N-ethyl-N-(3-methylphenyl)propionamide

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:

15 July 1996 to 18 July 1996

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1996

Report date:

1996

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:

N-ethyl-N-(3-methylphenyl)propionamide

EC Number:

423-640-6

EC Name:

N-ethyl-N-(3-methylphenyl)propionamide

Cas Number:

179911-08-1

Molecular formula:

C12H17NO

IUPAC Name:

N-ethyl-N-(3-methylphenyl)propanamide

Test material form:

liquid

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

Concentrations of Agarbois in the test media were determined at 0, 24, 48 and 72 hours by Ecotoxicology Analytical Unit by a gas chromatographic-mass spectrometric (GC-MS) method.

Test solutions

Vehicle:

no

Remarks:

Distilled water

Details on test solutions:

A nominal 1.0 g/l stock was prepared by dispersing 0.50 g of test item in 500 ml of distilled water, warming to 50°C and then high shear mixing at 16,000 rpm for 20 minutes. A range of test substance concentrations (nominally 0, 10, 18, 32, 56 and 100 mg/I) was prepared by diluting the stock with ISO medium

Test organisms

Test organisms (species):

Scenedesmus sp.

Details on test organisms:

TEST ORGANISM
- Common name: Scenedesmus subspicatus
- Source (laboratory, culture collection): Culture Centre for Algae and Protozoa. Freshwater Biological Association, Windermere Lab., The Ferry House, Ambleside, Cumbria, LA22 OLP


ACCLIMATION
- Culturing media and conditions (same as test or not): culture in synthetic media

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

None

Test conditions

Test temperature:

23-26°C

pH:

at 0 hours: 7.1-7.4
at 72 hours: 8.0-9.6

Nominal and measured concentrations:

Nominal: 0, 10, 18, 32, 56 and 100 mg/l
Measured concentration (geometric mean): 0, 6.3, 12, 24, 45 and 89 mg/l

Details on test conditions:

The test method is described in SOP 140 with additional details in the Study Plan. Six days before the start of the test an inoculum was prepared and incubated under test conditions. Three days prior to the start of the test this inoculum was subbed-on into 4 flasks of ISO medium to a concentration of 5 x 10^3 cells/ml. Just prior to the start of the test a calculated aliquot of the inoculum was transferred into each test vessel containing ISO medium and the specified concentration of test item to give a nominal algal density of 10^4 cells/ml. (The mean measured 0 hours algal density was 1.02x10^4 cells /ml.)

The test vessels were then loosely stoppered and placed according to a randomised distribution in an orbital illuminated incubator. The light intensity in the incubators was not measured, however the light source used was clearly adequate for the purposes of this study as indicated by the control culture growth.

The pHs of the test media were determined at 0 and 72 hours. The algal concentrations in the test media were determined at 0, 24, 48 and 72 hours using a Coulter Counter.

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

ca. 35 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Effect concentrations 2

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

24 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Effect concentrations 3

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

ca. 55 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 4

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

24 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

There was a 168 fold mean increase in the cell density of control cultures over 72 hours. The control growth was therefore qualitatively acceptable.

Reported statistics and error estimates:

The toxicity data were analysed according to the methods described in SOP 140. The "AlgaeSAS" program descibed uses linear regression and an analysis of variance followed by Dunnett's test to calculate % inhibition of growth rate and biomass and the no observed effect concentrations (NOECs).

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The EC50 of the test item to Scenedesmus subspicatus based on the Geometric Means of the Measured Concentrations are 35 mg/l (%inhibition biomass 72h) and 55 mg/l (%inhibition growth 72h).

Executive summary:

The toxicity of the test item to the freshwater green alga Scenedesmus subspicatus was determined in compliance with ISO, EEC and OECD methods.

 

A range of concentrations of the test substance (nominally 0, 10, 18, 32, 56 and 100 mg/l) was prepared in ISO medium.

 

Concentrations of Agarbois in the test media were analysed at 0, 24, 48 and 72 hours by a gas chromatographic and mass spectrometric method.

 

Results of the Test Substance Analysis (mg/l)                                                                                          

	Nomina concentration (mg/l)
	0.0	10	18	32	56	100	Stock
0 hour	0.18	7.1	14	25	45	91	860
24 hours	0	6.6	12	25	55	100	-
48 hours	0	6.2	13	24	43	86	-
72 hours	0	5.5	11	22	40	81	-
Geometric mean	-	6.3	12	24	45	89	-

The Toxicity of test item to Scenedesmus subspicatus based on the Geometric Means of the Measured Concentrations (mg/l)

Conc.	% Inhibition (biomass)			% Inhibition (growth)
	24 hours	48 hours	72 hours	24 hours	48 hours	72 hours
6.3	-2.0	-15	-8.5	1.1	-4.5	-0.9
12	5.5	13	20	-3.9	1.5	3.8
24	8.6	-5.5	8.7	1.9	-5.6	0.33
45	26	40	62	17	21	26
89	50	80	96	9.8	60	91
EC50	>89	55 (36 -120)	35 (24 -58)	>89	>89	55 (35 -120)
NOEC	24	24	24	>= 89	24	24

( ) 95% confidence limits