Butyl toluene-4-sulphonate

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

14 January 2020 to 16 January 2020

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)

Version / remarks:

2004

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Concentrations were adjusted for the purity of the test substance.

Analytical monitoring:

yes

Details on sampling:

One sample was taken (from the approximate midpoint from the surface, bottom, and sides of the vessel), at 0 hours (intermediate vessels prior to division into replicate vessels) and at 48 hours (composite of all replicates within each treatment level and the control), using a pipet.
Additional samples of the exposure solutions were also collected at each sampling interval and stored frozen as archive samples.
Additionally, three Quality Control (QC) samples were taken at each sampling interval, prepared in dilution water at nominal concentrations which approximated the test loading rate range.

Vehicle:

no

Details on test solutions:

The primary stock solution was prepared by adding 0.3530 g (0.3492 g as active ingredient) test material directly to a 4.0 L clear, glass aspirator bottle with a bottom side drain containing 3.5 L of fortified laboratory well water. The opening of the bottle was covered with parafilm and solution was set to slowly mix overnight using a magnetic stir plate and Teflon-coated stir bar. The solution was observed to be clear and colourless with visible, white, oily globules of test material on the bottom of the vessel as well as on the surface of the solution. Following mixing and a 5-minute settling period, the solution observations remained the same. Approximately 2.75 L of the soluble portion of the solution was drained from the aspirator bottle, avoiding the bottom and surface of the solution. The resulting solution was clear and colourless with no visible undissolved test material.
The primary stock solution was further diluted with fortified laboratory well water to make up the required exposure solutions.
The resulting exposure solutions were observed to be clear and colourless with no visible undissolved test material following mixing with a glass rod for approximately one minute. Control vessels were maintained under the same conditions as the treatment level solutions.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Justification for species: recommended by the study guidelines and are commonly used in acute freshwater invertebrate toxicity tests
- Age at study initiation: <24 hours old; immature daphnids were removed from culture 24 hours prior to exposure initiation, thus isolating sexually mature adults. Young produced by the parent organisms were used for the exposure.
- Source: Test facility culture
- Feeding during test : no

CULTURE AND CUULTURE CONDITIONS
- Culture vessel: 1.0-L glass beaker containing 0.80 L of water
- Food type: Unicellular green algae, Ankistrodesmus falcatus (4 × 10^7 cells/mL) and YCT suspension (yeast, cereal leaves, and flaked fish food) (based on the findings of periodic analyses, food sources were considered to be of acceptable quality since all analyte concentrations were below levels of concern).
- Feeding frequency: Once daily during culture
- Ephippia Observed: No
- Offspring Released in Culture 12 Days prior to Initiation: Yes
- Mortality of Culture Adults: 0% two days prior to initiation
- Daphnids Used in a Previous Test: No
- Water Type: Fortified laboratory well water (The culture water was prepared by fortifying well water based on the formula for hard water and filtering it through an Amberlite XAD 7 resin column to remove any potential organic contaminants)
- pH: 7.6 to 8.2
- Photoperiod: 16 hours light: 8 hours dark
- Light Intensity: 50 to 92 footcandles (540 to 990 lux)
- Temperature (°C): 19 to 21
- Dissolved Oxygen (mg/L): 7.1 to 9.7
- Conductivity (µS/cm): 820 to 850
- Total Hardness as CaCO3 (mg/L): 180
- Total Alkalinity as CaCO3 (mg/L): 86 to 92

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

180 mg/L (as CaCO3)

Test temperature:

21 - 22 °C

pH:

7.9 - 8.1

Dissolved oxygen:

8.3 - 9.3 mg/L

Conductivity:

850 µS/cm

Nominal and measured concentrations:

Nominal concentrations: 0 (control), 6.3, 13, 25, 50, and 100% of a 100 mg/L WAF
Geometric mean measured concentrations: 0 (control), 0.62, 1.4, 2.7, 5.3, and 10 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 250-mL glass beakers
- Fill volume: Approximately 200 mL
- Aeration: No
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Fortified laboratory well water (The culture water was prepared by fortifying well water based on the formula for hard water and filtering it through an Amberlite XAD 7 resin column to remove any potential organic contaminants)
- Total organic carbon: 0.94 mg/L
- Alkalinity: 92 mg/L (as CaCO3)
- Culture medium different from test medium: no, the dilution water used during this study was from the same source as the water used during culture and acclimation
- Intervals of water quality measurement: Representative samples of the dilution water source were analysed periodically for the presence of pesticides, PCBs, and toxic metals. None of these compounds were detected at concentrations that are considered toxic in any of the water samples analysed, in agreement with ASTM (2007) standard practice. In addition, the monthly TOC concentration fell within the recommendation of the guideline (i.e., ≤ 2 mg/L).

OTHER TEST CONDITIONS
- Photoperiod: 16 hours light: 8 hours dark with a 15- to 30-minute transition period controlled with an automatic timer
- Light intensity: 640 to 860 lux (approximately 60 to 80 footcandles) measured around the test area once during the exposure with a Fisher Scientific traceable light meter

EFFECT PARAMETERS MEASURED
Biological observations, number of immobilised daphnids, and observations of the physical characteristics of the exposure and control solutions (e.g., precipitate, film on solution’s surface) were recorded at exposure initiation and at each subsequent 24-hour interval until exposure termination (48 hours), if applicable. Immobilisation was defined as the inability to swim within 15 seconds after gentle agitation of the exposure vessel. Immobilised organisms were removed and discarded at each observation interval.

WATER QUALITY MEASUREMENTS
Water quality monitoring was conducted at 0, 24, and 48 hours from replicate vessel A. pH was measured with a pH meter (Yellow Springs Instrument (YSI) pH100A pH meter and combination electrode), dissolved oxygen was measured with a DO Meter (YSI Pro20 dissolved oxygen meter/temperature probe), and temperature was measured with a thermometer (Fisher Scientific Traceable minimum-maximum thermometer - located in a satellite vessel in the environmental chamber).

RANGE-FINDING STUDY
- Test concentrations: 0 (control), 0.10, 1.0, 10, 100 % of a 100 mg/L WAF
- Results used to determine the conditions for the definitive study: yes
Daphnids were exposed to test material (at the above test concentrations) for 48 hours under static conditions. 0% immobilisation was observed at exposure concentrations up to 10 % of a 100 mg/L WAF. 100 % immobilisation of daphnids was observed after 24 and 48 hours at the 100 % of a 100 mg/L WAF test concentration. Based on these results, nominal loading rates of 6.3, 13, 25, 50, and 100% of a 100 mg/L WAF, and a dilution water control were selected for the definitive exposure.

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

18 other: % of 100 mg/L WAF

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 95% Confidence Intervals 13 - 25 % of 100 mg/L WAF

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

1.9 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 95% Confidence Intervals 1.4 - 2.7 mg/L

Details on results:

WATER QUALITY MEASUREMENTS
Throughout the exposure period, all water quality parameters measured were unaffected by the concentrations of test material tested and remained within acceptable ranges for the survival of daphnids.

TEST MATERIAL CONCENTRATIONS
- Method validation: The analytical method was validated in AAP medium by dosing with test material at concentrations of 0.400 and 10,000 µg/L. Recoveries averaged 113 ± 2.35% with a limit of quantification (LOQ) of 0.400 µg/L, the lowest fortification level, and a method detection limit (MDL) of 0.200 µg/L. Acceptance criteria for mean recoveries of samples prepared during the method validation was 70.0 to 120% based on SANCO guidance. Defined limits for acceptance of individual quality control sample performance in subsequent studies were set at 70.0 to 120%.
- Measured concentrations: Measured concentrations declined throughout the exposure and maintained the expected concentration gradient.
Analysis of the QC samples resulted in measured concentrations which were consistent with the predetermined recovery range and ranged from 103 to 120% (N = 6) of the nominal fortified concentrations (0.000400, 0.500, and 10.0 mg/L). Based on these results, it was determined that the appropriate accuracy and quality control were maintained during the analysis of the exposure solutions.

BIOLOGICAL RESULTS
None of the daphnids exposed to the 0 (control), 6.3 or 13 % of a 100 mg/L WAF test concentrations were observed to be immobilised at 24 or 48 hours. All of the daphnids exposed to the 25, 50 and 100 % of a 100 mg/L WAF test concentrations were observed to be immobilised at 24 and 48 hours.

Results with reference substance (positive control):

Daphnids (< 24 hours old) were exposed to the reference substance (potassium dichromate, 100%) over a 24-hour study duration (from 10 December 2019 to 11 December 2019). The 24-hour EC50 was determined to be 2.5 mg/L, with a 95% confidence interval of 2.0 to 3.1 mg/L.

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of the study the 48-hour EC50 was estimated by binomial probability to be 18% of a 100 mg/L WAF, with a 95% confidence interval of 13 to 25% of a 100 mg/L WAF (equivalent to 1.9 mg/L, with a 95% confidence interval of 1.4 to 2.7 mg/L, based on geometric mean measured concentrations).

Executive summary:

The short-term toxicity of the test material to aquatic invertebrates was investigated in a study which was conducted in accordance with the standardised guideline OECD 202, and under GLP conditions.

Following a preliminary experiment, groups of 5 Daphnia magna were exposed to test material at nominal loading rates of 6.3, 13, 25, 50, and 100% of a 100 mg/L water-accommodated fraction (WAF), under static conditions, for a period of 48 hours. Analysis of the test solutions indicated that these loading rates were equivalent to geometric mean measured concentrations of 0.62, 1.4, 2.7, 5.3, and 10 mg/L.

During the exposure period the number of immobilised daphnids was observed at 24 and 48 hours.

None of the daphnids exposed to the 0 (control), 6.3 or 13 % of a 100 mg/L WAF test concentrations were observed to be immobilised at 24 or 48 hours. All of the daphnids exposed to the 25, 50 and 100 % of a 100 mg/L WAF test concentrations were observed to be immobilised at 24 and 48 hours.

Therefore, under the conditions of the study the 48-hour EC50 was estimated by binomial probability to be 18% of a 100 mg/L WAF, with a 95% confidence interval of 13 to 25% of a 100 mg/L WAF (equivalent to 1.9 mg/L, with a 95% confidence interval of 1.4 to 2.7 mg/L, based on geometric mean measured concentrations).

Description of key information

Under the conditions of the study the 48-hour EC50 was estimated by binomial probability to be 18% of a 100 mg/L WAF, with a 95% confidence interval of 13 to 25% of a 100 mg/L WAF (equivalent to 1.9 mg/L, with a 95% confidence interval of 1.4 to 2.7 mg/L, based on geometric mean measured concentrations).

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

1.9 mg/L

Additional information

The short-term toxicity of the test material to aquatic invertebrates was investigated in a study which was conducted in accordance with the standardised guideline OECD 202, and under GLP conditions.

Following a preliminary experiment, groups of 5 Daphnia magna were exposed to test material at nominal loading rates of 6.3, 13, 25, 50, and 100% of a 100 mg/L water-accommodated fraction (WAF), under static conditions, for a period of 48 hours. Analysis of the test solutions indicated that these loading rates were equivalent to geometric mean measured concentrations of 0.62, 1.4, 2.7, 5.3, and 10 mg/L.

During the exposure period the number of immobilised daphnids was observed at 24 and 48 hours.

None of the daphnids exposed to the 0 (control), 6.3 or 13 % of a 100 mg/L WAF test concentrations were observed to be immobilised at 24 or 48 hours. All of the daphnids exposed to the 25, 50 and 100 % of a 100 mg/L WAF test concentrations were observed to be immobilised at 24 and 48 hours.

Therefore, under the conditions of the study the 48-hour EC50 was estimated by binomial probability to be 18% of a 100 mg/L WAF, with a 95% confidence interval of 13 to 25% of a 100 mg/L WAF (equivalent to 1.9 mg/L, with a 95% confidence interval of 1.4 to 2.7 mg/L, based on geometric mean measured concentrations).