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Classification & Labelling & PBT assessment

PBT assessment

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Administrative data

PBT assessment: overall result

PBT status:
the substance is not PBT / vPvB

Classification of (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one for effects in the environment:

 The chemical (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one (CAS no. 89-80-5) is used as a flavour and fragrance agent. The aim was to assess whether the PBT criterion within Annex XIII was fulfilled for (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one. The PBT criterion was herein assessed based on experimental data in conjunction with standardized environmental fate models. Here follows a description of the PBT assessment.


Persistence assessment

The tested substance fulfils the P criterion within Annex XIII based on the assessment that here follows:


Biotic degradation

In an experimental key study from peer reviewed journal, biodegradation experiment was conducted for 21 days for evaluating the percentage biodegradability of test substance (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one (CAS no. 89-80-5) by using Pseudomonas citronellolis DSM 50332 as an inoculum. Test inoculum Pseudomonas citronellolis DSM 50332 was obtained from the Deutsche Sammlung von Mikroorganismen, Braunschweig, Germany. Initial test substance conc. used for the study was 308.5 mg/l (2 mM). Anoxic media was used for the study.The medium contained (per liter of distilled water) 1 g of NaCl, 0.1 g of MgCl2.7H2O, 0.04 g of CaCl2, 0.5 g of KCl, 0.125 g of NH4Cl, 0.2 g of Na2SO4, 0.4 g of KH2PO4, 1.2 g of K2HPO4, and 0.85 g of NaNO3. After autoclaving, 2 ml of a non-chelated trace element mixture, 2 ml of a selenite-tungstate solution, vitamins, and 20 ml of a 1 M NaHCO3 solution were added, and the pH was adjusted to 7.0.Enrichment cultures were inoculated with activated sludge obtained from a local wastewater plant (Lintel, Osterholz-Scharmbeck, Germany). Enrichment cultures were maintained and test chemical consumption was measured in 21-ml glass tubes containing 15 ml of anoxic medium (10 mM nitrate, 0.5 ml2,2,4,4,6,8,8-heptamethylnonane (HMN), and 2 mM menthone (test chemical)). The overpressure due to gas formation was measured with a syringe, and 10 mM nitrate was added when the electron acceptor was depleted. The gas formed was analyzed by gas chromatography. Bacterial growth was observed daily and required between 3 - 22 days. Monoterpene contents were determined with a gas chromatograph equipped with flame ionization detectors and connected to a digital data-analyzing system. The amounts of monoterpene dissimilated were calculated from the differences in monoterpene contents between the pasteurized controls and the grown enrichment cultures. A model MAT ITS 40 ion trap system was used for the gas chromatography-mass spectrometry analysis. Microbial growth on test chemical menthone was observed within 10 days to 3 weeks. The disappearance of test chemical in mud-free enrichment cultures was quantified. The percentage degradation of test substance (2R,5S)-5 -methyl-2 -(propan-2 -yl)cyclohexan-1 -one was determined to be 1.13% degradation by Test mat. analysis parameter in 21 days. Thus, based on percentage degradation, (2R,5S)-5 -methyl-2 -(propan-2 -yl)cyclohexan-1 -one is considered to be not readily biodegradable in nature. 


In a prediction using the Estimation Programs Interface Suite (2017), the biodegradation potential of the test compound (2R,5S)-5 -methyl-2 -(propan-2 -yl)cyclohexan-1 -one (CAS No. 89 -80 -5) in the presence of mixed populations of environmental microorganisms was estimated. The biodegradability of the substance was calculated using seven different models. The results indicate that chemical (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one is expected to be not readily biodegradable.


Experimental results from the read across substances (CAS: 2216-51-5 and 1490-04-6) also indicate that they are not readily biodegradable.


Thus, on the basis of various experimental biodegradation studies and predicted data results for the chemical (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one(CAS no. 89-80-5) and for its read across substances, it indicates that chemical (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one can be expected to be not readily biodegradable in water.



Bioaccumulation assessment

The tested substance does not fulfil the B criterion within Annex XIII based on the assessment that here follows:


The estimated BCF value from authoritative database was determined to be ranges from 15.0 to 58.2, respectively and the octanol water partition coefficient of the test chemical was determined to be 2.295, respectively, which is less than the threshold of 4.5. If this chemical is released into the aquatic environment, there should be a low risk for the chemical to bioaccumulate in fish and food chains.

Toxicity assessment

The tested substance does not fulfil the T criterion within Annex XIII based on the assessment that here follows:



The tested chemical is regarded to be not classified for carcinogenicity, mutagenicity and reprotoxicity, Further, there is no evidence of chronic toxicity, as identified by the classifications STOT (repeated exposure), category 1(oral, dermal, inhalation of gases/vapours, inhalation of dust/mist/fume) or category 2 (oral, dermal, inhalation of gases/vapours, inhalation of dust/mist/fume).


Aquatic organisms

All of the available short-term eco-toxicity estimations for fish, invertebrates and algae for the substance indicates the LC50/EC50 value to be in the range 12.905 - 20.973 mg/L. These value suggest that the substance is likely to be hazardous to Aquatic organisms at environmentally relevant concentrations and can be considered as classified in Aquatic chronic category 3 as per the CLP regulation


There are no available long-term toxicity evaluations for (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one. By speculation, long-term NOEC for aquatic organisms were not expected for the substance at concentration below 0.01 mg/L based on the data mentioned above


The chemical was therefore not considered as hazardous to aquatic environments as per the criteria set out in Annex XIII.



Based on critical, independent and collective evaluation of information summarized herein, the tested compound fulfils the P criterion but does not fulfil the B and T criterion and has therefore not been classified as a PBT compound within Annex XIII.