2,6-dimethyloct-7-en-2-yl acetate

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 12 May 2009 to 20 February 2012.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

This information is used for read-across to Dihydro Myrcenyl Acetate

Qualifier:

according to guideline

Guideline:

OECD Guideline 305 (Bioconcentration: Flow-through Fish Test)

GLP compliance:

yes

Radiolabelling:

yes

Details on sampling:

Collection of Water Samples:
Water samples were collected on pretest Days –10, -9, -8, -5 and -1 and on Days 0, 1, 4, 7, 14, 21, 28 and 33 of the uptake phase. Water samples were also collected on Days 1, 3, 7 and 10 of the depuration phase. Water samples were collected in glass vials from mid-depth in the test chamber using a volumetric pipette and were analyzed for total radioactivity. On Days 0, 7, 14, 21, 28 and 33 of the uptake phase, additional water was collected from mid-depth in the test chamber using a volumetric pipette into Teflon® centrifuge tubes containing hexane for the analysis of parent Verdox. All samples were processed immediately for analysis. Five water samples were collected at each sampling interval for the analysis of Verdox. On each sampling day, one water sample was analyzed from the control and two from each treatment group. Additionally, on Day 33 of uptake, two 1-L water samples were collected from each test chamber by siphoning from mid-depth into a graduated cylinder and stored frozen for possible metabolite identification in 2-L Nalgene® bottles. Prior to the beginning of the exposure period, adjustments were made to the dosing stock concentrations in an attempt to achieve the target test concentration in the test solutions for the study. Samples collected on Day –5 and Day –1 reflect the test conditions with the stock concentrations that were used during the uptake phase of the test.

Collection of Tissue Samples
Tissue samples were collected on uptake Days 0, 1, 4, 7, 14, 21, 28 and 33 of the 33-day uptake period, and on depuration Days 1, 3, 7 and 10 of the 10 day depuration period. At each tissue sampling interval, a sufficient number of fish were collected to provide at least two replicate samples of solvent control fish and four replicate samples of each Verdox treatment group. Fish were impartially removed from the test chambers and euthanized by making an incision from just posterior to the base of the pectoral fin dorsally through the spinal cord. The fish were blotted dry and measured for total length and wet weight within approximately 15 minutes of collection. Each fish was then dissected and divided into edible and non-edible tissues. The head, fins and viscera were removed from the body and were considered to be non-edible tissue. The remaining tissue was considered the edible tissue. Tissue samples were transferred to pre-weighed glass vials and weighed. All tissue samples were processed immediately or stored frozen.

Selected fish were collected to determine lipid content. Fish for lipid analysis were sampled prior to test initiation, on Day 33 of uptake and on Day 10 of depuration. All fish collected for lipid content were stored frozen until analysis.

Vehicle:

no

Details on preparation of test solutions, spiked fish food or sediment:

One stock was prepared using the 14C-labeled Verdox during the study by dissolving the test material in dimethylformamide (DMF). The radioactivity of the stock prepared was confirmed prior to use in the study by analyzing triplicate 10 µL samples of stock solution by liquid scintillation counting (LSC). The stock was found to have a concentration of 189 mg/L.

Six primary stock solutions of non-radiolabeled Verdox were prepared during the study on the same day dispensing stocks were prepared. The 1.0 mg/mL primary stock solutions were prepared in DMF by weighing a target amount of 0.100 g of test substance and bringing to a 100-mL final volume or a target amount of 0.500 g of test substance and bringing to a 500-mL final volume. The stocks were mixed by inversion. After mixing, the stock solutions appeared clear and colorless.

During the first two preparations, dispensing stock solutions were prepared at nominal concentrations of 0.017 and 0.17 mg/mL. After pretest analyses of the test solutions, stock concentrations were increased to compensate for loss of test material in the test system, in an attempt to achieve the targeted test concentrations in the test solutions. During the four subsequent preparations, dispensing stock solutions were prepared at nominal concentrations of 0.0567 and 0.567 mg/mL. The concentration of dispensing stocks was confirmed once prior to test initiation. An appropriate volume of the radiolabeled primary stock was used for each dispensing stock solution such that the radioactivity in the dispensing stock was approximately 350,000 dpm/mL in order to achieve a final nominal radioactivity in each of the aqueous exposure solutions of 35 dpm/mL. The remaining test material needed for each dispensing stock was added as the non-radiolabeled primary stock and DMF was added to bring the solution to a final volume as appropriate to achieve the nominal dispensing stock solution concentration. Dispensing stocks were prepared in 500 mL volumes.

The dispensing stock solutions were injected into the diluter mixing chambers (at a rate of 35 µL/minute) where they were mixed with well water (at a rate of 350 mL/minute) to achieve the desired aqueous test concentrations. The solvent control was achieved by injecting DMF into the diluter mixing chamber at the same rate.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

The rainbow trout, Oncorhynchus mykiss, was selected as the test species for this study based on past use history in the laboratory. Rainbow trout used in the test were obtained from Thomas Fish Company, Anderson, California and were hatched on February 16, 2009. Identification of the species was verified by the supplier.

During the 14-day period preceding the test, water temperatures ranged from 12.2 to 13.3°C, measured with a hand-held liquid-in-glass thermometer. The pH of the water ranged from 7.9 to 8.3, measured with a Fisher Scientific Accumet Model 915 pH meter. Dissolved oxygen ranged from 8.3 to 9.9 mg/L (≤77% of saturation), measured with Yellow Springs Instruments Model 85 dissolved oxygen meter. During this period, all fish showed no signs of disease or stress. At test initiation, the rainbow trout were collected from the holding tank and impartially distributed one to three at a time to the test chambers until each contained 85 fish.

Daily during the holding period and during the test, the rainbow trout were fed a commercially prepared diet (Salmon Starter) supplied by Zeigler Brothers, Inc., Gardners, Pennsylvania. Fish were not fed on the last day of the study.

All fish used in the test were from the same source and year class. Loading was defined as the total wet weight of fish per liter of test water that passed through the test chamber in 24 hours, and was determined to be 1.34 g fish/L/day. Instantaneous loading (the total wet weight of fish per liter of water in the tank) was 8.42 g/L. Loading was calculated based on the weight of fish sampled for tissue analysis on Day 0.

Route of exposure:

aqueous

Test type:

flow-through

Water / sediment media type:

natural water: freshwater

Total exposure / uptake duration:

33 d

Total depuration duration:

10 d

Hardness:

140 mg/L as CaCO3

Test temperature:

11.8 to 12.2 °C

pH:

7.8 to 8.5

Dissolved oxygen:

6.5 to 9.7 mg/L

TOC:

Total organic carbon (TOC) in the solvent control ranged from 42.74 to 50.37 mg/L, during uptake and 1.11 to 1.54 mg/L during depuration. The TOC in the dilution water ranged from 0.16 to 0.97 mg/L throughout the entire test.

Details on test conditions:

Test Initiation:
At test initiation, the rainbow trout were collected from the acclimation tanks and impartially distributed, using dip nets, one to three at a time to the test chambers until each contained 85 fish. When handling of the fish occurred it was done carefully, gently and quickly.

Test Apparatus:
A continuous-flow diluter was used to deliver the test substance to the test tank. A syringe pump (Harvard Apparatus, Massachusetts) was used to deliver the test substance stock solution into a mixing chamber prior to delivery to the test chamber. Syringe pump delivery volumes were verified prior to test initiation. The flow of dilution water to the test chambers was controlled by rotameters. The delivery of water from the rotameters was checked prior to the test and at approximately weekly intervals thereafter. Approximately 6 volume additions of test water were delivered to the test chambers every 24 hours. The general operation of the diluter was checked at least two times a day during the test, and at least once at the beginning and end of the test.

The test chambers were 127-L Teflon®-lined stainless steel aquaria filled with 80 L of test solution. On day 33 of uptake, the fish were transferred to a clean set of 59-L stainless steel aquaria filled with 42 L of dilution water (well water) for 10 days of depuration. The depth of the test water in one representative test chamber during uptake was approximately 18.1 cm. The depth of the test water in one representative test chamber during depuration was approximately 21.8 cm. Test chambers were positioned in a temperature-controlled water bath designed to maintain the target temperature throughout the test period. Two separate water baths were used for the uptake and depuration phases. Test chambers were siphoned daily during the test to remove excess feed, fecal matter, algae and bacterial growth. Test chambers were identified by the project number and test concentration.

Environmental Conditions:
Fluorescent light bulbs that emit wavelengths similar to natural sunlight were used for illumination of the test chambers. A photoperiod of 16 hours of light and 8 hours of dark was controlled with an automatic timer. A 30 minute transition period of low light intensity was provided when lights went on and off to avoid sudden changes in lighting. Light intensity at the surface of the water at the start of the uptake phase was 336 lux and was 317 lux at the start of the depuration phase. Light intensity was measured using a SPER Scientific Model 840006C light meter.

The target test temperature during the test was 12 ± 1 °C. Temperature was measured in the test chambers at the beginning and end of the test and at approximately weekly intervals during the test using a liquid in-glass thermometer. Temperature also was monitored continuously in the solvent control test chamber using a Fulscope ER/C Recorder, which was verified prior to test initiation and at approximately weekly intervals thereafter using a liquid-in-glass thermometer.

Dissolved oxygen measurements were made in the test chambers daily during the uptake and depuration phases using a Thermo Orion Model 850Aplus dissolved oxygen meter. Measurements of pH were made in each test chamber at the beginning and end of the test and approximately weekly during the test using a Thermo Orion Model 525Aplus pH meter.
Hardness, alkalinity and conductivity were measured in the solvent control at the beginning and end of the test, and approximately weekly during the test. Additionally, total organic carbon (TOC) was measured in the solvent control and dilution water at the beginning and end of the test and approximately weekly during the test. Hardness and alkalinity were measured by titration based on procedures in Standard Methods for the Examination of Water and Wastewater (4). Conductivity was measured using a Eutech Instruments, Acorn Series CON6 conductivity/temperature meter. Total organic carbon was measured using a Shimadzu model TOC-VCSH total organic carbon analyzer.

Nominal and measured concentrations:

- Target nominal: 1.7 and 17 µg/L
- Mean measured: 2.3 and 29 µg/L

Reference substance (positive control):

no

Details on estimation of bioconcentration:

The steady-state bioconcentration factor (BCF) values were determined from the mean tissue concentrations at apparent steady-state divided by the average water concentration. Tissue concentrations were considered to be at apparent steady-state if three or more consecutive sets of tissue concentrations were not significantly different (p>0.05). Tissue concentrations were evaluated for normality (Chi-Square Test) and homogeneity of variance (Levene’s Test) and were deemed normal with homogenous variances. Tissue concentrations were evaluated using All statistical tests were performed using a personal computer with The SAS System for Windows (5) software. Nonlinear regression was used to sequentially solve for k1 and k2 using fish tissue data from the uptake phase. These rate constants were used to calculate a kinetic bioconcentration factor (BCFK =k1/k2) and also to calculate half-life for clearance in tissue (t½) and, time to reach 90% of steady state (t90).
 
The kinetic uptake and depuration rate constants were determined using nonlinear regression described by Newman. In the sequential method, data from the depuration (elimination) phase was used to first estimate k2, and then using both the k2 estimate and fish tissue data from the uptake phase to estimate k1.

Lipid content:

8.4 %

Time point:

start of exposure

Remarks on result:

other: whole body

Lipid content:

6.5 %

Time point:

end of exposure

Remarks on result:

other: uptake phase whole body

Lipid content:

5.2 %

Time point:

end of exposure

Remarks on result:

other: depuration phase whole body

Key result

Conc. / dose:

2.3 µg/L

Temp.:

ca. 20

pH:

7

Type:

BCF

Value:

203 L/kg

Basis:

whole body w.w.

Time of plateau:

33 d

Calculation basis:

steady state

Remarks on result:

other: Conc.in environment / dose:2.3 µg/L

Key result

Conc. / dose:

29 µg/L

Temp.:

ca. 20 °C

pH:

7

Type:

BCF

Value:

179 L/kg

Basis:

whole body w.w.

Time of plateau:

33 d

Calculation basis:

steady state

Remarks on result:

other: Conc.in environment / dose:29 µg/L

Key result

Conc. / dose:

ca. 0.29 µg/L

Temp.:

ca. 20 °C

pH:

7

Type:

BCF

Value:

156 dimensionless

Basis:

whole body w.w.

Calculation basis:

other: based on 5% lipid content

Details on kinetic parameters:

- Uptake rate constant (k1): 57.6 day-1 at 2.3 µg/L and 81.8 day-1 at 29 µg/L
- Depuration (loss) rate constant (k2): 0.346 day-1 at 2.3 µg/L and 0.474 day-1 at 29 µg/L
- Uptake DT90: 6.6 days at 2.3 µg/L and 4.9 days at 29 µg/L
- Depuration DT50: 2.00 days at 2.3 µg/L and 1.46 days at 29 µg/L

Details on results:

Concentrations of 14C-Labeled Verdox in Water:
Measured concentrations of 14C-labeled Verdox in water samples collected prior to the test to verify the operation of the diluter are presented in Table 3. The measured concentrations of Verdox in the pretest samples collected eight days prior to initiation were
The measured concentrations of 14C-labeled Verdox ranged from approximately 109 to 164% of the target concentration in the low treatment group and 124 to 212% of the target concentration in the high treatment group. This resulted in an overall mean measured percent of target of 136 and 168% in the low and high treatment groups, respectively. The diluter system was checked periodically during the study and indicated that the correct test concentrations were being delivered to the test chambers. The results of the study were based on the mean measured test concentrations for the uptake phase of 2.3 and 29 µg/L, respectively.

The measured concentrations of 14C labeled Verdox in water during the depuration phase were below the LOQ in all samples collected except for one. On day 1, one sample from the high treatment group was measured at slightly above background.

Concentrations of 14C-Labeled Verdox in Fish Tissues:
The mean measured tissue concentration of 14C-labeled Verdox in edible, non-edible and whole fish at Day 33 of uptake was 151.3, 785.8 and 418.9 µg/kg, respectively at 1.7 µg/L. The steady-state BCF value based on total radioactivity and expressed µg Verdox equivalents/L was 65, 335 and 179 in edible, non-edible and whole fish tissue, respectively. Using nonlinear regression (7), similar kinetic BCF (BCFK) values were determined from total radioactivity data resulting in BCFK values of 65, 312 and 167 in edible, non-edible and whole fish tissue, respectively. The estimated time to reach 90% of steady state (t90) in edible, non-edible and whole fish was 13.5, 5.3 and 6.6 days, respectively. The mean measured concentration of 14C-labeled Verdox in edible, non-edible and whole fish by Day 10 of depuration was 10.1, 12.7 and 10.4 µg/kg, respectively, which is approximately 7, 2 and 2% of the mean tissue concentration at Day 33 of uptake. The estimated time to reach 50% clearance (t1/2 ) for edible, non-edible and whole fish tissue was 4.06, 1.61 and 2.00 days, respectively.
The mean measured tissue concentration of 14C-labeled Verdox in edible, non-edible and whole fish at Day 33 of uptake was 1926, 11664 and 5893 µg/kg, respectively at 17 µg/L. The steady-state BCF value based on total radioactivity and expressed µg Verdox equivalents/L was 66, 402 and 203 in edible, non-edible and whole fish tissue, respectively (Table 11). Using nonlinear regression (7), similar kinetic BCF (BCFK) values were determined from total radioactivity data resulting in BCFK values of 63, 328 and 173 in edible, non-edible and whole fish tissue, respectively. The estimated time to reach 90% of steady state (t90 ) in edible, non-edible and whole fish was 4.2, 4.8 and 4.9 days, respectively. The mean measured concentration of 14C-labeled Verdox in edible, non-edible and whole fish by Day 10 of depuration was 10.1, 165 and 68.9 µg/kg, respectively, which is approximately 0.5, 1 and 1% of the mean tissue concentration at Day 33 of uptake. The estimated time to reach 50% clearance (t1/2 ) for edible, non-edible and whole fish tissue was 1.28, 1.45 and 1.46 days, respectively.

Concentrations of Non-Radiolabeled Verdox in Water:
Measured concentrations of non-radiolabeled Verdox in water samples collected during the uptake phase are presented in Table 6. The measured concentrations of non-radiolabeled Verdox ranged from approximately 76.4 to 106% of the target concentration in the low treatment group and 102 to 117% of the target concentration in the high treatment group.

Observations of Mortality and Clinical Signs of Toxicity:
Observations of cumulative mortality and treatment-related effects are presented in Appendix 10. There was one mortality in the solvent control, two mortalities in the 1.7 µg/L group and one mortality in the 17 µg/L group. These mortalities were considered incidental and not treatment related. With the exception of one fish each in the solvent control group and the 29 µg/L treatment group observed with incidental tail injuries, all remaining fish appeared normal and healthy throughout the test.

Physical and Chemical Measurements of Water:
Water temperatures in the test chambers ranged from 11.8 to 12.2 °C, and both manual and continuous temperature measurements were within the range of 12 ± 1 °C established for the test . Dissolved oxygen remained ≥6.5 mg/L (60% of saturation) throughout the test. Measurements of water pH ranged from 7.8 to 8.5 during the test. Measurements of hardness, alkalinity and conductivity were typical of Wildlife International, Ltd. well water. Total organic carbon (TOC) in the solvent control ranged from 42.74 to 50.37 mg/L, during uptake and 1.11 to 1.54 mg/L during depuration. The TOC in the dilution water ranged from 0.16 to 0.97 mg/L throughout the entire test.

All test solutions appeared clear and colorless in the mixing chambers and test chambers at test initiation and termination during both the uptake and depuration phases

Reported statistics:

The steady-state bioconcentration factor (BCF) values were determined from the mean tissue concentrations at apparent steady-state divided by the average water concentration. Tissue concentrations were considered to be at apparent steady-state if three or more consecutive sets of tissue concentrations were not significantly different (p > 0.05). Tissue concentrations were evaluated for normality (Chi-Square Test) and homogeneity of variance (Levene’s Test) and were deemed normal with homogenous variances. Tissue concentrations were evaluated using the Tukey method of multiple comparisons. All statistical tests were performed using a personal computer with The SAS System for Windows software and TOXSTAT version 3.5. Linear regression of log concentration versus time during the depuration period was used to estimate k2. Nonlinear regression was then used to sequentially solve for k1 using concentrations of chemical in fish tissue from the uptake phase as described by Newman. These rate constants were used to calculate a kinetic bioconcentration factor (BCFK = k1/k2) and also to calculate half-life for clearance in tissue (t½) and, time to reach 90% of steady state (t90).

Validity criteria fulfilled:

yes

Conclusions:

The steady-state BCF values were 179 L/kg at 2.3 µg/L and 203 L/kg at 29 µg/L.

Executive summary:

The bioconcentration of Verdox in rainbow trout (Oncorhynchus mykiss) was determined in a GLP-compliant OECD guideline 305 study. In this flow-through test, groups of 85 fish were exposed for a 33 day uptake phase to nominal test concentrations of 0, 1.7 and 17 µg/L of the test substance followed by a 10 day depuration phase.

Steady-state concentrations of 14C-labelled Verdox were achieved in the tissues of rainbow trout (Oncorhynchus mykiss) after 33 days. The mean measured water concentrations based on total radioactivity were 2.3 and 29 μg/L. Steady-state BCF values for the 2.3 µg/L test concentration, based on total radioactivity Verdox concentrations were 65, 335 and 179 in edible, non-edible and whole fish tissue, respectively. Steady-state BCF values for the 29 µg/L test concentration, based on total radioactivity Verdox concentrations were 66, 402 and 203 in edible, non-edible and whole fish tissue, respectively. Verdox depurated quickly in fish tissue and ranged from 0.5 to 7% of Day 33 steady-state values by Day 10 of depuration.

Kinetic BCFK values derived by nonlinear regression for the 2.3 µg/L treatment group were 65, 312 and 167 for edible, non-edible and whole fish tissue, respectively. The time to reach 90% steady state based on kinetics was 13.5, 5.3 and 6.6 days and time to reach 50% clearance was 4.06, 1.61 and 2.00 days for edible, non-edible and whole fish tissue, respectively. The BCF whole fish of 203 will be used for the CSA.

Reference 2

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: read-across from a guideline study

Justification for type of information:

The read-across justification is presented in the Endpoint summary Bioaccumulation: aquatic / sediment. The accompanying files are also attached there.

Reason / purpose for cross-reference:

read-across source

Key result

Type:

BCF

Value:

156 L/kg

Basis:

whole body w.w.

Remarks on result:

other: read-across from Verdox

Description of key information

Dihydro Myrcenyl Acetate has a low potential for bioaccumulation based on read-across from Verdox, for which a BCF of 156 L/kg was determined in a study according to OECD TG 305.

Key value for chemical safety assessment

BCF (aquatic species):

156 L/kg ww

Additional information

The bioaccumulation potential is assessed based on read-across from Verdox to Dihydromyrcenyl acetate. The executive summary of the source information is presented below, followed by the read-across rationale.

Verdox bioaccumulation study

The bioconcentration of Verdox in rainbow trout (Oncorhynchus mykiss) was determined in a GLP-compliant OECD guideline 305 study. In this flow-through test, groups of 85 fish were exposed for a 33 day uptake phase to nominal test concentrations of 0, 1.7 and 17 µg/L of the test substance followed by a 10 day depuration phase. Steady-state concentrations of 14C-labelled Verdox were achieved in the tissues of rainbow trout (Oncorhynchus mykiss) after 33 days. The mean measured water concentrations based on total radioactivity were 2.3 and 29 ?g/L. Steady-state BCF values for the 2.3 µg/L test concentration, based on total radioactivity Verdox concentrations were 65, 335 and 179 in edible, non-edible and whole fish tissue, respectively. Steady-state BCF values for the 29 µg/L test concentration, based on total radioactivity Verdox concentrations were 66, 402 and 203 in edible, non-edible and whole fish tissue, respectively. Verdox depurated quickly in fish tissue and ranged from 0.5 to 7% of Day 33 steady-state values by Day 10 of depuration. Kinetic BCFK values derived by nonlinear regression for the 2.3 µg/L treatment group were 65, 312 and 167 for edible, non-edible and whole fish tissue, respectively. The time to reach 90% steady state based on kinetics was 13.5, 5.3 and 6.6 days and time to reach 50% clearance was 4.06, 1.61 and 2.00 days for edible, non-edible and whole fish tissue, respectively. The BCF whole fish of 203 will be used for the CSA.

Bioaccumulation of Dihydromyrcenyl acetate (CAS # 53767-93-4) based on read-across fromVerdox (20298-69-5)

 

Introduction and hypothesis for the analogue approach

 Dihydromyrcenyl acetate hasa C8 alk-1-ene chain with at C2 an acetate ester group and two methyl groups at C3 and C7 to which an acetate group is attached.For this substance there are no experimental bioaccumulation data available. According to REACH Annex XI 1.5 information can be generated by other means, i.e. applying alternative methods such as QSARs, grouping and read-across. For assessing the bioaccumulation potential of Dihydromyrcenyl acetate, the analogue approach is selected because for a related analogue, Verdox, bioaccumulation information is available which can be used for read-across.

Hypothesis: Dihydromyrcenyl acetate has the same bioaccumulation potential as Verdox.

Available information: For Verdox a bioaccumulation study with fish (rainbow trout) was performed using a flow-through exposure regime according to OECD TG 305 and in compliance with GLP criteria (Rel. 1).The steady-state BCF value at a test concentration of 29 µg/L Verdox, based on total radioactivity, was 203 L/kg in whole fish tissue. When converting this to a standard fish lipid content of 5% the BCF becomes 156 L/kg.

Target chemical and source chemical(s)

Chemical structures of the target chemical and the source chemical(s) are shown in the data matrix, including relevant physico-chemical properties.

Purity / Impurities

 Dihydromyrcenyl acetate is a mono-constituent with impurities similar to the parent substance and < 10%.

Analogue approach justification

According to Annex XI 1.5 read across can be used to replace testing when the similarity can be based on a common backbone and a common functional group. When using read across the result derived should be applicable for C&L and/or risk assessment and it should be presented with adequate and reliable documentation, which is presented below.

Analogue selection: For Dihydromyrcenyl acetate the analogue Verdox is found being a similar ester for which bioaccumulation information is available.

Structural similarities and differences: Dihydromyrcenyl acetate and Verdox have a similar hydrocarbon backbone with the same number of carbons and an ester as a functional group. The difference is that Dihydromyrcenyl acetate has an alkene chain while Verdox has a cyclohexyl-ring with a tert-butyl group. Both substances have an acetic ester, which will similarly hydrolyse/metabolise.

Bioavailability: Dihydromyrcenyl acetate and Verdox have similar physico-chemical characteristics and therefore very similar bioavailability: e.g. a measured water solubility (6.1 and 10 mg/l, respectively) and log Kows (4.9 and 4.75, respectively).

Bioaccumulation potential: For Dihydromyrcenyl acetate and Verdox the cleavage of the acetic ester bond by carboxyl esterases present abundantly in fish (Wheelock et al., 2008) will be the key feature for metabolism. BCFBAF (v3.01) predicts415 and 385 L/kg ww, respectively, further supporting the similar bioaccumulation potential of both substances and therefore the read across.

Other endpoints relevant for supporting the read across: Dihydromyrcenyl acetate is readily biodegradable supporting a low bioaccumulation potential. Verdox is not readily biodegradable and therefore may present a slightly more conservative BCF.

Uncertainty of the prediction: There is no remaining uncertainty other than those addressed above.

Data matrix

The relevant information on physicochemical properties and environmental characteristics are presented in the data matrix below.

Conclusions on hazard and risk assessment

For Dihydromyrcenyl acetate no experimental bioaccumulation information is available. For the analogue Verdox such information is available and this can be used for read across. When using read across the result should be applicable for classification and labelling and risk assessment as well as presented with reliable and adequate documentation. This documentation is presented in the current document. Verdox has a BCF of 156 (5% lipid content) and this information can be used for read across to Dihydromyrcenyl acetate.

Final conclusion: Dihydromyrcenyl acetate has a BCF of 156 L/Kg (5% lipid content).

 

Data matrix supporting the Bioaccumulation of Dihydromyrcenyl acetate using read across from Verdox

Common names	Dihydromyrcenyl acetate	Verdox
Source/target	Target	Source
Chemical structures
CAS no.	53767-93-4	20298-69-5
EINECS	258-751-7	243-718-1
REACH registration	2018	Registered
Empirical formula	C12H22O2	C12H22O2
Molecular weight	198	198.3
Phys-chem properties	IFF measured	IFF measured
Physical state	Liquid	Liquid
Vapour pressure (Pa)	14.4	9.72
Water solubility (mg/l)	6.1	10
Log Kow	4.9	4.75
Environmental fate
Bioaccumulation, BCF L/kg	156 (Read across)	156 L/kg (OECD TG 305, 5% lipid content)