Reaction mass of 5-[(Disubstituted-dihydrocarbopolycyclyl)diazenyl]-6-hydroxy-4-methyl-2-substituted-1-propyl-1,2-dihydropyridine-3-carbonitrile and 1-Butyl-5-[(disubstituted-dihydrocarbopolycyclyl)diazenyl]-6-hydroxy-4-methyl-2-substituted-1,2-dihydropyridine-3-carbonitrile

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other:

Remarks:

no statistically significant inhibitory effect on the growth of Scenedesmus subspicatus (biomass and growth rate) during the exposure period of 72 hours up to and including the highest loading rate of 100 mg/L

Details on results:

The test item FAT 41039/A had no statistically significant inhibitory effect on the growth of Scenedesmus subspicatus (biomass and growth rate) during the exposure period of 72 hours up to and including the highest loading rate of 100 mg/L (results of Dunnett-tests, one-sided, a = 0.05). The only exception was a significant test result for the growth rate at the loading rate of 3.2 mg/L after 72 hours test duration. However, the inhibition of the growth rate was only 10.8% at this loading rate and no concentration-effect relationship was determined. At all higher loading rates, the deviation of the growth rate to the control value was not statistically significant and below 10%.

Thus, the 72-hour NOEC (highest concentration tested without toxic effects after a test period of 72 hours) was determined to be at least the loading rate of 100 mg/L. The NOEC might even be higher but loading rates above 100 mg/L were not tested, in accordance with the EU Commission Directive 92/69/EEC. The 72-hour LOEC (lowest concentration tested with toxic effects) and the 72-hour EC10 and EC50 were clearly higher than the loading rate of 100 mg/L. These values could not be quantified, since the test item had no toxic effect on the algae up to the highest loading rate of 100 mg/L.

The microscopic examination of the algal cells after 72 hours test period showed no difference between the algae growing in the WAF with the loading rate of 100 mg/L and the algal cells in the control. The shape and size of the algal cells growing at loading rates up to and including 100 mg/L were obviously not affected.

Results with reference substance (positive control):

In the control, the cell density has increased from a nominal N = 1 x 10E4 cells/mL at the start of the test (0 hours) to N = 38 x 10E4 cells/mL (mean value) after 72 hours. Thus, the algal growth in the control was sufficiently high under the conditions of the test. The validity criterion of increase of cell density by at least a factor of 16 over 72 hours was fulfilled.

Reported statistics and error estimates:

Dunnett-tests, one-sided, a = 0.05

No remarkable observations were made concerning the appearance of test media. The WAFs with all loading rates were clear solutions throughout the entire test period.

At the start of the test, the pH value in the test media and the control was 7.9. At the end of the test, pH values between 7.9 and 8.1 were measured. The water temperature was between 22 and 23 °C.

The test item FAT 41039/A had no significant inhibitory effect on the growth of Scenedesmus subspicatus during the exposure period of 72 hours up to and including the highest loading rate of 100 mg/L.

The 72-hour NOEC (highest concentration tested without toxic effects after a test period of 72 hours) was determined to be at least the loading rate of 100 mg/L. The NOEC might even be higher but loading rates above 100 mg/L were not tested, in accordance with the EU Commission Directive 92/69/EEC. The 72-hour LOEC (lowest concentration tested with toxic effects), and the 72-hour EC10 and EC50 were clearly higher than the loading rate of 100 mg/L. These values could not be quantified, since the test item had no inhibitory effect on the growth of the algae up to the highest loading rate of 100 mg/L.

Validity criteria fulfilled:

yes

Conclusions:

FAT 41039/A, structural analogue of FAT 41048, had no toxic effect on the algae up to the loading rate of 100 mg/L. The 48 hour EC50 and NOEC values were determined to be greater than 100 mg/L, respectively.

Executive summary:

Currently no study to assess the toxicity of FAT 41048 to aquatic algae is available. However, the influence of FAT 41039/A, structural analogue of FAT 41048, on the growth of the green algal species Scenedesmus subspicatus CHODAT was investigated in a 72-hour static test according to the EU Commission Directive 92/69/EEC, C.3 (1992) and the OECD Guideline No. 201 (1984).

In order to assess the toxicity of the test item FAT 41039/A containing different components to algae, water accommodated fractions (WAFs) with the loading rates of 1.0, 3.2, 10, 32 and 100 mg/L were tested. The method is based on the Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures (2000).

The WAFs were prepared as follows: Test item dispersions with loading rates of 3.2, 10, 32 and 100 mg/L were prepared in test water using ultrasonic treatment for 15 minutes and intense stirring. The dispersions were stirred for 96 hours at room temperature in the dark to dissolve a maximum amount of the different components of the test item in the test media. Then, the dispersions were filtered through membrane filters (0.45 µm) and the undiluted

filtrates were tested as WAFs. The WAF with the lowest loading rate of 1.0 mg/L was prepared by dilution of the WAF with the loading rate of 3.2 mg/L for technical reasons.

The measured test item concentration in the WAF with loading rate of 100 mg/L was 2.9 µg/L at the start of the test and 2.2 µg/L at the end of the test. All biological results were based on the loading rates of the WAFs.

The test item FAT 41039/A had no significant inhibitory effect on the growth of Scenedesmus subspicatus during the exposure period of 72 hours up to and including the highest loading rate of 100 mg/L.

The 72-hour NOEC (highest concentration tested without toxic effects after a test period of 72 hours) was determined to be at least the loading rate of 100 mg/L. The NOEC might even be higher but loading rates above 100 mg/L were not tested, in accordance with the EU Commission Directive 92/69/EEC. The 72-hour LOEC (lowest concentration tested with toxic effects), and the 72-hour EC10 and EC50 were clearly higher than the loading rate of 100 mg/L. These values could not be quantified, since the test item had no inhibitory effect on the growth of the algae up to the highest loading rate of 100 mg/L.

In conclusion, the test item FAT 41039/A had no toxic effect on the algae up to the loading rate of 100 mg/L under the present conditions of the test.

Description of key information

FAT 41039/A, a structural analogue of FAT 41048, had no toxic effect on the algae up to the loading rate of 100 mg/L. The 48 hour EC50 and NOEC values were determined to be greater than 100 mg/L, respectively.

Key value for chemical safety assessment

EC50 for freshwater algae:

100 mg/L

EC10 or NOEC for freshwater algae:

100 mg/L

Additional information

Currently no study to assess the toxicity of FAT 41048 to aquatic algae is available. However, the influence of FAT41039/A, a structural analogue to FAT 41048, on the growth of the green algal species Scenedesmus subspicatus CHODAT was investigated in a 72 -hour static test according to the EU Commission Directive 92/69/EEC, C.3 (1992) and the OECD Guideline No. 201 (1984). In order to assess the toxicity of the test item FAT 41039/A containing different components to algae, water accommodated fractions (WAFs) with the loading rates of 1.0, 3.2, 10, 32 and 100 mg/L were tested. The method is based on the Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures (2000).

The test item FAT 41039/A had no significant inhibitory effect on the growth of Scenedesmus subspicatus during the exposure period of 72 hours up to and including the highest loading rate of 100 mg/L.