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Environmental fate & pathways

Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
2008
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Read-across from an analogue substance for which a guideline study (KIimish = 1) is available.
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
See reporting format for the analogue approach attached.
Reason / purpose:
read-across source
Duration of test (contact time):
d
Key result
Parameter:
% degradation (CO2 evolution)
Value:
1
Sampling time:
28 d
Remarks on result:
other: Not readily biodegradable based on a read-across from an analogue substance.
Remarks:
See summary and cross reference to source.

The data matrix is included in the reporting format attached.

Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
Based on the read-across approach from the analogue OS 1600 which attained 1% biodegradation within 28 days, the substance OS2600 is considered not readily biodegradable.
Executive summary:

The ready biodegradability test was performed on the analogue substance OS1600 in accordance with OECD Guideline 301B and EU Method C4 -C using the carbon dioxide (CO2) evolution test (modified Strum test). The substance was tested in duplicate at 12 mg TOC/L (43 mg/2 litres). The ThCO2 of OS1600 was calculated to be 2.05 mg CO2/mg. Preparation was as much as possible performed under yellow light and/or dimmed light conditions. The test solutions with microbial and mineral components were continuously stirred during the test (28 days) to ensure optimal contact. The relative degradation values based on CO2 consumption calculated from the measurements performed during the test period revealed no significant degradation of OS1600 (1% biodegradation within 28 days). In the toxicity control, the test substance was found not to inhibit microbial activity. The study was considered to be valid. In conclusion, the test item designated as not readily biodegradable. Based on these results, the read-across approach was applied and the substance OS2600 was also considered to be not readily biodegradable.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
Conducted with the hydrolysis product MPKO.
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Qualifier:
according to
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, adapted
Details on inoculum:
The source of test organism was activated sludge freshly obtained from a municipal sewage treatment plant: Waterschap de Maaskant, s-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage. The freshly obtained sludge was kept under continuous aeration until further treatment. The concentration of suspended solids was 4.4 g/l in the concentrated sludge (information obtained from the municipal sewage treatment plant) Before use, the sludge was allowed to settle (83 minutes) and the liquid was decanted for use as inoculum at the amount of 10 ml/l of mineral medium.
Duration of test (contact time):
29 d
Initial conc.:
12 other:
Based on:
other: TOC/L
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
Pre-incubation medium:Mineral components, Milli-RO water (ca. 80% total volume) and inoculum (1% final volume) were added to each bottle. This mixture was aerated with synthetic air overnight to purge the system of CO2.
Type and number of bottles: Test suspension: containing test substance and inoculum (2 bottles). Inoculum blank: containing only inoculum (2 bottles). Positive control: containing reference substance and inoculum (1 bottle). Toxicity control: containing test substance, reference substance and
inoculum (1 bottle).
Preparation: The test substance and positive control were added to the bottles containing the microbial organisms and mineral components (ca. 80% of total volume). The volumes of suspensions were made up to 2 litres with MiIIi-RO water, resulting in the mineral medium described before. Three CO2-absorbers (bottles filled with 100 ml 0.0125 M Ba(OH), were connected in series to the exit air line of each test bottle.
Experimental CO2 production: The CO2 produced in each test bottle reacted with the barium hydroxide in the gas scrubbing bottle and precipitated out as barium carbonate. The amount of CO2 produced was determined by titrating the remaining Ba(OH), with 0.05 M standardized HCI (1 :20 dilution from 1 M HCI (Titrisol® ampul), Merck, Darmstadt, Germany).
Measurements: Titrations were made every second or third day during the first 10 days, and thereafter at least every fifth day until the 28th day. Each time the CO2-absorber nearest to the test bottle was removed for titration; each of the remaining two absorbers was moved one position in the direction of the test bottle. A new CO2-absorber was placed at the far end of the series. Phenolphthalein (1 % solution in ethanol, Merck, Darmstadt, Germany) was used as pH-indicator. On the 28th day, the pH of the test suspensions was measured and 1 ml of concentrated HCI (37%, Merck, Darmstadt,Germany) was added to each bottle. The bottles were aerated overnight to drive off CO2 present in the test suspension. The final titration was made on day 29.
Theoretical CO, production: The theoretical CO2 production was calculated from the molecular formula.
Measurements and recordings: pH- at the start of the test and on the 28th day. Temperature of medium: Continuously in a vessel with Milli-RO water in the same room. Electronic data capture: Observations/measurements in the study were recorded electronically using the following programme:
REES version 1.5 (REES scientific, Trenton, NJ, USA): Temperature.
Data evaluation: Relative degradation values were calculated from the cumulative CO2 production relative to the total expected CO2 production based on the total carbon content of the amount of test material present in the test bottles. A figure of more than 10% degradation was considered as significant. The relative degradation values were plotted versus time together with the relative degradation of the positive control. If applicable, the number of days is calculated from the attainment of 10% biodegradation until 60% biodegradation. Should this period be: 10 days (1 O-day window), then the test substance is designated as readily biodegradable. Toxicity control: if less than 25% degradation (based on ThC02) occurred within 14 days, the test substance was assumed to be inhibitory. The total CO2 evolution in the inoculum blank was determined by the cumulative difference (in
ml of titrant) between the blank Ba(OH)2 traps and fresh Ba(OH)2.
Reference substance:
other: sodium acetate
Key result
Parameter:
% degradation (CO2 evolution)
Value:
9
Sampling time:
28 d
Results with reference substance:
In the toxicity control more than 25% degradation occurred within 14 days (33%, based on ThC02). Therefore, the test substance was assumed not to inhibit microbial activity.
Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
2-Pentanone oxime (Methyl propylketoxime) was not readily biodegradable under the conditions of the modified Sturm test presently performed.
Executive summary:

The ready biodegradability test was performed with MPKO in accordance with OECD Guideline 301B and EU Method C4 -C using the carbon dioxide (CO2) evolution test (modified Strum test). The substance was tested in duplicate at 12 mg TOC/L (40 mg/2 litres). The ThCO2 of test item was calculated to be 2.17 mg CO2/mg. The test solutions with microbial and mineral components were continuously stirred during the test (28 days) to ensure optimal contact. The relative degradation values based on CO2 consumption calculated from the measurements performed during the test period revealed 4 and 12% degradation within 28 days. In the toxicity control, the test substance was found not to inhibit microbial activity. The study was considered to be valid. In conclusion, the test item was designated as not readily biodegradable.

Description of key information

Based on the read-across approach from the analogue OS 1600 which attained 1% biodegradation within 28 days, OS2600 was considered not readily biodegradable. A ready biodegradation test was also performed on MPKO, the hydrolytic product of OS2600. It was also considered to be not readily biodegradable (4-12% degradation within 28 days).

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

Key study: Read-across approach from experimental data on the analogue substance OS1600: The ready biodegradability test was performed in accordance with OECD Guideline 301B and EU Method C4 -C using the carbon dioxide (CO2) evolution test (modified Strum test) (GLP study). Sewage was exposed to 12 mg TOC/L (43 mg/2 litres) of test substance under aerobic conditions for 28 days. The relative degradation values based on CO2 consumption calculated from the measurements performed during the test period revealed no significant degradation (1% biodegradation within 28 days). Based on these results OS2600 was designated as not readily biodegradable.

Supporting study: The ready biodegradability test was performed with the analogue substance MPKO in accordance with OECD Guideline 301B and EU Method C4 -C using the carbon dioxide (CO2) evolution test (modified Strum test) (GLP study). Sewage was exposed to 12 mg TOC/L (40 mg/2 litres) of MPKO under aerobic conditions for 28 days. The relative degradation values based on CO2 consumption calculated from the measurements performed during the test period revealed 4 and 12% degradation within 28 days. The study was considered to be valid. In conclusion, the test item was designated as not readily biodegradable.