tert-pentylbenzene

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:

2008

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP Guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 0, 6.25, 12.5, 25, 50 and 100 % of a saturated stock solution.
- Sampling method: At test initiation bulk solutions were sampled. After 24, 48 and 72 hours samples were taken from the test flasks.
- Sample storage conditions before analysis: 2-8°C.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: An amount of 200 mg tertiary-amylbenzene was dissolved in 2 litres algal medium. This stock solution was continuously stirred and placed at a temperature of 20°C. On the day of test initiation the stock solution was filtered with filter paper (S&S 595 1/2) to remove undissolved
test substance.
- Controls: controls with test medium only were included.
- Evidence of undissolved material: No.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: Selenastrum capricornutum
- Strain: ATCC 22662
- Source: Culture Collection of Algae and Protozoa, Ambleside, Cumbria, UK
- Age of inoculum (at test initiation): 4 days.
- Method of cultivation: Each week an inoculum (1 ml) is transferred into fresh algal medium.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

Not applicable.

Hardness:

No measurement.

Test temperature:

23.0 - 23.8°C

pH:

Controls: 8.1 (day 0) and 9.5 (day 3 )
Test concentrations: 8.5 - 9.5 (day 3)

Dissolved oxygen:

No measurement

Nominal and measured concentrations:

See Table 1.

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type: closed
- Material, size, headspace, fill volume: closed (glass) flasks with a volume of 100 ml were completely filled with test solution
- Aeration: No
- Initial cells density: 1.0 x 10E4 cells/ml
- Control end cells density: 75 x 10E4 cells/ml
- No. of vessels per concentration (replicates): 6 replicates
- No. of vessels per control (replicates): 6 replicates

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: not applicable, the medium was prepared in purified water
- Culture medium different from test medium: No.

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Photoperiod: 24 hours light
- Light intensity and quality: 76 µE.m-2.s-1 which is in agreement with the validity criterion of 60 – 120 µE.m-2.s-1.
- Other: During the test period, the flasks were placed in a horizontal position in a shaking incubator in a random order.

EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: the absorption of the test solutions at 750 nm was measured after 24, 48 and 72 hours using a spectrophotometer. After 24 hours, 1 replicate vessel was used for measurement; after 48 hours, 2 replicate vessels were used and after 72 hours, 3 replicates were used.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2 (0, 6.25, 12.5, 25, 50 and 100 % of a saturated stock solution).

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

3.2 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

3.9 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.8 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

biomass

Details on results:

See Table 2.

Table 2             Mean measured algal cell densities during the test period

Mean measured concentration (mg/l)	Cell density x 10^4  (cells/ml)
	Day 1 (n=1)	Day 2 (n=2)	Day 3 (n=3)
controls 0.53 0.80 1.4 2.6 5.7	4.653 4.706 4.466 3.418 3.353 1.462	16.91 15.91 17.40 17.56 13.55 1.976	75.35 79.51 74.03 64.99 48.67 1.698

Validity criteria fulfilled:

yes

Conclusions:

Under the test conditions of this study, The EC50/72h for biomass integral and growth rate were 3.2 and 3.9 mg/L respectively. The NOEC, based on mean measured concentrations was 0.80 mg/L.

Executive summary:

The acute toxicity of Tertiary-amylbenzne to algae (Selenastrum capricornutum) was tested according to OECD Guidelien 201 and in accordance with GLP compliance.

Based on a preliminary test the study was conducted at 0, 6.25, 12.5, 25, 50 and 100% of the filtrated stock solution. Because the test substance will volatilise from the test solutions, the test was conducted in closed flasks with a volume of 100 mL. The biological endpoints based on the average of the measured concentrations being 0, 0.53, 0.80, 1.4, 2.6 and 5.7 mg/L.

The cell density increased 75 times in the controls, which meets the validity criterion of a minimal 16 times increase. The pH of controls was 8.1 on day 0 and 9.5 on day 3 which is in accordance with the validity criterion of a maximum increase of 1.5 pH unit.

Under the test conditions of this study, the EC50/72 hours for biomass integral and growth rate were 3.2 and 3.9 mg/L respectively; The NOEC, based on biomass was 0.80 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

3.9 mg/L

EC10 or NOEC for freshwater algae:

0.8 mg/L