N-cyclohexyl-N-methylcyclohexylamine

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:

Initial study was carried out in 1998 and the recalculation was carried out in 2008.

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Test procedure following national standard with acceptable restrictions; not GLP

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1988

Report date:

1988

Reference 2

Reference Type:

other: recalculation

Title:

Unnamed

Year:

2008

Report date:

2008

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

other: German Standard DIN 38412, Part 9

Test guideline 2

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Cyclohexyldimethylamine

EC Number:

202-715-5

EC Name:

Cyclohexyldimethylamine

Cas Number:

98-94-2

Molecular formula:

C8H17N

IUPAC Name:

N,N-dimethylcyclohexanamine

Details on test material:

- Name of test material (as cited in study report): Dimethylcyclohexylamine

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):Not applicable

Sampling and analysis

Analytical monitoring:

no

Details on sampling:

Not applicable

Test solutions

Vehicle:

no

Details on test solutions:

Concentrations used: 15.62, 31.25, 62.5, 125, 250, 500, 1000, 2000 µg/L

Test organisms

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

Scenedesmus subspicatus, SAG 86.81

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

Not applicable

Test conditions

Hardness:

Not applicable

Test temperature:

23 °C

pH:

Not reported

Dissolved oxygen:

Not applicable

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal exposure concentrations - 15.62, 31.25, 62.5, 125, 250, 500, 1000, 2000 µg/L

Details on test conditions:

TEST SYSTEM- Test vessel: : Erlenmeyer flasks (nominal volume 250 ml) plugged with gas permeable silicon sponge caps - Type (delete if not applicable): open- Initial cells density: Initial count of algae cells/ml: 10000- No. of vessels per concentration (replicates): 4; blank per concentration: 4- No. of vessels per control (replicates): 4GROWTH MEDIUM- Standard medium used: yes; OECD MediumTemperature: 23 °CCulturing volume: 100 mlTEST MEDIUM / WATER PARAMETERSTest substance preparation: none- Culture medium different from test medium: noPre-culture: - medium: OECD-medium - test flasks: 250 ml-Erlenmeyer flasks plugged with gas permeable silicon-sponge caps - test volume: 100 ml - flasks were incubated in an incubation chamber for 72 h - flasks were shaken once a day to hold cells in suspension - illumination: permanent artificial light - light intensity: approx. 120 µE/(m2*s) Test conditions: - No. of algae in test flasks at test start: 10000 exponentially-growing cells - stock solution: 40 mg/L; stock solution was diluted in test medium to reach the final test concentrations - test vessels: 20 ml tubes plugged with gas permeable silicon-sponge caps (test was performed in non-sealed vessels) - replicates: per concentration and control: 4, blank per concentration (w/o cells): 2 - test volume: 10 ml - tubes were incubated in an incubation chamber for 72 h at 23 °C - tubes were shaken once a day to hold cells in suspension - illumination: permanent artificial light - light intensity: approx. 120 µE/(m2*s) - samples were taken at regular intervals (0, 24, 48, 72 h) - measurements: fluorescence (in vivo chlorophyll-a fluorescence at 685 nm as a size for the biomass (pulsed excitation with light flashes having a wavelength of 435 nm)), pH

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 2

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.062 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 3

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.79 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: 95% CL: 0.61 - 1.09 mg/L

Effect concentrations 4

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.062 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Results with reference substance (positive control):

Not relevant

Reported statistics and error estimates:

EC50 values calcuated using Probit analysis using linear max likelihood regression. Variance and confidence limits adjusted to metric data using Slope function after Litchfield and Wilcoxon.

Any other information on results incl. tables

Table 1: Results

Treatment [µg/L]	Growth Rate Inhibition [%]	Biomass Decrease [%]	Yield Decrease [%]
Control	0.0	0.0	0
15.62	0.5	3.4	-2.6
31.25	-1.6	6.3	3.8
62.5	5.4	11.4	13.7
125	13.2	21.2	32.3
250	19.0	28.2	44.2
500	40.4	48.8	69.2
1000	43.4	56.2	71.0
2000	44.1	60.3	73.0

 

Applicant's summary and conclusion

Validity criteria fulfilled:

no

Remarks:

Two of the vailidity criteria set out in OECD TG 201 (23 March 2006) were not met. However, these criterion should not be taken into account since they were not part of the standard at the time the test was conducted.

Conclusions:

Scenedesmus subspicatus were exposed DMCHA for a period of 72 hours. The results of the study were based nominal exposure concentrations. The 72 -hour EC50 based on growth rate > 2 mg/L. The 72 -hour EC50 based on biomass is 0.79 mg/L. The no-observed effect concentration for both variables was determined to 0.0625 mg/L. 

Executive summary:

Scenedesmus subspicatus were exposed to cyclohexyldimethylamine (DMCHA) for a period of 72 hours. The study was carried out according to German Standard DIN 38412, Part 9. Nominal exposure concentrations were control, 0.01562, 0.03125, 0.0625, 0.125, 0.25, 0.50, 1.0 and 2.0 mg/L. The results of the study were based nominal exposure concentrations. 

The 72 -hour EC50 based on growth rate > 2 mg/L. The 72 -hour EC50 based on biomass is 0.79 mg/L. The no-observed effect concentration for both variables was determined to 0.0625 mg/L. 

Validity according to OECD TG 201 (adopted 23 Mar 2006):

 

1. The factor of cell number measured in the control between 0 and 72 h was 19.7, which is >16. The test fulfils this validity criterion.

 

2. Evaluation of the sectional growth rates (the mean coefficient of variation of sectional growth rates calculated for the individual control replicates must not be higher than 35%). The coefficients of variation in control replicates from 0 to 72 h were:

Replicate 1: 39.9 %

Replicate 2: 30.9 %

Replicate 3: 34.3 %

Replicate 4: 32.8 %.

As one out of four replicates was found to be >35 % (replicate 1) the test does not fulfil this validity criterion. Nevertheless, this criterion is not taken into account, since it was not part of the standard at the time the test was conducted.

 

3. The coefficient of variation of average specific growth rates in control cultures was 8.8 % after 72 h, which is not <7 %. The test does not fulfil this validity criterion. However, again this criterion is not taken into account, since it was not part of the standard at the time the test was conducted.

 

4. The determination of the ErC50 (> 2 mg/l nominal) is confirmed by a QSAR-estimate using Ecosar v0.99: LC50 (96 h): 3.58 mg/L (calculated).

- model: Ecosar v0.99

- Ecosar class found: aliphatic amines

- used input-data: log Kow: 2.31 (KowWin estimate); Water solubility: 273.1 mg/L (calculated)

- Green algae: LC50 (96 h): 3.58 mg/L