3-methoxy-N,N-dimethylpropionamide

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:

31 August 2007 - 27 September 2007

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)

Version / remarks:

2006

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: "Algal growth inhibition test" stipulated in "Order Prescribing the Tests Relating to the New Chemical Substances" (Yaku-shoku-Hatsu No. 1121002, Heisei 15.11.13 Seikyoku No.2, Kanpoki-Hatsu No. 031121002 dated November 21, 2003

Version / remarks:

Partially amended on November 20, 2006

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Solubility in water: ≥ 300 g/100 g
Solubility in hexane: 50 g/100 g
Stability under storage conditions: stable

Analytical monitoring:

yes

Details on sampling:

Sampling method: at the start of the test, samples were taken from the preparation vessel (containing test solution before dividing between replicate vessels). An equal amount of test solutions was taken from one test vessel containing test soluion and from the control vessel, for determination after the end of exposure, which were mixed and centrifuged (3000 rpm for 10 minutes) to remove the algae.
Frequency: at t=0 h and t=72 h

Vehicle:

no

Details on test solutions:

- Preparation of test solution: The test solution was prepared with correction for purity. The required amount of the test substance was accurately weighed and dissolved to the medium to prepare a 100 mg/L stock solution. This solution was filtrated under pressure with a 0.22 µm membrane filter. The filtrate was colourless and transparent. It was divided between replicate vessels and used as the test solution.
- Control: medium without test substance was used as a control (blank-control)

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata
- Strain: ATCC 22662
- Source: American Type Culture Collection, subcultured at Kurume Laboratory
- Method of cultivation: the stock cultured algal cells were inoculated into a preculture medium and cultured for three days under the same conditions as those used in the test. Then, the algal (preculture) solution was inoculated into the test solution.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Test temperature:

22.0-22.4 °C throughout the test

pH:

Start: 7.8, end: 7.9

Nominal and measured concentrations:

Nominal concentration: 100 mg/L. The test concentration was corrected for purity (99.0%).
Measured concentration: 104 mg/L
Since the concentration showed to remain stable during the exposure period, final results were based on the nominal concentration.

Details on test conditions:

TEST SYSTEM
- Test vessel: sterilized 500 mL glass erlenmeyer flasks, with breathable silicose covers, fill volume: 100 mL
- Continuous shaking: yes, approx. 100 rpm
- Initial cells density: 1 x 10^4 cells/mL
- Control end cells density: 72.7 x 10^4 cells/mL (mean of replicates)
- No. of vessels per concentration (replicates): 6
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Culture medium different from test medium: no, OECD 201, sterilized
- Intervals of water quality measurement: pH of each test solution at t=0 and t=72, temperature and light intensity at least once a day.

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Light intensity and quality: continuous lighting was established around the liquid surface by the use of fluorescent lamps with a spectrum width of 400-700 nm and a light intensity of 60-120 µE/m^2/s (measured: 84-106)

EFFECT PARAMETERS MEASURED: algal growth after 72 hours
- Determination of cell concentrations: at t=0, t=24, t=48 and t=72, using a particle counter (Coulter Counter Z1, Beckman Coulter).
- Other: at the end, condition of the cells was observed for one vessel containing test solution and one control vessel, using a biological microscope (BX41, Olympus Co., Ltd.).

- Range finding study conducted: yes, no effects were seen at a test concentration of 100 mg/L
- Results used to determine the conditions for the definitive study: yes

Reference substance (positive control):

yes

Remarks:

potassium dichromate (July 2007)

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

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

Details on results:

- Growth was not inhibited at the tested concentration compard to the control, therefore the EC50 for growth rate exceeded 100 mg/L
- pH and temperature were within the prescribed ranged
- Because the test concentration in test solution maintained within 20% of the nominal concentration at the end of the exposure period, the result was based on the nominal concentration.
- No abnormalities on algal cells were observed either in the controls, nor in the test solutions.

Results with reference substance (positive control):

- 72h-EC50 for growth rate: 1.04 mg/L
- The result was within the expected range and confirmed the viability of the test system.

Reported statistics and error estimates:

Homogeneity of growth rate was tested by performing an F-test. As homogeneity was not observed at 5% significance level, a t-test of Aspin-Welch was performed. NOEC was evaluated based on these results and the observation of the test cells.

Table 1 Growth inhibition

Nominal concentration (mg/L)	No.	Growth rate (days 0-3)	Growth inhibition rate (%)
Control	A	1.38	-
	B	1.41	-
	C	1.31	-
	D	1.43	-
	E	1.53	-
	F	1.47	-
	Mean	1.42	-
100	A	1.39	2.14
	B	1.42	0.12
	C	1.42	0.24
	D	1.37	3.64
	E	1.35	4.81
	F	1.41	1.11
	Mean	1.39	2.01

Validity criteria fulfilled:

yes

Remarks:

The biomass in the control increased more than 16 fold (i.e., 72.7 ), the mean CV of daily growth in the control group was <35% (i.e., 23.4%) and the CV for growth rates in the replicate control medium was <7% (i.e., 5.35%).

Conclusions:

The 72h-EC50 of MDMPA for algal growth inhibition was >100 mg/L.

Executive summary:

In a 72 h toxicity study conducted according to OECD guideline 201 and GLP principles, freshwater algae (Pseudokirchneriella subcapitata) were exposed in six replicates to MDMPA to determine the effects on growth rate. A limit test was used with a nominal concentration of 100 mg/L. The exposure concentration was verified by a validated analytical method (HPLC) to be 104 mg/L at t=0 and 104 mg/L. Because the test concentration in test solution was within 80 -120% of the nominal concentration and the concentration remained stable during the exposure period, the final result was based on the nominal exposure concentration. No inhibition of growth rate was seen at 100 mg/L. Therefore, the EC50 for growth rate reduction was >100 mg/L. The 72h-NOEC for growth rate reduction was 100 mg/L. All validity criteria were met and the study was considered valid under the test conditions.

Description of key information

In a 72 h toxicity study conducted according to OECD guideline 201 and GLP principles, freshwater algae (Pseudokirchneriella subcapitata) were exposed in six replicates to MDMPA to determine the effects on growth rate. A limit test was used with a nominal concentration of 100 mg/L. The exposure concentration was verified by a validated analytical method (HPLC) to be 104 mg/L at t=0 and 104 mg/L. Because the test concentration in test solution was within 80 -120% of the nominal concentration and the concentration remained stable during the exposure period, the final result was based on the nominal exposure concentration. No inhibition of growth rate was seen at 100 mg/L. Therefore, the EC50 for growth rate reduction was >100 mg/L. The 72h-NOEC for growth rate reduction was100 mg/L. All validity criteria were met and the study was considered valid under the test conditions.

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:

100 mg/L