Methacrylic anhydride

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Rationale for reliability incl. deficiencies:

other: EPA guideline similar to 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 for cross-reference:

read-across source

Analytical monitoring:

yes

Details on sampling:

At each sampling period 5 ml aliquots of test water were collected from each of the four replicates of each test solution. Two replicates at each time
point were composited.

Vehicle:

no

Details on test solutions:

A primary stock standard of MAA was prepared and stored at room temperature. Subsequent dilutions were prepared in Milipore water for use as
spiking solutions and test dilution water.

Test organisms (species):

Daphnia magna

Details on test organisms:

ABC Laboratories in house culture. The primary culture was obtained from the Columbia National Fisheries Research Laboratory (CNFRL), Columbia, Missouri, in 1977
Age at study initiation: first instar (<=24 hours old).
Organisms were held in temperature controlled area at 20°C.
Lighting was 50-70 footcandles on a 16 hr photoperiod, with 30 minute dawn and dusk transition periods.
During the holding period, the daphnids were fed a suspension of algae (Selenastrum capricornutum) supplemented with Tetramin®/cereal leaves/yeast suspension.
Organisms were not fed during the 48 hr treatment period.

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

172-178 mg/L

Test temperature:

20°C

pH:

7.0-7.9

Dissolved oxygen:

7.7-8.2 mg/L

Nominal and measured concentrations:

Nominal = 7.2, 14, 30, 60 and 120 mg/L.
Mean measured (sampling at 0 and 48 hrs) = 6.7, 13, 32, 62 and 130 mg/L.

Details on test conditions:

Method: flow-through bioassay as described in American Public Health Association and Standard Methods for the Examination of Water and 
Wastewater.

A half liter proportional diluter system was used for intermittent introduction of dilution water and MAA into the test chambers. The test system contained six sets of four replicate one liter test chambers designated as control, and level 1 through level 5. The proportional diluter was calibrated preior to use in the test.

Dilution water was a blend of reverse osmosis water and ABC laboratory well water.

10 organisms were assigned to each of the four replicate test chambers (40 Daphnids per concentration).
Water quality measurements were recorded at 0 and 48 hours.

Reference substance (positive control):

no

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

130 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: based on lack of immobilization and or abnormal effects

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 130 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: The 48 hr dose response slope could not be determined because of the lack of an effect level

Details on results:

Overall, the measured concentrations represent 101-7.4% of nominal concentrations. Quality control samples analyzed with each sample day over a range of 6.00 to 150 mg/L with recoveries averaging 94+/-19%. Low recovery for the 0 hour sampling was obtained. Duplicate low spikes at teh 48 hour sampling were analyzed to verify the recovery of MAA at the 6.00 mg/l concentration.

Measurement at 0 and 48 hrs of the MAA diluter stock solution averaged 12,000 mg/L which represented 100% of the nominal concentration (12,000 mg/L).

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 48 hour EC50 for Daphnia magna was >130 mg/L Methacrylic acid.

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.

Methacrylic acid was tested in an acute test to aquatic invertebrates acc. EPA OTS 797.1300 (Aquatic Invertebrate Acute Toxicity test Test) with Daphnia magna. The definitive flow-through acute toxicity of Methacrylic Acid to Daphnia magna was conducted the following nominal concentrations: 7.2, 14, 30, 60 and 120 mg/1.

Forty first-instar daphnids were exposed to each of the test concentrations and control.

The mean measured concentrations calculated from analytical sampling at 0 and 48 hours are as follows: 6.7, 13, 32, 62 and 130 mg/1. The toxicity of Methacrylic Acid based on mean measured test

concentrations were EC50 (48h): > 130 mg/l, NOEC (48h): 130 mg/l

Water quality parameters of temperature, dissolved oxygen and pH were measured in all test concentrations at 0- and 48-hours and were determined to be within acceptable limits. The overall ranges for these

parameters were: daily diluter temperature observations = 20°C, pH = 7.0 - 7.9 and dissolved oxygen= 7.7 - 8.2 mg/1.

Description of key information

EC50 (48 h) of the hydrolysis product methacrylic acid for freshwater invertebrates: > 130 mg/l 

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

130 mg/L

Additional information

Methacrylic anhydride is hydrolytically unstable in water. The initial hydrolysis product is methacrylic acid. The EC50 (48 h) of methacrylic acid for fresh water invertebrates was > 130 mg/l (measured concentration). Methacrylic acid was also tested with marine invertebrates with EC50 (48 h) of 210 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:

EC50 (48 h) of the hydrolysis product methacrylic acid for fresh water invertebrates: > 130 mg/l