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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Remarks:
test performed accoring OECD 301D guidelines
Adequacy of study:
key study
Study period:
17-01-2017 - 16-02-2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
See chapter 13 for Read across document
Reason / purpose for cross-reference:
read-across source
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
yes
Remarks:
only minor devation
Principles of method if other than guideline:
A minor deviation from the guidelines of the Closed Bottle test was introduced; ammonium chloride was omitted from the medium to prevent oxygen consumption due to nitrification (omission does not result in nitrogen limitation as shown by the biodegradation of the reference compound).
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
Secondary activated sludge (12-01-2017) was obtained from the wastewater treatment plant Nieuwgraaf in Duiven, The Netherlands. This plant 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 (van Ginkel and Stroo, 1992). The inoculum was not pre-adapted to the test substance.
Duration of test (contact time):
28 d
Initial conc.:
2 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Test procedures
The Closed Bottle test (OECD TG 301D) was performed according to the study plan. The study plan was developed from ISO Test Guidelines (1994). Use was made of 10 bottles con¬taining mineral salts medium and inoculum, 6 bottles con¬taining mineral salts medium, inoculum and sodium acetate, 10 bottles containing mineral salts medium, inoculum and test substance. The con¬centrations of the test substance and sodium ace¬tate 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 com¬pletely 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.
Reference substance:
acetic acid, sodium salt
Remarks:
SIGMA ALDRICH Batch no. BCBP8197V
Key result
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
28 d
Details on results:
Lack of biodegradation does not mean that Naphthalenesulfonic acid, bis(1-methylethyl)-, methyl derivs., sodium salt is recal¬citrant in nature. The stringency of the test procedures could account for the recalcitrance in the Closed Bottle test.

Toxicity

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 Naphthalenesulfonic acid, bis(1-methylethyl)-, methyl derivs., sodium salt to micro­organisms degrading acetate is not relevant. Inhibition of the endogenous respiration of the inoculum by the test substance at day 7 was not detected (Table I). Therefore, no inhibition of the biodegradation due to the "high" initial test substance concentration is expected.

 

Test conditions

The pH of the media was 7.3 at the start and the end of the test (control, and test). The pH of the media at day 28 remained 7.3 (control and test). Tem­peratures were within the prescribed temperature range of 22 to 24°C.

 

Validity of the test

The validity of the test is demonstrated by an endogenous respiration of 0.7 mg/L at day 28 (Ta­ble I). Furthermore, the differences of the replicate values at day 28 were less than 20%. The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 81 (Table II and Figure). Final­ly, the validity of the test is shown by oxygen concentrations >0.5 mg/L in all bottles during the test period.

Validity criteria fulfilled:
yes
Remarks:
endogenous respiration of 0.7 mg/L at day 28; differences of the replicate values at day 28 were less than 20%. Biodegradation sodium acetate, at day 14 was 81,oxygen concentrations >0.5 mg/L in all bottles during the test period.
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
Test performed according guidelines meeting specific criteria. Test performed under GLP and results well documented.
Naphthalenesulfonic acid, bis(1-methylethyl)-, methyl derivs., sodium salt was not biodegraded in the Closed Bottle test and should therefore not be classified as readily biodegradable.
Lack of biodegradation does not mean that Naphthalenesulfonic acid, bis(1-methylethyl)-, methyl derivs., sodium salt is recalcitrant in nature. The stringency of the test procedures could account for the recalcitrance in the Closed Bottle test.
Executive summary:

In order to assess the biotic degradation of Naphthalenesulfonic acid, bis(1-methylethyl)-, methyl derivs., sodium salt, a ready biodegradability test was performed which allows the biodegradability to be measured in an aerobic aqueous medium. The ready biodegradability was determined in the Closed Bottle test performed according to slightly modified OECD, EU and ISO Test Guidelines, and in compliance with the OECD principles of Good Laboratory Practice.

Naphthalenesulfonic acid, bis(1-methylethyl)-, methyl derivs., sodium salt was not biodegraded in the Closed Bottle test and should therefore not be classified as readily biodegradable. The lack of biodegradation in the Closed Bottle test does not mean that Naphthalenesulfonic acid, bis(1-methylethyl)-, methyl derivs., sodium salt is recalcitrant in nature because the stringency of the test procedures could account for the recalcitrance in the Closed Bottle test.

The test is valid as shown by an endogenous respiration of 0.7 mg/L and by the complete degradation of the reference compound, sodium acetate. Sodium acetate was degraded by 81% of its theoretical oxygen demand after 14 days. Finally, the most important criterion was met by oxygen concentrations >0.5 mg/L in all bottles during the test period.

Toxicity: No inhibition of the endogenous respiration of the inoculum by 2 mg/L test substance at day 7.

Description of key information

Sodium diisobutylnaphthalenesulphonate (CAS no.: 27213 -90 -7) is like its analogue Naphthalenesulfonic acid, bis(1 -methylethyl)-, methyl derivatives, sodium salts (CAS no.: 68909 -82 -0) not expected to be readily biodegradable.

Naphthalenesulfonic acid, bis(1 -methylethyl)-, methyl derivatives, sodium salts was not found to be readily biodegradable in the Closed Bottle Test.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

Sodium diisobutylnaphthalenesulphonate (CAS no.: 27213 -90 -7)is like its analogue Naphthalenesulfonic acid, bis(1 -methylethyl)-, methyl derivatives, sodium salts (CAS no.: 68909 -82 -0) not expected to be readily biodgradable.

Naphthalenesulfonic acid, bis(1-methylethyl)-, methyl derivatives, sodium salts has been tested in a closed bottle test according to OECD 301D. The substance was not found to be readily biodegradable.