Styrene

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:

07 February to 14 September 1995

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OTS 797.1050 (Algal Toxicity, Tiers I and II)

Deviations:

no

GLP compliance:

yes

Remarks:

no attest of authority

Analytical monitoring:

yes

Details on sampling:

- Concentrations: measured at test initiation, 24 h and test termination (96 h)
- Quality control samples were taken at test initiation, 24 h and 96 h
- Temperature: measured continuously in a flask of water adjacent to the test flasks, minimum and maximum temperature was recorded daily
- Shaking rate: recorded daily
- Light intensity: measured at test initiation and than at each 24-hour interval of exposure period
- pH and conductivity: measured at test initiation (conducted on the test solution remaining in mixing flasks after filling of individual test flasks) and at test termination after 96 h (conducted in a composite of individual replicate solutions monitored on that day for each treatment and control)
- Sample storage conditions before analysis: refrigerated

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Dilution of 0.967 mL Styrene in 4.4 L water (sterile, deionised) to give a stock solution of 200 mg A.I./L. Appropriate volumes of the stock solution were diluted to 4.0 L with dilution water in order to prepare test solutions with nominal concentrations of Styrene equal to 0.073, 0.24, 0.81, 2.7, 9.0, 30 and 100 mg A.I./L

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: freshwater green alga
- Strain: 1648
- Source (laboratory, culture collection): originally obtained from Carolina Biological Supply Company, Burlington, North Carolina, USA, than in stock solution at Springborn Laboratories
- Age of inoculum (at test initiation): from stock solution culture that had been transferred to fresh medium three days prior to testing
- Method of cultivation: Culture medium was Algal Assay Procedure (AAP) medium prepared with sterile and deionized water. Stock cultures were grown in 125 mL glass flasks containing 50 mL medium

ACCLIMATION
- Culturing media and conditions (same as test or not): test medium deviates from culture medium due to the addition of 500 mg/L of sodium bicarbonate (NaHCO3)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Test temperature:

24 - 25°C

pH:

7.6 at test initiation and 8.5 - 9.4 at test termination

Nominal and measured concentrations:

nominal: 0.073, 0.24, 0.81, 2.7, 9.0, 30, 100 mg A.I./L
measured (mean): 0.023, 0.063, 0.28, 0.68, 2.0, 7.0, 28 mg A.I./L
percent of nominal: 31, 26, 35, 25, 22, 23, 28

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: glass, zero headspace, 265 mL
- Initial cells density: 253 x 10E4 cells/mL
- Control end cells density: 108 x 10E4 cells/mL (mean)
- No. of vessels per concentration (replicates): 12 (3 replicates at each observation interval: 24, 48, 72, 96 h)
- No. of vessels per control (replicates): 12 (3 replicates at each observation interval: 24, 48, 72, 96 h)


GROWTH MEDIUM
- Standard medium used: yes (APP medium acc. to US. EPA), deviations: 1.368 mg/L K2HPO4 x 3H2O, 1.88 µg/L Na2SeO4


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: sterile, deionised water
- Total organic carbon: 0.65 mg/L (analysed in May 1995)
- Metals: none detected at concentrations that are considered toxic
- Pesticides: none detected at concentrations that are considered toxic
- Conductivity: 500 µmhos/cm
- Culture medium different from test medium: no
- Intervals of water quality measurement: at test initiation and termination


OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: 7.5 ± 0.1
- Photoperiod: continuous
- Light intensity and quality: 300 - 500 footcandles


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : cell density (interval of 24 h at 24, 48, 72 and 96 h)
- Determination of cell concentrations: counting chamber


TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.3
- Range finding study
- Test concentrations: 0.020, 0.20, 2.0, 20, 200 mg A.I./L (nominal)
- Results used to determine the conditions for the definitive study: cell densities at test termination in treatment levels 0.020 - 200 mg A.I./L averaged 116, 111, 96, 82 and 0.13 x 10E4 cells/mL

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

4.9 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

6.3 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

96 h

Dose descriptor:

EC10

Effect conc.:

0.28 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

- Exponential growth in the control (for algal test): no
- Observation of abnormalities (for algal test):
- Unusual cell shape: at test termination cell fragments and bloated cells in 0.68, 2.0 and 7.0 mg A.I./L test solutions, only cell fragments in 28 mg A.I./L
- other: due to severe growth inhibition at concentration 7.0 mg A.I./L an aliqout was removed to determine algicidal/algistatic effects of the test material. After being diluted with fresh medium to a concentration equal to the established NOEC the observation of growth indicates an algistatic rather than an algicidal effect at 7.0 mg A.I./L.

Reported statistics and error estimates:

Statistical analysis was conducted (Williams' Test)

EC50(96h) = 0.72 mg/L, cell density

EC10(96h) = 0.13 mg/L, cell density

EC50(72h) = 1.4 mg/L, cell density

Validity criteria fulfilled:

yes

Conclusions:

The 72 h EC50 on Styrene showed acute tocixity of 4.9 mg/L on green algae.

Executive summary:

Styrene was testet for possible toxicological effects on the green algae Scenedesmus. The EC 50 after 72 h was found to be 4.9 mg/L. 

Description of key information

Acutely toxic to aquatic algae.

Styrole was testet for possible toxicological effects on the green algae Scenedesmus. The EC 50 after 72 h was found to be 4.9 mg/L. 

Key value for chemical safety assessment

EC50 for freshwater algae:

4.9 mg/L

Additional information

The effect of styrene on the green alga Selenastrum capricornutum was tested using a test method in accordance with US EPA Guideline, modified in order to minimise the volatilisation of the test compound from the test vessels. Concentrations were measured at 0, 24 and 96 hours during the test (Springborn 1995). The test is considered to be valid. The 72 -hours EC50 based on growth rate (ErC50) was calculated to be 4.9 mg/l.

The toxicity treshold for Scenedesmus quadricauda of > 200 mg/l after eight days of exposure ((Bringmann & Kühn, 1977) is considered as not valid, since it was not clear whether a stable test substance concentration was maintained during the test.

The effect of styrene on the green alga R. subcapitata was tested using a test method in accordance with OECD Guideline. Concentrations were measured at 0, 72 hours during the test (Yoshikawa et al. 2022). The test is considered to be valid. The 72 -hours EC50 based on growth rate (ErC50) was calculated to be 5.99 mg/l.