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Biodegradation in water

Biodegradability of 2 -isopropyl-5 -methylcyclohexanone (CAS no. 1074-95-9) is predicted using OECD QSAR toolbox version 3.4 (2017). Test substance undergoes 31.60% degradation by CO2 evolution parameter in 28 days. Thus, based on percentage degradation, the test chemical 2 -isopropyl-5 -methylcyclohexanone was estimated to be not readily biodegradable in water.

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 2 -isopropyl-5 -methyl cyclohexanone (CAS No.1074 -95 -9). 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 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 moderate to low whereas the half-life period of test chemical 2 -isopropyl-5 -methylcyclohexanone 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 2 -isopropyl-5 -methylcylcohexanone is not persistent in nature.

Biodegradation in soil

The half-life period of 2 -isopropyl-5 -methylcyclohexanone (CAS No. 1074 -95 -9) 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, 73.8% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of 2 -isopropyl-5 -methylcyclohexanone in soil is estimated to be 30 days (720 hrs). Based on this half-life value of 2 -isopropyl-5 -methylcyclohexanone, 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

Various predicted data for the target compound 2-isopropyl-5-methylcyclohexanone (CAS No. 1074-95-9) and 3 supporting studies (1 study from authoritative database and 2 studies from secondary source) for its closest read across substance with logKow as the primary descriptor were reviewed for the biodegradation end point which are summarized as below:

 

In a prediction done by SSS (2017) by usingQSAR toolbox version 3.4 with logKow as the primary descriptor, percentagebiodegradability of test chemical 2 -isopropyl-5 -methylcyclohexanone (CAS no. 1074-95-9) was estimated. Test substance undergoes 31.60% degradation by CO2 evolution parameter in 28 days. Thus, based on percentage degradation, the test chemical 2-isopropyl-5-methylcyclohexanone was estimated to be not readily biodegradable in water.

 

In another prediction using the Estimation Programs Interface Suite (EPI suite, 2017), the biodegradation potential of the test compound 2 -isopropyl-5 -methylcyclohexano ne (CAS no. 1074 -95 -9) 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 2 -isopropyl-5 -methylcyclohexanone is expected to be not readily biodegradable.

 

Biodegradation study was conducted for 20 days for evaluating the percentage biodegradability of read across substance Dipropylene glycol monomethyl ether (CAS no. 34590-94-8) (HSDB, 2016). The percentage degradation of read across substance was determined to 0, 0 and 31% degradation by ThOD parameter in 5, 10 and 20 days, respectively. Thus, based on percentage degradation, Dipropylene glycol monomethyl ether was considered to be not readily biodegradable in nature.

 

Another weight of evidence study of biodegradation was conducted for 28 days for evaluating the percentage biodegradability of read across substance Dipropylene glycol monomethyl ether (CAS no. 34590-94-8) (OECD SIDS, 2001). Initial test substance conc. used in the study was10 mg/l, respectively. The percentage degradation of read across substance was determined to be 34% degradation in 28 days. At a concentration of 20 mg/l degradation was <10% after 28 days. Thus, based on percentage degradation, Dipropylene glycol monomethyl ether was considered to be not readily biodegradable in nature.

 

In addition to the above weight of evidence studies, another biodegradation study of read across substance Dipropylene glycol monobutyl ether (CAS no. 29911-28-2) from secondary source (OECD SIDS, 2003), was carried out for 28 days for evaluating the percentage biodegradability of read across substance Dipropylene glycol monobutyl ether. The study was performed according to OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test). Initial test substance conc. used in the study was 0, 1.86, or 9.29 mg/l, respectively. Domestic sewage was used as a test inoculum collected from a local municipal sewage treatment facility. To test for its ready biodegradability potential, read across chemical was incubated for 28 days in continuously agitated closed bottles in the dark at two concentrations with inoculum (secondary effluent) collected from a local municipal sewage treatment facility. The incubation temperature of the water was 19.7-20.0°C, pH ranged from 7.2 to 7.4, hardness was not reported, and the concentration of inoculum was one droplet per liter of test solution. Oxygen concentration was the measured variable. Degradation of read across chemical was monitored by assessing the dissipation of oxygen in the test solution over time (i.e., measuring dissolved oxygen content with an oxygen electrode at various time points). Oxygen content was measured (in duplicate bottles) on days 0, 5, 15, and 28. Degradation was calculated by dividing the biochemical oxygen demand (BOD) expressed as mg O2 per mg DPnB, by the theoretical oxygen demand (ThOD).The percentage degradation of read across substance was determined to be 0% by %ThOD parameter in 28 days. Thus, based on percentage degradation, Dipropylene glycol monobutyl ether was considered to be not readily biodegradable in water.

 

On the basis of above results for target chemical 2-isopropyl-5-methylcyclohexanone (study 1, 2 from OECD QSAR toolbox 3.4 and EPI suite) and for its read across substance (study 3 from authoritative database HSDB and study 4 and 5 from secondary source), it can be concluded that the test substance 2 -isopropyl-5 -methylcyclohexanone 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 2 -isopropyl-5 -methyl cyclohexanone (CAS No.1074 -95 -9). 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 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 moderate to low whereas the half-life period of test chemical 2 -isopropyl-5 -methylcyclohexanone 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 2 -isopropyl-5 -methylcylcohexanone is not persistent in nature.

Biodegradation in soil

The half-life period of 2 -isopropyl-5 -methylcyclohexanone (CAS No. 1074 -95 -9) 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, 73.8% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of 2 -isopropyl-5 -methylcyclohexanone in soil is estimated to be 30 days (720 hrs). Based on this half-life value of 2 -isopropyl-5 -methylcyclohexanone, 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 2-isopropyl-5-methylcyclohexanone can be considered to be not readily biodegradable in nature.