2,3,5,6-tetrachloropyridine

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:

11 March 1991 to 16 September 1991

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1991

Report date:

1991

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

2,3,5,6-tetrachloropyridine

EC Number:

219-283-9

EC Name:

2,3,5,6-tetrachloropyridine

Cas Number:

2402-79-1

Molecular formula:

C5HCl4N

IUPAC Name:

2,3,5,6-tetrachloropyridine

Details on test material:

Reference: AGR 289294
Purity = 98.6%

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

The algal cell densities (or biomass) of the inoculum and test cultures were determined by electron particle counting using the Coulter Multisizer. Total cell counts were determined at approximately 24h, 48h, 72h, 96h, and 120 hours. Test flasks were removed from the incubator and appropriate dilutions prepared from each. The test flasks were then randomly placed back in the incubator after the sample volume was taken. Cells were cumulatively counted at a lower threshold equivalent spherical diameter of approximately 2.7 µm to a higher threshold equivalent spherical diameter of approximately 8.4 µm. The background particle count was concurrently subtracted from that of the sample dilution to obtain the cell density. A blank correction for the isotonic saline solution used in preparing the dilutions was also compensated for in the calculations.

Test solutions

Vehicle:

yes

Details on test solutions:

Each test concentration and control was set in triplicate. Due to the difficulty in dissolving the test material in aqueous solution, the solvent acetone was used as a carrier. Initially a stock solution for each test concentration was prepared in acetone so that the maximum limit of 10 µl of solvent/100 mL of algal assay medium would provide the required concentration. These tests were carried out axenically throughout the 5 - day test period.

Test organisms

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

Selenastrum capricornututn Printz (strain 1648) was the test species. Axenic samples of this algae were received on June 10, 1982 from the Starr Algal Collection at the University of Texas, Austin, Texas. Stock cultures of this organism are maintained axenically by weekly transfer into fresh sterile medium.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

120 h

Post exposure observation period:

Not applicable

Test conditions

Hardness:

Not determined

Test temperature:

25 +/- 2 °C

pH:

7.0 - 7.5

Dissolved oxygen:

Not determined

Salinity:

Not determined

Nominal and measured concentrations:

Nominal concentration (mg/L) Mean measured concentration (mg/L)
50 31.6
30 20.28
18 11.48
10.8 6.81
6.70 3.34
3.93 2.26
2.32 1.42
1.33 0.85
0.88 0.71

Details on test conditions:

Test vessels were sterilized 250 ml borosilicate Erlenmeyer flasks with Shimadzu closures containing 100 ml algal test medium. Each test flask was labeled with a unique number for identification purposes. The test flasks were placed in an incubator with the temperature set at 25 ± 2 °C with continuous light at 400 ± 100 foot candles and continuous agitation at approximately 100 rpm.

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

14.3 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: AAM control without acetone

Effect concentrations 2

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

11.7 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: AAM control without acetone

Effect concentrations 3

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

6.8 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: AAM control without acetone

Effect concentrations 4

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

16.8 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: AAM control with acetone

Effect concentrations 5

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

9.7 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: AAM control with acetone

Effect concentrations 6

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

6.8 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: AAM control with acetone

Effect concentrations 7

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

14.4 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: AAM control without acetone

Effect concentrations 8

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

9.6 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: AAM control without acetone

Effect concentrations 9

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

2.3 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: AAM control without acetone

Effect concentrations 10

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

8.5 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: AAM control with acetone

Effect concentrations 11

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

14.1 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: AAM control with acetone

Effect concentrations 12

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

3.3 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: AAM control with acetone

Effect concentrations 13

Duration:

120 h

Dose descriptor:

EC50

Effect conc.:

14.1 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: AAM control without acetone

Effect concentrations 14

Duration:

120 h

Dose descriptor:

EC50

Effect conc.:

8.8 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: AAM control without acetone

Effect concentrations 15

Duration:

120 h

Dose descriptor:

NOEC

Effect conc.:

3.3 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: AAM control without acetone

Effect concentrations 16

Duration:

120 h

Dose descriptor:

EC50

Effect conc.:

13.9 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: AAM control with acetone

Effect concentrations 17

Duration:

120 h

Dose descriptor:

EC50

Effect conc.:

8.2 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: AAM control with acetone

Effect concentrations 18

Duration:

120 h

Dose descriptor:

NOEC

Effect conc.:

3.3 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: AAM control with acetone

Details on results:

See above.

Results with reference substance (positive control):

Not applicable.

Reported statistics and error estimates:

No data provided.

Any other information on results incl. tables

Test concentrations were set in a range of 0.71 to 31.6 mg/L in triplicate with an initial cell density of 10,000 cells/mL. The measured test concentrations of 2,3,5,6-tetrachloropyridine were approximately 60% of nominal at the start of the test. A stability study of the test material in algal assay medium has demonstrated after 72 hours that 1.2% of the initial concentration of test material remained in solution and by 96 hours there was essentially no presence of test material in the algal assay medium.

The EC50 for biomass and growth rate did not significantly change after 48 hours. Whether this was due to an initial toxic response of the algae to sym-tet or the fact that very little test material remained insolution by72hours (the stability study showed approximately 1.3% of initialtest material present in algal assay medium by 72 hours) remainsquestionable. Temperature may have contributed to the instability of sym-tet.During a rainbow trout toxicity study which was conducted at 12±2°C, 94% ofsym-tet was present at 72 hours, and by the end of the test period 79% remained in solution [8]. The temperature of the algal study conducted was 25±2°C.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The EC50 values and the 95% confidence intervals based on initial measured concentrations were determined on the endpoints, biomass (total cell count/mL) and growth rate (% inhibition), as well as the no observable effect concentrations (NOEC'S) on biomass, in comparison to the controls. Results are quoted above.

Executive summary:

A GLP compliant study conducted in accordance with OECD Guideline 201 was conducted in order to determine the effect of the test substance on algal growth. The EC50 values and the 95% confidence intervals based on initial measured concentrations were determined on the endpoints, biomass (total cell count/mL) and growth rate (% inhibition), as well as the no observable effect concentrations (NOEC'S) on biomass, in comparison to the controls.

EC50 values varied between 8.2 mg/L (120 h, based on growth rate, AAM control with acetone) to 16.8 mg/L (72h, based on biomass, AAM control with acetone).

NOEC values varied between 2.3 mg/L (96h, based on biomass, AAM control without acetone) to 6.8 mg/L (72h, based on biomass, AAM control with and without acetone).