Magnesium potassium titanium oxide

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

18 October 2000-31 May 2001

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study has been performed according to the appropriate ISO and OECD and EC guidelines and according to GLP principles.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2001

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

ISO 8692 (Water Quality - Fresh Water Algal Growth Inhibition Test with Scenedesmus subspicatus and Selenastrum capricornutum)

Version / remarks:

(1989)

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

(1992)

Test guideline 3

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

(1984)

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

-

EC Number:

436-900-9

EC Name:

-

Cas Number:

39290-90-9

Molecular formula:

Hill Empirical formula: K(0.2-0.7) Mg(0.4) Ti(1.6) O(3.7-3.95) CAS Empirical formula: K(0.2-0.7) Mg(0.4) Ti(1.6) O(3.7-3.95)

IUPAC Name:

Magnesium Potassium Titanium Oxide

Details on test material:

Batch: 0G99
White powder
Expiry date: 21 August 2001
Storage at room temperature in the dark

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

- Concentrations:
- Sampling method: samples (10 mL) were taken from each concentration before introduction of algae at the start of the exposure. After 24 h and at the end of the exposure (t=72 h), the replicates incubated with and without algae were pooled at each concentration. Subsequently, samples were taken from all pooled solutions.

- Sample storage conditions before analysis: all samples were stored in a deep freeze until shipment to Solvias AG, Basel, Switzerland.

Test solutions

Vehicle:

no

Details on test solutions:

Supersaturated solutions were prepared at nominally 100 mg/L and magnetically stirred for 4 days to achieve maximum solubility. The resulting solutions were filtered through a paper filter to remove the larger undissolved test substance particles (ca. > 5µm). The filtrates were used to prepare the lower test concentrations (10, 18, 32 and 56% of the filtrate). The undiluted filtrate and the concentration containing 56% of the filtrate were slightly turbid (hazy). All lower test concentrations were clear and colourless. After preparation, volumes of 50 ml were added to each replicate of the respective test concentration. Subsequently, adequate volumes of an algal suspension were added to each replicate providing a cell density of 10E4 cells/mL.

Test organisms

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata
- Strain: CCAP 278/4.
- Source (laboratory, culture collection): In-house laboratory culture
- Age of inoculum (at test initiation): not indicated
- Method of cultivation: Algae stock cultures were started by inoculating growth medium with algal cells from a pure culture on agar. The suspensions were continuously aerated and exposed to light (4000-9000 lux) in a climate room at a temperature of 23 ± 2°C.

ACCLIMATION
- Acclimation period: 4 days
- Culturing media and conditions (same as test or not): test medium and pre-culture medium is M2 according to the ISO standard "Algal growth inhibition test" .

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

No post exposure observation method.

Test conditions

Hardness:

24 mg CaCO3/L

Test temperature:

20.9 - 24.0 °C.

pH:

8.1 - 10.0

Nominal and measured concentrations:

The determination of the TERRACESS P concentrations in the water phase was based on measurement of TITANIUM (Ti) concentrations. The titanium was present in samples at approximately 28%. Detailed specification of the analytical procedures was put down in a Study Part (L01-000672).
The concentrations represented as percentage (%) are the nominal ones prepared by the dilution of the 5 µm filtrate prepared at nominal 100 mg/l. The concentrations measured as ug/L represent the measured Ti concentrations in water.

Sampling time: t=0

32%: 574 µg/L
56%: 937 µg/L
100% : 321 µg/L
100% (without algae): 2331 µg/L

Sampling time: t=72h

32%: 88 µg/L
56%: 268 µg/L
100% : 298 µg/L
100% (without algae): 117 µg/L

As expected, analysis of the samples showed that concentrations decreased (significantly) during the test period as a consequence of the extremely poor solubility in water. The variation in measurements at the start of the test in the 100 mg/L solution with and without algae was probably a consequence of the inhomogenity of the samples, i.e. undissolved test material, which was related to the infact only indicative for the concentrations present in the test solutions. All analysed concentrations at the end of the test period (72 h) showed measured concentrations that were still above the maximum calculated solubility level  for the test substance. Hence, the conclusion can be made that these concentrations (32% to 100% of the filtrate) were inhomogeneous dispersions with undissolved test substance particles present in various amounts.     

Details on test conditions:

TEST SYSTEM
- Test vessel: 100 mL, all-glass, containing 50 mL of test solution
- Initial cells density: 1 x 104 cells/mL.
- No. of vessels per concentration (replicates): 3 replicates of each test concentration, 6 replicates of the blank control, 1 replicate of each concentration without algae, 1 extra replicate of each test concentration for sampling purposes, 2 extra replicates of the highest concentration without algae.

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Sterile test conditions: no
- Adjustment of pH: no
- Photoperiod: continuous
- Light intensity and quality: Cool-white TLD-lamps of 30 Watt, with a light intensity whithin the range of 99 to 132 µE.m-2.s-1.

EFFECT PARAMETERS MEASURED (at t=0, 24 h, 48 h and 72h) :
- Determination of cell densities: microscope/counting chamber (t=0) and spectrophotometer (t> 0)

TEST CONCENTRATIONS
- Spacing factor for test concentrations: approx. 1.8

- Range finding study
- Test concentrations: Algae were exposed to a 5 µm filtrate prepared at nominal 100 mg/l and to dilutions containing 0.1, 1.0 and 10% of the filtrate.
- Results used to determine the conditions for the definitive study: no significant inhibition of algal growth was observed at concentrations corresponding with 10% of the filtrate and lower. The undiluted filtrate inhibited algal growth by just over 50% (54.7%). Hence, the EC50 for algal cell growth inhibition was expected to be just below a 5 µm filtered solution prepared at 100 mg/L, i.e. just below the expected maximum solubility in the test medium.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

>= 2.185 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

other: Terraces P

Basis for effect:

growth rate

Effect concentrations 2

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

>= 602 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Remarks:

Titanium

Basis for effect:

growth rate

Effect concentrations 3

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

> 1.21 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

other: Terraces P

Basis for effect:

growth rate

Effect concentrations 4

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

> 331 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Remarks:

Titanium

Basis for effect:

growth rate

Details on results:

TERRACESS P inhibited growth and reduced growth rate of the fresh water algae species significantly at concentrations corresponding with 56% and higher of a 5 µm filtered solution prepared at a nominal loading of 100 mg/l. This corresponded with a measured concentration decreasing from 3.4 mg/L at the start to 0.97 mg/L Terraces P at the end of the test period, i.e. concentrations above the maximum solubility limit in water (< 36 µg/L Terraces P).

The NOEC for cell growth inhibition and growth rate reduction corresponded with 32% of a 5 µm filtered solution prepared at a nominal loading of 100 mg/l. This corresponded with a measured concentration decreasing from 2.1 mg/L at the start to 0.32 mg/l Terraces P at the end of the test period.
The concentration measured at the end of the test period was above the calculated solubility limit in water (< 36 µg/L Terraces P).

In conclusion: effects from TERRACESS P on growth of the fresh water algae species Selenastrum capricornutum only occurred at concentrations above the water solubility limit.

- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): no abnormalities observed
- Any stimulation of growth found in any treatment: no

Results with reference substance (positive control):

The EC50 for cell growth inhibition (EBC50:0-72h) was 0.59 mg/L with a 95 % confidence interval ranging from 0.32 to 1.1 mg/L.

The EC50 for growth rate reduction (ERC50:0-72h) was 1.1 mg/L with a 95 % confidence interval ranging from 0.71 to 1.7 mg/L.

Reported statistics and error estimates:

The ISO-Standard gives a range for the EC50 for cell growth inhibition between 0.20 to 0.75 mg/L based on 16 inter-laboratory tests. Hence, the EBC50:0-72h for the present batch corresponds with this range.
The ISO-Standard gives a range for the EC50 for cell growth inhibition between 0.60 to 1.03 mg/L based on 16 inter-laboratory tests. Hence, the ERC50:0-72h for the present batch was slightly higher than the upper limit of the ISO standard range. However, the lower limit of the 95% confidence interval was still within the ISO standard range.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

Effects from Terracess P on growth of the fresh water algae species Selenastrum capricornutum only occurred at concentrations above the water solubility limit which calculated to be 36 ug/L Terraces P .