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Short-term toxicity to fish

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Reference
Endpoint:
short-term toxicity to fish
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
23.03.1989 - 27-03-1989
Rationale for reliability incl. deficiencies:
other: The study was performed to an EPA guidline which is very similar to the relevant OECD guideline.
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
Specific details on test material used for the study:
purity: 99.72 % (glacial MAA). Lot 5-0523-88. received from Rohm and Hass Company. Light yellow liquid stored at room temperature
Analytical monitoring:
yes
Details on sampling:
Samples for analytical measurements were taken at 0 and 96 hrs. Comtrol and glacial MAA fortified samples were also determined at each sampling period.
Vehicle:
no
Details on test solutions:
A diluter stock solution (38 mg/ml) was prepared by dissolving 76 g of test substance in 2 liters of dilution water. The injector volume was adjusted
to deliver 5 ml of stock to 1.9 liters of dilution water.
Test organisms (species):
Oncorhynchus mykiss (previous name: Salmo gairdneri)
Details on test organisms:
Lot 5588 from Mt Lassen Trout Farms in Red Bluff, CA.
Control fish had a mean weight of 1.0 g and a mean length of 41 mm at the end of the test. The biomass loading was 0.093 g/l/day. Fish were temperature acclimated in the absence of food for 72 hours before intiation of the test.
Test type:
flow-through
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h
Hardness:
47 - 48 mg CaCO3/l
Test temperature:
11 - 12 °C
pH:
5.3 - 7.8
Dissolved oxygen:
8.2 - 9.4 mg/l
Nominal and measured concentrations:
Nominal 6.5, 13, 25, 50 and 100 mg/L
Measured 6.2, 12, 23, 46, and 97 mg/L
Details on test conditions:
Twenty fish per concentration plus a dilution water control were used in a duplicate nominal dosing regimine. Temperature, dissolved oxygen and pH measured at all test concentrations at 0, 48 and 96 hours.
Reference substance (positive control):
no
Duration:
96 h
Dose descriptor:
NOEC
Effect conc.:
12 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
mortality
Key result
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
85 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
mortality
Details on results:
65 % mortality ocurred at 97 mg/L. Sublethal behavior responses were noted in the 23, 46 and 97 mg/L groups.

Mortality during the acute flow-through toxicity test of methacrylic acid to Rainbow trout (Salmo gairdneri)

Meas. Test conc. [mg/l]

Number placed in Test

24-hour mortality

48-hour mortality

72-hour mortality

96-hour mortality

control

20

0

0

0

0

6.2

20

0

0

0

0

12

20

0

0

0

0

23

20

0

0

0

0

46

20

0

0

0

0

97

20

0

1

8

13

 

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 an acute toxicity study to fish under flow through conditions study with Salmo gairdneri (new name: Oncorhynchus mykiss), methacrylic acid was testet in duplicate at nominal test concentrations of 6.5, 13, 25, 50 and 100 mg/l upt to 96 hours. LC50 (96 h) was estimated to be 85 mg/l based on the mean measured concentrations of 6.2, 12, 23, 46 and 97 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 an acute toxicity study to fish under flow through conditions study with Salmo gairdneri (new name: Oncorhynchus mykiss), methacrylic acid was testet in duplicate at nominal test concentrations of 6.5, 13, 25, 50 and 100 mg/l upt to 96 hours. LC50 (96 h) was estimated to be 85 mg/l based on the mean measured concentrations of 6.2, 12, 23, 46 and 97 mg/l.

Description of key information

LC50 (96h)  for freshwater fish of the hydrolysis product methacrylic acid: 85 mg/l 

Key value for chemical safety assessment

LC50 for freshwater fish:
85 mg/L

Additional information

Methacrylic anhydride is hydrolytically unstable in water. The initial hydrolysis product is methacrylic acid. The LC50 (96 h) of methacrylic acid for fresh water fish was 85 mg/l (measured concentration). Methacrylic acid was also tested with salt water fish with LC50 (96h) of 833 mg/l (nominal;concentration analytically confirmed, 0-8 % differing from nominal concentrations under test conditions). 

The following information is taken into account for any hazard / risk / persistency assessment:

LC50 (96 h) of methacrylic acid for freshwater fish: 85 mg/l