Incorporating potency into classification for carcinogenicity and reproductive toxicity

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.