cis-4-[3-(p-tert-butylphenyl)-2-methylpropyl]-2,6-dimethylmorpholine

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:

18.01. to 29.02.2000

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Strain: specication: SAG 61.81 Pseudokirchneriella subcapitata
- Source (laboratory, culture collection): At least once per year fresh strains are obtained from the "Sammlung von Algenkulturen" Göttingen (Germany)
- Method of cultivation: according to OECD 201 recommendations

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

22 ± 1 °C

pH:

7.93 - 8.04

Nominal and measured concentrations:

nominal concentrations: 0.0003, 0.001, 0.003, 0.01. 0.03, 0.1, 0.3 and 1 mg/L;
average measured values were 111% of nominal at test initiation and 90% of nominal at the end of the test, confirming in general the nominal concentrations

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer dimple flasks, 100ml
- Fill volume: 60 ml per replicate
- Initial cells density: 1 x 10^4 cells/mL
- Control end cell number: 1.789 x 10^7 cells/mL
- No. of vessels per concentration (replicates): 5
- No. of vessels per control (replicates): 10

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Preparation of Test medium: adding 10.35 mg of the test substance to 1000 mL
nutrient solution (to ease solution, the pH was first adjusted to 3.5 - 4);
stock solution was diluted with algal nutrient solution to reach the desired concentrations;
pH of bulk solutions for each concentration was then adjusted again to 8.0

OTHER TEST CONDITIONS
- pH: 8.0 at test initiation
- Photoperiod: continuous light, (white fluorescent lamps);
continuous shaking at 135 rpm.
- Light intensity and quality: about 8000 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: in each ask was determined 24, 48, and 72 hours after starting the experiment with a spectrophotometer (623 nm, 5 cm glass cuvettes). Algal medium was used as a blank.

TEST CONCENTRATIONS
- Spacing factor for test concentrations:
- Justification for using less concentrations than requested by guideline:
- Range finding study: Yes
- Test concentrations: 0, 0.0003, 0.001, 0.003, 0.01, 0.03, 0.1, 0.3 and 1 mg/L

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.327 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.005 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.058 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

Analytical measurements: Analytical verification of the test substance was carried out in each test concentration at the beginning and at the end of the test after 72 hours (with the exception of the two highest concentrations which were determined at the end of the test only). Average measured values were 111% of nominal (range: 94% - 137%) at the beginning and 90% of nominal (range: 73% - 103%) at the end of the test. In addition water samples without algae were analyzed 72 h after test beginning. Recovery results of 85% - 118% underlined the results with the test samples. The following results are therefore based on nominal concentrations.

Biological results: No morphological effects on the algae could be observed up to 0.1 mg/L. At the two highest concentrations, 0.3 mg a.s./L and 1.0 mg a.s./L the algal cells appeared smaller and rounder in comparison to the algal cells in the control.

ErC50 (0-72 h) > 1.0 mg a.s./L
ErC10 (0-72 h) = 0.058 mg a.s./L (95% limits: 0.048 – 0.070 mg a.s./L)
EbC50 (0-72 h) = 0.327 mg a.s./L (95% limits: 0.284 – 0.377 mg a.s./L)
EbC10 (0-72 h) = 0.005 mg a.s./L (95% limits: 0.004 – 0.006 mg a.s./L)

Reported statistics and error estimates:

Standard procedures, probit analysis

Table 8.2/28     Effect of Fenpropimorph on the growth of Pseudokirchneriella subcapitata
Concentration [mg a.s./L] nominal	0.0003	0.001	0.003	0.01	0.03	0.1	0.3	1.0
Inhibition (biomass) [%]	-10.6	7.4	6.3	14.7	21.2	38.8	47.7	63.3
Inhibition (growth rate) [%]	-1.9	2.3	2.4	4.6	7.5	13.5	17.2	26.1

Conclusions:

In a 72-hour algae test with Pseudokirchneriella subcapitata the ErC50 of fenpropimorph was determined to be >1.0 mg a.s./L; the ErC10 was 0.058 mg a.s./L (nominal).

Description of key information

In a 72-hour algae test with Pseudokirchneriella subcapitata the E_rC₅₀ of fenpropimorph was determined to be >1.0 mg/L, the E_rC₁₀ was 0.058 mg/L (nominal) based on growth rate.

Key value for chemical safety assessment

EC50 for freshwater algae:

1 mg/L

EC10 or NOEC for freshwater algae:

0.058 mg/L

Additional information

Additionally the effect of the main metabolite fenpropimorph-acid on the growth of the green alga Pseudokirchneriella subcapitata was tested (Dohmen G.P. 1997(b); Reg: 1997/11036) and is summarized below.

No morphological effects on the algae could be observed at any of the test substance concentrations. However the two highest concentrations seemed to have caused morphological changes. Some algal cells appeared smaller and more round in shape.

E_rC₅₀ (0-72 h) > 100 mg/L
E_rC₁₀ (0-72 h) > 100 mg/L
E_bC₅₀ (0-72 h) > 100 mg/L
E_bC₁₀ (0-72 h) > 100 mg/L
NOEC = 25 mg/L

In a 72-hour algae test with Pseudokirchneriella subcapitata the E_rC₅₀ of fenpropimorph-acid was determined to be >100 mg/L; the E_rC₁₀ was >100 mg/L (nominal).