1H-Pyrrolo[2,3-b]pyridine, 5-bromo-

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

Study period:

2010-02-01 to 2010-02-05

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Study conducted in compliance with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. The study report was conclusive and done to a valid guideline. However, the highest nominal concentration exceeded the water solubility of the test substance.

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2010

Reference 2

Reference Type:

other: Report Amendment

Title:

Unnamed

Year:

2014

Report date:

2014

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

5-bromo-1H-pyrrolo[2,3-b]pyridine

EC Number:

629-247-8

Cas Number:

183208-35-7

Molecular formula:

C7H5BrN2

IUPAC Name:

5-bromo-1H-pyrrolo[2,3-b]pyridine

Test material form:

solid: particulate/powder

Remarks:

migrated information: powder

Details on test material:

White to off white powder
Purity >99%

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

HPLC analyses of the test substance concentrations were conducted at the beginning and after 24, 48 and 72 h of exposure, respectively. Effect concentrations (ECx) were based on the time weighted average values.

Test solutions

Vehicle:

yes

Details on test solutions:

Based on the results of a non-GLP range finding test with 1, 10, and 100 mg/l nominal concentrations, a definitive test with 6.25, 12.5, 25, 50 and 100 mg/l nominal concentrations of the test substance was performed. A stock solution of the test substance was prepared in acetone. Respective amounts of this acetonic stock solution were transferred to empty glass vessels. After complete evaporation of the solvent under a stream of compressed air, the OECD medium was added to give the respective nominal test concentrations.
The solutions were moderately stirred for 24 h at room temperature. After this incubation time the undissolved material was removed by sterile filtration (0.45 pm) to obtain sterile test substance solutions for the algal test. The resulting water accommodated fractions were used in the test.
The pH of the OECD medium was not adjusted before the test. Blanks of test medium without test substance served as controls. Three replicates for each concentration of the test substance and five replicates for the blank control were prepared. An exponentially growing preculture of algae is used to inoculate sterile test flasks. Test flasks are placed on an orbital shaker at a nominal shaking speed of about 140 revolutions per min.

Test organisms

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

The test organism used for the study was axenic slope culture of Desrnodesrnus subspicatus 86.81 SAG (Collection of Algal Cultures, Institute of Freshwater Ecology, University of Göttingen, 0-37073 Göttingen, Germany

Study design

Test type:

static

Water media type:

freshwater

Total exposure duration:

72 h

Test conditions

Hardness:

not stated

Test temperature:

22 +/- 2 °C

pH:

Not adjusted. The pH of the algal medium was 8.0 +/- 0.2.

Nominal and measured concentrations:

Time weighted average concentrations of 3.35, 7.52, 16.2, 23.7 and 38.6 mg/l were measured for the nominally applied concentrations of 6.25, 12.5, 25, 50 and 100 mg/l, respectively. Hence, with increasing nominal concentrations a lower percentage of the test substance was dissolved. However, on average the concentration remained at about 70% of the concentration measured at the beginning of the test and hence was stable during the test. The water solubility of the test substance was 66.4 mg/L.

Details on test conditions:

Test vessel: 250 ml flasks, all-glass, with 100 ml of test medium, shaken (125 rpm)
Recommended OECD medium
Preculture:Exponentially growing liquid culture of Desrnodesrnus subspicatus
Light: Continuous, from high pressure sodium lamp Eye Sunlux Ace (Eye, Tokio, Japan) (6000-12000 lux)
Temperature: 22 +/- 2C, thermo-controlled room
Test type: Static exposure conditions over a period of 72 h
Starting cell density: 0.5-0.85 ug dry weight / ml (i.e. OD680 of about 0.010)

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

3 d

Dose descriptor:

NOEC

Effect conc.:

7.52 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 2

Duration:

3 d

Dose descriptor:

EC50

Effect conc.:

21.8 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% (19.2-24.6 mg/L)

Effect concentrations 3

Duration:

3 d

Dose descriptor:

EC10

Effect conc.:

11 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% (6.20-13.9 mg/L)

Effect concentrations 4

Duration:

3 d

Dose descriptor:

EC20

Effect conc.:

14.4 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% (10.0-17.0 mg/L)

Effect concentrations 5

Duration:

3 d

Dose descriptor:

NOEC

Effect conc.:

< 3.35 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

biomass

Effect concentrations 6

Duration:

3 d

Dose descriptor:

EC50

Effect conc.:

15.1 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: 95% (13.5-16.3 mg/L)

Effect concentrations 7

Duration:

3 d

Dose descriptor:

EC10

Effect conc.:

7.4 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: 95% (5.10-9.20 mg/L)

Effect concentrations 8

Duration:

3 d

Dose descriptor:

EC20

Effect conc.:

9.9 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: 95% (7.60-11.4 mg/L)

Reported statistics and error estimates:

Statistical analysis was performed with respect to 95% confidence limits and regression data.
Calculation of EC and NOEC values were performed using ToxRat software and statistical differences determined by Dunnett's test

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The NOEC levels were 7.52 mg/L and <3.35 mg/L for growth rate and yield, respectively.

Executive summary:

Methods: The median growth inhibiting concentration (ErC50/EyC50) and the low-effect concentrations (ErC10/EyC10, ErC20/EyC20), based on the average specific growth rate and the yield (algal biomass production) within 3 days, of the test substance to the green alga Desmodesmus subspicatus were investigated over a period of 72 h.

The nominal concentrations of the test substance were 6.25, 12.5, 25, 50 and 100 mg/l, respectively. These test concentrations were prepared as water accommodated fractions. 3 parallel test vessels were used for each concentration of the test substance.

HPLC analyses of the test substance concentrations were conducted at the beginning and after 24,48 and 72 h of exposure. The water solubility of the test substance was 66.4 mg/L. Time weighted average concentrations of 3.35, 7.52, 16.2, 23.7 and 38.6 mg/L were measured for the nominally applied concentrations of 6.25, 12.5, 25, 50 and 100 mg/L, respectively. Hence, with increasing nominal concentrations a lower percentage of the test substance was dissolved. However, on average the concentration of the test substance remained at about 70% of the concentration measured at the beginning of the test and hence was stable during the test.

Results: With respect to algal growth rate inhibition and nominal concentrations the following effects as compared to the untreated controls were observed: 100 mg/l (82%), 50 mg/l (70%) and 25 mg/l (16%). No significant effects (determined by Dunnett's Test) were observed at 12.5 and 6.25 mg/l. Based on these data and the time weighted average concentrations the median effect concentration with respect to growth rate (ErC50 /24-72 h) of the test substance to Desmodesmus subspicatus was calculated to be 21.8 mg/L (95% confidence limits: 19.2-24.6 mg/L). The low effect concentrations for the average specific growth rate, ErCl0 and EyC20, were 11.0 mg/L (95% confidence limits: 6.20-13.9 mg/L) and 14.4 mg/L (95% confidence limits: 10.0-17.0 mg/L), respectively. The no-observed-effect concentration with respect to growth rate (NOErC) was 7.52 mg/l.

For the endpoint yield (biomass production) the following effects as compared to the untreated controls were observed at the respective nominal test concentrations: 100 mg/L (99%), 50 mg/L (97%), 25 mg/L (51%), 12.5 mg/L (15%) and 6.25 mg/L (1 1 %). No significant effects (determined by Dunnett's Test) were not observed. Based on these data and the time weighted average concentrations the median effect concentration with respect to yield (EyC50/0-3 days) of the test substance to Desmodesmus subspicatus was calculated to be 15.1 mg/L (95% confidence limits: 13.5-1 6.3 mg/L). The low effect concentrations with respect to yield, EyCl0 and EyC20, were 7.40 mg/L (95% confidence limits: 5.10-9.20 mg/L) and 9.90 mg/L (95% confidence limits: 7.60-

11.4 mg/L), respectively. The no-observed-effect concentration with respect to yield (NOEyC) was <3.35 mg/L.

Conclusions: The NOEC levels were 7.52 mg/L and <3.35 mg/L for growth rate and yield, respectively.