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Toxicity to microorganisms

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Reference
Endpoint:
toxicity to microorganisms, other
Remarks:
Growth inhibition test
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1990-07-30 to 1990-08-01
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with national standard methods
Qualifier:
according to guideline
Guideline:
DIN 38412-8 (Pseudomonas Zellvermehrungshemmtest)
Principles of method if other than guideline:
other: Pseudomonas-growth inhibition test: Umweltbundesamt "Bewertung wassergefaehrdender Stoffe" (1979): Bestimmung der biologischen
Wirkung von Wasserinhaltsstoffen auf Bakterien im Zellvermehrungshemmtest; DEV DIN 38 412 (L8), draft.
GLP compliance:
yes
Specific details on test material used for the study:
Supplier: Degussa, Hanau, Germany
Purity: 99.9 %
Production date: 1989-07-26
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
Stock solutions of MAA were prepared by dissolving 1.6722 g in 1505 g test medium and neutralized to pH =7 by addition of NaOH solution. From
this stock solution, appropriate dilutions were prepared in test medium to yield final concentrations 0, 1.0, 10, 100, 180, 320, 560, and 1000 mg/L.
Test organisms (species):
Pseudomonas putida
Details on inoculum:
A culture of the gram negative bacteria (Stamm Berlin 33/2) was supplied by Deutsche Sammlung von Mikro-organismen, Braunschweig, Germany. A pre-culture was prepared for the growth inhibition test by innoculating the appropriate medium with a suspension prepared from a stock culture with an optical density of 0.194 and incubating at 21+/- 1°C for 15-16 hours after which the optical density was 1.243. The pre-culture was centrifuged and the bacteria re-suspended in fresh test medium.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
16.5 h
Test temperature:
approx. 21 degree C
pH:
7.0 (neutralized samples)
3.4 to 4.7 (non-neutralized samples)
Nominal and measured concentrations:
Nominal = 0, 1.0, 10, 100, 180, 320, 560, and 1000 mg/L.
Details on test conditions:
There were three flasks per concentration of neutralized test substance, two flasks of the unneutralized test substance and two control series
containing (neutralized and unneutralized) test substance but no bacteria to allow for correction of the OD of the test substance.
Reference substance (positive control):
no
Duration:
17 h
Dose descriptor:
EC50
Effect conc.:
270 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks on result:
other: 95% CI =216-338
Key result
Duration:
17 h
Dose descriptor:
EC10
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Details on results:
Results with non-neutralized test-solution (pH = 3.4-4.7):
EC10 = 12 mg/l
EC50 = approx. 32 mg/l
The acidic substance is considerably more toxic than the neutralized one.

Percentage inhibition of bacterial growth by different concentrations of methacrylic acid after 16.5 hours of incubation,

 

Concentration

MAA (mg/l)

0

1.0

10

100

180

320

562

1000

% inhibition (neutralized)

0

-3.2

-0.8

7.7

35.6

65.0

76.9

84.3

% inhilbition (unneutralized)

0

3.2

2.0

99.8

 

 

 

 

Validity criteria fulfilled:
yes
Conclusions:
In a valid guideline study, the EC50 for MAA to Pseudomonas putida was 270 mg/L after 17 hours; the EC10 was 100 mg/L.
Executive summary:

In a valid guideline study acc. DIN 38412-8 (Pseudomonas Zellvermehrungshemmtest), the EC50 for MAA to Pseudomonas putida was 270 mg/L after 17 hours; the EC10 was 100 mg/L in neutralized test solution..

Description of key information

In a valid guideline study acc. DIN 38412-8 (Pseudomonas Zellvermehrungshemmtest), the EC50 for MAA to Pseudomonas putida was 270 mg/L after 17 hours; the EC10 was 100 mg/L in neutralized test solution..

Key value for chemical safety assessment

EC50 for microorganisms:
270 mg/L
EC10 or NOEC for microorganisms:
100 mg/L

Additional information

Additional information is available from an activated sludge inhibition test acc. ISO 8192 where methacrylic acid was tested for 3 hours in concentrations of 5 -25 g/l. EC50 (3h) activated sludge inhibition was determined with 13.500 mg/l. This valid study supports the data of the key study and confirms that the data of key study are the most conservative data.

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