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Environmental fate & pathways

Biodegradation in water: screening tests

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Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Experimental Phase 04 May 2011 to 08 June 2011. Report issue: 02 August 2011.
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Report on substance meets the criteria for classification as reliable without restriction according to Klimisch et al (1997)
Justification for type of information:
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The read-across is based on the hypothesis that the Source and Target substances will have similar toxicological and ecotoxicological properties, due to their extremely close physico-chemical properties and structural similarities. For example, both the Source and Target substances are mono-constituents which share structural similarities and contain the same functional groups.
The Source substance has a comprehensive data set generated for a REACH Annex VII registration and this along with its similarity to the Target substance are considered sufficient to consider the read-across an appropriate adaptation to the standard information requirements of Annex VII of the REACH regulation for the Target substance in accordance with the provisions of Annex XI, 1.5 of the REACH regulation.
As can be seen from the structure the Source substance and the Target substance are structurally identical the difference lies in the salt form i.e. the counter ion. In the case of the Source substance the counter ion is a potassium ion whereas in the Target substance the counter ion is a hydrogen .
SOURCE TARGET
mono-constituent substance mono-constituent substance

Potassium salt
Free acid


Both the Source and Target substances have similar molecular weights of 1073 and 921 respectively. The difference in molecular weight is due to the counter ions. The Source substance is the potassium salt of the Target substance.


2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)

The Source and Target substance have similar purity profiles. Water is the main impurity in both substances. Both substances contain impurities that are analogues of the Source molecule. Neither substance contains purposely added diluents or additives.
The Source and Target are manufactured using the same chemical synthetic route. The difference in salt form is the difference between the two substances.

3. ANALOGUE APPROACH JUSTIFICATION
The Target substance is the free acid salt of the Source substance, hence the Target contains all the same functional groups as the Source substance. It is anticipated that the physicochemical results of the Target and the Source substance will be very similar.
It is expected that the water solubility of the Target Substance will be slightly lower than the Source substance, although environmental conditions will impact on the degree of solubility. Even though the water solubility values are differ , both the Source and Target substance are extremely water soluble and neither will have a tendency to partition into lipids or body fats. The potential for systemic absorption is considered to be low for both substances as their bioavailability is expected to be low due to the high molecular weights of the molecules and low lipophilicity, which precludes easy passage across biological membranes.
For the full read across assessment dossier see the attached Read-across assessment framework report


4. DATA MATRIX
See Read-Across Assessment Framework Report

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2011
Report Date:
2011

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, adapted
Details on inoculum:
- Source of inoculum/activated sludge: Totnes Sewage Treatment Works, Totnes, Devon, UK
- Storage conditions: Room temperature, aerated, maintained at pH 7.0 +/- 1 degree centigrade.
- Preparation of inoculum for exposure: Centrifuged, washed and resuspended in mineral medium
- Concentration of sludge: 30 mg/L
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Test temperature: 22 degrees centigrade +/- one degree
- pH: 6.7-7.5
- Continuous darkness: yes

TEST SYSTEM
- Measuring equipment: Oxitop respirometer
- Test performed in open system: no
- Details of trap for CO2 and volatile organics if used:CO2 absorbed by KOH solution in a seal cup in neck of bottle

SAMPLING
- Sample storage before analysis: ambient temperature
Reference substance
Reference substance:
benzoic acid, sodium salt
Remarks:
100 mg/L

Results and discussion

% Degradationopen allclose all
Key result
Parameter:
% degradation (O2 consumption)
Value:
< 5
Sampling time:
5 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
< 5
Sampling time:
10 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
< 5
Sampling time:
15 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
< 5
Sampling time:
20 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
< 5
Sampling time:
28 d

BOD5 / COD results

Results with reference substance:
Sodium benzoate attained a maximum mean level of biodegradation (based on BOD:ThOD ratio) of 67%. >60% degradation was acheived in the 10 day window.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
It is concluded that in this study the test substance failed to meet the criteria for ready biodegradability.
Executive summary:

Introduction.

A study was performed to assess the ready biodegradability of the test material in an aerobic aqueous medium. The method followed that described in the OECD Guidelines for Testing of Chemicals No 301F, "Ready Biodegradability; : Manometric Respirometry. Adopted 17 July 1992.

Methods.

The test material, at a concentration of 100mg/l , was exposed to activated sewage sludge micro-organisms with culture medium in sealed culture vessels in the dark at 21°C for 28 days. The degradation of the test material was assessed by the determination of carbon dioxide produced. Control solutions with inoculum and the standard material, sodium benzoate, together with a toxicity control were used for validation purposes.

Results and Conclusion.

The test material attained <5% degradation after 28 days and therefore cannot be considered to be readily biodegradable accordign to OECD Guideline No 301F.