Styrene

Toxicity to soil macroorganisms except arthropods

Link to relevant study record(s)

Reference

Endpoint:

toxicity to soil macroorganisms except arthropods: short-term

Type of information:

experimental study

Adequacy of study:

key study

Study period:

21 June to 5 July 1995

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 207 (Earthworm, Acute Toxicity Tests)

Version / remarks:

Artificial Soil Test

Deviations:

no

GLP compliance:

yes

Remarks:

no attest of authority

Analytical monitoring:

yes

Details on sampling:

- Sampling method: on test days 0, 7 and 14 removal of approx. 10 g wet weight from each treatment level and control
- Sample storage conditions before analysis: upon receipt, test material stored under refrigeration

Vehicle:

no

Details on preparation and application of test substrate:

- Method of mixing into soil (if used): Mixed using a glass rod through a small hole in the glass container covering aluminium foil

Test organisms (species):

Eisenia fetida

Animal group:

annelids

Details on test organisms:

TEST ORGANISM
- Common name: earthworm
- Source: Carolina Biological Supply Company, Burlington, North Carolina
- Age at test initiation (mean and range, SD): mature with clitellum
- Weight at test initiation (mean and range, SD): mean (incl. control) 0.346 g, range: 0.31 - 0.40 g, SD: 0.033


ACCLIMATION
- Acclimation period: removal from culture and placing into acclimation vessel on the day before test initiation
- Acclimation conditions (same as test or not): same
- Health during acclimation (any mortality observed): no

Study type:

laboratory study

Substrate type:

artificial soil

Limit test:

no

Total exposure duration:

14 d

Test temperature:

20 ± 2°C

pH:

6.1 - 6.5

Moisture:

25 - 29%

Details on test conditions:

TEST SYSTEM
- Test container (material, size): 1-liter wide-mouth glass vessels, ratio width to height 1:2
- Amount of soil or substrate: approximately 750 g per container (equivalent to 0.5 kg dry weight)
- No. of organisms per container (treatment): 10
- No. of replicates per treatment group: 4
- No. of replicates per control: 4


SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Composition (if artificial substrate): 70% industrial sand (Wedron Silicea Co.), 20% U.S. Pharmacopia kolin collodial powder (Mallinckrodt), 10% sphagnum peat moss (Magic Products, Inc.)
- Pretreatment of soil: preparation at initiation of definitive exposure and at 7-day renewal period
- Stability and homogeneity of test material in the medium: test material and artificial soil were mixed using a Hobart Mixer (Model # 200 A), Hobart mixing bowls were covered with aluminium foil


OTHER TEST CONDITIONS
- Photoperiod: 24 h
- Light intensity: 40 to 67 footcandles

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : mortality (7 and 14 days after test initiation)


TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2
- Range finding study
- Test concentrations: nominal concentrations of 0.10, 1.0, 10, 1000 mg A.I./kg; additional pilot study with concentrations of 100, 1000 and 2000 mg A.I./kg and covering of mixing bowls with aluminium foil in order to provide information regarding the potential volatilization
- Results used to determine the conditions for the definitive study: 100% survival in first range finding study versus 100% (100 mg/kg), 15% (1000 mg/kg) and 0% (2000 mg/kg) in additional pilot study

Nominal and measured concentrations:

nominal: 125, 250, 500, 1000, 2000 mg A.I./kg
measured (mean): 23, 44, 65, 180, 500 mg A.I./kg
percent of nominal: 18, 18, 13, 18, 25

Reference substance (positive control):

yes

Remarks:

Chloroacetamide

Duration:

14 d

Dose descriptor:

LC50

Effect conc.:

120 mg/kg soil dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: 95% CL: 99 - 150

Duration:

14 d

Dose descriptor:

LOEC

Effect conc.:

65 mg/kg soil dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: burrowing time and mean percent weight change

Duration:

14 d

Dose descriptor:

LOEC

Effect conc.:

180 mg/kg soil dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: survival

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

34 mg/kg soil dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: mean percent weight change

Remarks on result:

other: * see remarks below

Duration:

14 d

Dose descriptor:

LC50

Effect conc.:

> 500 - < 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Details on results:

- Mortality at end of exposure period: 0% (23 mg A.I./kg), 15% (44 mg A.I./kg), 22% (65 mg A.I./kg), 60% (180 mg A.I./kg), 100% (500 mg A.I./kg)
- Total mass of adults at beginning of test: individal mean at beginning: 0.346 g, thus total mass approximately 83.04 g (0.346 x 40 individuals x 6 (control + 5 concentrations)
- Changes in body weigth of live adults (% of initial weight) at end of exposure period: -10.78% (control), -10.18% (23 mg A.I./kg), -15.83% (44 mg A.I./kg), -32% (65 mg A.I./kg), -7.8% (180 mg A.I./kg), not applicable (500 mg A.I./kg)
- Behavioural abnormalities:
- Other biological observations: Burrowing time

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Relevant effect levels: LC50: 14 mg A.I./kg
- Other:

Alexander (1997) re-evaluated the study in terms of the minimum concentration to which the worms were exposed over the course of the study. He concluded that the NOEC value could be assumed to be 34 mg/kg, if not higher.

Taking into account the very large discrepancy between nominal concentrations and analytical masurementes (even at day 0) in the test, it seems more appropriate to base the effects on nominal concentrations. Basing the results on nominal concentrations the EC50 would lie in the range 500 - 1000 mg/kg dw.

Description of key information

No data on chronic terrestrial toxicity are available. However, the substance is not persistent in the soil compartment. The equilibrium partitioning method has been used for assessing the hazard to soil organisms.
The acute toxicity was tested on Eisenia fetida. The LC50 after 14 d was determined to be 120 mg/kg soil.

Key value for chemical safety assessment

Short-term EC50 or LC50 for soil macroorganisms:

120 mg/kg soil dw

Additional information

A study on the toxicity of styrene to earthworms (Eisenia foetida) was carried out using OECD Guideline 207 (Springborn, 1995). The test was conducted under a cover to reduce volatilisation of the test substance. The concentration of styrene in the soil was measured at the start and at the end of each seven-days period. Total exposure time was 14 days. Results of the test were a 14 -day LC50 of 120 mg/kg and a NOEC for weight change of 44 mg/kg. However, Alexander (1997) re-evaluated the study in terms of the minimum concentration to which the worms were exposed over the course of the study. He concluded that the NOEC value could be assumed to be 34 mg/kg, if not higher.

Taking into account the very large discrepancy between nominal concentrations and analytical masurementes (even at day 0) in the test, it seems more appropriate to base the effects on nominal concentrations.

Basing the results on nominal concentrations the EC50 would lie in the range 500 - 1000 mg/kg dw