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Environmental fate & pathways

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Description of key information

Biodegradation in water

Biodegradability of 1,1-diethoxy-3,7-dimethylocta-2,6-diene (CAS no. 7492 -66 -2) is predicted using OECD QSAR toolbox version 3.3 (2017) with logKow as the primary descriptor. Test substance undergoes 1.57% degradation by BOD in 28 days. Thus, based on percentage degradation, the test chemical

1,1-diethoxy-3,7-dimethylocta-2,6-diene 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

1,1 -diethoxy-3,7 - dimethylocta-2,6 -diene (CAS No. 7492 -66 -2). If released in to the environment, 15.9% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of 1,1 -diethoxy-3,7 -dimethylocta-2,6 -diene in water is estimated to be 37.5 days (900 hrs). 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 whereas the half-life period of 1,1 -diethoxy-3,7 -dimethylocta-2,6 -diene in sediment is estimated to be 337.5 days (8100 hrs). However, as the percentage release of test chemical into the sediment is less than 1% (i.e, reported as 0.572%), indicates that 1,1 -diethoxy-3,7 -dimethylocta-2,6 -diene is not persistent

in sediment.

Biodegradation in soil

The half-life period of 1,1 -diethoxy-3,7 -dimethylocta-2,6 -diene (CAS No. 7492 -66 -2) 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, 83.5% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of 1,1 -diethoxy-3,7 -dimethylocta-2,6 -diene in soil is estimated to be 75 days (1800 hrs). Based on this half-life value of

1,1 -diethoxy-3,7 -dimethylocta-2,6 -diene, 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.

Bioaccumulation: aquatic / sediment

From BCFBAF (v3.00) model of EPI suite Program, the estimated bio concentration factor (BCF) for 1,1-diethoxy-3,7-dimethylocta-2,6-diene is 699.3 L/kg whole body w.w which does not exceed the bio concentration threshold of 2000. Thus it is concluded that 1,1-diethoxy-3,7-dimethylocta-2,6-diene is not expected to bioaccumulate in the food chain.

Adsorption / desorption

The Soil Adsorption Coefficient i.e Koc value of 1,1-diethoxy-3,7-dimethylocta-2,6-diene was estimated using EPI suite  KOCWIN (v2.00) program as Koc 655 L/kg(log Koc=2.81)  by means of MCI method at 25 deg.C. This Koc value indicates that the substance 1,1-diethoxy-3,7-dimethylocta-2,6-diene has a Moderate sorption to soil and sediment and therefore have slow migration potential to groundwater.

Additional information

Biodegradation in water

Various predicted data for the target compound1,1-diethoxy-3,7-dimethylocta-2,6-diene(CAS No. 7492-66-2) and various supporting weight of evidence studies 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) using OECD QSAR toolbox version 3.3 with logKow as the primary descriptor, percentage biodegradability of test chemical 1,1-diethoxy-3,7-dimethylocta-2,6-diene(CAS No. 7492-66-2) was estimated.Test substance undergoes 1.57% degradation by BOD in 28 days (2017). Thus, based on percentage degradation, the test chemical 1,1-diethoxy-3,7-dimethylocta-2,6-diene 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 compound1,1-diethoxy-3,7-dimethylocta-2,6-diene(CAS No. 7492-66-2) 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 1,1 -diethoxy-3,7 -dimethylocta-2,6 -diene is expected to be not readily biodegradable.

 

In a supporting weight of evidence study from authoritative database (HSDB, 2017) for the read across chemical 2,3 -dichloro-1,4 -naphthoquinone (CAS no. 117 -80 -6), biodegradation experiment was conducted for 14 days for evaluating the percentage biodegradability under aerobic conditions. Initial test substance conc. used for the study was 100 mg/l. The percentage degradation of read across substance was determined to be in the range of 0 -5% by using BOD parameter in 14 days. Thus, based on percentage degradation, 2,3 -dichloro-1,4 -naphthoquinone is considered to be not readily biodegradable in nature.

 

For the same read across chemical 2,3 -dichloro-1,4 -naphthoquinone (CAS no. 117 -80 -6), biodegradation study was conducted for 14 days for evaluating the percentage biodegradability (J-CHECK, 2017). 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 read across substance was determined to be 5% by GC parameter in 14 days. Thus, based on percentage degradation, 2,3 -dichloro-1,4 -naphthoquinone is considered to be not readily biodegradable in nature.

 

Another biodegradation study was conducted for 28 days for evaluating the percentage biodegradability of read across substance 2,2'-biindole-3,3'(1H,1'H)-dione (CAS no. 482 -89 -3) (OECD SIDS, 1994). The study was performed according to OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I)) under aerobic conditions. Concentration of inoculum i.e, sludge used was 30 mg/l as suspended solid. The percentage degradation of read across substance was determined to be 0% by BOD parameter in 28 days. Thus, based on percentage degradation, 12,2'-biindole-3,3'(1H,1'H)-dione is considered to be not readily biodegradable in nature.

 

In a supporting weight of evidence study for the read across chemical 1,1'-sulfonylbis(4 -chlorobenzene) (CAS no. 80 -07 -9), biodegradation experiment was conducted for 28 days for evaluating the percentage biodegradability (J-CHECK, 2017). 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 read across substance was determined to be 1 and 0% by BOD and HPLC parameter in 28 days. Thus, based on percentage degradation, 1,1'-sulfonylbis(4 -chlorobenzene) is considered to be not readily biodegradable in nature.

 

On the basis of above results for target chemical1,1-diethoxy-3,7-dimethylocta-2,6-diene(from OECD QSAR toolbox version 3.3 and EPI suite, 2017) and for its read across substance (from authoritative database J-CHECK, HSDB and secondary source OECD SIDS), it can be concluded that the test substance 1,1-diethoxy-3,7-dimethylocta-2,6-diene 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

1,1 -diethoxy-3,7 - dimethylocta-2,6 -diene (CAS No. 7492 -66 -2). If released in to the environment, 15.9% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of 1,1 -diethoxy-3,7 -dimethylocta-2,6 -diene in water is estimated to be 37.5 days (900 hrs). 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 whereas the half-life period of 1,1 -diethoxy-3,7 -dimethylocta-2,6 -diene in sediment is estimated to be 337.5 days (8100 hrs). However, as the percentage release of test chemical into the sediment is less than 1% (i.e, reported as 0.572%), indicates that 1,1 -diethoxy-3,7 -dimethylocta-2,6 -diene is not persistent

in sediment.

Biodegradation in soil

The half-life period of 1,1 -diethoxy-3,7 -dimethylocta-2,6 -diene (CAS No. 7492 -66 -2) 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, 83.5% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of 1,1 -diethoxy-3,7 -dimethylocta-2,6 -diene in soil is estimated to be 75 days (1800 hrs). Based on this half-life value of 1,1 -diethoxy-3,7 -dimethylocta-2,6 -diene, 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 1,1 -diethoxy-3,7 -dimethylocta-2,6 -diene can be considered to be not readily biodegradable in nature.

 

Bioaccumulation: aquatic / sediment

Four results including different predicted data from validated models for bioaccumulation (BCF) endpoint of target chemical 1,1-diethoxy-3,7-dimethylocta-2,6-diene (Cas no. 7492-66-2) were summarized as follows:

 

First prediction done using BCFBAF (v3.00) model indicate the estimated bio concentration factor (BCF) for 1,1-diethoxy-3,7-dimethylocta-2,6-diene is 699.3 L/kg wet-wt which does not exceed the bioconcentration threshold of 2000. Thus it is concluded that 1,1-diethoxy-3,7-dimethylocta-2,6-diene is not expected to bio accumulate in the aquatic environment.

 

From PBT profiler predicted database the Bioaccumulation factor (BCF) for test substance 1,1-diethoxy-3,7-dimethylocta-2,6-diene was estimated to be 700 L/kg wet-wt at 25 deg.C. Based on the BCF concentration it is concluded that the test chemical 1,1-diethoxy-3,7-dimethylocta-2,6-diene is non bioaccumulative in nature as it does not exceed the BCF criteria of 2000. 

Above all prediction assist by result from CompTox Chemistry Dashboard using OPERA (OPEn (quantitative) structure-activity Relationship Application)  V1.02 model in which calculation based on PaDEL descriptors (calculate molecular descriptors and fingerprints of chemical) indicate  the bioaccumulation i.e BCF for test substance 1,1-diethoxy-3,7-dimethylocta-2,6-diene was estimated to be 845 dimensionless . The predicted BCF result based on the 5 OECD principles. Thus based on the result it is concluded that the test substance 1,1-diethoxy-3,7-dimethylocta-2,6-diene non-bioaccumulative in nature as it does not exceed the BCF criteria of 2000.

Also from U.S. Environmental Protection Agency,Hazard Characterization Document, September 2009 the Bioconcentration (BCF) factor of test chemical Citral diethyl acetal  (Cas no.7492-66-2) i.e 1,1-diethoxy-3,7-dimethylocta-2,6-diene  was reported to be 1020 (Dimensionless).This BCF value suggest that the chemical non bioaccumulative in aquatic environment as it does not exceed the threshold of 2000.

 

Thus based on the above information for bioaccumulation endpoint, it can be concluded that the test substance 1,1-diethoxy-3,7-dimethylocta-2,6-diene (Cas no. 7492-66-2) is expected to be non Bioaccumulative in aquatic environment as none of the study indicate the 1,1-diethoxy-3,7-dimethylocta-2,6-diene exceed the BCF threshold of 2000.

Adsorption / desorption

Three results including different predicted data from validated models and from US EPA screening report for adsorption (KOC) endpoint of target chemical 1,1-diethoxy-3,7-dimethylocta-2,6-diene (Cas no. 7492-66-2)were summarized as follows:

 

First study from prediction by KOCWIN model (v2.00) of EPI suite which indicate the adsorption value of 1,1-diethoxy-3,7-dimethylocta-2,6-diene was estimated as 655 L/kg(log Koc=2.81) by means of MCI method at 25 deg.C. This Koc value indicates that the substance 1,1-diethoxy-3,7-dimethylocta-2,6-diene has a Moderate sorption to soil and sediment and therefore have slow migration potential to groundwater. 

Above result is assist by U.S. Environmental Protection Agency September,Hazard Characterization Document, 2009 which suggest the Adsorption in soil (log Koc) factor of test chemical Citral diethyl acetal  (Cas no.7492-66-2) i.e 1,1-diethoxy-3,7-dimethylocta-2,6-diene  was reported to be 2.13 (Dimensionless).This Log Koc suggest that the chemical has moderate mobility in soil compartment.

And Result From CompTox Chemistry Dashboard using OPERA (OPEn (quantitative) structure-activity Relationship Application)  V1.02 model in which calculation based on PaDEL descriptors (calculate molecular descriptors and fingerprints of chemical) indicate the adsorption coefficient i.e KOC for test substance 1,1-diethoxy-3,7-dimethylocta-2,6-diene was estimated to be 257 L/Kg.The predicted KOC result based on the 5 OECD principles. Thus based on the result it is concluded that the test substance 1,1-diethoxy-3,7-dimethylocta-2,6-diene has moderate mobility in soil compartment.

Thus all available studies for adsorption endpoint come to conclusion that the test substance 1,1-diethoxy-3,7-dimethylocta-2,6-diene (Cas no. 7492-66-2) is expected to have low to moderate mobility in soil and sediment compartment.