Hexamethylene diisocyanate, oligomers, reaction products with 3-methoxypropylamine

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From September 04, 2017 to September 08, 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

CAS No.: 162492-07-1; EINECS-No.: 500-740-9; Batch No.: 1591ZG-101; Purity: >98 %; Appearance: homogeneous, white powder

Analytical monitoring:

yes

Details on sampling:

The concentration of the test substance in the test vessels was measured at the start and at the end of the test.

Vehicle:

no

Details on test solutions:

The water-accommodated fractions (WAF) of the concentrations to be tested were prepared. This was done by weighing the nominal load, adding the appropriate amount of algal medium (demineralised water enriched with minerals but without algae) and shaking for 24 hours. After membrane filtration through 0.45 μm PTFE filters, the solutions were used to prepare the treatments.

Nominal concentration in mg/L: 1.0, 3.2, 10, 32, 100
Real load in mg/L: 1.0, 3.2, 10, 32, 100.33

All solutions were sterilised before use. The algal medium corresponds to the OECD TG 201 medium.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

Unicellular freshwater green alga.
Genus: Desmodesmus
Species: subspicatus
SAG Strain Number: 86.81
Taxonomic position: Chlorophyta - Chlorophyceae
Origin and Culture: 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.

Test type:

static

Water media type:

other: demineralised water enriched with minerals but without algae

Limit test:

no

Total exposure duration:

72 h

Test temperature:

21.0 – 21.6 °C

pH:

7.6 - 8.1

Nominal and measured concentrations:

Nominal concentrations in mg/L: 1.0, 3.2, 10, 32, 100
Geometric mean of measured concentrations in μg/L: 0.47, 0.75, 2.92, 7.57, 49.06

Details on test conditions:

Number of replicates: 6 replicates for the blank control, 3 replicates for each treatment
Vessels: glass flasks, total volume 65 mL
Lighting: 4500 lux
Replicates (Blank control): algal medium and algae
Replicates (Treatments): test solution and algae

Reference substance (positive control):

yes

Remarks:

Potassium dichromate K2Cr2O7

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: Corresponding to >49.06 µg/L mean measured concentration

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: Corresponding to >49.06 µg/L mean measured concentration

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: Corresponding to 49.06 µg/L mean measured concentration

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: Corresponding to 49.06 µg/L mean measured concentration

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: Corresponding to 49.06 µg/L mean measured concentration

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: Corresponding to 49.06 µg/L mean measured concentration

Details on results:

Because of the poor solubility of the test substance, the measured concentrations were in a very low rage. At the beginning and at the end of the test, an extra replicate for each treatment without algae was measured. In the highest concentrated treatment the measured concentration in the replicate with algae was higher than in the replicate without algae. Therefore, the determination of the results was based on the geometric mean of the measured concentrations in the replicates with algae.
Geometric mean is calculated by multiplication of the n participating concentrations and taking the n-th root.

Results with reference substance (positive control):

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).

Reported statistics and error estimates:

Calculation of results was performed with the help of validated software (Microsoft Excel). In the test an increased algal growth was observed in all tested concentrations.
Therefore, no statistical evaluation was performed.

Measured test substance concentrations:

Nominal concentration test substance	Measured concentrations test substance with algae	Measured Concentrations test substance without algae	Measured Concentrations test substance with algae
	t = 0 h	t = 72 h	t = 72 h
mg/L	µg/L	µg/L	µg/L
Blank control	--	--	--
1	0.5	0.4	0.5
3.2	0.9	0.8	0.6
10	4.6	2.5	1.9
32	8.6	5.2	6.7
100	58.6	23.0	41.1

Validity criteria fulfilled:

yes

Conclusions:

Under the study conditions, the 72 h EC50 for growth rate and biomass were both >100 mg/L, corresponding to >49.06 µg/L (mean measured). The NOEC and EC10 for growth rate and biomass were both 100 mg/L, corresponding to 49.06 µg/L (mean measured).

Executive summary:

A study was conducted to determine the toxicity of the test substance to the green algae Desmodesmus subspicatus according to OECD Guideline 201 and EU Method C.3, in compliance with GLP. Individual water-accommodated fractions (WAF) were prepared at 5 concentrations ranging from 1.0 to 100 mg/L (nominal), with incubation time of 72 h. The cell concentration of each replicate was determined by measuring the cell numbers every 24 h with an electronic particle counter. Growth rate and yield were determined from the cell number at the respective observation time. Significant inhibition of algal growth was not observed. Furthermore, at all tested concentrations, increased algal growth could be observed. Therefore, no statistical evaluation was performed. At the start and at the end of the test, the concentration of the substance in the solutions was determined using HPLC. Due to poor solubility, the measured concentrations were in the low range. The 72 h EC50s for potassium dichromate were determined in a separate reference test. The values lay within the range of the laboratory. Under the study conditions, the 72 h EC50 for growth rate and biomass were both >100 mg/L, corresponding to >49.06 µg/L (mean measured). The NOEC and EC10 for growth rate and biomass were both 100 mg/L, corresponding to 49.06 µg/L (mean measured) (Muckle, 2017).

Key value for chemical safety assessment

EC50 for freshwater algae:

49.06 µg/L

EC10 or NOEC for freshwater algae:

49.06 µg/L

Additional information

A study was conducted to determine the toxicity of the test substance to the green algae Desmodesmus subspicatus according to OECD Guideline 201 and EU Method C.3, in compliance with GLP. Individual water-accommodated fractions (WAF) were prepared at 5 concentrations ranging from 1.0 to 100 mg/L (nominal), with incubation time of 72 h. The cell concentration of each replicate was determined by measuring the cell numbers every 24 h with an electronic particle counter. Growth rate and yield were determined from the cell number at the respective observation time. Significant inhibition of algal growth was not observed. Furthermore, at all tested concentrations, increased algal growth could be observed. Therefore, no statistical evaluation was performed. At the start and at the end of the test, the concentration of the substance in the solutions was determined using HPLC. Due to poor solubility, the measured concentrations were in the low range. The 72 h EC50s for potassium dichromate were determined in a separate reference test. The values lay within the range of the laboratory. Under the study conditions, the 72 h EC50 for growth rate and biomass were both >100 mg/L, corresponding to >49.06 µg/L (mean measured). The NOEC and EC10 for growth rate and biomass were both 100 mg/L, corresponding to 49.06 µg/L (mean measured) (Muckle, 2017).