Fumaric acid

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:

November 2009 to April 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study conducted to GLP.

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Activated sludge was collected from a sewage treatment works A-2500 Baden, which has a waste-water catchment that is predominantly domestic. On arrival in the laboratory and after sedimentation the clear supernatant was decanted and the sludge was filled up with tap water to its original volume to reduce the carbon content. The sample was aerated by means of filtered compressed air before being used for the study.

The suspended solids concentration was determined by filtering a 5 mL sample through a pre-dried and pre-weighed glass filter (Whatman GF/C). The filter with solids were dried at 105 °C and re-weighed and the sludge solids determined by difference.

The inoculum was not acclimatised or adapted to "FUMARIC ACID" before exposure to the test substance in this study.

Duration of test (contact time):

> 0 - <= 28 d

Initial conc.:

ca. 36.2 mg/L

Based on:

test mat.

Initial conc.:

ca. 15 mg/L

Based on:

other: mg carbon/L

Initial conc.:

55 mg/L

Based on:

other: theorectical CO2 (ThCO2)/L

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

Pre-incubation: On day 1, an appropriate volume of prepared activated sludge was added to all flasks, which contained only mineral medium components and deionised water. The media were filled up to a total volume of 3000 mL with deionised water, to give a concentration of suspended solids of approximately 15 mg/L in the final inoculated mixture. The vessels were sealed and aerated overnight with CO2-free air to purge the medium of CO2 prior to the beginning of the study.
Apparatus for carbon dioxide scrubbing and a mixture of CO2-free oxygen and CO2-free nitrogen, from gas cylinders (Linde Gase, A-2492 Eggendorf), in the correct proportions (20 % O2: 80 % N2) were used. The air flow was regulated for each vessel individually. Air flow was determined volumetrically in intervals. Adjustments were made as necessary to maintain a flow rate in the range of 30 to 100 mL per minute (1 3 bubbles per sec). As an added precaution, a 0.0125 M barium hydroxide solution was used as CO2 absorber. On Day 0, the relevant vessels were opened to add the test or reference substance. The test substance was added to vessels A and TK, the reference substance was added to vessels PK and TK. The test solutions were continuously stirred during the test. The vessels were incubated in darkness until the end of the study and the medium continually supplied with CO2-free air. Barium hydroxide (Merck, D-64271 Darmstadt) was used to trap the CO2 formed by the degradation of the test substance. Three absorption bottles each containing 100 mL of 0.0125 M barium hydroxide solution, were connected in series to each 5-litre flask.
On the days of CO2 measurement, the barium hydroxide absorbers closest to the test vessels were disconnected. The remaining absorbers were moved up one position and a new absorber containing fresh barium hydroxide solution was placed at the far end of the series. In case a substantial precipitation was seen in the first trap, also the second bottle was analysed.
Test duration: 28 days exposure, with measurement of the last sample on Day 29.

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (CO2 evolution)

Value:

ca. 67.5

Sampling time:

28 d

Parameter:

% degradation (CO2 evolution)

Value:

ca. 60.3

Sampling time:

11 d

Remarks on result:

other: 10 day window

Details on results:

The mean degradation of "FUMARIC ACID" was 67.5 % after 28 days. More than 60 % (60.3 % based on the mean of two replicates) biodegradation was obtained within the 10 d window which started at about Day 1.

Results with reference substance:

The plateau of biodegradation was reached on about Day 11 and the degradation of the positive reference substance sodium benzoate exceeded the pass level of 60 % on about Day 11. The theoretical CO2 production of the positive control reached 60.1% on day 11.
Degradation in the toxicity control, which contained sodium benzoate and the test substance, was not indicative of an inhibition of the microbial activity by the test substance. The final biodegradation was 60.8 %.

Table 1: Biodegradation as percentage of the theoretical CO2yield

 

Elapsed time	test substance			Positive control	Toxicity control
day	A3	A4	mean	PK5	TK6
1	8.9	10.5	9.7	8.1	12.0
3	24.3	29.0	26.6	25.2	25.0
6	39.0	45.9	42.5	41.3	37.1
8	48.8	57.1	52.9	52.4	48.8
10	52.8	62.0	57.4	57.5	54.7
11	55.5	65.0	60.3	60.1	57.9
13	56.4	66.8	61.6	60.7	58.5
17	57.6	67.5	62.5	61.4	58.8
22	58.2	70.3	64.3	62.8	59.9
27	59.2	74.1	66.6	64.7	60.8
28	59.6	75.4	67.5	69.0	60.8

The positive control (sodium benzoate) only narrowly exceeded the pass threshold of 60% theoretical CO2 production (60.1% on day 11), a threshold it should - by definition as a readily biodegradable substance have reached easily. The similar performance of sodium benzoate and "FUMARIC ACID" is seen as a justification for considering "FUMARIC ACID" to be readily biodegradable, in spite of the slight contra-indication of the lower of the two replicates.

Another possible contributory factor to the scarce result of this study is the relatively high blank CO2 production mentioned at point 5.6. It is an underlying assumption of the test method that the background respiratory processes of the inoculum in the test and reference vessels are identical to those in the blank control where the inoculum is starved of external substrate. Blank CO2 production is therefore subtracted from the contemporary test and reference yields before calculating degradation percentages. However the assumption of parallel and identical background respiration is rather unrealistic, and when blank CO2 production is uncharacteristically high, there is a likelihood of over-correction and causing the calculated percentage degradation to appear lower than it really is.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

Fumaric acid is readily biodegradable.

Executive summary:

The ready biodegradability of fumaric acid was determined using the OECD 301B guideline in a GLP study reported in 2010.

Using a non adapted sludge from a domestic source the percentage of biodegradation observed comprised 60.1% after 11 days (i.e. within the 10d window) and 67.5% after 28 days. The reference substance (sodium benzoate) incubated under the same conditions showed a percentage biodegradation of 60.1% after 11 days. Incubation of the test substance and the reference substance demonstrated that the test substance did not significantly inhibit the microbial activity of the activated sludge.

Fumaric acid is readily biodegradable.

Description of key information

Fumaric acid is readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

The ready biodegradability of fumaric acid was determined using the OECD 301B guideline in a GLP study.

Using a non-adapted sludge from a domestic source the percentage of biodegradation observed comprised 60.1 % after 11 days (i.e. within the 10-d window) and 67.5 % after 28 days. The reference substance (sodium benzoate) incubated under the same conditions showed a percentage biodegradation of 60.1 % after 11 days. Incubation of the test substance and the reference substance demonstrated that the test substance did not significantly inhibit the microbial activity of the activated sludge.

Accordingly, fumaric acid is considered to be readily biodegradable.