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Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From November 21, 2017 to January 19, 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
GLP compliance:
yes
Test material information:
Composition 1
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, adapted
Details on inoculum:
- Source of activated sludge: Joint Abbotsford Mission Environmental System (JAMES) wastewater treatment plant, Abbotsford, BC.
Duration of test (contact time):
28 d
Initial conc.:
65.3 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
- Test temperature: 20°C
- Suspended solids concentration: ~20 mg/L
Reference substance:
benzoic acid, sodium salt
Remarks:
Sodium benzoate (CAS No. 532-32-1)
Parameter:
% degradation (O2 consumption)
Remarks on result:
other: I850 cannot be considered readily biodegradable under the test conditions as I850 did not enter the 10 day window and a result did not surpass 60% biodegradation by the end of the 10-day window.
Results with reference substance:
At Test completion (Day 28), the biodegradation was 76%.

At the end of the test, the difference between replicates was 13%. At Day 14 during the study, the biodegradation of the Reference Item was 74% and the percent biodegradation in the Toxicity Control was 48%. The mean oxygen uptake of the blanks was 17.9 mg O2/L. The pH values were 7.1-7.6 between test initiation and completion.

 

Table 1. Percent Biodegradation of the Test and Reference Items

Treatment

Biodegradation at Start of 10-day Window

Biodegradation at End of 10-day Window***

Biodegradation at Day 14*

Biodegradation at Test Completion (28-d)

Test 1

6%

N/A

 

6%

Test 2

14%

N/A

 

19%

Mean

10%

N/A

 

13%

Reference Item

 

 

74%

76%

Toxicity Control**

 

 

48%

50%

*     Validity criteria for Reference Item and Toxicity Control are measured on Day14.

**  Calculation of biodegradation in the Toxicity Control is based on the combined ThOD value for the Reference Item and Test Item.

*** Biodegradation at the End of the 10 day window could not be determined as the test ended on day 7 of the 10 day window.

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
According to OECD 301F test method, I850 was not be considered readily biodegradable.
Executive summary:

This test using the procedures outlined in the Maxxam Study Plan for TOX1739 which is based on the SOP for the OECD 301F (BBY2 SOP-00023) and OECD 301F (OECD, 1992). The results of this OECD 301F test for I850 show that all validity criteria were met. I850 cannot be considered readily biodegradable under the test conditions as I850 did not enter the 10 day window and a result did not surpass 60% biodegradation by the end of the 10-day window. Due to the stringency of this test, test items which do not achieve pass levels may still be biodegradable in the environment.

Description of key information

Not readily biodegradable. (OECD TG 301F).

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed
Type of water:
freshwater

Additional information

At the end of the test, the difference between replicates was 13%. At Day 14 during the study, the biodegradation of the Reference Item was 74% and the percent biodegradation in the Toxicity Control was 48%. The mean oxygen uptake of the blanks was 17.9 mg O2/L. The pH values were 7.1-7.6 between test initiation and completion. All test validity criteria were met. I850 cannot be considered readily biodegradable under the test conditions as I850 did not enter the 10 day window and a result did not surpass 60% biodegradation by the end of the 10-day window. Due to the stringency of this test, test items which do not achieve pass levels may still be biodegradable in the environment.