2,4-dimethyl-4-phenyltetrahydrofuran

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Remarks:

The test was extended from 28 to 56 days.

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

29 January to 25 March 1992

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

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

Version / remarks:

The test was conducted using a test design using sealed vessels, similar to what was later adopted as the OECD 310 guideline.

Deviations:

yes

Remarks:

The test duration was extended from 28 to 56 days.

Principles of method if other than guideline:

The sealed vessel test is a CO2 production test based on OECD Guideline 301B and recent studies conducted by the OECD aimed at harmonising the various tests of ready biodegradability. The ready test guidelines specify a maximum test duration of 28 days. If the test duration is extended to 56 days then the test is no longer an assessment of ready and ultimate biodegradability but is indicative of inherent and ultimate biodegradability, albeit under modified ready test conditions. This version of the sealed vessel test is not a recognised OECD/EEC test of inherent biodegradability. However, the test system is closed and it is therefore suitable for the examination of volatile materials.

GLP compliance:

yes (incl. QA statement)

Remarks:

GLP Compliance statement signed on June 17, 1993

Specific details on test material used for the study:

store at room temperature in the dark

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, industrial, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Secondary effluent from an unacclimatised activated sludge plant at URL North.

The inoculum used was 10% by volume of activated sludge plant secondary effluent. Filtered through a Whatman filter paper (541) to remove coarse particulate matter. The level of dissolved inorganic carbon (DIC) was reduced by sparging the filtered effluent with nitrogen after prior adjustment of the pH to 6.5. The test substances were added directly to the appropriate vessels with a high-quality liquid delivery syringe. The volume added (1-2 µl) is negligible compared to the total volume of 100 ml in each vessel and is not taken into consideration when determining the results. Analysis of both the headspace gas and the liquid medium for CO2/DlC was performed using an Ionics 555 Inorganic Carbon Analyser.

Duration of test (contact time):

56 d

Initial conc.:

10 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation:

inorg. C analysis

Reference substance:

other: mentioned but not specified

Key result

Parameter:

% degradation (inorg. C analysis)

Value:

28.5

Sampling time:

56 d

Remarks on result:

other: (20.8 - 36.2) (95% Confidence Limits)

The air temperature during the 56 da test period was in the range of 14 - 22°C. The percentage biodegradation of the test substances is 28.5% (20.8 - 36.2) with 95% confidence limits.

 

The test conditions employed in this study were based on those of the ready biodegradability test with the exception that the incubation period was extended from 28 to 56 days. Because of this modification the test cannot be considered as an assessment of ready biodegradability but it is an indicator of inherent and ultimate biodegradability. However, it must be noted that this modified sealed vessel test is not an OECD/EEC method for the assessment of inherent biodegradability and the results are not comparable. However, for the modified sealed vessel test a substance was considered to classify as inherently biodegradable if the extent of biodegradation (measured as CO₂ production) after 56 days was 60% or greater. This level was selected on the basis that as a pass criterium in tests of ready biodegradability 60% CO₂ production is equivalent to 70% Dissolved Organic Carbon (DOC) removal.

Validity criteria fulfilled:

not specified

Interpretation of results:

other: partial biodegradation (10-60 % CO2 production) under modified ready test conditions

Conclusions:

In a biodegradability test similar to OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test), test substance exhibited partial biodegradation 28.5 % (10-60% CO2 production) under modified ready test conditions.

Executive summary:

Biodegradability was evaluated for the test substance in a test similar to OECD Guideline 301 B (Ready Biodegradability: CO₂ Evolution Test).

 

The test used was based on the sealed vessel test which is suitable for determining the ready and ultimate biodegradability of organic substances. However, by extending the test duration to 56 days from 28 days it is possible to obtain an indication of the inherent biodegradability of a substance. The test is conducted in 160 ml vessels (hypo vials) containing 100 ml mineral salts medium inoculated with secondary effluent and the respective test or reference substance. Multiple vessels are prepared per substance sealed with a butyl rubber septum and an aluminium crimp seal. The headspace in each vessel has a volume of 60 ml and. When filled with air. contains approximately 6 times the mass of oxygen required for the complete oxidation of the substance.

 

From a knowledge of the initial organic carbon concentration added as test substance, the extent of mineralisation can be determined. Nominal carbon concentrations (unless specified otherwise) of the test substances were used based on the calculated percentage carbon (from molecular formula) and assuming 100% purity of the test compound.

 

The inoculum used was 10% by volume of activated sludge plant secondary effluent. Filtered through a Whatman filter paper (541) to remove coarse particulate matter. The level of dissolved inorganic carbon (DIC) was reduced by sparging the filtered effluent with nitrogen after prior adjustment of the pH to 6.5. The test substances were added directly to the appropriate vessels with a high-quality liquid delivery syringe. The volume added (1-2 µl) is negligible compared to the total volume of 100 ml in each vessel and is not taken into consideration when determining the results. Analysis of both the headspace gas and the liquid medium for CO₂/DlC was performed using an Ionics 555 Inorganic Carbon Analyser.

 

The air temperature during the 56 day test period was in the range of 14 - 22°C. The percentage biodegradation of the test substances is 28.5% (20.8 - 36.2) with 95% confidence limits. Test substance exhibited partial biodegradation (10-60% CO₂ production) under modified ready test conditions.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

11 March to 8 April 1991

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

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

GLP compliance:

yes (incl. QA statement)

Remarks:

GLP compliance statement included: Date of Report 22/07/96, signed on 24/07/96

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

The inoculum used was 10% by volume of activated sludge plant secondary effluent filtered through a Whatman filter paper (541) to remove coarse particulate matter. The level of dissolved inorganic carbon (DIC) was reduced by sparging the filtered effluent with nitrogen after prior adjustment of the pH to 6.5. The test substances were added directly to the appropriate vessels with a-high quality liquid delivery syringe. The volume added (1-2 µl) is negligible compared to the total volume of 100 ml in each vessel and is not taken into consideration when determining the results. Analysis of both the headspace gas and the liquid medium for CO2/DIC was performed on day numbers: 4, 8, 14, 22, 24, and 28 using an Ionics 555 Inorganic Carbon Analyser and the extent of biodegradation determined.- Source of inoculum/activated sludge: Secondary effluent from an unacclimatised activated sludge plant at URL North.

The inoculum used was 10% by volume of activated sludge plant secondary effluent filtered through a Whatman filter paper (541) to remove coarse particulate matter. The level of dissolved inorganic carbon (DIC) was reduced by sparging the filtered effluent with nitrogen after prior adjustment of the pH to 6.5. The test substances were added directly to the appropriate vessels with a-high quality liquid delivery syringe. The volume added (1-2 µl) is negligible compared to the total volume of 100 ml in each vessel and is not taken into consideration when determining the results. Analysis of both the headspace gas and the liquid medium for CO2/DIC was performed on day numbers: 4, 8, 14, 22, 24, and 28 using an Ionics 555 Inorganic Carbon Analyser and the extent of biodegradation determined.

Duration of test (contact time):

28 d

Initial conc.:

10 mg/L

Based on:

TOC

Reference substance:

other: not specified, only reference substance mentioned

Key result

Parameter:

% degradation (inorg. C analysis)

Value:

21.5

Sampling time:

28 d

Remarks on result:

other: 95%CI: -5.7 - 48.6

The air temperature during the 28-day test period was in the range of 18 - 22 °C. The percentage biodegradation is described in the table below.

 

Table 5.2.1/1: Percentage biodegradation of test substances

Day	% Biodegradation
4	-2.7
8	8.2
14	4.9
22	22.4
24	32.5
28	21.5
95% confidence interval	-5.7 to 48.6

 

Interpretation of results:

not readily biodegradable

Conclusions:

In a biodegradability test similar to OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test), test substance was found to be not readily biodegradable.

Executive summary:

Biodegradability was evaluated for the test substance in a test similar to OECD Guideline 301 B (Ready Biodegradability: CO₂Evolution Test).

 

The test used was the sealed vessel test which is suitable for determining the ready and ultimate biodegradability of organic substances. The test is conducted in 160 ml vessels (hypo vials) containing 100 ml mineral salts medium inoculated with secondary effluent and the respective test or reference substance. Multiple vessels are prepared per substance sealed with a butyl rubber septum and an aluminium crimp seal. The headspace in each vessel has a volume of 60 ml and, when filled with air, contains approximately 6 times the mass of oxygen required for the complete oxidation of the substance.

The sealed vessels are incubated at 20“C on a rotary shaker. At intervals during the 28-day test period a vessel is removed and concentration of carbon dioxide in the headspace gas determined. The seal is then broken and the concentration of inorganic carbon in the test medium is also determined. The total inorganic carbon in the vessel is calculated and corrected by subtracting the total inorganic carbon produced in a control. The control vessels are identical to the test vessels except for the omission of the test substance. From a knowledge of the initial organic carbon concentration added as test substance. the extent of mineralisation can be determined.

 

Nominal carbon concentrations (unless specified otherwise) of the test substances were used based on the calculated percentage carbon (from molecular formula) and assuming 100% purity of the named compound. 

 

From a knowledge of the initial organic carbon concentration added as test substance, the extent of mineralisation can be determined. Nominal carbon concentrations (unless specified otherwise) of the test substances were used based on the calculated percentage carbon (from molecular formula) and assuming 100% purity of the test compound.

 

The inoculum used was 10% by volume of activated sludge plant secondary effluent. filtered through a Whatman filter paper (541) to remove coarse particulate matter. The level of dissolved inorganic carbon (DIC) was reduced by sparging the filtered effluent with nitrogen after prior adjustment of the pH to 6.5. The test substances were added directly to the appropriate vessels with a-high quality liquid delivery syringe. The volume added (1-2 µl) is negligible compared to the total volume of 100 ml in each vessel and is not taken into consideration when determining the results. Analysis of both the headspace gas and the liquid medium for CO2/DIC was performed on day numbers: 4, 8, 14, 22, 24, and 28 using an Ionics 555 Inorganic Carbon Analyser and the extent of biodegradation determined.

 

The air temperature during the 28-day test period was in the range of 18 - 22°C. The percentage biodegradation of the test substances is 21.5% (-5.7 to 48.6) with 95% confidence limits. Test substance is not readily biodegradable.

Description of key information

OECD Guideline 301B, GLP, key study, validity 1
21.5% biodegradation after 28 days
Not readily biodegradable

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

Three experimental studies are available to assess the potential biodegradation of the registered substance.

In the key study, the ready and ultimate biodegradability of the test substance was examined in a CO2 evolution test which was conducted to a method largely in accordance with the OECD 301B, and in accordance with studies aimed at harmonising tests of ready biodegradability, and was conducted to GLP standard. The study was assigned a reliability score of 1, in accordance with Klimisch (1997). The test substance was assessed to have achieved 21.5 % (95 % CL of -5.7 to 48.6) degradation after 28 days. The test substance can therefore not be considered to be readily and ulimately biodegradable.

In the supporting study, assessing the ready biodegradability of the test substance, in a modified MITI test using activated sludge, the test substance was concluded to be not readily biodegradable. No biodegradation was observed. The study was conducted in accordance with the OECD 301C guideline and to GLP standard. It is included only as supporting data as the pre-treatment of the inoculum such as in the MITI test (OECD 301C) impacts on the diversity of the microbes and hence the MITI test often gives lower levels of biodegradation than other OECD ready tests. 

In a second supporting study, the biodegradability was evaluated for the test substance in a test similar to OECD Guideline 301 B (Ready Biodegradability: CO2Evolution Test). The test used was based on the sealed vessel test which is suitable for determining the ready and ultimate biodegradability of organic substances. However, the test duration was extended to 56 days from 28 days.  The air temperature during the 56 day test period was in the range of 14 - 22°C. The percentage biodegradation of the test substances is 28.5% (20.8 - 36.2) with 95% confidence limits. Test substance exhibited partial biodegradation (10-60% CO2 production) under modified ready test conditions.