Dimethyl(octyl)amine

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:

01 – 11 Dec 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Test item name: AD 1
Batch number: 4500083770EAS
Test item code: M-00000740
Appearance / colour: liquid / clear
Chemical name: N,N-dimethyloctylamine
Purity (nominal): > 95 % w/w
CAS number: 7378-99-6
Molecular weight: 157.3 g/mol
Relative density (nominal):0.765 g/cm³
Signal word(s): danger
Issue date of certificate: 21 Jan 2015
Expiry date: 23 Sep 2016
*Storage conditions: ambient ( ≤ +30 °C), dark, dry

Analytical monitoring:

yes

Details on sampling:

Analytical data are required by the OECD guidelines to determine the concentration and stability of the test item over the entire test period.Due to limitation of the analytical method (LOQ = 1.00 mg/L AD 1) the stock solutions 15.0 and 3.00 mg/L and control were taken and analysed at test start (t = 0 hours) and after 72 hours.

Vehicle:

no

Details on test solutions:

Two stock solutions (S1 and S2) were prepared by directly weighing 15 mg into 1000 and 5000 mL AAP-medium, respectively. The stock solutions were homogenised by shaking and afterwards the solutions were clear and transparent. Both stock solutions were used for preparation of the test item concentrations V1 – V5 by dilution. All stock and test solutions were prepared with AAP-medium containing algae cells with a density of 0.5 × 104 algae per mL.

Test organisms (species):

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

Details on test organisms:

The test organism is Pseudokirchneriella subcapitata Hindák, strain SAG 61.81. The algae used in this study are purchased from the MBM Sciencebridge GmbH, Hans-Adolf-Krebs-Weg 1, D-37077 Göttingen, Germany.The algae were grown semi-continuously in sterile cultures under permanent illumination in the laboratory. Old medium was periodically replaced by fresh mineral solution in order to keep the algae in an exponential growth state. Stock cultures were ordered regularly from the culture collection.

Test type:

static

Water media type:

other: AAP-Medium

Limit test:

no

Total exposure duration:

72 h

Test temperature:

22.0 - 22.4

pH:

7.27 - 7.99

Nominal and measured concentrations:

see table below

Details on test conditions:

Test procedure: Static
Duration: 3 days (72 hours)
Initial cell density: 0.5 × 104 cells/mL
Temperature: 22.0 – 22.4°C
pH of control: 7.32 – 7.85
Illumination: Continuously from the side, 70.9 -82.1 µEm-2s-1
Culture flasks: 100 mL Erlenmeyer flasks with aluminium caps
CO2 supplied: By continuously shaking

Reference substance (positive control):

yes

Remarks:

Potassium dichromate (EC50 growth rate = 1.77 mg/L; EC50 yield = 0.749 mg/L; EC50 biomass = 0.843 mg/L))

Duration:

72 h

Dose descriptor:

EC10

Remarks:

Growth rate

Effect conc.:

0.048 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Duration:

72 h

Dose descriptor:

EC20

Remarks:

Growth rate

Effect conc.:

0.095 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Key result

Duration:

72 h

Dose descriptor:

EC50

Remarks:

Growth rate

Effect conc.:

0.264 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Key result

Duration:

72 h

Dose descriptor:

LOEC

Remarks:

Growth rate

Effect conc.:

0.03 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Key result

Duration:

72 h

Dose descriptor:

NOEC

Remarks:

Growth rate

Effect conc.:

0.01 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Duration:

72 h

Dose descriptor:

EC10

Remarks:

Yield

Effect conc.:

0.015 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Duration:

72 h

Dose descriptor:

EC20

Remarks:

Yield

Effect conc.:

0.025 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Key result

Duration:

72 h

Dose descriptor:

EC50

Remarks:

Yield

Effect conc.:

0.067 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Key result

Duration:

72 h

Dose descriptor:

LOEC

Remarks:

Yield

Effect conc.:

0.03 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Key result

Duration:

72 h

Dose descriptor:

NOEC

Remarks:

Yield

Effect conc.:

0.01 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Details on results:

Statistically significant inhibitory effects for the test item were observed at concentrations of 0.0305 mg/L and above after 72 hours for growth rate and for yield. The EC50-value for growth rate (ErC50) was 0.264 mg/L. The EC50-value for yield (EyC50) was 0.0668 mg/L. The overall LOEC was determined to be at 0.0305 mg/L and the overall NOEC was determined to be at 0.00954 mg/L.

Results with reference substance (positive control):

Potassium dichromate is tested as the toxic reference item in a separate study twice a year to confirm the sensitivity of the test organism against compounds with known effects under the test conditions. The ECx values calculated in this reference test were considered to be within an acceptable range therefore it can be considered that the algae cells are sensitive.

Average cell number for each sampling time and concentration

Conc.	Average cell numbers/mL^1)
[mg/L]	0 h	24 h	48 h	72 h
Control	0.51	1.83	7.97	32.60
0.00954	0.51	1.63	8.23	35.74
0.0305	0.51	1.37	5.73	20.02
0.0977	0.51	1.34	5.17	15.64
0.313	0.51	1.15	2.59	3.37
1.00	0.51	0.84	1.00	0.62

¹⁾Algae numbers are divided by 10⁴.

Percentage inhibition of growth rate

Conc.	% Inhibition of growth rate
[mg/L]	0 – 24h	0h – 48h	0h – 72h
Control	0.0	0.0	0.0
0.00954	9.0	-1.3	-2.4^1)
0.0305	22.9	12.0	11.6*
0.0977	24.8	15.6	17.5*
0.313	36.5	40.7	54.5*
1.00	62.0	75.5	96.0*

¹⁾Values were set to zero for ECx calculation

*statistically significant different to the control

Percentage inhibition of yield

Conc.	% Inhibition of yield
[mg/L]	0 – 24h	0h – 48h	0h – 72h
Control	0.0	0.0	0.0
0.00954	15.2	-3.5	-9.8^1)
0.0305	34.8	30.0	39.2*
0.0977	37.1	37.5	52.9*
0.313	51.5	72.1	91.1*
1.00	75.0	93.4	99.7*

¹⁾Values were set to zero for ECx calculation

*statistically significant different to the control

Endpoints for test item after 72 h

	Endpoint	AD 1  [mg/L] nominal
Growth rate	ErC10^1)	0.0483
	95% confidential limits	0.0126 – 0.0924
	ErC20^1)	0.0951
	95% confidential limits	0.0366 – 0.157
	ErC50^1)	0.264
	95% confidential limits	0.160 – 0.402
Yield	EyC10^2)	0.0152
	95% confidential limits	0.000898 – 0.0353
	EyC20^2)	0.0252
	95% confidential limits	0.00318 – 0.0531
	EyC50^2)	0.0668
	95% confidential limits	0.0254 – 0.163
	LOEC^3)	0.0305
	NOEC^3)	0.00954

¹⁾probit analysis following the Gompertz distribution,

²⁾probit analysis following the normal distribution

³⁾Welch Bonferroni-Holms corrected for growth rate and yield

Concentrations of AD 1 in the test medium

AD 1	Sampling	AD 1 found
nominal (mg/L)		mg L	% of nominal
0	0 h	n.d.	-
	72 h aged	n.d.	-
3.00	0 h	2.58	86
	72 h aged	2.24	75
15.0	0 h	12.5	83
	72 h aged	10.8	72

Limit of quantification (LOQ) =1.00 mg/L AD 1

n.d. not detectable

Validity criteria fulfilled:

yes

Conclusions:

The test item EC50-value for growth rate (ErC50) was 0.264 mg/L (nominal). The test item EC50-value for yield (EyC50) was 0.0668 mg/L (nominal). The LOEC was determined to be at 0.0305 mg/L and the NOEC was determined to be at 0.00954 mg/L (nominal) for growth rate and yield.

Executive summary:

The measured content of AD 1 in both stock solutions was 83 and 86 % of nominal at test start. At test end the measured content of AD 1 was 72 % and 75 %. Since the measured concentrations at test start were within the range of 80 to 120% of nominal the toxicological endpoints were evaluated using the nominal concentrations.

Statistically significant inhibitory effects for the test item were observed at concentrations of 0.0305 mg/L and above after 72 hours for growth rate and for yield. The EC₅₀-value for growth rate (ErC₅₀) was 0.264 mg/L. The EC₅₀-value for yield (EyC₅₀) was 0.0668 mg/L.The overall LOEC was determined to be at 0.0305 mg/L and the overall NOEC was determined to be at 0.00954 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

66.8 µg/L

EC10 or NOEC for freshwater algae:

9.54 µg/L