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Long-term toxicity to aquatic invertebrates

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Reference
Endpoint:
long-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
test procedure in accordance with national standard methods with acceptable restrictions
Qualifier:
according to guideline
Guideline:
other: U.S. EPA Whole Effluent Testing Program method, modified to minimize volatilization
Qualifier:
according to guideline
Guideline:
other: ASTM (1994). Standard Guide for Conducting Three-Brood, Renewal Toxicity Tests with Ceriodaphnia dubia, E 1295—89. Am. Soc. Testing and Materials, Philadelphia.
Principles of method if other than guideline:
Method was modified to minimize volatilization
GLP compliance:
no
Analytical monitoring:
yes
Details on sampling:
In tests with individual components, toxicant concentrations were measured at the beginning and end of the experiment. Newly prepared test solution and 24-h-old test solution composited from three replicates from each treatment level were analyzed. Acute toxicological results are based on the geometric mean of the two measured concentrations for each treatment level measured at the beginning of the test. Chronic toxicological results are based on the geometric mean of the four measured concentrations for each treatment level measured during the duration of the experiment.
Vehicle:
no
Details on test solutions:
Stock solutions of test chemicals were prepared by adding amounts of chemical below their reported water solubility to dilution water using glass syringes.
No carriers were used.
Stocks were proportionally diluted to yield other concentrations.
Test organisms (species):
Ceriodaphnia dubia
Details on test organisms:
C. dubia were obtained from Aquastar, Inc. (Mobile, Alabama) and cultured in house.
Tests were conducted in artificial moderately hard water.
Light was provided by full spec- trum fluorescent bulbs with a color rendering index '90 at an intensity of 20 mE/m 􏰔/S and a photoperiod of 16L : 8D.
Daphnids were fed an algae and cereal leaf mix containing equal numbers of cells of Selenastrum capricornutum and Chlorella vulgaris mixed with a rye grass infusion.
Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
7 d
Hardness:
68.3
pH:
7.6
Dissolved oxygen:
Dissolved oxygen was monitored on 24-h-old solutions and always remained above 7.0 ppm.
Conductivity:
207.8
Nominal and measured concentrations:
0, 13, 24, 54, 90, 212 µmol
Details on test conditions:
To minimize volatilization, instead of 30-ml beakers, individual organ- isms were tested in 25-ml borosilicate glass vials filled to capacity and closed tightly using teflon PTFE-lined silicon septa held in place by polypropylene screw-on caps. Solutions were renewed daily.
Dissolved oxygen was monitored on 24-h-old solutions and always remained above 7.0 ppm.
Survival, behavior, and reproduction were observed at the time of daily renewal. Because the chemicals tested commonly have a sedating effect, care was taken to distinguish dead from narcotized individuals; daphnids that did not move when gently prodded were examined for a heartbeat at a magnification of 100X. Tests were continued until 60% of the control animals had completed three broods, i.e., 6 or 7 days.
Reference substance (positive control):
not specified
Key result
Duration:
2 d
Dose descriptor:
LC50
Effect conc.:
17 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
act. ingr.
Basis for effect:
mortality
Key result
Duration:
7 d
Dose descriptor:
LC50
Effect conc.:
17 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
act. ingr.
Basis for effect:
mortality
Key result
Duration:
7 d
Dose descriptor:
NOEC
Effect conc.:
7.1 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
act. ingr.
Basis for effect:
reproduction
Key result
Duration:
7 d
Dose descriptor:
LOEC
Effect conc.:
12 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
act. ingr.
Basis for effect:
reproduction
Key result
Duration:
7 d
Dose descriptor:
IC50
Effect conc.:
11 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
act. ingr.
Basis for effect:
reproduction
Details on results:
2-day LC50: 130 µM (99 - 170)
7-day LC50: 129 µM (113 - 147)
NOEL for reproduction: 54 µM
LOEL for reproduction: 90 µM
IC50 reproduction 82 µM (77-86)
Mean chemical retention: 86.4
Values were recalculated based on a molecular weight for TCE of 131.4 g/mol
Reported statistics and error estimates:
Toxicity tests with individual chemicals were analyzed to determine criterion effect levels for mortality and reproduction following standard methods (U.S. EPA, 1994). Both 2- and 7-day LC􏰗􏰒s (concentrations lethal to 50% of the organisms) were calculated using binomial or trimmed Spearman—Karber tests, as appropriate.
After appropriate tests of normality, effects on reproduction (number of young per female through the end of the test) were analyzed with ANOVA, followed by one-sided Dunnett’s comparison of means to the control to determine NOELs (no-observed- effect levels) and LOELs (lowest-observed-effect levels). In addition, IC􏰗􏰒s (concentrations inhibiting reproduction by 50% relative to mean control performance) were calculated from smoothed data using bootstrap analysis (Norberg- King, 1993).
Validity criteria fulfilled:
not specified
Conclusions:
In a study conducted according to U.S. EPA Whole Effluent Testing Program method, Ceriodaphnia dubia were exposed to concentrations of 0, 13, 24, 54, 90, 212 µmol TCE and continued until 60% of the control animals had completed three broods, i.e., 6 or 7 days.
Mortality was observed at higher concentrations resulting in an EC50 of 17 mg/L both after 48 hours and 7 days.
The NOEC for reproduction was found to be 7.1 mg/L and the LOEC was 12 mg/L.
The concentration inhibiting reproduction by 50% relative to mean control performance (IC50) was calculated to be 11 mg/L.

Description of key information

The NOEC for reproduction obtained from a study according to to U.S. EPA Whole Effluent Testing Program method of 7.1 mg/L was used for assessment.

 

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
7.1 mg/L

Additional information

One reliable study is available to predict long-term toxicity of TCE.

In a study conducted according to U.S. EPA Whole Effluent Testing Program method, Ceriodaphnia dubia were exposed to concentrations of 0, 13, 24, 54, 90, 212 µmol TCE and continued until 60% of the control animals had completed three broods, i.e., 6 or 7 days.

Mortality was observed at higher concentrations resulting in an EC50 of 17 mg/L both after 48 hours and 7 days.

The NOEC for reproduction was found to be 7.1 mg/L and the LOEC was 12 mg/L.

The concentration inhibiting reproduction by 50% relative to mean control performance (IC50) was calculated to be 11 mg/L.

 

 

Additional information is available from two long-term studies with Daphnia magna. However, these studies were not found to be reliable as for one study there were possible problems with infection of the test organisms (Kordel et al., 1984) and for the other it was found that a 21-day test was not possible unless the Daphnia had been treated with streptomycin (Scheubel, 1984). Use of the food supplement could also cause problems as it did not dissolve fully. It is not entirely clear from the report whether the problems described affected the outcome of the tests.

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