Bis(2-ethylhexyl) adipate

Sediment toxicity

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

sediment toxicity: long-term

Data waiving:

other justification

Justification for data waiving:

other:

Reference 2

Endpoint:

sediment toxicity: short-term

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

13 - 17 Dec 1988

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: GLP Guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

other: ASTM E729-80: Standard practice for conducting acute toxicity test with fishes, macroinvertebrates and amphibians adopted in 1980

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

OVERLYING WATER
- Concentrations: Samples were taken from each replicate solution. Each exposure solution sample was collected from approximately the midpoint of the aquarium using a siphon comprised of glass and Silastic tubing. In addition, three quality assurance (QA) blind samples were prepared at each sampling interval and remained with the set of exposure solution samples through analysis.
- Sampling interval: at test inition and termination

Vehicle:

yes

Details on sediment and application:

PREPARATION OF SPIKED WATER
- Details of spiking: A clear, colorless stock solution of 10 mg/mL was prepared by adding the appropriate quantity of DOA to acetone to
volume in a volumetric flask (e.g., 1.0 grams DOA per 100 mL acetone). A Sage Syringe Pump was used to deliver the DOA stock solution into the diluter system where it was diluted (65% dilution factor) to provide the desired exposure concentration range. A similar system was used to deliver acetone to the solvent control aquaria.
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): acetone
- Concentration of vehicle in final test solution: 100 µL/L (in the highest treatment)

Test organisms (species):

other: Chironomus riparius, Gammarus fasciatus and Assellus spec.

Details on test organisms:

The midge larvae, (Chironomus riparius) used in this toxicity test were obtained from cultures maintained at SLS. The original culture stock was received at SLS on 27 November 1987. The culture water was from the same source as the dilution water used during the toxicity test. The midge culture area received a regulated photoperiod of 16 hours of light and 8 hours of darkness. Liqht at an intensity 32 - 60 footcandles was provided by Durotest Vitalite fluorescent bulbs. The culture vessel was a 57 L glass aquarium containing approximately 10 L of culture water and several centimeters of organic sediment. The culture received continuous gentle aeration and was fed daily a commercial fish food and chocolate blend. Room temperature was controlled to maintain the culture temperature at 20 ± 2°C.
The amphipods (Gammarus fasciatus) used in this toxicity test were collected in Wareham, Massachusetts on 6 December 1988. The organisms were maintained within SLS's laboratory for seven days prior to test initiation. The culture water was from the same source as the test dilution
water. The amphipod culture was maintained under a similar light regime as the midge culture. The culture vessels were 19 L glass aquaria each containing approximately 15 L of culture water and 5 cm detritus obtained from the organism collection site. Each vessel received continuous, gentle aeration and was fed a commercial fish food once daily. Room teroperature was controlled to maintain the culture solution temperature at 20 ± 2 °C.
The isopods (Asellus spec.) used in this toxicity test were collected in Wareham on 6 December 1988. The organisms were maintained with SLS's laboratory for seven days prior to test initiation. The culture water was from the same source as the test dilution water. All culture conditions were similar to the conditions previously described for the amphipod culture.

Study type:

laboratory study

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Duration:

96 h

Exposure phase:

total exposure duration

Hardness:

30 - 32 mg/L as CaCO3

Test temperature:

21 - 22 °C

pH:

6.7 - 7.6

Dissolved oxygen:

7.0 - 9.2 mg/L

Nominal and measured concentrations:

Nominal: 0.087, 0.14, 0.26, 0.38 and 0.73 mg/L
Measured (arith. mean): 0.087, 0.14, 0.26, 0.38 and 0.73 mg/L

Details on test conditions:

TEST SYSTEM
- Test container: glass aquarium (39 x 20 x 25 cm)

EXPOSURE REGIME
- No. of organisms per container (treatment): 10
- No. of replicates per treatment group: 2
- No. of replicates per control / vehicle control: 2
- Type and preparation of food: commercial fish food (Asellus, Gammarus, midge larvae were not fed)
- Amount of food: daily

RENEWAL OF OVERLYING WATER
- Details on volume additions: via an intermittent-flow proportional diluter. The diluter was constructed to deliver 0.5 L of exposure solution per cycle to each replicate test aquarium (39 x 20 x 25 cm) at a dilution ratio of 65%. Intermittent siphons placed on each aquarium drain caused a fluctuation of the aquarium volume between 4 and 9 cm depth, corresponding with 3.1 and 7.0 L volumes, respectively. This process ensured an exchange of test solution within the test organism exposure chambers. During the study, the diluter provided the exposure solutions at a rate of approximately 13 volume additions per aquarium per day. For each species, duplicate retention chambers, cylindrical glass jars (5.1 cm diameter, 10 cm high) containing two, 1.9 cm diameter holes covered with nylon screen (363 micrometer opening) were placed in each aquarium. Durinq each diluter cycle, 0.251 mL of the stock solution (10 mg/mL) was delivered from a 50-mL Glenco gas-tight glass syringe into a mixinq chamber containing 2.515 L of dilution water. Mixing was further promoted by continuous stirring using a teflon-coated, maqnetic stirring bar and ultrasonication for approximately 8
minutes between each diluter cycle. The 2.515 L solution was then siphoned from the mixing chamber into the diluter chemical cells. A solenoid valve, controlled by a float switch, regulated water flow into the dilution water cells. During each diluter cycle a flow-splittinq chamber was used between the diluter cells and the aquaria to promote mixing of the dilution water and solution containing DOA from the chemical cells. Within each flow-splitting chamber, two standpipes with umbrella siphons were employed to equally split the test solution between the duplicate aquaria and produce two replicates of five concentrations of the test material, a dilution water control and a solvent (acetone) control. Test aquaria were impartially positioned in a temperature-controlled water bath.
- Flow-rate: 13 aquarium volumes per day

OVERLYING WATER CHARACTERISTCS
- Type of water:
- Alkalinity: 24 - 29 mg/L
- Conductivity: 110 - 130 µmhos/cm
- Total organic chlorine compounds and PCBs: none

OTHER TEST CONDITIONS
- Light quality: Durotest Vitalite fluorescent bulbs
- Photoperiod: 16h light: 8h dark
- Light intensity: 30 -70 footcandles

EFFECT PARAMETERS MEASURED: Mortality was recorded after test periods of 0, 24, 48, 72 and 96h.

VEHICLE CONTROL PERFORMED: yes

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 0.73 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: for Chironomus riparius, Gammarus fasciatus and Assellus spec.

Details on results:

- Mortality of test animals at end of exposure period: Following 96 hours of exposure to the highest treatment level (0.73 mg/L DOA), mortality of 0 and 10% was observed among the exposed amphipods and isopods, respectively. Mortality of 5 to 35% was observed among the exposed midge larvae at all treatment levels and the controls. Since midge larvae are benthic organisms which are generally found burrowed in sediment, the mortalities observed during this study were determined tobe a response to the exposure condicions (i.e., absence of Sediment) and not related to the toxicity of DOA.

Throughout the exposure period a clear, colorless oily film was observed on the surface of the two highest treatment levels (0.73 and 0.38 mg/L).

The mean measured concentrations established a maximum test concentration of 0.73 mg/L which was consistent with the previously determined limit of water solubility for this material.

Validity criteria fulfilled:

yes

Conclusions:

Based on these data it was established that DEHA is not acutely toxic to the tested sediment dwelling invertebrates at concentrations equal to and greater than the material's limit of water solubility.

Description of key information

DEHA is unlikely to pose a risk for sediment organisms.

Additional information

Acute toxicity

One study investigating the toxicity to sediment organisms is available for Bis(2-ethylhexyl) adipate (CAS 103-23-1, DEHA). The study was performed according to ASTM guideline E729-80 (Standard practice for conducting acute toxicity test with fishes, macroinvertebrates and amphibians adopted in 1980) under GLP conditions. Chironomus riparius, Gammarus fasciatus and Asellus spec. were used as test organisms. Analytically verified test concentrations between 0.087 and 0.73 mg/L were applied using acetone as vehicle. Throughout the exposure period a clear, colorless oily film was observed on the surface of the two highest treatment levels (0.73 and 0.38 mg/L) indicating that the solubility in medium is lower. Due to the presence of the surface film of undissolved test material, the retention chambers were placed into the test solutions at test initiation and not removed during biological observations. This procedure prevented direct exposure of the organisms to undissolved test material. Following 96 hours of exposure to the highest treatment level (0.73 mg/L), mortality of 0 and 10% was observed among the exposed amphipods and isopods, respectively. Mortality of 5 to 35% was observed among the exposed midge larvae at all treatment levels and the controls. Since midge larvae are benthic organisms which are generally found burrowed in sediment, the mortalities observed during this study were determined to be a response to the exposure conditions (i.e., absence of sediment) and not related to the toxicity of the substance. The 96h-LC50 value for all tested species is determined to be > 0.73 mg/L.

Based on this data DEHA is considered to be not acutely harmful to sediment dwelling organisms up to solubility of the substance in water. 

 

Long-term toxicity

Since the substance is readily biodegradable and does not bioaccumulate, chronic exposure of sediment organisms is unlikely:

 

Intrinsic properties and fate

DEHA is readily biodegradable (> 90% in 28 days, BASF 1987). According to the Guidance on information requirements and chemical safety assessment, Chapter R.7b, readily biodegradable substances can be expected to undergo rapid and ultimate degradation in most environments, including biological Sewage Treatment Plants (STPs) (ECHA 2012a). Therefore, after passing through conventional STPs, only low concentrations of the substance is likely to be (if at all) released into the environment. Furthermore, the substance has a log Koc value of 4.56 and low water solubility (0.0032 mg/L). The Guidance on information requirements and chemical safety assessment, Chapter R7.b (ECHA 2012a) states that once insoluble chemicals enter a standard STP, they will be extensively removed in the primary settling tank and fat trap and thus, only limited amounts will get in contact with activated sludge organisms. Nevertheless, once this contact takes place, these substances are expected to be removed from the water column to a significant degree by adsorption to sewage sludge (Guidance on information requirements and chemical safety assessment, Chapter R.7a, (ECHA 2012b)) and the rest will be extensively biodegraded (due to ready biodegradability). Considering this one can assume that the availability of DEHA in the sediment environment is generally very low, which reduces the probability of chronic exposure of sediment organisms in general.

   

Bioaccumulation

DEHA is not expected to be bioaccumulative. If present in the aquatic compartment, biodegradation will occur and, depending on their log Pow, water solubility and adsorption potential, DEHA (and its metabolites) will be bioavailable to aquatic organisms such as fish mainly via water or on the other hand via feed and contact with suspended organic particles. After uptake by fish species, extensive and fast biotransformation of DEHA by carboxylesterases into adipic acid and via 2-ethylhexanol to 2-ethylhexanoic acid is expected. The alcohol is used by these organisms as their main source of energy throughout all the different life stages (early development, growth, reproduction, etc.). Adipic acid does not have the potential to accumulate in adipose tissue due to their low log Pow. The key study reports a BCF value of 27, which clearly indicate that rapid metabolism takes place even when log Pow values are above the trigger value of 3. Supporting BCF/BAF values, estimated using EPISuite and Catalogic models, confirm the experimental result (all well below 2000).

The information above provides strong evidence supporting the statement that rapid metabolism and low bioaccumulation potential can be expected for DEHA and its metabolites.

 

Conclusion

Since the substance is readily biodegradable, extensive degradation of this substance in conventional STPs will take place and only low concentrations are expected to be released (if at all) into the environment. DEHA will be bioavailable to sediment organisms mainly via feed and contact with suspended organic particles. The key study reports a BCF value of 27, which clearly indicate that rapid metabolism takes place even when log Pow values are above the trigger value of 3. Supporting BCF/BAF values, estimated using EPISuite and Catalogic models, confirm the experimental result (all well below 2000). Furthermore, aquatic toxicity data (including sediment organisms) show that no effects occur up to the limit of water solubility. Therefore, DEHA is unlikely to pose a risk for sediment organisms in general and long-term testing is thus omitted.