Zeolite, cuboidal, crystalline, synthetic, non-fibrous

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

Study period:

May 17 - Aug. 4, 2006; experimental phase: May 18 - Jul. 28, 2006

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

A structural analogue substance was used for assessment since the performed study is well documented, according to current guidelines and GLP compliant. The "Structural Analogues Substances Approach" is provided in chapter 13.2.

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

Jun. 7, 1984

Deviations:

yes

Remarks:

The concentration of NaHCO3 was increased to be twice of that indicated in the Guideline 201. This concentration has been found to be optimal.

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Name: SYLOBEAD MS 562 CS (crystalline aluminiumsilicate)
Appearance: Beige solid in the form of pearls
Lot-No.: 5210057495
Sample ID: 173.06.N
Density: 2.1 g/cm³
Storage conditions: At room temperature in the dark
Degree of purity: No information
Water solubility: insoluble

Analytical monitoring:

yes

Details on sampling:

As agreed with the sponsor a supporting chemical analysis for quantification of the test item in the test solutions was performed. The aim of the investigations was the determination of the recovery rate of the test item (fraction of aluminium-ions in the water-dissolved material of the test item) in test solutions in order to verify the necessary stability of the test item under test conditions within 72h. The quantification of the test item (fraction of aluminium-ions in the water-dissolved material of the test item) in the test solutions of the algae-test was performed according DIN EN 11885 using ICP-OES.

Details on test solutions:

The mineral nutrient medium was prepared from the following three stock solutions and NaHCO3: Mineral Nutrient Salts, Fe-Complex and TraceElements.
An aliquot of the algal stock culture was diluted with test medium to an extinction value of E578 nm = 0.057 of the algal suspension giving an initial algal cell concentration of ca.1.81*10^4 cells/mL in the test solutions. The determination of cell concentration was performed by photometrical measurement using a calibration curve prepared by using a spectrophotometer at 578 nm.
The test item was applied as follows: A stock solution was made in ultrapure water. Aliquots of the stock solution were made up with ultrapure water, "intermediate dilution" and algal inoculum (or diluted "intermediate dilution") to give 50 mL of final volume.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

Desmodesmus subspicatus CHODAT was used as the test system (Origin: Sammlung von Algenkulturen, Pflanzenphysiologisches Institut der Universitat Gottingen [SAG], Strain-No. 86.81).

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Test temperature:

24-25 °C (in incubation chamber)

pH:

7.39-9.71

Nominal and measured concentrations:

1000 mg/l (nominal)

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Basis for effect:

biomass

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Basis for effect:

growth rate

Details on results:

An increase of biomass by a factor of at least 16 was achieved. Within that test, in the control a cell concentration of 2.18 * 10^6 algal cells / mL was determined after 72h of incubation. Starting from 1.83*10^4 algal cells/mL at the beginning of the test, an algal cell concentration of 2.93 * 10^5 algal cells / mL should have to be obtained. Thus, the test was considered valid.

Validity criteria fulfilled:

yes

Conclusions:

There was no toxic effect within the limit test at a nominal concentration of 1000 mg/l.

Executive summary:

The chronic toxicity of SYLOBEAD MS 562 CS towards algae was tested according to OECD-Test Guideline 201, performed with an aqueous extract from the test item. The toxic effect was investigated by determination of the inhibition of the biomass production and the growth rate of the algae after an exposure period of 72 h.

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Qualifier:

no guideline followed

Principles of method if other than guideline:

Algal Assay Procedure: bottle test, three algae, several concentrations, cell growth inhibition

GLP compliance:

not specified

Specific details on test material used for the study:

Type-A zeolite

Analytical monitoring:

yes

Details on sampling:

Actual test concentrations of zeolite were measured during all partial and full chronic studies with macroinvertebrates and fish by digesting the aluminosilicate to molybdate-reactive silica after APHA.

Test organisms (species):

other: Selenastrum capricornutum, Microcystis aeruginosa, Navícula seminulum

Details on test organisms:

Cultures were maintained and tested according to the Algal Assay Procedure: Bottle Test.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

5 d

Remarks on exposure duration:

also 14 days for Microcystis aeruginosa with a concentration range of 0.5-50 mg/l

Nominal and measured concentrations:

50 to 1000 mg/L
Microcystis aeruginosa also with a concentration range of 0.5 to 50 mg/l (14-day)

Reference substance (positive control):

no

Duration:

5 d

Dose descriptor:

LOEC

Effect conc.:

ca. 100 - ca. 1 000 mg/L

Nominal / measured:

nominal

Basis for effect:

cell number

Remarks on result:

other: Selenastrum capricornutum

Duration:

5 d

Dose descriptor:

LOEC

Effect conc.:

ca. 50 - ca. 100 mg/L

Nominal / measured:

nominal

Basis for effect:

cell number

Remarks on result:

other: Microcystis aeruginosa, Navícula seminulum

Details on results:

The concentrations of zeolite which allowed no increase in cell numbers for three algal species, Selenastrum capricornutum, Microcystis aeruginosa, and Navícula seminulum during a 5-day exposure, but did not kill the test species, ranged from 50 to 1000 mg/L.
There was no demonstrable difference in cell numbers among cultures of M. aeruginosa exposed to various concentrations of zeolite and the control throughout a 14-day exposure with concentrations ranging from 0.5 to 50 mg/L.

Validity criteria fulfilled:

not specified

Conclusions:

The concentrations of zeolite which allowed no increase in cell numbers for three algal species, Selenastrum capricornutum, Microcystis aeruginosa, and Navícula seminulum during a 5-day exposure, but did not kill the test species, ranged from 50 to 1000 mg/L.
But the assumption that effects observed during exposure to suspensions
greater than 50 mg/L were due to the reactions of zeolite with nutrients essential for algal growth caused by the ion-exchange capacity of zeolite was proved in a further experiment.

Executive summary:

Algal toxicity and growth stimulation studies were done with the green alga, Selenastrum capricornutum; a blue-green, Microcystis aeruginosa; and a diatom, Navícula seminulum.

Reference 3

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

May 29, 1991 - Feb. 28, 1992; experimental phase: Aug. 19-23, 1991

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

1984

Deviations:

yes

Remarks:

duration extended to 94 hours; increased NaHCO3 part in stock solution

GLP compliance:

yes

Specific details on test material used for the study:

Wessalith P (Natrium-Aluminiumsilikat) (A Zeolite)
white, crystalline powder

Analytical monitoring:

not specified

Vehicle:

yes

Details on test solutions:

The medium was prepared from concentrated stock solutions in Milli-Q filtered water. It was sterilized by micropore filtration and contained 150 mg/l NaHCO3 (not 50 mg/l as specified in the OECD Guideline)

Test organisms (species):

Scenedesmus sp.

Details on test organisms:

The freshwater green alga Scenedesmus subspicatus (SAG 86.81), which belongs to the order of Chlorococcales was used as the test organism.
The culture was supplied by the Collection of Algal Cultures, Institute for Plant Physiology, University of Göttingen, Göttingen, Germany.
A preculture of algae in the exponential growth Phase was prepared as detailed in OECD guideline no. 201.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

94 h

Test temperature:

23 +/-1 °C

pH:

8.0 (start) to 10.6 (after 4 days)

Dissolved oxygen:

7.0-9.3 mg/l

Nominal and measured concentrations:

2.9, 10.5, 38, 103 and 328 mg/l (nominal)

Details on test conditions:

The four day growth inhibition test was conducted as detailed in the protocol (GLP 91/082). This protocol was developed on the basis of OECD guideline no. 201, with a test duration of four days.
A suspension of algae in the algal medium containing 1x10^6 cells/ml was prepared by dilution of a preculture containing 4.9 x 10^6 cells/ml. Addition of 1 ml of this algal suspension to 100 ml of the appropriate dispersions and solutions of the test substance in the test flasks, yielded a mean measured inoculum cell density in the control cultures of 1.4 x 10^4 cells/ml. The test was carried out with a duplicate concentration series containing filtered test substance solutions and algae, with four controls with algae only. A Single background series containing filtered test substances olutionsw ithout algae was added. In addition a single concentration series of unfiltered test substanced ispersions and algae with one
control with algae only, and a Single background series containing unfiltered test substance dispersions without algae w ere tested.

Reference substance (positive control):

no

Key result

Duration:

94 h

Dose descriptor:

NOEC

Remarks:

filtered solutions

Effect conc.:

38 mg/L

Nominal / measured:

nominal

Basis for effect:

growth rate

Key result

Duration:

94 h

Dose descriptor:

NOEC

Remarks:

unfiltered dispersions

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Basis for effect:

growth rate

Details on results:

These algal toxicity values have to be considered with caution, since it is well known and supported by numerous investigations that the growth-inhibiting effects of complexing agents and ion-exchanging materials which are often observed in the nutrient-poor culture-media of ecotoxicological standard tests result from the depletion of trace heavy metals essential for algal growth. (HERA: Zeolite A, 2003, p. 16)

Unfiltered dispersions, using particle counts

The EC50 with respect to the yield after logistic growth (EyC50) was found to be 18 mg/l, with a 95% confidence interval of 10-32 mg/l. The corresponding EyC10 and EyC90 values were 4.9 and 66 mg/l, respectively.

The EC50 with respect to the area under the growth curve (EbC50) was found to be 34 mg/l (in the range 10.5-38 mg/l). The corresponding EbC10 and EbC90 values were 5.7 mg/l (2.9-10.5 mg/l) and 130 mg/l (105-328 mg/l), respectively.

 

Unfiltered dispersions, using fluorescence measurements

The EC50 with respect to the growth yield after logistic growth (EyC50) was found to be 34 mg/l, with a 95% confidence interval of 22-52 mg/l. The corresponding EyC10 and EyC90 values were 14.6 and 79.2 mg/l, respectively. The EC50 with respect to the area under the growth curve (EbC50) was found to be 45 mg/l (in the range 38-103 mg/l). The corresponding EbC10 and EbC90 values were 12 mg/l (10-38 mg/l) and 200 mg/l (105 -328 mg/l), respectively.

 

Filtered solutions

The EC values with respect to the growth rate during Iogistic growth (ErC10, ErC50 and ErC90) were found to be > 330 mg/l, as were the EbC50 and EbC90 values with respect to the area under the growth curve. The EbC10 was found to be 77 mg/l (in the range 38-103 mg/l).

 

The much lower toxicity of the filtered test solutions compared with that of the unfiltered dispersions could best be explained by a release of toxic substances from the particulate matter during the test. The effect on the growth yield found with the unfiltered dispersions suggest this mechanism. This is further supported by approximately the same EyC10 and EbC10 and EyC50 and EbC50 values found with the particle counts and the fluorescence determinations.

 

The no-observed-effect-concentration (NOEC) with respect to the effects referred to above was estimated to be 38 mg/l (filtered solutions) and 10 mg/l ( unfiltered dispersions).

 

The concentrations given arc nominal concentrations of the test substance Wessalith P.

Validity criteria fulfilled:

yes

Conclusions:

The NOEC was estimated to be 38 mg/l (filtered solutions) and 10 mg/l (unfiltered dispersions). However, these algal toxicity values have to be considered with caution, since it is well known and supported by numerous investigations that the growth-inhibiting effects of complexing agents and ion-exchanging materials which are often observed in the nutrient-poor culture-media of ecotoxicological standard tests result from the depletion of trace heavy metals essential for algal growth. (HERA: Zeolite A, 2003, p. 16)

Executive summary:

The toxicity of Wessalith P to the fresh-water green alga Scenedesmus suhpicarus was determined in a growth inhibition test according to the OECD Guideline no. 201 and the OECD principles of Good Laboratory Practice. The duration on the test was extended to four days. However, the derived algal toxicity values have to be considered with caution, since it is well known and supported by numerous investigations that the growth-inhibiting effects of complexing agents and ion-exchanging materials which are often observed in the nutrient-poor culture-media of ecotoxicological standard tests result from the depletion of trace heavy metals essential for algal growth.

Description of key information

The most sensitive NOEC value was determined in a study with a the type A zeolite that differentiates between filtered and unfiltered solutions. Here, the no-observed-effect-concentration (NOEC) to the freshwater green alga Scenedesmus subspicatus was estimated to be 38 mg/l (filtered solutions) and 10 mg/l (unfiltered dispersions). However, these algal toxicity values have to be considered with caution, since it is well known and supported by numerous investigations that the growth-inhibiting effects of complexing agents and ion-exchanging materials which are often observed in the nutrient-poor culture-media of ecotoxicological standard tests result from the depletion of trace heavy metals essential for algal growth.

 

This is also supported by the studies carried out by Maki and Macek. Here, the concentrations of zeolite which allowed no increase in cell numbers for three algal species, Selenastrum capricornutum, Microcystis aeruginosa, and Navícula seminulum during a 5-day exposure, but did not kill the test species, ranged from 50 to 1000 mg/l. But the assumption that effects observed during exposure to suspensions greater than 50 mg/l were due to the reactions of zeolite with nutrients essential for algal growth caused by the ion-exchange capacity of zeolite was proved in a further experiment:

A 1000-mg/l suspension of zeolite was placed inside a dialysis membrane bag impermeable to algal cells and zeolite and immersed in the culture vessel with algal inoculum and nutrient media. Growth in these flasks was reduced to an extent similar to flasks in which zeolite was mixed directly with the media, thus indicating the observed effects on algae could be reproduced without direct exposure of algal cells to zeolite, supporting the theory that nutrient exchange with high concentrations of zeolite was responsible for reduced algal growth.

 

In the key study in a crystalline aluminiumsilicate actually no toxic effect was observed within the limit test at a nominal concentration of 1000 mg/l.

In summary, it is assumed that the observed effects were not provoked by the substances themselves, but due to nutrient-poor culture-media. Only the studies mentioned in the last paragraph managed this problem correctly, and, therefore, are the only reliable ones for deriving a threshold limit. In conclusion, the actual NOEC value of zeolites against freshwater algae is greater than 1000 mg/l.

No marine species were tested.

Additional information

The study in the Ca++-loaded Zeolite against the freshwater algae Desmodesmus subspicatus that was part of the former dossier has been removed from this updated version, because the Ca++-loaded zeolite, as a surface coated one, is not consistent with the boundary composition.