Zeolite, cuboidal, crystalline, synthetic, non-fibrous

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to microorganisms, other

Remarks:

bacterium growth inhibition test

Type of information:

experimental study

Adequacy of study:

key study

Study period:

May 29, 1991 - Sep. 8, 1992; experimental phases: Jul. 4-5, 1991 (range-finding test) and Aug. 8-9, 1991 (main test)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

DIN 38412-8 (Pseudomonas Zellvermehrungshemmtest)

Version / remarks:

March 1991

Deviations:

not specified

GLP compliance:

yes

Specific details on test material used for the study:

Wessalith P (A Zeolite)
white crystalline powder
stored at room temperature
not soluble in water

Analytical monitoring:

yes

Vehicle:

no

Details on test solutions:

The media were prepared from sterilized concentrated stock solutions in Milli-Q filtered water. The Milli-Q-filtered water was sterilized.

Test organisms (species):

Pseudomonas putida

Details on inoculum:

A culture of the Gram negative bacterium Pseudomonas putida (Stamm Berlin 33/2) was used as the test organism. A lyophilized culture (DSM 50026) was supplied by the Deutsche Sammlung von Mikroorganismen, Braunschweig, Germany.

A preculture was prepared for the range-finding test by inoculating the appropriate medium with a suspension prepared from a stock culture and incubating this at 21 +/- 1°C for 7 h, after which time the optical density (OD), measured in a disposable polystyrene cuvette with a 10 mm lightpath with a Pye Unicam PU 8600 spectrometer at 436 nm, was 0.545. The preculture was diluted in fresh test medium until the bacteria suspension had an optical density of 0.421.

A preculture was prepared for the growth inhibition test by inoculating the appropriate medium with a Suspension prepared from a stock culture with an OD of 0.094 and incubating this at 21 +/- 1°C for 7 h, after which time the OD, measured as described above, was 0.455. The preculture was diluted in fresh test medium (Annex D), until the bacteria suspension had an OD of 0.432.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

16 h

Remarks on exposure duration:

incubation time

Test temperature:

21 +/- 0.5°C

pH:

4.9 - 7.4
The bacterial growth generally resulted in a decrease of the pH of the medium. The highest decrease was found with neutralized test substance (pH 4.9 at 3.3 g/l). The inhibition was also stronger after neutralization, indicating that at least a part of the inhibition was caused by this decrease. The low pH values in the test medium is not easily explained but is routinely observed in this type of test.

Nominal and measured concentrations:

range-finding test:0, 0.01, 0.1, 1.0 and 10 g
growth inhibition test: 0, 0.01, 0.03, 0.10, 0.33, 1.0, 3.3, 5.5 and 10 g/l

Reference substance (positive control):

no

Duration:

16 h

Dose descriptor:

EC10

Effect conc.:

0.33 g/L

Nominal / measured:

nominal

Basis for effect:

growth inhibition

Key result

Duration:

16 h

Dose descriptor:

EC50

Remarks:

neutralized samples

Effect conc.:

ca. 0.95 g/L

Nominal / measured:

nominal

Basis for effect:

growth inhibition

Remarks on result:

other: 95% confidence interval of 0.57 - 1.59 g/l

Key result

Duration:

16 h

Dose descriptor:

EC50

Remarks:

not neutralized samples

Effect conc.:

ca. 1.55 g/L

Nominal / measured:

nominal

Basis for effect:

growth inhibition

Remarks on result:

other: 95% confidence interval of 0.53-4.54 g/l

Validity criteria fulfilled:

yes

Conclusions:

The EC50 value with respect to the bacterial growth in the neutralized samples was found to correspond to 0.95 g Wessalith P per litre with 95% confidence interval of 0.57-1.59 g/l. The EC50 value with respect to the bacterial growth in the not neutralized sarnples was found to correspond to 1.55 g Wessahth P per litre with a 95% confidence interval of 0.53-4.54 g/l.

Executive summary:

The toxicity of the product Wessalith P to the bacterium Pseudomonas putida was determined.The objective of the study was to determine the EC10 and the EC50 for that product. The determination was conducted as described in the Standard method DIN 38 412 (Teil 8): Determination of the inhibitory effect of water constituents on bacteria (Pseudomonas cell multiplication test).

Description of key information

In the only study in microorganisms the EC50 value with respect to the bacterial growth in the neutralized samples was found to correspond to 0.95 g of a type A zeolite per litre with 95% confidence interval of 0.57-1.59 g/l. The EC50 value with respect to the bacterial growth in the not neutralized samples was found to correspond to 1.55 g of type A zeolite per litre with a 95% confidence interval of 0.53-4.54 g/l.

Key value for chemical safety assessment

EC50 for microorganisms:

0.95 g/L

Additional information

The lower EC50 value, for neutralized samples, was chosen as key value, because in case of an accidental release of the substance, it is estimated that only a small portion of the substance, not sufficient to change the pH value of the contaminated water body (significantly), passes into the waters.