Registration Dossier

Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2017

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
liquid
Specific details on test material used for the study:
Lot No. : GR-86-6599-43
Purity : 96.5% (sum of the isomers, GC-MS)
Expiration date : September 05, 2017

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (Bois-de-Bay, Satigny, Switzerland) was used.

The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 minutes, discarding the supernatant and resuspending in mineral medium) and kept aerobic until being used on the same
Duration of test (contact time):
61 d
Initial test substance concentration
Initial conc.:
20 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
The method used is basically the one described under No. 301 F in the OECD Guidelines for Testing of Chemicals.

A measured volume of inoculated mineral medium, containing a known concentration of test substance as the nominal sole source of organic carbon, is stirred in a closed flask at a constant temperature (± 1°C) for up to 28 days. Evolved carbon dioxide is absorbed in sodium hydroxide pellets. The consumption of oxygen is determined by measuring the pressure drop in the respirometer flask. The Biological Oxygen Demand (BOD), amount of oxygen taken up by the microbial population during biodegradation of the test chemical (corrected for uptake by blank inoculum, run in parallel) is expressed as a percentage of ThOD (Theoretical Oxygen Demand, calculated from the elemental composition, assuming that carbon is oxidized to carbon dioxide, hydrogen to water and nitrogen to ammonium, nitrite or nitrate).
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

Test performance:
Everyday the oxygen consumption of each flask is recorded and correct temperature and stirring are checked.
At the end of the test period (normally 28 days), the pH of each flask is measured again.

% Degradation
Key result
Parameter:
% degradation (O2 consumption)
Value:
62
Sampling time:
28 d
Details on results:
Oxygen uptakes, as read on the Oxitop controller, are corrected to account for the small differences between actual and nominal concentrations of test and reference substances.

Oxygen uptake curves can be found in Appendix 1. Calculated % biodegradation curves and detailed results are reported in Appendixes 2 to 4.

Degradation of sodium benzoate exceeded 40% after 7 days and 65% after 14 days: the activity of the inoculum was thus verified (validity criterion).

The repeatability validity criterion (not more than 20% difference between replicates) is fulfilled. Therefore, the test is considered valid.

BOD5 / COD results

Results with reference substance:
Degradation of sodium benzoate exceeded 40% (observed = 72%) after 7 days and 65% after 14 days (observed = 77%): the activity of the inoculum was thus verified (validity criterion).

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
GR-86-6599 did not inhibit the intrinsic respiration of the inoculum at the test concentration and was therefore considered to be non-toxic to the inoculum at the test concentration.

GR-86-6599 undergoes 62% biodegradation after 28 days in the test conditions. The 10-day window criterion is not fulfilled (11% biodegradation on day 4 and 41% on day 14). The 10-day time window criterion was developed on the assumption that a test substance is degraded according to a “standard” growth curve in ready biodegradability tests. The OECD Guidelines for Testing of Chemicals, Section 3. Part 1: Principles and strategies related to the testing of degradation of organic chemicals (adopted 23 March 2006), states that if a substance consists of “constituents with different chain-lengths, degree and/or site of branching or stereo-isomers, even in their most purified commercial forms” and “it is anticipated that a sequential biodegradation of the individual structures is taking place, then the 10-day window should not be applied to interpret the results of the test.” The 10-day time-window should therefore not be applied as a pass / fail criterion for GR-86-6599, which is a mixture of isomers. Thus, GR-86-6599 should be regarded as readily biodegradable according to this test based on the biodegradation percentage of 62% at day 28.
Executive summary:

The Ready Biodegradability of GR-86-6599 was determined by the Manometric Respirometry Test.

GR-86-6599 did not inhibit the intrinsic respiration of the inoculum at the test concentration and was therefore considered to be non-toxic to the inoculum at the test concentration.

GR-86-6599 undergoes 62% biodegradation after 28 days in the test conditions.The 10-day window criterion is not fulfilled (11% biodegradation on day 4 and 41% on day 14).The 10-day time window criterion was developed on the assumption that a test substance is degraded according to a “standard” growth curve in ready biodegradability tests. The OECD Guidelines for Testing of Chemicals, Section 3. Part 1: Principles and strategies related to the testing of degradation of organic chemicals (adopted 23 March 2006), states that if a substance consists of “constituents with different chain-lengths, degree and/or site of branching or stereo-isomers, even in their most purified commercial forms” and “it is anticipated that a sequential biodegradation of the individual structures is taking place, then the 10-day window should not be applied to interpret the results of the test.” The 10-day time-window should therefore not be applied as a pass / fail criterion forGR-86-6599, which is a mixture of isomers.