p-tert-butylstyrene

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

28 December 2017 - 26 October 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

Version / remarks:

2012

Deviations:

yes

Remarks:

No significant deviations that had an impact on the study outcome.

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Synonyms: p-tert-butylstyrene
CAS No: 1746-23-2
Purity: 96.4%

Analytical monitoring:

yes

Details on sampling:

- Nominal concentrations: 5.1, 13, 32, 80, 200, and 500 µg/L
- Geometric mean measured concentrations: 4.0, 10, 25, 61, 170, and 400 µg/L
- Intervals of analytical monitoring:
Days 0, 7, 14, and 20 (new solutions)
Days 1, 8, 15, and 21 (aged solutions)
- Due to the volatile nature of the test substance, new solutions were sampled directly after being prepared. Aged solutions were sampled directly after being composited. These measures were taken in order to obtain the most accurate analytical results for this closed-system exposure.

Vehicle:

yes

Remarks:

Dimethylformamide (DMF, CAS No. 68-12-2), 0.1 mL/L

Details on test solutions:

The primary stock solution (5000 µg/mL) was mixed with inversions of the flask and was observed to be clear and colorless with no visible undissolved test substance following preparation.
Secondary stock solutions were mixed with inversions of the flask and were observed to be clear and colorless with no visible undissolved test substance following preparation.
Exposure solutions were mixed thoroughly using a glass rod for approximately one minute. The exposure solutions were observed to be clear and colorless with no visible undissolved test substance following preparation. Freshly prepared solutions were divided into 10 replicate vessels, each labeled with the study number, treatment/control, and replicate designation. Control and solvent control vessels were maintained under the same conditions as the treatment level solutions.
Exposure solutions were newly prepared and renewed every 24 hours.

Test organisms (species):

Daphnia magna

Details on test organisms:

The daphnids used in this toxicity test were obtained from laboratory cultures maintained at Smithers Viscient. Daphnids were obtained for testing by removing all immature daphnids from the culture vessel, thus isolating sexually mature daphnids approximately 24 hours prior to exposure initiation. Young produced by these daphnids within 24 hours of isolation were used in the exposure. The culture water was prepared by fortifying well water based on the formula for hard water (U.S. EPA, 1975) and filtering it through an Amberlite XAD 7 resin column to remove any potential organic contaminants.
Representative samples of the food source were periodically analyzed for the presence of pesticides, PCBs, and toxic metals by Eurofins Lancaster Laboratories Environmental, Lancaster, Pennsylvania (U.S. EPA, 1997). None of these compounds have been detected at concentrations considered toxic in any of the samples analyzed, in agreement with ASTM (2007) standard practice. Based on the analysis for pesticides, the food source was considered to be of acceptable quality since all analyte concentrations were below levels of concern.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Hardness:

160-180 mg/L CaCO3

Test temperature:

20-22°C

pH:

7.8-8.3

Dissolved oxygen:

7.5-8.9 mg/L

Conductivity:

750-840 µS/cm

Nominal and measured concentrations:

- Nominal concentrations: 5.1, 13, 32, 80, 200, and 500 µg/L
- Geometric mean measured concentrations: 4.0, 10, 25, 61, 170, and 400 µg/L

Details on test conditions:

- 1.0 L glass beakers containing 0.8L of water
- Food type: Unicellular green algae, Ankistrodesmus falcatus (4 × 107 cells/mL) and a suspension of YCT (yeast, cereal leaves and flaked fish food)

Reference substance (positive control):

no

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

170 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mortality

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

61 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mortality: Number of living offspring produced per surviving parental animal {for Daphnia magna, TG 211}

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

61 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mortality: Total number living offspring produced at the end of the test per parent daphnia at the start of the test excluding from the analysis parental accidental and/or inadvertent mortality {TG 211}

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

61 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth

Duration:

21 d

Dose descriptor:

EC10

Basis for effect:

mortality

Remarks on result:

not determinable

Duration:

21 d

Dose descriptor:

EC10

Effect conc.:

70 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mortality: Number of living offspring produced per surviving parental animal {for Daphnia magna, TG 211}

Duration:

21 d

Dose descriptor:

EC10

Effect conc.:

69 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mortality: Total number living offspring produced at the end of the test per parent daphnia at the start of the test excluding from the analysis parental accidental and/or inadvertent mortality {TG 211}

Duration:

21 d

Dose descriptor:

EC10

Effect conc.:

> 170 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

400 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mortality

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

170 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mortality: Number of living offspring produced per surviving parental animal {for Daphnia magna, TG 211}

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

170 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mortality: Total number living offspring produced at the end of the test per parent daphnia at the start of the test excluding from the analysis parental accidental and/or inadvertent mortality {TG 211}

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

170 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth

Reported statistics and error estimates:

At the termination of the study, data obtained on organism survival, reproduction (total living offspring per female and total living offspring per surviving female daphnid), and growth (as total body length) were statistically analyzed to identify significant treatment-related effects. Analyses were performed using the individual response values.
All statistical analyses were conducted at the 95% level of certainty, except tests to assess normality and homogeneity of variance, where the 99% level of certainty was applied. CETIS Version 1.8 was used to perform the statistical computations. The highest test concentration that elicited no statistically significant difference between the exposed organisms and the control (NOEC) was determined. The lowest test concentration that elicited a statistically significant effect on organism performance is defined as the LOEC.

Validity criteria fulfilled:

yes

Conclusions:

Based on reproduction (total living offspring per female and total living offspring per surviving female) and length, the most sensitive endpoints, the 21 d NOEC and LOEC were determined to be 61 and 170 µg/L, respectively.

Executive summary:

A study was conducted to determine the long term toxicity of the substance on Daphnia magna, according to OECD Guideline 211, in compliance with GLP. The study was carried out in a closed exposure system to minimize volatilization of the test substance. Groups of 10 daphnids (<24 h old) were exposed to nominal test substance concentrations of 0, 5.1, 13, 32, 80, 200 and 500 µg/L under daily static-renewal conditions. A solvent (dimethyl formamide) control group was also included. At exposure initiation and at each renewal interval (every 24 h), the test substance solutions were freshly prepared. Analytical concentration verification were performed every 7 d by gas chromatography with mass selective detection. The parameters monitored included daphnid survival, reproduction and total body length. Measured concentrations in newly prepared solutions were representative of nominal concentrations, but test substance concentrations decreased (12 to 44%) over the 24 h exposure periods. This concentration gradient was observed consistently despite precautionary measures taken to minimize loss (e.g., closed exposure system). Test results were therefore expressed based on the basis of geometric mean measured concentrations (4.0, 10, 25, 61, 170 and 400 µg/L). As demonstrated by the performance of the control and solvent control, conditions appropriate for promoting acceptable survival and reproduction of the test species were achieved in the exposure system. Control survival and reproduction met the minimum criteria established by OECD guidelines (≥80% survival and ≥60 offspring per female). Time of the first brood release was within the normal performance expectation for this species. Under the study conditions and based on reproduction (total living offspring per female and total living offspring per surviving female) and length, the 21 d NOEC of the test substance in Daphnia was determined to be 61 µg/L (Shaw, 2018).

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

61 µg/L

Additional information

A study was conducted to determine the long term toxicity of the substance on Daphnia magna, according to OECD Guideline 211, in compliance with GLP. The study was carried out in a closed exposure system to minimize volatilization of the test substance. Groups of 10 daphnids (<24 h old) were exposed to nominal test substance concentrations of 0, 5.1, 13, 32, 80, 200 and 500 µg/L under daily static-renewal conditions. A solvent (dimethyl formamide) control group was also included. At exposure initiation and at each renewal interval (every 24 h), the test substance solutions were freshly prepared. Analytical concentration verification were performed every 7 d by gas chromatography with mass selective detection. The parameters monitored included daphnid survival, reproduction and total body length. Measured concentrations in newly prepared solutions were representative of nominal concentrations, but test substance concentrations decreased (12 to 44%) over the 24 h exposure periods. This concentration gradient was observed consistently despite precautionary measures taken to minimize loss (e.g., closed exposure system). Test results were therefore expressed based on the basis of geometric mean measured concentrations (4.0, 10, 25, 61, 170 and 400 µg/L). As demonstrated by the performance of the control and solvent control, conditions appropriate for promoting acceptable survival and reproduction of the test species were achieved in the exposure system. Control survival and reproduction met the minimum criteria established by OECD guidelines (≥80% survival and≥60 offspring per female). Time of the first brood release was within the normal performance expectation for this species. Under the study conditions and based on reproduction (total living offspring per female and total living offspring per surviving female) and length, the 21dNOEC of the test substance in Daphnia was determined to be 61µg/L(Shaw, 2018).