Tetracopper hexahydroxide sulphate

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

Study period:

Experimental Phase: 20 July 2001 to 03 August 2001. Report issued: 26 November 2001.

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

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Samples were taken for analysis of total and dissolved copper at the start (0 hours) and at the end (72 hours) of the experiment from both preliminary and definitive tests. Samples were taken from the preparations remaining after filling the test and control flasks at the start and from the pooled replicates at the end of the tests.

Two sets of samples were taken for analysis of copper at each sampling time. One set was unfiltered (for total copper) and one set was filtered (for dissolved copper) using 0.45 μm 'Acrodisc' filters. Each 25 ml sample was acidified with 0.5 ml of 70% nitric acid (AR grade). The samples were stored in a refrigerator prior to transportation to the analytical laboratory at the end of the study for analysis of copper.

Vehicle:

no

Details on test solutions:

For the preliminary test 31.98 mg of the test substance as received (tribasic copper sulphate technical) was weighed out and made up to 1000 ml with algal medium. This stock solution was stirred at high speed using a magnetic stirrer for 19 hours before test dilutions were prepared. Ten minutes of ultrasonication was also applied to disperse the test substance, which consisted of a paste. After dispersion a very pale blue slightly cloudy solution was formed.

Test dilutions were prepared by taking aliquots of the stock solution while it was still being stirred at high speed. The aliquots taken were weighed to the nearest 0.01g before making up to 500 ml with the test medium.

Test organisms (species):

other: Selenastrum capricornutum

Details on test organisms:

The alga was originally obtained from the CCAP, Institute of Freshwater Ecology, Far Sawrey, Ambleside, Cumbria. A culture in liquid medium containing Jaworski's medium was received at CEMAS on 06 June 2001 from CCAP and designated SC05. Sub-cultures were held in liquid medium until used for testing.

The inoculum used for the test was obtained from cultures growing in the medium recommended by CCAP (Jaworski's medium). From experience gained during the culture of Selenastrum capricornutum it was found that variability in growth between replicates was reduced when inoculum was taken from cultures growing in Jaworski's medium, rather than those growing in the medium described in EEC92/69 Part C3, l383, 1992.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

Not stated

Test temperature:

During the definitive test temperatures ranged from 21.5°C to 23.5°C with a mean value of 22.6°C.

pH:

During the definitive test the pH ranged from 7.50 to 7.70 with a mean value of 7.60.

Dissolved oxygen:

Not stated

Salinity:

Not stated

Conductivity:

Not stated

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

26.5 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

318.6 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

30.9 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

92.2 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Reported statistics and error estimates:

A t-test was undertaken on the growth curves.

Validity criteria fulfilled:

yes

Conclusions:

Based on nominal concentrations, growth of Selenastrum capricornutum was almost completely inhibited at and above 3103.3 μg tribasic copper sulphate technical/L. Growth was significantly (P=0.05) inhibited at 92.2 μg/L, but was not affected at 30.9 μg/L. The LOEC was therefore 92.2 μg tribasic copper sulphate technical/L (equivalent to 29.7 μg Cu/L) and the NOEC was 30.9 μg tribasic copper sulphate technical/L (equivalent to 10.0 μg Cu/L). The EC50 was 318.6 μg/L.

Executive summary:

Introduction

This study was carried out to determine the toxicity of the tribasic copper sulphate technical to the green algae Selenastrum capricornutum . The test was conducted following the method described in: 

OECD test guideline 201, Freshwater Alga and Cyanobacteria, Growth Inhibition Test. Adopted 23 March 2006.

And

EU test guideline No.L383, A/179-186, C3 Algal Inhibition Test, (Official Journal of the European Communities, 29.12.92).

Method

The alga was exposed to a series of concentrations of tribasic copper sulphate technical prepared by vigorously mixing the tribasic copper sulphate technical with the dilution water for approximately 24 hours. A preliminary or range finding test was carried out to establish a range of concentrations for use in the definitive test. For the definitive test the following concentrations of tribasic copper sulphate technical were used; 0 (control), 9.2, 30.9, 92.2, 310.9, 930.6, 3103.3 and 9309.6 μg/L.

 

The test vessels consisted of 250 ml conical flasks containing 100 ml of the test or control medium. The vessels were continuously illuminated and the pH and temperature of the test solutions in the definitive test ranged from 7.50 to 7.70 and 21.5°C to 23.5°C respectively. Algal growth in each vessel was measured by carrying out absorbance measurements on samples removed each day. Growth was determined in three ways; (1) final cell numbers at 72 hours, (2) rate of increase in cell numbers per day and (3) areas under the growth curves. Samples of filtered (0.45 μm) and unfiltered exposure media for the analytical determination of dissolved and total copper concentrations were taken at the start and end of the preliminary and the definitive tests.

Results and Conclusion

Based on nominal concentrations, growth of Selenastrum capricornutum was almost completely inhibited at and above 3103.3 μg tribasic copper sulphate technical/L. Growth was significantly (P=0.05) inhibited at 92.2 μg/L, but was not affected at 30.9 μg/L. The LOEC was therefore 92.2 μg tribasic copper sulphate technical/L (equivalent to 29.7 μg Cu/L) and the NOEC was 30.9 μg tribasic copper sulphate technical/L (equivalent to 10.0 μg Cu/L). The EC50 was 318.6 μg/L.

 

Description of key information

Based on nominal concentrations, growth ofSelenastrum capricornutumwas almost completely inhibited at and above 3103.3 μg tribasic copper sulphate technical/L. Growth was significantly (P=0.05) inhibited at 92.2 μg/L, but was not affected at 30.9 μg/L. The LOEC was therefore 92.2 μg tribasic copper sulphate technical/L (equivalent to 29.7 μg Cu/L) and the NOEC was 30.9 μg tribasic copper sulphate technical/L (equivalent to 10.0 μg Cu/L). The EC50 was 318.6 μg/L.

 

Key value for chemical safety assessment

EC50 for freshwater algae:

0.319 mg/L