The added value of the 90-day repeated dose oral toxicity test for industrial chemicals with a low (sub)acute toxicity profile in a high quality dataset: An update.

A previous retrospective analysis of substances in the ECHA CHEM database concluded that, for industrial chemicals with a 'low (sub)acute toxicity profile', further testing in the 90-day study is unlikely to change this profile (Taylor et al., 2014). We have further tested this hypothesis by assessing the outcome of substances with testing proposals for which a prediction was made in that paper that the NOAEL based on the 90-day study would be 1000 mg/kg bw/d. Indeed, for seven out of ten substances for which data was available, the profile was shown to be held. For three substances, the reduced NOAEL was explained by renal effects in the rats, two of which had been seen in the 28-day study but had been dismissed by the study submitter. We conclude that the low toxicity profile will be even more protective if the NOEL is used from the 28-day study and an independent expert view is taken of the human relevance of any effects reported in the 28-day study.

The added value of the 90-day repeated dose oral toxicity test for industrial chemicals with a low (sub)acute toxicity profile in a high quality dataset.

A survey conducted on the EU Notification of New Substances (NONS) database suggested that for industrial chemicals with a profile of low toxicity in (sub)acute toxicity tests there is little added value to the conduct of the 90-day repeated dose study. Avoiding unnecessary animal testing is a central aim of the EU REACH chemicals legislation; therefore we sought to verify the profile using additional data. The OECD's eChemPortal was searched for substances that had both a 28-day and a 90-day study and their robust study summaries were then examined from the ECHA CHEM database. Out of 182 substances with high quality 28-day and 90-day study results, only 18 reported no toxicity of any kind in the (sub)acute tests. However, for 16 of these there were also no reported signs of toxicity at or close to the limit dose (1000mg/kgbw/d) in the 90-day study. Restricting the 'low (sub)acute toxicity in a high quality dataset' profile to general industrial chemicals of no known biological activity, whilst allowing irritant substances, increases the data set and improves the prediction to 95% (20 substances out of 21 substances). The low toxicity profile appears to be of low prevalence within industrial chemicals (10-15%), nevertheless, avoidance of the conduct of a redundant 90-day study for this proportion of the remaining REACH phase-in substances would avoid the use of nearly 50,000 animals and save industry 50million Euros, with no impact on the assessment of human health.

Can acute dermal systemic toxicity tests be replaced with oral tests? A comparison of route-specific systemic toxicity and hazard classifications under the Globally Harmonized System of Classification and Labelling of Chemicals (GHS).

Acute systemic toxicity data (LD50 values) and hazard classifications derived in the rat following oral administration and dermal application have been analysed to examine whether or not orally-derived hazard classification or LD50 values can be used to determine dermal hazard classification. Comparing the oral and dermal classifications for 335 substances derived from oral and dermal LD50 values respectively revealed 17% concordance, and indicated that 7% of substances would be classified less severely while 76% would be classified more severely if oral classifications were applied directly to the dermal route. In contrast, applying the oral LD50 values within the dermal classification criteria to determine the dermal classification reduced the concordance to 15% and the relative 'under-classification' to 1%, but increased the relative 'over-classification' to 84%. Both under- and over-classification are undesirable, and mitigation strategies are discussed. Finally, no substance with an oral LD50 of >2000mg/kg was classified for acute systemic toxicity by the dermal route, suggesting that dermal testing for acute systemic toxicity of such substances adds nothing to the hazard characterisation and should be removed from routine regulatory data requirements.