[2-(1-ethoxyethoxy)ethyl]benzene

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

17-01-2017 until 20-03-2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

The biodegradation information of this source substance is used for read across to Hyacinth body.

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Secondary activated sludge was obtained from the wastewater treatment plant Nieuwgraaf in Duiven, The Netherlands, which is an activated sludge plant treating predominantly domestic wastewater. The activated sludge was preconditioned to reduce the endogenous respiration rates. To this end, 0.40 g Dry Weight (DW)/L of activated sludge was aerated for one week. The sludge was diluted in the bottles to 2.0 mg/L and the inoculum was not pre-exposed to the test substance.

Duration of test (contact time):

60 d

Initial conc.:

2 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Remarks:

as a percentage of ThOD

Details on study design:

Test bottles:
The test was performed in 0.30 L BOD (biological oxygen demand) bottles with glass stoppers.

Nutrients, stocks and administration:
The nutrient medium of the Closed Bottle test contained per liter of deionized water; 8.5 mg KH2PO4, 21.75 mg K2HPO4, 33.4 mg Na2HPO4·2H2O, 22.5 mg MgSO4·7H2O, 27.5 mg CaCl2, 0.25 mg FeCl3·6H2O. Accurate administering of the test substance was accomplished by preparing a solid stock of 3.0 mg of the test substance per g of silica gel in a 50-mL serum flask. Only part of the top layer of the silica gel was brought into contact with the test substance. The serum flask was closed with a screw top with aluminium foil and the content was mixed vigorously. Subsequently 0.2 g of silica gel with the test substance was added to the test bottles. The resulting concentration of test substance in the bottles was 2.0 mg/L. Next the bottles were filled with nutrient medium with inoculum and closed. Sodium acetate was added to the bottles using a stock solution of 1.0 g/L.

Test procedure:
Use was made of 10 bottles containing only inoculum, 10 bottles containing silica gel and inoculum, 10 bottles containing inoculum, silica gel, and test substance, and 6 bottles containing sodium acetate and inoculum. The concentrations of the test substance, and sodium acetate in the bottles were 2.0 and 6.7 mg/L, respectively. Each of the prepared solutions was dispensed into the respective group of BOD bottles so that all bottles were completely filled without air bubbles. The zero time bottles were immediately analyzed for dissolved oxygen using an oxygen electrode. The remaining bottles were closed and incubated in the dark. Two duplicate bottles of all series were withdrawn for analyses of the dissolved oxygen concentration at day 7, 14, 21, and 28. The test was prolonged by measuring the course of the oxygen decrease in the bottles of day 28 using a special funnel which fitted exactly in the BOD bottle. Subsequently, the oxygen electrode was inserted to measure the oxygen concentration. The medium dissipated by the electrode is collected in the funnel and flows back into the BOD bottle after withdrawal of the electrode, followed by removal of the funnel and closing the bottle.

Test conditions:
The pH of the media was 7.3 at the start of the test. The pH of the media at day 28 was 7.3 (controls) and 7.2 (test). Temperatures were within the prescribed temperature range of 22 to 24°C.

Reference substance:

acetic acid, sodium salt

Remarks:

Purity >99%

Test performance:

The validity of the test is demonstrated by an endogenous respiration of 0.7 mg/L on day 28. Furthermore, the differences of the replicate values on day 28 were less than 20%. The biodegradation percentage of the reference compound, sodium acetate, on day 14 was 80. Finally, the validity of the test is shown by oxygen concentrations >0.5 mg/L in all bottles during the test period.

Key result

Parameter:

% degradation (O2 consumption)

Value:

52

Sampling time:

28 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

71

Sampling time:

60 d

Parameter:

% degradation (O2 consumption)

Value:

4

Sampling time:

7 d

Parameter:

% degradation (O2 consumption)

Value:

37

Sampling time:

14 d

Parameter:

% degradation (O2 consumption)

Value:

42

Sampling time:

21 d

Parameter:

% degradation (O2 consumption)

Value:

63

Sampling time:

42 d

Details on results:

Hyacinth body #3 was biodegraded by 52% on day 28 in the Closed Bottle test. In the prolonged Closed Bottle test the test substance is biodegraded by 71% on day 60. A biodegradation in excess of 60% within the 60-day test period allows classification of Hyacinth body #3 as not persistent.

Results with reference substance:

The biodegradation percentage of the reference compound, sodium acetate, on day 14 was 80.

Inhibition of the degradation of a well-degradable compound, e.g. sodium acetate, by the test substance in the Closed Bottle test was not determined because possible toxicity of Hyacinth body #3 to microorganisms degrading acetate is not relevant. Inhibition of the endogenous respiration of the inoculum by the test substance on day 7 was not detected. Therefore, no inhibition of the biodegradation due to the "high" initial test substance concentration is expected.

Validity criteria fulfilled:

yes

Remarks:

Endogenous respiration on day 28 was 0.7 mg/L; the differences of the replicate values on day 28 were < 20%; the reference compound biodegradation on day 14 was 80; oxygen concentrations were >0.5 mg/L in all bottles during the test period.

Interpretation of results:

not readily biodegradable

Conclusions:

Hyacinth body #3 was biodegraded by 52% on day 28 in the Closed Bottle test. In the prolonged Closed Bottle test the test substance is biodegraded by 71% on day 60. A biodegradation in excess of 60% within the 60-day test period allows classification of Hyacinth body #3 as not persistent.

Executive summary:

In order to assess the biodegradation of Hyacinth body #3, a screening test was performed according to OECD TG 301D (Closed Bottle test) and under GLP conditions (Klimisch 1). In this study, secondary active sludge inoculum was exposed to 2 mg/L of the substance for 60 days. Hyacinth body #3 was not toxic to inoculum because it did not cause a reduction in the endogenous respiration. Furthermore, the validity criteria of the test were met. Hyacinth body #3 was biodegraded by 52% on day 28 in the standard Closed Bottle screening test, not being readily biodegradable. In the prolonged Closed Bottle test, the test item was biodegraded by 71% on day 60 (enhanced biodegradability testing). A biodegradation percentage of >60 within a 60 -day time period allows classification of Hyacinth body #3 as not persistent.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

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: The result derived from read across

Justification for type of information:

The read across justification for biodegradation is presented in the Endpoint summary Biodegradation in water: screening tests and the accompanying files are also attached there.

Reason / purpose for cross-reference:

read-across source

Key result

Parameter:

% degradation (O2 consumption)

Value:

52

Sampling time:

28 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

71

Sampling time:

60 d

Parameter:

% degradation (O2 consumption)

Value:

4

Sampling time:

7 d

Parameter:

% degradation (O2 consumption)

Value:

37

Sampling time:

14 d

Parameter:

% degradation (O2 consumption)

Value:

42

Sampling time:

21 d

Parameter:

% degradation (O2 consumption)

Value:

63

Sampling time:

42 d

Validity criteria fulfilled:

yes

Remarks:

adequate and reliable documentation on the read across is provided

Interpretation of results:

not readily biodegradable

Remarks:

not persistent

Conclusions:

Based on the results of the study performed according to OECD 301D for read-across substance Hyacinth body #3, Hyacinth body is not readily biodegradable and not persistent.

Description of key information

Biodegradation (read across from Hyacinth body #3 (CAS number 7493 -57 -4) tested in OECD 301D study): not readily biodegradable, not persistent.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

The biodegradation information for Hyacinth body is derived from Hyacinth body #3, a close analogue. First the biodegradation study of Hyacinth body #3 will be summarized below. Thereafter, the read-across justification is presented. The accompanying files are attached in the study record.

The OECD 301D biodegradation study with Hyacinth body #3 used for read-across to Hyacinth body:

In order to assess the biodegradation of Hyacinth body #3, a screening test was performed according to OECD TG 301D (Closed Bottle test) and under GLP conditions (Klimisch 1). In this study, secondary active sludge inoculum was exposed to 2 mg/L of the substance for 60 days. Hyacinth body #3 was not toxic to inoculum because it did not cause a reduction in the endogenous respiration. Furthermore, the validity criteria of the test were met. Hyacinth body #3 was biodegraded by 52% on day 28 in the standard Closed Bottle screening test, not being readily biodegradable. In the prolonged Closed Bottle test, the test item was biodegraded by 71% on day 60 (enhanced biodegradability testing). A biodegradation percentage of >60 within a 60 -day time period allows classification of Hyacinth body #3 as not persistent.

Hyacinth body (target; CAS no. 2556-10-7) and its biodegradability in water using read across information from Hyacinth body #3 (source; CAS no. 7493-57-4)

 

Introduction and hypothesis for the read across

Hyacinth body has a benzyl ring with an ethyl chain to which an acetal is attached and another ethyl chain. For this substance no experimental data on biodegradation in water are available. Therefore additional information is used in accordance with Article 13 of REACH where it is said that lacking information could be generated whenever possible by other means, i.e. applying alternative methods such as in vitro tests, SARs, grouping and read-across. For assessing the biodegradation of Hyacinth body (target) in water the analogue approach is selected because for one closely related analogue, Hyacinth body #3, reliable data on biodegradation in water are available which can be used for read across.

Hypothesis: Hyacinth body is expected to have similar biodegradability in water as its analogue Hyacinth body #3.

Available experimental information: The source chemical Hyacinth body #3 has biodegradability information from a reliable OECDTG301D screening test (K. 1). The biodegradation percentage was 52 at day 28 and 71% at day 60. The substance is therefore not readily biodegradable, however also not persistent.

Target and Source chemical(s):

Chemical structures of the target chemical (Hyacinth body) and the source chemical (Hyacinth body #3) are shown in data matrix, including physico-chemical properties and other information, considered relevant for the biodegradability of both substances.

Purity / Impurities:

Hyacinth body and Hyacinth body #3 are mono-constituents. The impurities in both target and source are all below 2 %.

Analogue approach justification

According to REACH Annex XI, an analogue approach can be used to replace testing when information from different sources provides sufficient evidence. The result derived should be applicable for C&L and/or risk assessment and be presented with adequate and reliable documentation.

Analogue selection: Hyacinth body #3 was selected as an analogue, being the very close analogue (it has just one carbon more than Hyacinth body) and being a substance from IFF portfolio, for which the adequate data are available.

Structural similarities and differences: The target chemical, Hyacinth body and the source chemical, Hyacinth body #3 have the same backbone and same functional group being an acetal. The structural difference is that Hyacinth body #3 has an additional aliphatic CH₂group compared to Hyacinth body (propoxy compared to ethoxy).

Bioavailability: The molecular weights of the target and source are very similar (194.28 and 208.30, respectively). The water solubility of Hyacinth body is somewhat higher and the log Kow somewhat lower compared to Hyacinth body #3, which can be expected due to the additional CH₂group in Hyacinth body#3. Therefore, the read across is considered conservative.

Biodegradability: Because of the very high similarity in structure, it is expected that both substances will present similar biodegradability behaviour.

Remaining uncertainties: There are no remaining uncertainties other than which are discussed above.

Conclusions for biodegradation

When using read across the result derived should be applicable for C&L and/or risk assessment and be presented with adequate and reliable documentation. The source substance Hyacinth body #3 is not readily biodegradable and therefore the target substance Hyacinth body is also not readily biodegradable based on similarities in structure and physico-chemical properties.

Final conclusion on ready biodegradability: Hyacinth body is ‘not readily biodegradable’ but ‘not persistent’.

Data matrix for the read across from Hyacinth body #3 to Hyacinth body

CHEMICAL NAME	Hyacinth body	Hyacinth body #3
Molecular structure
CAS	2556-10-7	7493-57-4
REACH registration	For 2018	For 2018
Einecs	219-868-9	231-327-9
Tanimoto*	1	0.93
Molecular weight	194.28	208.30
Physico-chemical properties
Appearances	Liquid	Liquid
Melting point (°C)	<-20 (IFF, 2015)	<-20 (IFF, 2015)
Boiling point (°C)	248.2 (IFF, 2015)	263.4 (IFF, 2015)
Vapour pressure (Pa, at24^oC)	3.1 (IFF, 2015)	0.60 (IFF, 2015)
Water solubility (mg/L, at 20˚C)	453 (IFF, 2015)	86.0 (IFF, 2015)
LogKow	3.5 (IFF, 2015)	4.1 (IFF, 2015)
LogKow (calculated**)	2.91	3.40
Biodegradation
OECD TG301D 28 d (% biodeg)	Not readily biodegradable (read across from Hyacinth body #3)	52 (not readily biodegradable)
OECD TG301D 60 d (% biodeg)	Not persistent (read across from Hyacinth body #3)	71 (not persistent)

* The Tanimoto similarity of the selected analogue to Hyacinth body was calculated using Chemmine tools: http://chemmine.ucr.edu/similarity/

** Calculated in EPISuite