Pyridine-2,6-dicarboxylic acid

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

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:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Deviations:

yes

Remarks:

the deviations can be considered uncritical

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

Sampling and analysis

Analytical monitoring:

yes

Test solutions

Vehicle:

no

Details on test solutions:

A stock solution containing 100.2 mg/L test item in algal medium (demineralised water enriched with minerals but without algae) was prepared. Lower test concentrations were prepared by dilution of the stock solution in algal medium.

Test organisms

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

The culture of Desmodesmus subspicatus was obtained in January 2016 by MBM Sciencebridge GmbH (Institut für Pflanzenphysiologie of Universität Göttingen). The algae are kept as stock culture on solid agar at 2 - 8 °C. From the stock culture, a permanent culture was prepared. From an aliquot of the permanent culture, the pre-culture was prepared.

Study design

Test type:

flow-through

Water media type:

freshwater

Total exposure duration:

72 h

Test conditions

Test temperature:

21.7 – 23.5 °C

pH:

ca. 8.8

Nominal and measured concentrations:

1 / 3.2 / 10 / 32 / 100 mg/L nominal concentration
The measured concentrations lay between 92 % and 125 % of the nominal concentrations in all treatments respectively between 92 % and 104 % in the concentrations to be used for evaluation. Therefore, the determination of the results was based on the nominal concentrations.

Reference substance (positive control):

yes

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

ca. 107.63 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: extrapolated

Effect concentrations 2

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

43.98 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 3

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Any other information on results incl. tables

Two experiments were performed. In the 1^stexperiment one of the validity criteria was not met. Therefore, the experiment was repeated. The results of the 1^stexperiment are not stated in the report, but will be kept together with the other raw data in the GLP archive of the test facility.

 

The study was performed using 5 concentrations ranging from 1.0 to 100 mg/L. Incubation time (test systemDesmodesmus subspicatus)was 72 hours. The cell concentration of each replicate was determined by measuring the cell numbers every 24 hours with an electronic particle counter. Growth rate µ and the yield[1] were determined from the cell number at the respective observation times.

 

In the 3 highest concentrated treatments a clear dose response relationship was observed. However in the 2 lowest concentrated treatments the cell number was strong scattering and in some replicated the algal cells were agglomerated. This effect was not caused by the test item because in the next highest test concentration no inhibition of algal growth was observed. Therefore, the two lowest treatments were not used for statistical evaluation.

 

At the start and at the end of the test, the content of the test item in the test solutions was determined using HPLC.

The measured concentrations lay between 92 % and 125 % of the nominal concentrations in all treatments respectively between 92 % and 104 % in the concentrations to be used for evaluation. Therefore, the determination of the results was based on the nominal concentrations.

 

The 72h-EC50s of potassium dichromate were determined in a separate reference test. For the estimation of the 72h-EC50s of the positive control, the fits showed sufficient statistical correspondence of the data with the dose-response-equation. The values were within the range of the laboratory.

 

The pH of the blank control should not fluctuate by more than 1.5 units. The change was 0.3 units in the blank control.

 

All validity criteria were met.

No observations were made which might cause doubts concerning the validity of the study outcome. The result of the test can be considered valid.

[1]Yield (according to OECD Guideline 201) is defined as the biomass at the end of the exposure period minus the biomass at the start of the exposure period. Calculation see under 8.2 Growth and growth inhibition are quantified from measurements of the algal biomass as a function of time. Algal biomass is defined as the dry weight per volume, e.g. mg algae/L test solution. However, dry weight is difficult to measure and therefore surrogate parameters are used. Of these surrogates, cell counts are most often used.

Parameter	Value	95% confidence interval
NOEC (Growth Rate) 72 h	10.00 mg/L	--
NOEC (Yield) 72 h	10.00 mg/L	--
LOEC (Growth Rate) 72 h	32.00 mg/L	--
LOEC (Yield) 72 h	32.00 mg/L	--
72h ErC10	43.98 mg/L	39.44 – 49.05 mg/L
72h EyC10	26.03 mg/L	21.15 – 32.02 mg/L
72h ErC50	107.63 mg/L (extrapolated)	93.37 – 122.88 mg/L
72h EyC50	50.28 mg/L	39.80 – 63.45 mg/L

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

Endpoint NOEC LOEC EC10 EC50
Growth Rate 10.00 mg/L 32.00 mg/L 43.98 mg/L 107.63 mg/L
(extrapolated)
Yield 10.00 mg/L 32.00 mg/L 26.03 mg/L 50.28 mg/L

Executive summary:

Two experiments were performed. In the 1^stexperiment one of the validity criteria was not met. Therefore, the experiment was repeated. The results of the 1^stexperiment are not stated in the report, but will be kept together with the other raw data in the GLP archive of the test facility.

 

The study was performed using 5 concentrations ranging from 1.0 to 100 mg/L. Incubation time (test system Desmodesmus subspicatus) was 72 hours. The cell concentration of each replicate was determined by measuring the cell numbers every 24 hours with an electronic particle counter. Growth rate µ and the yield[1] were determined from the cell number at the respective observation times.

 

In the 3 highest concentrated treatments a clear dose response relationship was observed. However in the 2 lowest concentrated treatments the cell number was strong scattering and in some replicated the algal cells were agglomerated. This effect was not caused by the test item because in the next highest test concentration no inhibition of algal growth was observed. Therefore, the two lowest treatments were not used for statistical evaluation.

 

At the start and at the end of the test, the content of the test item in the test solutions was determined using HPLC.

The measured concentrations lay between 92 % and 125 % of the nominal concentrations in all treatments respectively between 92 % and 104 % in the concentrations to be used for evaluation. Therefore, the determination of the results was based on the nominal concentrations.

 

The 72h-EC50s of potassium dichromate (K₂Cr₂O₇, CAS No. 7778-50-9) were determined in a separate reference test. The values lay within the range of the laboratory (growth rate 0.73 - 1.10 mg/L, yield 0.21 – 0.66 mg/L).

[1]Yield (according to OECD Guideline 201) is defined as the biomass at the end of the exposure period minus the biomass at the start of the exposure period. Calculation see under 8.2 Growth and growth inhibition are quantified from measurements of the algal biomass as a function of time. Algal biomass is defined as the dry weight per volume, e.g. mg algae/L test solution. However, dry weight is difficult to measure and therefore surrogate parameters are used. Of these surrogates, cell counts are most often used.