Chemical exposure standards “should be revisited” because low level exposures to a mix of substances which individually might be harmless can together present a cancer risk, a major study has concluded.
The Halifax Project, a high-profile taskforce formed in 2013 by the international organisation Getting to Know Cancer, involved 174 scientists in 28 countries and investigated 85 chemicals that were not considered to be carcinogenic to humans.
The paper published in the journal Carcinogenesis notes: “Our current understanding of the biology of cancer suggests that the cumulative effects of (non-carcinogenic) chemicals acting on different pathways that are relevant to cancer, and on a variety of cancer-relevant systems, organs, tissues and cells could conspire to produce carcinogenic synergies that will be overlooked using current risk assessment methods. Cumulative risk assessment methods that are based on ‘common mechanisms of toxicity’ or common ‘modes of action’ may therefore be underestimating cancer-related risks.”
It concludes “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.”
Lead researcher William Goodson III, from San Francisco’s California Pacific Medical Center, said his results show one-at-a-time testing is out of date and must be modernised. “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,” he said.
- William H Goodson III and others. Assessing the carcinogenic potential of low-dose exposures to chemical mixtures in the environment: the challenge ahead, Carcinogenesis, volume 36, Supplement 1, pages S254-S296, 2015.