Phosphorodithioic acid, O,O-di-dodecyl-esters, zinc salts, neutral and basic

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

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:

guideline study with acceptable restrictions

Remarks:

Guideline study; restriction due to test material not being measured analytically

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

yes

Remarks:

the 100 mg/L test concentration was incorrectly prepared resulting in a 220 mg/L stock solution;e the test concentration ratio between the 32 and 220 mg/l test concentrations was 6.9; the test concentration ratio between the 220 and 320 mg/L was 1.5

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

yes

Remarks:

the 100 mg/L test concentration was incorrectly prepared resulting in a 220 mg/L stock solution;e the test concentration ratio between the 32 and 220 mg/l test concentrations was 6.9; the test concentration ratio between the 220 and 320 mg/L was 1.5

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method:
1) OECD 2000. Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures
2) ECETOC 1996. Aquatic Toxicity Testing of Sparingly Soluble, Volatile and Unstable Substances

- Evidence of undissolved material (e.g. precipitate, surface film, etc): Microscopic observations of the WAFs were performed after filtering and showed there to be no microdispersions of test material to be present.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Common name: Green alga
- Strain: Scenedesmus subspicatus, strain CCAP 276/20
- Source (laboratory, culture collection): Liquid cultures were obtained from the Culture Collection of Algae and Protozoa (CCAP) Institute of Freshwater Ecology, The Ferry House, Far Sawrey, Ambleside, Cumbria.

- Method of cultivation: Cultures were maintained in the laboratory at a temperature of 21 °C under continuous illumination (intensity approximately 7000 lux) and constant aeration.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

Temperature was maintained at 24 °C throughout the test

pH:

pH at 0 hours in control and test material solutions ranged from 7.1 to 7.8. pH values at 72 hours in control and test material solutions ranged from 7.3 to 8.0.

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 mL glass conical flasks were used. Three flasks each containing 100 mL of test preparations were used for the control and each treatment group. The flasks were plugged with polyurethane foam bungs and incubated at 24 °C under continuous illumination (intensity approximately 7000 lux) and constantly shaken at approximately 150 rpm for 72 hours.

- Initial cells density: Preculture conditions gave an algal suspension in log phase growth characterized by a cell density of 1.78 x10^6 cells per mL. Inoculation of test medium gave an initial cell density of 10^4 cells per mL.

- Control end cells density: Mean cell density of control at 0 hours was 1.60X10^4 cells per mL
Mean cell density of control at 72 hours was 1.37 x10^6 cells per mL

- No. of vessels per concentration (replicates): triplicate
- No. of vessels per control (replicates): triplicate

GROWTH MEDIUM
The culture medium used for the range finding and definitive tests was the same as that used to maintain the stock culture. Stock solutions of the culture medium was prepared using reverse osmosis purified deionized water. The culture medium contained the following macronutrients: NaNO3, MgCl2.6H2O, CaCl2.2H2O, MgSO4.7H2O, K2HPO4, NaHCO3. The culture medium contained the following micronutrients: H3BO3, MnCl2.4H2O, ZnCl2, FeCl3.6H2O, CoCl2.6H2O, Na2MoO4.2H2O, CuCl2*2H2O; Na2EDTA.2H2O, Na2SeO3.5H2O

- Standard medium used: yes

- Intervals of water quality measurement:

OTHER TEST CONDITIONS
- Light intensity and quality: 7000 lux continuous illumination

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: [counting chamber; electronic particle counter; fluorimeter; spectrophotometer; colorimeter]
Samples were taken at 1, 24, 48, and 72 hours and the cell densities determined using a Coulter Multisizer Particle Counter.

TEST CONCENTRATIONS

- Range finding study: The loading rates to be used in the definitive test were determined by a preliminary range finding test. The range finding test was conducted by exposing Scenedesmus subspicatus cells to a series of nominal loading rates of 10, 100, and 1000 mg/L for a period of 72 hours. The test was conducted in 250 mL glass conical flasks plugged with polyurethane foam bungs to reduce evaporation. Two replicate flasks were prepared for each control and test concentration. The test material was prepared as a WAF. After addition of the test material, the culture medium was stirred by magnetic stirrer using a stirring rate such that a vortex was formed to give a slight dimple at the water surface. These were stirred for 24 hours. The stirring was stopped and the mixtures allowed to stand for 1 hour. Microscopic observations made on the WAFs indicated that dispersed test material was present in the water column and hence it was considered justifiable to remove the undissolved material by filtering through a glass wool plug (2-4 cm in length). Microscopic observations of the WAFs performed after filtering showed that there were no globules/microdispersions of test material to be present.

The cell densities and percentage inhibition of growth values from the exposure of the alga to the test material during the range finding test showed no effect on growth at 10 mg/L loading rate WAF, however growth was observed to be reduced at 100 and 1000 mg/L loading rate WAFs. Based on this information and in order to ensure that both EL50 and NOEL values were obtained, loading rates of 10, 32, 100, 320, and 1000 mg/L using a stirring period of 24 hours followed by 1 hour standing period were selected for the definitive test. Due to a technical error the 100 mg/L loading rate WAF was incorrectly prepared resulting in a 220 mg/L loading rate WAF being used.

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

410 mg/L

Nominal / measured:

nominal

Conc. based on:

other: WAF

Basis for effect:

growth rate

Remarks on result:

other: 320 - 520 mg/L

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

240 mg/L

Nominal / measured:

nominal

Conc. based on:

other: WAF

Basis for effect:

biomass

Details on results:

- Exponential growth in the control (for algal test): yes

- Observation of abnormalities (for algal test): All test and control cultures were inspected microscopically at 72 hours. After 72 hours there were no abnormalities detected in the control or test cultures at 10, 32, and 220 mg/L loading rate WAFs, however few intact cells were observed to be present in the test cultures at 320 and 1000 mg/L loading rate WAF.

Table. Inhibition of Growth Rate and Biomass

Nominal Loading Rate (mg/L)	Area Under Curve at 72 h	% Inhibition	Growth Rate (0-72 h)	% Inhibition
Control	2.82E7	--	0.062	--
10	2.61E7	7	0.065	[5, increase compared to controls]
32	2.46E7	13	0.057	8
220	2.65E7	6	-0.064	[3, increase compared to controls]
320	7.72E5	97	-0.016	74
1000	-4.09E5	101	-0.012	119

Validity criteria fulfilled:

yes

Conclusions:

Exposure of Scenedesmus subspicatus to the test material gave an EbL50 (72h) value of 240 mg/L loading rate WAF and an ErL50 (0-72hr) value of 410 mg/L loading rate WAF. The No Observed Effect Loading rate was 220 mg/L loading rate WAF.

Executive summary:

Introduction. A study was performed to assess the effect of the test material on the growth of the green algaScenedesmus subspicatus. The method followed that described in the OECD Guidelines for Testing of Chemicals (1984) No. 201, “Alga Growth Inhibition Test”. 

 

Methods:

Following a preliminary range finding test, the alga were exposed to Water Accommodated Fractions of test material over a range of nominal loading rates of 10, 32, 220, 320, and 1,000 mg/L (three replicate flasks per concentration) for 72 hours, under constant illumination and shaking at a temperature of 24 degrees C. Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group using a Coulter Multisizer Particle Counter.

 

Results:

Exposure ofScenedesmus subspicatusto the test material gave an EbL50 (72h) value of 240 mg/L loading rate WAF and an ErL50 (0-72hr) value of 410 mg/L loading rate WAF. The No Observed Effect Loading rate was 220 mg/L loading rate WAF.

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Please refer to the analogue justification provided in Section 13.

Reason / purpose for cross-reference:

read-across source

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

410 mg/L

Nominal / measured:

nominal

Conc. based on:

other: WAF

Basis for effect:

growth rate

Remarks on result:

other: 320 - 520 mg/L

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

240 mg/L

Nominal / measured:

nominal

Conc. based on:

other: WAF

Basis for effect:

biomass

Description of key information

ErL50 (72 h) = 410 mg/L (loading rate, OECD 201, Scenedesmus subspicatus, nominal)

NOELR (72 h) = 220 mg/L (loading rate, OECD 201, Scenedesmus subspicatus, nominal)

Key value for chemical safety assessment

EC50 for freshwater algae:

410 mg/L

EC10 or NOEC for freshwater algae:

220 mg/L

Additional information

No data are available on the toxicity of Phosphorodithioic acid, O,O-di-dodecyl-esters, zinc salts, neutral and basic (CAS No.4563-56-8) towards aquatic algae and cyanobacteria. Therefore data from the analogue substance zinc bis[O,O-bis(2-ethylhexyl)] bis(dithiophosphate) (CAS 4259-15-8) were used for read across. This read-across is in accordance with Regulation (EC) No. 1907/2006 Annex XI, 1.5 In this case of read-across, the best suited (highest degree of structural similarity, nearest physico-chemical properties) read-across substance was used for the assessment. This read-across is justified in within the analogue justification in IUCLID Section 13.

The short-term toxicity of Zinc bis[O,O-bis(2-ethylhexyl)] bis(dithiophosphate) (CAS 4259-15 -8) (Safepharm Laboratories Ldt, 2004) to algae was investigated in a study according to OECD 201 and following GLP principles. Following a preliminary range finding test, the alga were exposed to Water Accommodated Fractions of test material over a range of nominal loading rates of 10, 32, 220, 320, and 1000 mg/L (three replicate flasks per concentration) for 72 hours, under constant illumination and shaking at a temperature of 24 °C. Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group using a Particle Counter. Exposure of Scenedesmus subspicatus to the test material gave an EbL50 (72 h) value of 240 mg/L loading rate WAF and an ErL50 (0-72 h) value of 410 mg/L loading rate WAF. The No Observed Effect Loading Rate was 220 mg/L loading rate WAF.