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Regul Toxicol Pharmacol. 2016 Dec;82:158-166. doi: 10.1016/j.yrtph.2016.10.014. Epub 2016 Oct 22.

Classification schemes for carcinogenicity based on hazard-identification have become outmoded and serve neither science nor society.

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Centre for Pharmacology & Therapeutics, Toxicology Unit, Department of Medicine, Hammersmith Campus, Imperial College London, London, W12 0NN, UK.
Department of Pathology and Microbiology, Havlik-Wall Professor of Oncology, University of Nebraska Medical Center, Omaha, NE 68198-3135, USA.
Independent Consultant, Silver Spring, MD 20901, USA.
Parker Doe LLP, Carpenter Court, Maple Road, Bramhall, Stockport, Cheshire SK7 2DH, UK. Electronic address:
Independent Consultant, North Garden, VA 22959, USA.
Dipartimento di Scienze Biochimiche e Cliniche (Department of Biomedical and Clinical Sciences), Università degli Studi di Milano, Milan, Italy.
Pastoor Science Communication, LLC, Greensboro, NC 27455, USA.
Rita Schoeny LLC, Washington DC, 20002, USA.
Independent Consultant, Alexandria, VA 22301, USA.
Syngenta Crop Protection, LLC, Greensboro, NC 27419, USA.


Classification schemes for carcinogenicity based solely on hazard-identification such as the IARC monograph process and the UN system adopted in the EU have become outmoded. They are based on a concept developed in the 1970s that chemicals could be divided into two classes: carcinogens and non-carcinogens. Categorization in this way places into the same category chemicals and agents with widely differing potencies and modes of action. This is how eating processed meat can fall into the same category as sulfur mustard gas. Approaches based on hazard and risk characterization present an integrated and balanced picture of hazard, dose response and exposure and allow informed risk management decisions to be taken. Because a risk-based decision framework fully considers hazard in the context of dose, potency, and exposure the unintended downsides of a hazard only approach are avoided, e.g., health scares, unnecessary economic costs, loss of beneficial products, adoption of strategies with greater health costs, and the diversion of public funds into unnecessary research. An initiative to agree upon a standardized, internationally acceptable methodology for carcinogen assessment is needed now. The approach should incorporate principles and concepts of existing international consensus-based frameworks including the WHO IPCS mode of action framework.


Carcinogenicity; Classification; GHS; Hazard characterization; IARC; Risk assessment

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