Incorporating potency into EU classification for carcinogenicity and reproductive toxicity

Authors: Hennes C, Batke M, Bomann W, Duhayon S, Kosemund K, Politano V, Stinchcombe S, Doe J

Hennes C, Batke M, Bomann W, Duhayon S, Kosemund K, Politano V, Stinchcombe S, Doe J. 2014. Incorporating potency into EU classification for carcinogenicity and reproductive toxicity.
Accepted for publication in Regulatory Toxicology & Pharmacology
doi: 10.1016/j.yrtph.2014.07.022  [Epub ahead of print]

In a Nutshell

Classification should give guidance on the potential hazards of chemicals. Once the nature of the hazard is known, potency is the most important indicator of the degree of the hazard. Classification for carcinogenicity and reproductive toxicity does not distinguish between chemicals with up to 7 orders of magnitude difference in potency.  This can cause problems in communication and has downstream consequences for the use of chemicals which may be inappropriate.  There is methodology in the EU guidelines for assessing potency which is scientifically valid and should be used more widely. Classification schemes which incorporate potency have been developed.  These would promote clarity of communication and more relevant downstream risk management for chemicals. It is hoped this work will start a discussion on changing the GHS criteria.
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Abstract

Although risk assessment, assessing the potential harm of each particular exposure of a substance, is desirable, it is not feasible in many situations. Risk assessment uses a process of hazard identification, hazard characterisation, and exposure assessment as its components. In the absence of risk assessment, the purpose of classification is to give broad guidance (through the label) on the suitability of a chemical in a range of use situations. Hazard classification in the EU is a process involving identification of the hazards of a substance, followed by comparison of those hazards (including degree of hazard) with defined criteria. Classification should therefore give guidance on degree of hazard as well as hazard identification. Potency is the most important indicator of degree of hazard and should therefore be included in classification. This is done for acute lethality and general toxicity by classifying on dose required to cause the effect. The classification in the EU for carcinogenicity and reproductive toxicity does not discriminate across the wide range of potencies seen (6 orders of magnitude) for carcinogenicity and for developmental toxicity and fertility. Therefore potency should be included in the classification process. The methodology in the EU guidelines for classification for deriving specific concentration limits is a rigorous process for assigning substances which cause tumours or developmental toxicity and infertility in experimental animals to high, medium or low degree of hazard categories by incorporating potency. Methods are suggested on how the degree of hazard so derived could be used in the EU classification process to improve hazard communication and in downstream risk management.

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