Isotridecyl 3,5,5-trimethylhexanoate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

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

Adequacy of study:

other information

Justification for type of information:

See attached

Reason / purpose for cross-reference:

read-across source

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

08 August to 11 August 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Batch P7560

Analytical monitoring:

no

Vehicle:

no

Remarks:

WAF

Details on test solutions:

At the start of the test, an amount of test substance (99.98 mg) was added to 1000 mL of EC medium. The preparation was stirred for ca 24 hours (with a vortex no deeper
than 1 cm), media were then allowed to settle for ca 1 hour The final media was then syphoned from the mid-section (aqueous phase) of the vessel. A control treatment was
prepared by adding EC medium only to the control vessels.

Test organisms (species):

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

Details on test organisms:

The test organism, Pseudokirchneriella subcapitata (Strain 278/4), was originally obtained from the Culture Collection of Algae and Protozoa (CCAP) and is a
representative species of the freshwater aquatic phytoplankton. Prior to testing, duplicate starter cultures were prepared and incubated under test
conditions (as detailed in Appendix 2) to obtain sufficient algal cells in exponential growth and to achieve a starting algae cell density of 1 × 104 cells/mL.

Test type:

semi-static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Test temperature:

22.0-23.1 °C

pH:

with algae. The pH tended to increase relative to increases in algal densities, which is typical for tests conducted with P. subcapitata. The pH in the control increased by a maximum of 1.77 units, which exceeds the OECD 201 guideline requirement of an increase, not greater than 1.5 units. This change in pH was not considered to be detrimental to this study since increases in pH of greater than 1.5 units are commonly observed and this change had no impact on the growth of the control, which met the established validity criteria for the test.

Nominal and measured concentrations:

100 mg/L WAF

Details on test conditions:

All flasks were loosely-capped and incubated in a temperature controlled laboratory under a light bank. The vessels were placed on an orbital shaker (ca 100 rpm) under conditions of constant light (4440 to 8880 Lux), using florescent tube lights, emitting light across the visible portion of the spectrum (400 - 700 nm). The light intensity within the test area was monitored at the start and end of the test. At the start of the test, the pH of freshly prepared test media was determined. The pH in each test vessel was also determined at the end of the test. The laboratory temperature was set within the range 21 to 24°C and maintained within ± 2°C for the duration of the test. The temperature was recorded continuously using a digital thermometer.
Based on the results of the range-finding test, the definitive limit test was conducted with a control and nominal test concentration of 100 mg/L LR WAF.
Six test vessels were prepared for the control (EC medium only) and test concentration, each with an initial cell concentration of 1 × 104 cells/mL. A blank
vessel (not inoculated with algae) was prepared during the definitive limit test at control only.
At the start of the test, an amount of test substance (99.98 mg) was added to 1000 mL of EC medium. The preparation was stirred for ca 24 hours (with a vortex no deeper than 1 cm), media were then allowed to settle for ca 1 hour The final media was then syphoned from the mid-section (aqueous phase) of the vessel. A control treatment was prepared by adding EC medium only to the control vessels.
The appearance, colour and behaviour of the test substance in the test media were recorded at the start and end of the test.
Algae cell counts were performed at 24, 48 and 72 hours during the test.

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

other: NOEL

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Growth rate, yield and biomass

Details on results:

The results indicated that there was no toxicity at the limit of solubility of the test. Based on nominal loading rate concentrations, the 72-hour EyL50, EbL50 and ErL50
values were calculated to be >100 mg/L LR WAF.
The corresponding NOEL values for yield, biomass and specific growth rate after 72 hours were 100 mg/L LR WAF.
All validity criteria were met therefore the test was considered valid.

Validity criteria fulfilled:

yes

Conclusions:

Based on nominal loading rate concentrations, the 72-hour EyL50, EbL50 and ErL50 values were calculated to be >100 mg/L LR WAF.
The corresponding NOEL values for yield, biomass and specific growth rate after 72 hours were 100 mg/L LR WAF.
All validity criteria were met therefore the test was considered valid.

Executive summary:

Based on nominal loading rate concentrations, the 72-hour EyL50, EbL50 and ErL50 values were calculated to be >100 mg/L LR WAF.

The corresponding NOEL values for yield, biomass and specific growth rate after 72 hours were 100 mg/L LR WAF.

All validity criteria were met therefore the test was considered valid.

Additional information

Based on nominal loading rate concentrations, the 72-hour EyL50, EbL50 and ErL50 values were calculated to be >100 mg/L LR WAF.

The corresponding NOEL values for yield, biomass and specific growth rate after 72 hours were 100 mg/L LR WAF.

All validity criteria were met therefore the test was considered valid.