On June 1, 2015 the peer-reviewed journal Carcinogenesis published a supplement issue on “Assessing the carcinogenic potential of low-dose exposures to chemical mixtures in the environment: the challenge ahead”. In a series of 11 reviews and one summary paper, 174 international scientists report on the Halifax Project Task Force’s findings how everyday chemicals, present at low levels in the human environment including food, can lead to malignant cancers. A total of 85 chemicals not considered carcinogenic to humans were investigated during two years in a project initiated by the non-profit group Getting to Know Cancer.
The Halifax Project scientists applied a novel approach, using the Hallmarks of Cancer conceptual framework which describes on a molecular level how normal human cells transition into malignant cancer cells (Hanahan and Weinberg 2000, 2011). These different “rules” include for example evasion of growth suppression, cell immortality, sustained proliferative signaling, and tissue invasion and metastasis. Different chemicals can affect various steps of cancer formation, and when present together in a mixture or ‘cocktail’, their concerted action on different Hallmarks of Cancer can lead to the malignant disease, according to scientist William H. Goodson III and colleagues. Therefore, understanding how individual chemicals contribute on a molecular level to the intrinsically complex process of cancer formation can help with assessing chemical safety and preventing cancer from developing at all. Notably, 59% of the investigated 85 chemicals showed no evidence for a threshold, while 15% did. For the remainder (26%), no dose information was available. Several of the substances are also present in food contact materials, like phthalates and bisphenol A.
“The relative contribution of the environment, genetic susceptibility and DNA replication errors to cancer causation has been a longstanding area of investigation in the fields of molecular epidemiology of cancer and carcinogenesis”, writes Curtis C. Harris, Editor-in-Chief of Carcinogenesis. The novel approach outlined and applied by the Halifax Project can be instrumental in improving understanding of how large the contribution of everyday (environmental) chemicals at low doses actually is on the development of cancer.
The primary recommendation of the Halifax Project Task Force is focused on research and regulatory risk assessment practices worldwide: using their novel approach, priority mixtures of (non-carcinogenic) chemicals can be identified that have substantial carcinogenic relevance. This information can then be utilized in the development of new regulatory strategies focusing on primary cancer prevention.
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