2-ethyl-3-hydroxy-4-pyrone

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:

15 January 1993 - 12 February 1993

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

Adaptations in line with Birch, R. R., & Fletcher, R. J. (1991)

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

Secondary effluent from an unacclimatised activated sludge plant at URL North in Liverpool. The inoculum was 10% by volume and was filtered through a Whatman filter paper to remove the coarse particulate matter. The level of dissolved inorganic carbon was reduced by sparging the filtered effluent with nitrogen at pH 6.5.

Duration of test (contact time):

28 d

Initial conc.:

9.19 mg/L

Based on:

other: organic carbon

Parameter followed for biodegradation estimation:

inorg. C analysis

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Preparation stock solutions:
Stock solutions of the test substances with the exception of benzyl alcohol, were prepared by dissolving an appropriate mass in warm distilled water (approx. 55 °C) After shaking for 3 h in a closed vessel the stock solutions were filtered (Whatman 541 filter) and the total carbon (TC) concentration of the filtrate determined using an Ionics total carbon analyser. Since the test substance is volatile the acidification and sparging step in the analysis were omitted. Therefore, in order to determine the dissolved organic carbon concentration of the stock solutions, a water blank was also analysed by the same procedure to give an estimate of the total inorganic carbon content of the water used to prepare the stock solutions (assuming a minimal DOC content).

The DOC concentrations of the stock solutions were determined by subtractions of the water blank value from the TC values of the stock solutions. A 5 mL volume of each test substance stock solution was added to the appropriate test vessels. Benzyl alcohol was added directly using a high precision volumetric syringe. (1.2 µL)

TEST SYSTEM
- Culturing apparatus: 160 mL sealed vessels hypovials containing 100 mL mineral salts medium inoculated with secondary effluent and the respective test or reference substance. Vessels were incubated at 20°C on a rotary shaker.
- Number of culture flasks/concentration: 5 vessels per test/reference substance
- Method used to create aerobic conditions: The headspace in each vessel had 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.
- Measuring equipment: Ionics 555 Inorganic Carbon Analyser
- Test performed in closed vessels due to significant volatility of test substance: yes, sealed with butyl rubber septum and an aluminium crimp seal.

SAMPLING
- Sampling frequency: day 3, 7, 10, 14, 17, 21, 24, and 28
- Sampling method: Carbon dioxide was measured in the head space gas and inorganic carbon was measured in the liquid medium of 1 vessel. On the final test day more than one vessel is analysed for both the test compound and the control.

CONTROL AND BLANK SYSTEM
The control vessels are identical to the test vessel except for the omission of the test substance. Benzyl alcohol was used as reference substance.


The percentage biodegradation is given by:
(TICt – TICc) /TC * 100%

TICt = µg Total Inorganic Carbon in test bottle
TICc = µg Total Inorganic Carbon in control bottle
TC = µg organic carbon added to test vessel as test compound.

The total inorganic carbon is the summation of the results of the analysis of the liquid and gas phases of each bottle after reference to the appropriate inorganic standard curve.

Reference substance:

other: Benzyl alcohol

Test performance:

Benzyl alcohol achieved 95.8 % biodegradation at day 28 and the 60% pass level was reached within 10 days after achieving 10% biodegradation.

Key result

Parameter:

% degradation (inorg. C analysis)

Value:

104.4

Sampling time:

28 d

Remarks on result:

other: 95% CL: 100.2 - 108.5

Remarks:

based on 5 samples

Details on results:

The air temperature over the 28 day test period was in the range of 18 - 21 °C. The degradation showed 2.7, 79.4, 93.5, 99.4, 102.3, 108.5 and 105.6 at day 3, 7, 10, 14, 17, 21 and 24 days. The apparent biodegradation values in exess of 100% can be attributed to small inaccuracies associated with the analysis and subsequent extrapolation of values from the stock solutions to the actual test system.

Results with reference substance:

Benzyl alcohol achieved 95.8% biodegradation after 28-days and the 60% "pass"level was reached within 10 days of exceeding the 10% level. Confirming the suitability of the inoculum and the test conditions.

Validity criteria fulfilled:

yes

Remarks:

Most validity criteria are met. The substance is clearly readily bbiodegradable but raw data on replicates are not available and the pH measurements are not included in the report

Interpretation of results:

readily biodegradable

Conclusions:

The test substance exceeded the 60% pass level and met the 10 day window therefore, the test substance is considered readily biodegradable.

Executive summary:

The ready biodegradability was determined with a CO2 Evolution Test in accordance with OECD Guideline for Testing of Chemicals 301B and in compliance with GLP in a closed system. The test concentration was 15.5 mg/l Ethyl Maltol (9.19 mg/L organic carbon content). The test medium was inoculated with secondary effluent from a unacclimatised activated sludge plant. Carbon dioxide was measured in the head space gas and inorganic carbon was measured in the liquid medium on day 3, 7, 10, 14, 17, 21, 24, and 28. Benzyl alcohol was used as a reference substance and achieved 95.8% biodegradation after 28-days. The 60% "pass" level was reached within 10 days of exceeding the 10% level, confirming the suitability of the inoculum and the test conditions. After 28 days a biodegradability of 104.4% was measured for Ethyl Maltol with a 95% confidence interval of 100.2 – 108.5. The test substance exceeded the 60% pass level and met the 10 day window therefore, the test substance is considered readily biodegradable.

Description of key information

The ready biodegradability was determined with a CO2 Evolution Test in accordance with OECD Guideline for Testing of Chemicals 301B and in compliance with GLP in a closed system. The test concentration was 15.5 mg/l Ethyl Maltol (9.19 mg/L organic carbon content). The test medium was inoculated with secondary effluent from a unacclimatised activated sludge plant. Carbon dioxide was measured in the head space gas and inorganic carbon was measured in the liquid medium on day 3, 7, 10, 14, 17, 21, 24, and 28. Benzyl alcohol was used as a reference substance and achieved 95.8% biodegradation after 28-days. The 60% "pass" level was reached within 10 days of exceeding the 10% level, confirming the suitability of the inoculum and the test conditions. After 28 days a biodegradability of 104.4% was measured for Ethyl Maltol with a 95% confidence interval of 100.2 – 108.5. The test substance exceeded the 60% pass level and met the 10 day window therefore, the test substance is considered readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable