(S)-2-methyl-5-(1-methylvinyl)cyclohex-2-en-1-one

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Classification of (5S)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-onefor effects in the environment:

 

The chemical (5S)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one(CAS no. 2244-16-8) isused as a flavouring agent in foods and as a fragrances in perfumes, lotions,soaps as well as in non-cosmetic products such as detergents etc. The aim was to assess whether the PBT criterion within Annex XIII was fulfilled for(5S)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-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 does not fulfil the P criterion within Annex XIII based on the assessment that here follows:

 

Biotic degradation

Biodegradation experiment of test chemical (S)-2-methyl-5-(1-methylvinyl)cyclohex-2-en-1-one was conducted by using Pseudomonas ovalis, strain 6-1, as inoculums for 4 days. In this experiment Ten milliliters of the cell suspension of Pseudomonas ovalis, strain 6-1 was pre incubated for 24 hr in the growing medium containing 5 mg of (S)-2-methyl-5-(1-methylvinyl)cyclohex-2-en-1-one and 0.1 ml of ethanol in a 30 ml test tube. Then it was added to 90 mL of growing medium containing 60-100 mg of test chemical (S)-2-methyl-5-(1-methylvinyl)cyclohex-2-en-1-one  in 500 mL flask. Then it was incubated at 30 oC temperature at 8.0 pH for 4 days. Then the culture broth was centrifuged at 8000 rpm for 10 mins. Then supernatant was subjected to ether extraction after that ether layer obtained was evaporated then GLC and Column chromatography was performed to determined transformation products. By using above techniques The test chemical (S)-2-methyl-5-(1-methylvinyl)cyclohex-2-en-1-one undergoes 100 % degradation by considering test material analysis by GLC as parameter and Pseudomonas ovalis, strain 6-1, as inoculum in 4 days. The transformation products identified of test chemical (S)-2-methyl-5-(1-methylvinyl)cyclohex-2-en-1-one was (-)-isodihydrocarvone, (-)-isodihydrocarveol,( - )-neoisodihydrocarveol, (-) dihydrocarvone, (-)-neodihydrocarveol, and (+ )-dihydrocarveol. On the basis of percent degradability value it is concluded that test chemical (S)-2-methyl-5-(1-methylvinyl)cyclohex-2-en-1-one is readily biodegradable.

 

Biodegradability of test chemical (5S)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one (CAS no. 2244 -16 -8) was estimated by using OECD QSAR tool box v3.3 by considering six closest read across chemicals with log Kow as primary descriptor. The percent degradation of test chemical (5S)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one was estimated to be  86.71 % by considering BOD as parameter and microrganisms as inoculum in 28 days. On the basis of percent degradability value it can be concluded that test chemical (5S)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one is readily biodegradable.

 

Experimental results from the read across substances (CAS: 99-49-0 and 78-59-1) also indicate that they are readily biodegradable.

 

Environmental fate

According to the fugacity model levels III, the most likely environmental fate for this test chemical is soil (i.e.estimated to 74.3%). In soil,(5S)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-onewas expected to have moderate to slow mobility based upon a Log KOC value ranging from 1.927 to 2.9, respectively. The half-life in soil (75 days estimated by EPI suite) indicates that the chemical is not persistent in soil and the exposure risk to soil dwelling animals is moderate to low.

 

If released in to the environment, 25.4% of the chemical will partition into water according to the Mackay fugacity model level III in EPI suite version 4.1 (2017). However, the half-life (37.5 days estimated by EPI suite) indicates that the chemical is not persistent in water and the exposure risk to aquatic animals is moderate to low.

 

Moreover, its persistent characteristic is only observed in the sediment compartment but Fugacity modelling shows that sediment is not an important environmental fate (less than 1% i.e. reported as 0.183% when estimated by EPI Suite version 4.1).

 

Hence it has been concluded that(5S)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-oneis not persistent in nature.

 

Bioaccumulation assessment

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

 

Theestimated BCF value from authoritative database was determined to be range from 4.53 to 79.31, respectively and theoctanol water partition coefficient of the test chemical is 3.07, 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:

 

Mammals

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 50– 249.516 mg/L, respectively. 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(5S)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-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.

 

Conclusion

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