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Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2002-05-14 - 2002-07-22
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Guideline study according to GLP. The actual concentration of dissolved test material was not measured analytically.
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
CYANOX® 1790 Antioxidant
IUPAC nomenclature - Tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanurate
Synonym - [tris(4-t-butyl-3-hydroxy-2,6-dimethyl-benzyl)-s-triazine-2,4,6-(1H,3H,5H) trione]
Lot PA2010802
Appearance - White powder, odorless
CAS No. 40601-76-1
Molecular Formula - C42H57N3O6
Molecular Weight - 699.92 g/mole
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
Water was treated by vigorous aeration, filtered to 20 microns, passed through activated carbon and re-aerated prior to use.

Test water was prepared by directly adding the test material (0.5 g) to 0.5 liters of dilution water. The test vessel was placed onto a mechanical stir plate with a rotating stir bar. The test material was spiked directly into the vortex and allowed to mix for approximately 30 minutes. The liquid was then filtered through a Gelman minicapsule (0.45 microns) Versapore membrane filter. The test filtrate (which appeared clear) was transferred into a glass test chamber, placed onto a 20 degrees C water table, and allowed to reach the desired test temperature (20 +/- 1 degrees C). A control solution containing dilution water only also was prepared.
Test organisms (species):
Daphnia magna
Details on test organisms:
Daphnia magna used in the test were progeny from animals obtained from Aquatic Research Organisms, Hampton New Hampshire in August 2000. A subculture of adults was isolated from these cultures and maintained on site prior to testing. The cultures were fed the green algae, Selenastrum capricornutum and a solution prepared from yeast, cereal leaves (Cerophyll) and trout chow daily. Less than 24 hours prior to testing, the adults were placed in food-free dilution water. Neonates (< 24 hours old) were collected on July 2, 2002.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
48 h
Post exposure observation period:
None.
Hardness:
The hardness (as calcium carbonate), alkalinity (as calcium carbonate) and specific conductivity were 76 mg/l, 31 mg/l and 407 microSiemens, respectively
Test temperature:
Target: 20 +/- 2 degrees C. The temperature ranged from 20.1 - 20.9 degrees C during the test.
pH:
Target range: 6.5-8.0. pH values ranged from 7.1 - 7.3 at the beginning of the test and from 7.2 - 7.3 at the end of the test..
Dissolved oxygen:
The dissolved oxygen concentrations in the test water ranged from 8.2 - 8.8 mg/l (92-98 % of saturation) at the beginning of the test and 8.0 - 8.4 mg/l (89-93% of saturation) for the remainder of the test
Salinity:
No data
Nominal and measured concentrations:
Preliminary test: nominal concentrations of 0.0 (control), 0.2, 1, 11, 99 and 1000 mg whole material/l.
Main test: limit test with 1000 mg whole material (nominal concentration).
Details on test conditions:
The test organisms were cultured and isolated in moderately hard fresh water (pH 6.5 - 8.0, temperature 20 +/- 2 degrees C), which originated from Jupiter Florida. Water was treated by vigorous aeration, filtered to 20 microns, passed through activated carbon and re-aerated prior to use. The hardness (as calcium carbonate), alkalinity (as calcium carbonate) and specific conductivity were 76 mg/l, 31 mg/l and 407 microSiemens, respectively. Chemical characteristics were listed in an Appendix to the study. No ephippia were produced during culture and the organisms appeared in good physical condition at test initiation.

A 48-hr preliminary range-finding test was conducted at nominal concentrations of 0.0 (control), 0.2, 1, 11, 99 and 1000 mg whole material/l. Five Daphnia were tested for each condition. None of the organisms exposed to concentrations < 1000 mg/l died in the experiment. Twenty percent of Daphnia exposed to 1000 mg/l died. The test material was insoluble at each concentration used.

Due to the insolubility of the test material in the preliminary test, the definitive test was initiated as a limit test with 1000 mg whole material/l. Test water was prepared by directly adding the test material (0.5 g) to 0.5 liters of dilution water. The test vessel was placed onto a mechanical stir plate with a rotating stir bar. The test material was spiked directly into the vortex and allowed to mix for approximately 30 minutes. The liquid was then filtered through a Gelman minicapsule (0.45 microns) Versapore membrane filter. The test filtrate (which appeared clear) was transferred into a glass test chamber, placed onto a 20 degrees C water table, and allowed to reach the desired test temperature (20 +/- 1 degrees C). A control solution containing dilution water only also was prepared.

After initial water quality parameters (temperature, pH, dissolved oxygen) were measured, 5 organisms (one or two at a time) were added to each test chamber. Four replicate chambers were established for the control and test solutions (for a total of 20 control and test organisms). The test chambers were 50-ml glass vials (2.5 cm x 9.5 cm) containing 50 ml of dilution water or test solution (which provided a final water depth of 9.5 cm). All chambers were covered to reduce evaporation. The chambers were placed in a water bath and maintained under a photoperiod of 16 hours light/8 hours darkness (at 9.5-10.6 micromoles/m2/sec light intensity). Organisms were not fed during the test and the water was not aerated. Survival and condition of Daphnia and water quality were monitored daily. The test was terminated after 48-hr evaluations had been performed.

The no effect concentration (NOEC) and EC50 values were to be calculated using ToxCalc Comprehensive Toxicity Data Analysis and Database Software (Version 5.0, 1996).
Duration:
48 h
Dose descriptor:
EL50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Duration:
48 h
Dose descriptor:
NOELR
Effect conc.:
1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Details on results:
The rate of mortality in the controls was 5 % (1/20) at 24 hours, and 10% (2/20) at 48 hours. For treated organisms, the mortality rate was 10% at both 24 and 48 hours (2/20). The no effect concentration (NOEL) and EL50 value at 48 hours were 1000 mg whole material/l and > 1000 mg whole material/l, respectively.
Conclusions:
A 48-h limit test at a nominal concentration of 1000 mg/L indicated no significant toxicity to Daphnia magna.
Executive summary:

In a limit test conducted according to OECD Guideline 202 and under GLP condtions, a nominal concentration of 1000 mg/L of the test material caused no significant mortality. The 48-hour EC50 could not be calculated due to the lack of signification mortality at the specified time, and therefore can be stated to be > 1000 mg/L. The no-observable-effect concentration (NOEL) was 1000 mg/L based on the lack of significant mortality and sublethal effects at this test concentration.

Description of key information

A 48-h limit test at a nominal concentration of 1000 mg/L indicated no significant toxicity to Daphnia magna.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
1 000 mg/L

Additional information

In a 48 -h limit test conducted according to OECD Guideline 202 in Daphnia magna, a nominal concentration of 1000 mg/L of the test material caused no significant mortality.