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Environmental fate & pathways

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Description of key information

Biodegradation in water

Biodegradation study was conducted for 21 days for evaluating the percentage biodegradability of test substance (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one by usingPseudomonas citronellolis DSM 50332 as an inoculum (Jens Harder and Christina Probian, 1995).Test inoculumPseudomonas citronellolisDSM 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.

Biodegradation in water and sediment

Estimation Programs Interface (EPI Suite, 2017) prediction model was run to predict the half-life in water and sediment for the test compound (2R,5S)-5 -methyl-2 -(propan-2 -yl)cyclohexan-1 -one (CAS No. 89 -80 -5). If released in to the environment, 24.8% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one 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 moderate to low whereas the half-life period of (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-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 0.179%), indicates that (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one is not persistent in sediment.

 

Biodegradation in soil

The half-life period of (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one (CAS No.89 -80 -5) 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, 73.6% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one in soil is estimated to be 30 days (720 hrs). Based on this half-life value of (2R,5S)-5 -methyl-2 -(propan-2 -yl)cyclohexan-1 -one, it is concluded that the chemical is not persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

Additional information

Biodegradation in water:

Experimental study and predicted data for the target compound (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one (CAS No. 89-80-5) and varioussupporting studiesfor its structurally similar read across substance were reviewed for the biodegradation end point which are summarized as below:

 

In an experimental key study from peer reviewed journal (1995), 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 (EPI 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 such as Linear Model, Non-Linear Model, Ultimate Biodegradation Timeframe, Primary Biodegradation Timeframe, MITI Linear Model, MITI Non-Linear Model and Anaerobic Model (called as Biowin 1-7, respectively) of the BIOWIN v4.10 software. The results indicate that chemical (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one is expected to be not readily biodegradable.

 

Next study was experimental study done from from authoritative database (HSDB, 2017), in this study the biodegradation study was conducted for 28 days for evaluating the percentage biodegradability of test chemical. Activated sludge was used as a test inoculum for the study. The percentage degradation of test chemical was determined to be 0% by BOD parameter in 28 days. Thus, based on percentage degradation, test chemical is considered to be not readily biodegradable in nature.

 

In a supporting study from authoritative database (J-CHECK and HSDB, 2017) biodegradation experiment was conducted for 28 days for evaluating the percentage biodegradability of test chemical. The study was performed according to OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I) under aerobic conditions. Activated sludge was used as a test inoculums for the study. Concentration of inoculum i.e, sludge used was 30 mg/l and initial test substance conc. used in the study was 100 mg/l, respectively. The percentage degradation of test substance was determined to be 0% and 5% by BOD, TOC removal and GC parameter in 28 days. Thus, based on percentage degradation, test chemical is considered to be not readily biodegradable in nature.

 

On the basis of above results for target chemical (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one (from peer reviewed journal and EPI suite, 2017) and for its read across substance (from authoritative database J-CHECK and HSDB, 2017), it can be concluded that the test substance (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one can be expected to be not readily biodegradable in nature.

 Biodegradation in water and sediment

Estimation Programs Interface (EPI Suite, 2017) prediction model was run to predict the half-life in water and sediment for the test compound (2R,5S)-5 -methyl-2 -(propan-2 -yl)cyclohexan-1 -one (CAS No. 89 -80 -5). If released in to the environment, 24.8% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one 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 moderate to low whereas the half-life period of (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-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 0.179%), indicates that (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one is not persistent in sediment.

 

Biodegradation in soil

The half-life period of (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one (CAS No.89 -80 -5) 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, 73.6% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one in soil is estimated to be 30 days (720 hrs). Based on this half-life value of (2R,5S)-5 -methyl-2 -(propan-2 -yl)cyclohexan-1 -one, it is concluded that the chemical is not persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

On the basis of available information, the test substance (2R,5S)-5-methyl-2-(propan-2-yl)cyclohexan-1-one can be considered to be not readily biodegradable in nature.