Bicyclo[3.1.1]hept-2-ene, 2,6,6-trimethyl-, phosphosulfurized

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 15 January 2016 to 21 March 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Deviations:

yes

Remarks:

Temperature variance slightly outside of recommended range

Principles of method if other than guideline:

The guideline states that the required temperature of the test is 22 ± 2 °C. However, the actual temperature range recorded was 18.4-24.0 ºC. This deviation is expected to have no effect on the outcome of the study.

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

The activated sludge was obtained from Cambridge Sewage Treatment works on the 19th January 2016. It was pre-treated by being sieved through a 850 µm sieve to remove coarse particulates, allowed to settle and then centrifuged at around 4000 rpm for between 5 and 10 minutes. The supernatant was removed and discarded and the sludge resuspended in de-chlorinated water before another centrifugation at around 4000 rpm for between 5 and 10 minutes. This process was repeated once more and the pellet homogenised by mechanical stirring with a spoon at a concentration of 7.5 %.

Duration of test (contact time):

60 d

Initial conc.:

10 - 20 mg/L

Based on:

other: Total organic carbon

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

2000 mL conical flasks were filled with 1500 mL inoculated mineral medium. The test material was added to appropriate bottles at a concentration of 15 and 20 mg carbon/L. Due to the poor solubility of the test substance it was weighed onto glass microscopes cover slips which were then added directly to the test flasks. Air was pumped into a vessel of soda lime which removed any external carbon dioxide before being funnelled into the test flask. The air then passed through two carbon dioxide traps of 0.05 M sodium hydroxide solution. This was allowed to stand for 60 days. The percent biodegradation was then calculated by knowing the total carbon content of the test item at the start and how much was in the carbon dioxide traps over time. This was repeated twice, giving two replicates that a mean can be drawn from.

Reference substance:

other: Sodium acetate

Parameter:

% degradation (CO2 evolution)

Value:

0

Sampling time:

7 d

Remarks on result:

other: mean

Parameter:

% degradation (CO2 evolution)

Value:

5

Sampling time:

19 d

Remarks on result:

other: mean

Parameter:

% degradation (CO2 evolution)

Value:

10

Sampling time:

28 d

Remarks on result:

other: mean

Parameter:

% degradation (CO2 evolution)

Value:

14

Sampling time:

42 d

Remarks on result:

other: mean

Parameter:

% degradation (CO2 evolution)

Value:

24

Sampling time:

61 d

Remarks on result:

other: mean

See background material.

Validity criteria fulfilled:

yes

Interpretation of results:

not inherently biodegradable

Conclusions:

After 60 days in activated sludge only 24 % of the test substance was reported to have degraded.

Executive summary:

The ready biodegradation of the test substance was analysed according to OECD guideline 301B. Due to the low water solubility of the test item, it was spread across the surface of a glass coverslip and then added into the inoculated mineral medium. The carbon dioxide given off was collected and quantified by Non-Dispersive Infrared (NDIR). The test was originally run for 28 days but then extended to 60 days due to the slow degradation. The toxicity control showed 34 % degradation in 14 days indicating that the test item is not inhibitory to the degrading organisms. At the end of the 60 days only 24 % of the test substance was reported to have degraded meaning the test substance is not readily biodegradable under the conditions of this test.

Description of key information

A study was performed on the registered substance. It was found not to be readily biodegradable with a biodegradation of 24 % after 60 days according to the OECD guideline 301B.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

The substance was found to not be readily biodegradable according to the OECD guideline 301B. Due to the low water solubility of the test item it was spread across the surface of a glass coverslip which was then added into the inoculated mineral medium. By day 14 the toxicity control was found to have 34 % biodegradation, indicating that the test item is not inhibitory to the degrading organisms. Under the test conditions, the substance was found to be not readily biodegradable after 28 days showing an average of 10 % degradation from 2 replicates. The study was extended to 60 days and upon analysis at termination showed and average of 24 % degradation. The results from the test concluded that the substance is not readily biodegradable.