Methacrylic anhydride

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

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

Adequacy of study:

key study

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

GLP, analytical monitoring, closed vessels

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

GLP compliance:

yes

Specific details on test material used for the study:

Methyacrylic acid (CAS: 79-41-4)
Purity: 99.87 %; supplied by ICI Acrylics. Certificate of Analysis stated sample purity determined by GC.
Clear and colorless liquid, stored under refrigeration.

Analytical monitoring:

yes

Details on sampling:

At the start of the test, samples were taken of each test solution, using the excess remaining after filling the test vessels, and were analyzed for test substance concentration. At the end of the test each blank solution was sampled and analyzed in the same manner.

Vehicle:

no

Details on test solutions:

Two stock solutions were prepared by direct addition of the test substance to 1000 ml of sterile culture medium to give final concentrations of 410 and 10000 mg/L. The three lowest concentrations were prepared by addition of aliquots of the nominal 410 mg/L solution to sterile medium, to a final volume of 1000 ml. The remaining test concentrations were prepared by addition of aliquots of the nominal 10000 mg/l solution to sterile medium, to a final volume of 1000 ml. Test solutions were all clear and colorless.

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

Test organisms were from laboratory cultures maintained under axenic conditions. A culture in the exponential growth phase was used as inoculum for the test.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

standard test medium used

Test temperature:

24°C

pH:

start of test 6.39-8.21
end of test 6.11 - 9.69

Nominal and measured concentrations:

Nominal = 0.86, 1.9, 4.1, 9.1, 20, 45 and 100 mg/L
Geometric mean measured = 0.85, 2.0, 3.7, 8.2, 19, 45, 100 mg/L

Details on test conditions:

Test vessels were borosilicate glass bottles of 50 ml nominal capacity, filled completely with airtight, teflon faced disc/crimp closures. Cultures were incubated at 24+/-2°C under continous "cool white" illumination with orbital shaking. Four replicates of the control and duplicates of the test substance were employed. At 24, 48 and 72 hours replicate vessels were sacrificed and counted.
pH was measured at the start of the test and at the end of the test the pH of two repliacte test solutions (containing algae) from each control and test concentration was determined.

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

8.2 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: growth rate and biomass

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

45 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

20 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

Mean measured concentration of the test substance ranged from 88 -105% of nominal exposure concentrations

MEAN GROWTH RATES OVER THE TEST PERIOD AND PERCENTAGES OF

THE CONTROL, INDICATING STATISTICALLY SIGNIFICANT DIFFERENCES

 

Meanmeasuredconcofmethacrylicacid(mg/l)	Mean growthrate (0 - 3days)	% ofcontrol
<0.031 (Control)	1.935	-
0.85	1.840	95
2.0	1.841	95
3.7	1.778	92
8.2	1.855	96
19	1.657*	86
45	1.223•	63
105	0.124*	6

*Significant difference from the control (P=0.05)

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 72 hr EbC50 and ErC50 were 20 and 45 mg/L, respectively for MAA with Selenastrum capricornutum (new name: Pseudokirchnerella subcapitata). The NOEC for growth and biomass was 8.2 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 alga growth inhibition test acc. OECD 201 Official Journal of the European Communities, L383, Part C.3, Algal inhibition test methacrylic acid was tested against Selenastrum capricornutum (new name: Pseudokirchnerella subcapitata) at nominal concentrations of 0.86, 1.9, 4.1, 9.1, 20, 45 and 100 mg/L (corresponding to geometric mean measured concentrations of 0.85, 2.0, 3.7, 8.2, 19, 45, 100 mg/L) for 72 hours in closed vessel under static conditions. EbC50 (biomass) was 20 mg/l, ErC50 (growth rate) was 45 mg/L, NOEC for growth and biomass was 8.2 mg/L based on geometric mean measured concentrations.

Description of key information

EC50 (72 h) of the hydrolysis product methacrylic acid for freshwater algae: 45 mg/l (growth rate) and NOEC (72 h): 8.2 mg/l (growth rate).

Key value for chemical safety assessment

EC50 for freshwater algae:

45 mg/L

EC10 or NOEC for freshwater algae:

8.2 mg/L

Additional information

Methacrylic anhydride is hydrolytically unstable in water. The initial hydrolysis product is methacrylic acid. The EC50 (72 h) of methacrylic acid for fresh water algae was 45 mg/l and a NOEC (72 h) of 8.2 mg/, both based on growth rate and measured concentrations. Methacrylic acid was also tested with marine algae with EC50 (72 h) > 1260 mg/l and NOEC 530 mg/l both based on growth rate and measured concentrations.