O,O-tert-butyl isopropyl monoperoxycarbonate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Deviations:

yes

Remarks:

The NaHCO3 concentration of the test medium was 150 mg/L instead of 50 mg/L. Biomass (dry weight) was not determined at the end of the test.Parallel non inoculated replicates were incubated in the event that the test substance itself was not detectable.

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

EC name: O,O-tert-butyl isopropyl monoperoxycarbonate
CAS no.: 2372-21-6
Water solubility: 2.2 g/L
Storage conditions: -25°C
Lot number: 1203442069
Purity: 74.6 %

Analytical monitoring:

yes

Details on sampling:

Samples were taken daily from all concentrations with and without algae.
At least 10 mL was sampled in each case. Samples from the actual test replicates were filtered using a 0.45 μm filter to remove algae prior to analysis. Filters were primed with the relevant solution before use. Further dilution to within the range of the calibration curve was then carried out as required and samples were then added to HPLC vials. The samples were analyzed as soon as possible after sampling no storage took place.

Vehicle:

no

Details on test solutions:

Preparation of the stock solutions:
The test substance is sufficiently soluble to dilute the test concentrations from a stock solution. To prepare the stock solution 0.0029 g of test substance was weighed on an analytical balance and then dissolved directly in approx. 100 mL test medium. The stock solution was agitated mechanically for 60 minutes in the dark to completely dissolve the test substance.
The pH of the stock solution was checked and found to be 8.0 and was not adjusted. A clear stock solution with a nominal concentration of 29 mg/L was obtained.

Preparation of the test solutions:
The test solutions were prepared in triplicate by addition of the adequate amounts of stock solution (So as to reach desired concentration in 40 mL) to the test vessels, then test medium was added up to the required final volume. Six control vessels containing only test medium were included in the test. An additional parallel series with the same concentrations but without addition of inoculum was prepared as well as an additional sacrificial replicate with inoculum for daily chemical analyses.

Test organisms (species):

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

Details on test organisms:

The test was carried out with the freshwater unicellular algae P. subcapitata (CCAP 278/4) obtained from the Culture Collection of Algae and Protozoa SAMS Research Services Ltd. Dunstaffnage Marine Laboratory, Dunbeg, Argyll, Scotland. After purchasing this strain was cultured and maintained. Cultures on sloped agar tubes were stored at 4°C in the dark until required. Exponentially growing cultures are maintained at 23 ± 2°C in a temperature-controlled illuminated orbital incubator and are re-cultured under sterile conditions weekly to keep the algae in this phase.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

22.4 to 23.1 °C

pH:

8.1 to 8.8

Nominal and measured concentrations:

Nominal: 0.02, 0.064, 0.20, 0.65, and 1.31 mg/L
Geometric mean measured: 0.005, 0.021, 0.042, 0.147 and 0.371 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 100 mL glass Erlenmeyers
- Type (delete if not applicable): closed with cotton wool stoppers
- Initial cells density: 1E+04
- Control end cells density: 1.1E+06
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes, OECD medium

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: OECD medium
- Culture medium different from test medium: No

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: no
- Photoperiod: continuous light
- Light intensity and quality: 98.8 and 94.1 μmol·m-2·s-1 at the beginning and the end of the test, respectively

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: spectrophotometer

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.2
- Range finding study
- Results used to determine the conditions for the definitive study: significant grwoth inhibition occurred at 1 mg/L

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.002 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.059 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.01 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Validity criteria fulfilled:

yes

Executive summary:

In order to predict the effects of the test chemical in an aquatic environment, the toxicity of O,O-tertbutyl isopropyl monoperoxycarbonate to freshwater algae was determined using the Algal Growth Inhibition Test in accordance with OECD, EC and ISO test guidelines and with the OECD Principles of Good Laboratory Practice. Slight modifications to the guideline were applied to ensure good growth and pH control of the cultures.

The toxicity of the test substance to an exponentially growing culture of P. subcapitata was determined over an exposure period of 72 hours. All endpoints are based on geometric mean measured concentrations. Significant effect (growth rate) was observed on growth rate at 0.005 mg/L. The NOEC is therefore < 0.005 mg/L and LOEC is 0.005mg/L. The ErC10 is 0.002 mg/L and the ErC50 is 0.059 mg/L. The EbC50 was found to be 0.01 mg/L.

The test is valid as shown by:

The increase of the extinction of the control over 72 h by a factor of 110.

The mean coefficient of variation for section-by-section specific growth rates in the control cultures did not exceed 35%.

The coefficient of variation of average specific growth rates during the whole test period in the replicate control cultures did not exceed 7%.

The set quality criteria for chemical analysis were all met.

The most recent reference test for the algae species tested demonstrated acceptable sensitivity according to the test guideline.

In addition

pH variation in the control did not vary more than 0.7 pH units as recommended in the study guideline.

The results of the chemical analyses show that the test substance did not remain stable in the test system. However sufficient quantification was possible to allow calculations of geometric means of the measured concentrations as is acceptable in the study guideline.

Description of key information

One valid study perforemd with the freshwater alga P. subcapitata is available. The study was performed according to OECD 201 under GLP.

The ErC10 is 0.002 mg/L and the ErC50 is 0.059 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

0.059 mg/L

EC10 or NOEC for freshwater algae:

0.002 mg/L