer.
Hosted by the U.S. National Institute of Environmental Health Sciences (NIEHS), the symposium follows the release of new work by a task force looking into low dose chemical exposures and their role in cancer causation. Conservative estimates suggest that seven to 19 per cent of cancers can be attributed to toxic environmental exposures. Cancer now surpasses heart disease as the leading cause of death for Canadians.

The Halifax Project

The recent symposium highlights the work of some 174 scientists from 26 countries working with the Halifax Project task force, named after an initial meeting that brought the group together in Halifax, Nova Scotia in 2013. The project, a unique collaboration of researchers including cancer biologists and environmental health experts, is coordinated by the non-profit group Getting To Know Cancer.
The scientists organized into 11 working groups around known hallmarks of cancer. Cells that acquire one or more of these hallmarks, for instance disruption of the immune system or inflammation, can contribute to the growth of cancer. The groups then reviewed the scientific literature on 85 selected chemicals to see if they act on any of the cancer hallmarks. The chosen chemicals are not known human carcinogens nor related to lifestyle factors, but are ones the general population is often unavoidably exposed to at low levels through food, water, air and many consumer products. Many of these chemicals for example are used to make plastics, personal care products and pesticides. 

Key findings

A separate report from each working group and an overarching paper were published in the June 2015 special edition of the journal Carcinogenesis.
Of the 85 chemicals reviewed:
  • 50 chemicals exerted low dose effects at levels the general population would be exposed to in the environment
  • 26 per cent lacked dose-response information
  • Just 15 per cent had evidence of a dose-response threshold.

This research goes some way towards redefining cancer as a complicated multi-step process, influenced by multiple factors, through different pathways which may result in cumulative health effects. The scientists conclude, given the unacceptably high incidence of cancer and the findings of their research, “Populations worldwide are continually exposed to a wide range of chemicals, so keeping the precautionary principle in mind, there is a need to take the risks related to the cumulative effects of these chemicals seriously.”

Implications for research and public policy

The findings support a more protective approach to environmental toxins and lay bare the need to rethink how chemicals are assessed, researched and regulated. The authors call for:
  • Studies and new assessment methods to determine the impact of chronic low dose exposures
  • Research into chemical mixtures rather than focusing on single cancer-causing chemicals, or ‘complete’ carcinogens (substances that cause cancer in and of themselves)
  • Consideration of the synergistic and additive effects from multiple chemical exposures.

The scientists also point to the fact that thousands of chemicals in wide use have undergone minimal or no testing for their toxicity making the case for preventive action even more pressing.
According to the International Agency for Research in Cancer (IARC) about 14 million new cases of cancer are reported every year, a number expected to rise to 22 million in the next two decades. About half of these cancers could be prevented if current knowledge was acted upon says IARC in its latest World Cancer Report (2014). IARC is among those calling for a greater reliance on primary prevention initiatives, including adequate legislation to protect people against environmental and occupational carcinogens.
WHSC offers a wide range of training programs and resources to help workplace parties understand and exercise their legal duties and responsibilities related to workplace hazards, including the prevention of toxic exposures. Many of these resources also offer essential insight into the information and tools needed to eliminate or reduce harmful workplace and environmental exposures.
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To learn more contact the WHSC and ask to speak with a training services representative.
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