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Toxicity to microorganisms

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Reference
Endpoint:
toxicity to microorganisms
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Rationale for reliability incl. deficiencies:
other: DIN-method (draft), GLP.
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
Methacrylic acid is the hydrolysis product of Methacrylic anhydride. One molecule of methacrylic anhydride willl hydrolyse into two molelules methacrylic acid.


2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source substance: Methacrylic acid, purity >= 98 %
Target substance: Methacrylic anhydride: purity: >=94 %, other components: Methacrylic acid and adducts of methacrylic aanhydride and adducts of methacrylic acid and methacrylic anhydride.

3. ANALOGUE APPROACH JUSTIFICATION
Like other acid anhydrides, methacrylic anhydride was found to be hydrolytically unstable in water at pH 4, 7 and 9. The half lives (DT50) were found to be 56.4 min at pH 4 (25 °C), 25.5 min at pH 7 (25 °C) respectively 10.3 min at 37 °C and 2.29 min at pH 9. The initial hydrolysis product is methacrylic acid (Noack 2012).

4. Data Matrix
Target: Methacrylic anhydride CAS 760-93-0
Source: Methacrylic acid CAS 79-41-4
Reason / purpose:
read-across source
Qualifier:
according to
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
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+/- 1C 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
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 th OD of the test substance.
Reference substance (positive control):
no
Key result
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.
Validity criteria fulfilled:
yes
Conclusions:
Methacrylic anhydride rapidly hydrolysis to methacrylic acid in aqueous media. Therefore assessment of aquatic toxicity to Methacrylic anhydride based on studies with methacrylic acid is recommended.
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:

Methacrylic anhydride rapidly hydrolysis to methacrylic acid in aqueous media. Therefore assessment of aquatic toxicity to Methacrylic anhydride based on studies with methacrylic acid is recommended.

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.

Description of key information

EC10 (17 h) of the hydrolysis product methacrylic acid for freshwater microorganisms: 100 mg/l

Key value for chemical safety assessment

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

Additional information

Methacrylic anhydride is hydrolytically unstable in water. The initial hydrolysis product is methacrylic acid. The EC10 (17 h) of methacrylic acid for fresh water microorganisms was tested to be 100 mg/l with pseudomonas putida in a DIN 38412 growth inhibition test. EC50 (17 h) was 270 mg/l.