2-pentylcyclopentan-1-one

Endpoint summary

Description of key information

Short term toxicity to Fish: Read-across, EU Method C.1, OECD Guideline 203, GLP, key study, validity 2:
96h-LC50 = 13 mg/L (95% CI: 7.5-23 mg/L)

Short term toxicity to aquatic invertebrates: Read-across, EU Method C.2, OECD Guideline 202, GLP, key study, validity 2:
48h-EC50 = 18 mg/L (95% CI: 10-32 mg/L).

Additional information

To assess the aquatic toxicity of the registered substance, 2 -pentylcyclopentan-1-one, three valid acute studies based on international guidelines are available for the three aquatic trophic levels (algae, aquatic invertebrate and fish) on a read-across substance, 2 -pentylcyclopentan-1-ol, which has the same mode of action and very similar solubility, log Kow and vapour pressure to the reference substance.

According to the decision tree of ToxTree v2.6.13 (2015) and using Verhaar scheme (modified), the registered substance is classified as non-polar narcotic compound (Class 1 or MoA 1). The read-across substance is classed as unclassified compound (Class 5). Specific cases of misclassification relating to unsaturated alcohols have been detected and analysed (see KREATiS position paper n20151101 in attachment). These misclassifications occur when dealing with an alcohol containing a cycle or containing a double bond. In the first case (cycles), the compound is not considered by Verhaar scheme and related tools to be a saturated alcohol acting with a non-polar narcotic MOA (Class 1) but stay unclassified (Class 5). In conclusion, both compounds (the registered substance and the read-across substance) should be classified as non-polar narcotic.

Among all data available, a toxic effect was observed for the three aquatic trophic levels and these all occurred at similar levels. The fish Brachydanio rerio (now Danio rerio) is the most sensitive species with a 96h-LC50 at 13 mg/L. For the algae Pseudokirchneriella subcapitata, the 72h-ErC50 was determined to be 14 mg/L, and for the aquatic invertebrates Daphnia magna, the 48h-EC50 was determined to be 18 mg/L.

Both compounds (the registered substance and the read-across substance) are structurally related, in that each has an alkyl chain with five carbon (pentyl) with a cyclopentane ring. Both compounds contain a 2 -pentylcyclopentane skeleton. The cyclopentane ring is associated with a ketone functional group for the registered substance and with an alcohol functional group for the read-across substance. This supporting substance is considered adequate for read-across purposes based on structural similarity, on similar basic physico-chemical properties and similar environmental profile, as well as the same mode of action (MOA 1), between the registered substance and the analogue material used. Indeed, physico-chemical properties directly govern the toxicity of MOA 1 substances. If basic physico-chemical properties are very similar, the toxicity will also be because MOA 1 substances are on the same regression, governed by the solubility. In addition, as the log Kow value of the analogue material is slightly greater than the registered substance, the read-across approach is considered as a worst case scenario (see IUCLID section 13 for justification).