Trichloroethylene

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:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Although the study was not carried out according to a guideline and GLP, it is well described and the result is considered acceptable.

Principles of method if other than guideline:

In this study, a new, closed system is used, in which a KHCO3/K2CO3 buffer to supply the algae with CO2 is employed, but the buffer is separated
from the test medium to avoid growth inhibition due to the ionic strength.

GLP compliance:

no

Analytical monitoring:

yes

Vehicle:

not specified

Details on test solutions:

Saturated solutions in growth medium were prepared. Defined aliquots of these solutions were added to the medium.

Test organisms (species):

Chlamydomonas reinhardtii

Details on test organisms:

7-day old precultures; cell density at start of exposure 5.103 cells/ml.
Strain number 11-32a SAG, from the University of Göttingen, Germany.
Precultures and test cultures were grown in the medium for unicellular algae according to Kuhl (1962). Incubation of all cultures was done in a Orbital Incubator (Gallenkamp). The cultures were shaken permanently with a frequency of 120 rpm. They were illuminated from above with 130 uE/m2s
without light-dark cycle. The photosynthetically effective light was determined with a Quantum Sensor from Licor Inc.

Test type:

other: closed system

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

None

Hardness:

Not specified

Test temperature:

20 ± 1 °C

pH:

6.5-7.5

Dissolved oxygen:

Not specified

Salinity:

Not applicable

Nominal and measured concentrations:

Measured

Details on test conditions:

A CO2 buffer and the contaminated medium were filled into the test vessel at least 15 hours before the assay was started by adding the algal
inoculum. The inoculum was prepared from 7 day old precultures at a concentration of 3x105 cells/mL. For the test 0.5 mL inoculum was added to 30 mL medium. The cell density in the test cultures amounted to 5x103 cells/mL at the beginning of the assay. The test was run for 72 hours. After this period, the algae, which have multiplicated at least by factor 100 during the 72-h incubation time, were taken for determination of biomass.

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

36.5 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% CI 35.1-38.2 mg/l

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

12.3 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% CI 9.76-14.3 mg/l

Reported statistics and error estimates:

The 72-h EC10 and 72-h EC50 values could be determined very precisely, as demonstrated by the small 95% confidence intervals.

Description of key information

For freshwater algae the lowest toxicity values were the 72-h EC50 of 36.5 mg/l and the 72-h EC10 of 12.3 found in Chlamydomonas reinhardtii.

Key value for chemical safety assessment

EC50 for freshwater algae:

36.5 mg/L

EC10 or NOEC for freshwater algae:

12.3 mg/L

Additional information

A cell multiplication test with Chlamydomonas reinhardii (algae) was available. Although not conducted according to a guideline the study was found to be acceptable as no major deviations were present (Brack and Rottler, 1994). The 72-h EC50 was 36.5 mg/l and the 72-h EC10 was 12.3 mg/l, these values are used in the assessment. Other studies were found to be less critical, not reliable or the information was not enough to assess validity.