Trichloro-p-tolylsilane

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

28 - 30 Oct 2009

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Sampling method: At test initiation, samples were removed from the intermediate mixing vessels for analysis of the hydrolysation product (trihydroxy(phenyl)silane). At test termination, the replicate solutions from the treatment levels and the control were composited within the treatments prior to sampling.

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Prior to test solution preparation, a dosing stock solution was prepared by mixing 304 μL of trichloro(phenyl)silane with 400 μL of tetrahydrofuran (THF) using a Hamilton syringe. A 100 mg test item/L stock solution was prepared prior to test initiation by adding 352 μL of the dosing stock solution to 1600 mL dilution water using a Hamilton syringe. Prior to addition of the dosing stock solution, the glass beaker containing the dilution water was placed on a magnetic stirrer. The spiked solution was stirred continuously over night. The pH of the solution was then adjusted to 7.01 with 1 N hydrochloric acid (HCl) and 1 N sodium hydroxide (NaOH). Thereafter, the stock solution was further diluted to a final volume of 2000 mL with dilution water, resulting in a solvent (THF) concentration of 0.10 mL/L. Nominal concentrations of 2.0, 4.3, 9.4, 20.7, 45.5 and 100 mg/L were prepared by diltion of the stock solution. and addition of THF to a final concentration of 0.1 mL/L. All resulting test solutions were shaken by hand for 30 seconds and observed to be clear and colourless, with no visible undissolved test item.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM

- Source: The Daphnia magna used in this toxicity test were obtained from laboratory cultures maintained at Springborn Smithers Laboratories (Europe), originally obtained from a culture at Springborn Smithers Laboratories Wareham (MA), USA.

- Culture conditions: Prior to testing, the daphnids were held in glass beakers under a photoperiod of 16 hours light and 8 hours darkness with a 30 minute transition period.

- Culture medium: The culture water consisted of modified Elendt M4 medium. After preparation the medium was aerated using an air pump to bring the pH and dissolved gases into equilibrium with the atmosphere. The modified Elendt M4 medium was allowed to equilibrate for at least two days prior to use. Total hardness, total alkalinity, pH and specific conductivity of the dilution water were determined after preparing each batch to verify that these parameters are within the acceptable ranges.

- Feeding: During culture the daphnids were fed 1.5 - 2.0 mL of a solution containing approximately 4 x 10^7 cells/mL of the unicellular green alga, Ankistrodesmus falcatus (ANK) and approximately four drops or 0.5 mL of a combination of yeast, cereal leaves and flaked fish food (YCT) daily.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

150 mg/L as CaCO3

Test temperature:

19.1 to 21.2 °C

pH:

7.31 to 7.94

Dissolved oxygen:

8.00 to 8.61 mg/L

Nominal and measured concentrations:

Nominal test concentrations: 0 (Control), 0 (solvent control), 2.0, 4.3, 9.4, 20.7, 45.5 and 100 mg/L

The concentration of the test item (determined as trihydroxy(phenyl)silane) in the newly prepared solutions at test start ranged from 92.9 to 103% of nominal concentrations. The concentration of the test item in the aged solutions at test termination (hour 48) ranged from 92.9 to 104% of nominal concentrations.

Based on these results, the nominal test concentrations were used for the evaluation of the biological data.

Details on test conditions:

TEST SYSTEM
- Replication: Four test vessels per treatment level and the controls were prepared.
- Age of test organisms: Daphnids, < 24 hours old
- Distribution of test organisms to treatments: Daphnids were impartially selected and distributed using an intermediate vessel by adding no more than two daphnids to each vessel until all intermediate vessels contained two daphnids. This procedure was repeated until each vessel contained 20 daphnids. The test was initiated when 5 daphnids were introduced to each replicate exposure vessel (replicates A to D). A total of 20 organisms were exposed to each treatment level and control solutions. Each test vessel was labeled with the study number, concentration and replicate designation.
- Feeding: The daphnids were not fed during the 48 hour exposure period.
- Dilution water: The batch of modified Elendt M4 medium used for the definitive test had a total hardness and alkalinity of 150 and 34 mg/L as CaCO3, respectively, a pH of 8.05 and a specific conductivity of 400 μS/cm.
- Observations: The number of immobilized daphnids observed in each replicate test vessel was recorded at test initiation and after 24 and 48 hours of exposure. Immobilization was defined as those animals not able to swim within 15 seconds after gentle agitation of the test vessel or by pipette. Biological observations (e.g., abnormal behavior or appearance of the test organisms) and observations of the physical characteristics of the test solutions (e.g., precipitate, film on the surface of the test solution) were also made and recorded after 0, 24 and 48 hours of exposure.
- Water quality: The pH, dissolved oxygen (DO) concentration and temperature were measured at 0, 24 and 48 hours in one replicate of each treatment level and the control. Continuous temperature monitoring was performed in an additional vessel adjacent to the test vessels throughout the exposure period. The pH was measured with a WTW 323 pH meter, dissolved oxygen and daily temperature were measured using a WTW Oxi 325 dissolved oxygen meter. Light intensity was measured with a Pancontrol LX 1308 lux meter.

Reference substance (positive control):

no

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

9.4 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

- Immobilisation of Control: 0% in Control, 5% in solvent Control

Reported statistics and error estimates:

There were insufficient levels of immobilisation in the treatments to derive an EC50 value.

The No-Observed-Effect Concentration (NOEC) was determined by visual observation of the raw data and is defined as the highest concentration tested at which there was no toxicant-related immobilization or physical and behavioural abnormalities (e.g., lethargy) with respect to the control organisms.

Table 1. Results of analysis of test media (measured as Trihydroxy(phenyl)silane)

Nominal test substance concentration (mg/L)	Initial measured concentration (mg/L) and (Percentage of nominal)	Measured concentration after 48 hours (mg/L) and (Percentage of nominal)
0 (Control)	<LOQ	<LOQ
0 (Solvent control)	<LOQ	<LOQ
2.0	1.86 (92.9)	1.86 (92.9)
4.3	4.22 (98.1)	4.18 (97.1)
9.4	9.22 (98.1)	9.49 (101)
20.7	20.5 (99.0)	20.5 (99.2)
45.5	46.8 (103)	47.5 (104)
100	99.0 (99.0)	97.6 (97.6)

Table 2. Test results

Nominal test substance concentration (mg/L)	Mean percentage immobilisation after 24 hours	Mean percentage immobilisation after 48 hours
0 (Control)	0	0
0 (Solvent control)	0	5
2.0	0	0
4.3	0	5
9.4	0	0
20.7	0	15
45.5	0	15
100	0	25

Validity criteria fulfilled:

yes

Conclusions:

A 48 hour EC50 value of >100 mg/L and a NOEC of 9.4 mg/L have been determined for the effects of the test substance on mobility of Daphnia magna (OECD 202).

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Please refer to the attached justification below and the overall justification for grouping of substances attached in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across source

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Description of key information

EC50 (48 h) > 100 mg/L (nominal, OECD 202, Daphnia magna) based on read across from CAS 98-13-5

Additional information

No data on the toxicity of trichloro(4-methylphenyl)silane (CAS 701-35-9) towards aquatic invertebrates are available. In accordance with Regulation (EC) No. 1907/2006 Annex XI, 1.5 “Grouping of substances and read across” and in accordance with the read across assessment framework (RAAF, ECHA 2017) a read across from the analogue substance trichloro(phenyl)silane (CAS 98-13-5) has been performed to support the environmental hazard assessment of the substance. Details on the read across justification can be found in the attached justification in the respective target entry and in the overall justification for grouping of substances attached in IUCLID Section 13.

The study with the analogue substance trichloro(phenyl)silane (CAS 98-13-5) was performed according to OECD 202 and GLP standards with Daphnia magna as the test organism (2009). D. magna was exposed in a static testing regime to the nominal concentrations of 0 (control), 0 (solvent control), 2.0, 4.3, 9.4, 20.7, 45.5 and 100 mg/L for 48 h. Tetrahydrofuran (THF) was used as a solvent in a final concentration of 0.1 mL/L. The test item concentrations were prepared by diluting the 100 mg/L stock solution, which was stirred overnight. The concentrations of the hydrolysis product trihydroxy(phenyl)silane were analytically monitored at test start and at the end of the exposure period, since the parent substance is not stable and hydrolysis rapidly. The recoveries were between 92.9 and 104% of the nominal values and therefore the results were expressed in terms of nominal concentrations. The study resulted in an EC50 (48 h) of > 100 mg/L. 

Based on the results of the analogue substance, trichloro(4-methylphenyl)silane (CAS 701-35-9) is not assumed to cause short term adverse effects towards aquatic invertebrates.