Pyridine-2,6-dicarboxylic acid

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

At one sampling point during the exponential degradation phase samples were tak-en after 4 days instead after 2 – 3 days. Because the available date were plausible and sufficient this can be stated as uncritical for the outcome of the study.

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Pyridine-2,6-dicarboxylic acid

EC Number:

207-894-3

EC Name:

Pyridine-2,6-dicarboxylic acid

Cas Number:

499-83-2

Molecular formula:

C7H5NO4

IUPAC Name:

pyridine-2,6-dicarboxylic acid

Test material form:

solid: crystalline

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

The sludge was taken from the activation basin of the ESN (Stadtentsorgung Neustadt) sewage treatment plant, Im Altenschemel, NW-Lachen-Speyerdorf.
Date of collection: 21. Apr. 2017, batch no: 20170421.
6.3.2.2 Pre-Treatment
The sludge was filtrated, washed with tap water (2x), then washed with and re-suspended in test medium. It was then aerated until use. The dry matter was determined as 4040 mg suspended solids/L.

Duration of test (contact time):

ca. 14 d

Initial test substance concentration

Initial conc.:

ca. 39.9 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

The medium was prepared from the stock solutions. The stock solution of the positive control was prepared and its DOC was measured. The inoculum was taken from its source, washed, aerated and the dry matter was determined.
The test vessels were filled with medium and inoculum. Then, all flasks were aerated for 72 hours with purified, CO2-free, moistened air to purge the system of CO2.

Reference substance

Reference substance:

aniline

Results and discussion

% Degradation

Key result

Parameter:

% degradation (CO2 evolution)

Value:

ca. 89.2

Sampling time:

14 d

Remarks on result:

other: St.dev. could not be determined

Any other information on results incl. tables

Degradation values in %

Day	Positive Control 1	Positive Control 2	Positive Control Mean	Test 1	Test 2	Test Mean	Abiotic Control	Toxicity Control
2	-0.6	1.5	0.5	11.1	2.0	6.5	2.4	2.0
4	17.9	21.2	19.5	33.8	21.4	27.6	1.8	45.5
8	55.6	69.1	62.3	87.9	76.0	81.9	1.0	81.6
10	68.8	80.7	74.7	94.0	83.1	88.6	0.6	86.3
14	84.4	86.7	85.5	98.3	91.2	94.7	0.4	89.2
18	85.0	84.7	84.8	96.5	90.3	93.4	0.4	88.1
23	86.8	85.4	86.1	98.2	88.6	93.4	0.1	88.8
29	86.4	82.9	84.6	98.2	88.9	93.5	-0.6	89.0

 

Because the values of day 29 are the sum of the IC values in scrubber flasks A and B, an increase (IC values in flasks B of the test higher than in those of the control) or a decrease (IC values in flasks B of the test lower than in those of the control) of degradation can be observed.

As the measured IC values in the abiotic control are very low, measurement uncertainties lead to negative degradation values while in fact no degradation has taken place.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

All validity criteria were met.
Degradation behaviour of positive control and toxicity control was normal. Abiotic degradation was not observed. Both replicates of the test item showed good correspondence.
If degradation in the toxicity flask is below 25% after 14 days, the test item can be considered as toxic towards the inoculum. As degradation in the toxicity flask was 89.2 % after 14 days, the test item can be stated as “not toxic towards the inoculum in a concentration of 39.9 mg/L”.
Ready degradability is defined in the guidelines as degradation surpassing 60% within 10 days after reaching a level of 10%. Therefore, the test item Dipicolinic acid (DPA) can be considered as “readily biodegradable”.
No observations were made which might cause doubts concerning the validity of the study outcome.
The result of the test can be considered valid.

Executive summary:

The test itemDipicolinic acid (DPA)was tested using a concentration of nominally 20 mg organic carbon/L (corresponding to 39.7 mg Dipicolinic acid (DPA)/L) in test medium following OECD 301B and EU-Method C.4-C. 

Aniline was chosen as positive control.

Activated sludge was used as inoculum (concentration in the test 25.0 mg dry matter/L). The test was left running for 28 days.

All validity criteria were met. Degradation of the positive control was 62 % after 8 days. 

The following data were determined for the test itemDipicolinic acid (DPA):

10-day-window:                                                                                                                 day 3 – 13
degradation at the end of 10-day-window                                                                              92 %
degradation at the end of the test                                                                                            94 %
pass level following guideline:          60% at the end of 10-day-window for pure substances

                                                                       respective 60 % at the end of the test for mixtures 

Therefore, when applying the 10-day-window, Dipicolinic acid (DPA)is readily biodegradable following OECD 301B and EU C.4-C respectively.