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Environmental fate & pathways

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Description of key information

Biodegradation in water:

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.

Biodegradation in water and sediments:

Estimation Programs Interface (EPI Suite, 2017) prediction model was run to predict the half-life in water and sediment for the test compound (5S)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one (CAS No. 2244 -16 -8). If released in to the environment, 25.4 % of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of test chemical in water is estimated to be 15 days (360 hrs). The half-life (15 days estimated by EPI suite) indicates that the chemical is not persistent in water and the exposure risk to aquatic animals is low whereas the half-life period of test chemical (5S)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one in sediment is estimated to be 135 days (3240 hrs). However, as the percentage release of test chemical into the sediment is less than 1 % (i.e, reported as 0.183 %), indicates that test chemical (5S)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one is not persistent in sediment.

Biodegradation in soil:

The half-life period of test chemical (5S)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one (CAS No.2244 -16 -8) in soil was estimated using Level III Fugacity Model by EPI Suite version 4.1 estimation database (EPI suite, 2017). If released into the environment, 74.3 % of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of test chemical (5S)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one in soil is estimated to be 30 days (720 hrs). Based on this half-life value of test chemical (5S)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one, it is concluded that the chemical is not persistent in the soil environment and the exposure risk to soil dwelling animals is low .

Additional information

Biodegradation in water:

One Experimental study and one predicted data study for target chemical (S)-2-methyl-5-(1-methylvinyl)cyclohex-2-en-1-one  and three supporting experimental studies for its structurally similar read across chemicals have been conducted for biodegradation in water endpoint and their results are summarized below.

 

In first study the 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.

 

In next supporting experimental study the 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 microorganisms as inoculums 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.

 

In another supporting experimental study which is done from CLH report of Committee for Risk Assessment RAC –ECHA (2013) for structurally similar read across chemical biodegradation of read across chemical (5R)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one was determined by using test guideline OECD 301 D. The initial read across chemical concentration used was 1 mg/L and 3 mg/L. The read across chemical (5R)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one undergoes 68% and 62% biodegradability in 28 days at 1 mg/L and 3 mg/L initial read across substance concentration respectively.60% degradation was reached within the 14-day window,(5R)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-oneis considered readily biodegradable.

 

Further in one more experimental study which is done from authoritative database (HSDB, 2017) for same read across chemical as mentioned in above study Biodegradation was determined by using Manometric Respirometry test. The initial concentration of read across chemical used was 100 mg/L. The read across chemical (5R)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one undergoes 90% biodegradation using activated sludge as inoculums in aerobic conduction in 28 days. On the basis of percent biodegradability value it is concluded that read across chemical (5R)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one is readily biodegradable.

 

Last experimental study was also done from authoritative database (HSDB, 2017) in this study the biodegradation of test chemical 1,1,3-Trimethyl-3-cyclohexene-5-one (CAS no. 78 -59 -1) was determined by using 7 days static incubation in dark and settled domestic wastewater as inoculums. The initial test chemical concentration used was 5 and 10 mg/L. The test chemical 1,1,3-Trimethyl-3-cyclohexene-5-one undergoes 100% biodegradation using settled domestic waste as inoculums in 7 days. On the basis of % biodegradability value it is concluded that test chemical (5R)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one is readily biodegradable.

 

One the basis of all the studies mentioned above it is concluded that test chemical chemical (S)-2-methyl-5-(1-methylvinyl)cyclohex-2-en-1-one is expected to be readily biodegradable.

Biodegradation in water and sediments:

Estimation Programs Interface (EPI Suite, 2017) prediction model was run to predict the half-life in water and sediment for the test compound (5S)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one (CAS No. 2244 -16 -8). If released in to the environment, 25.4 % of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of test chemical in water is estimated to be 15 days (360 hrs). The half-life (15 days estimated by EPI suite) indicates that the chemical is not persistent in water and the exposure risk to aquatic animals is low whereas the half-life period of test chemical (5S)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one in sediment is estimated to be 135 days (3240 hrs). However, as the percentage release of test chemical into the sediment is less than 1 % (i.e, reported as 0.183 %), indicates that test chemical (5S)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one is not persistent in sediment.

Biodegradation in soil:

The half-life period of test chemical (5S)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one (CAS No.2244 -16 -8) in soil was estimated using Level III Fugacity Model by EPI Suite version 4.1 estimation database (EPI suite, 2017). If released into the environment, 74.3 % of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of test chemical (5S)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one in soil is estimated to be 30 days (720 hrs). Based on this half-life value of test chemical (5S)-2-methyl-5-(prop-1-en-2-yl)cyclohex-2-en-1-one, it is concluded that the chemical is not persistent in the soil environment and the exposure risk to soil dwelling animals is low .