Ethyl acrylate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

01 Mar 1996 - 04 Mar 1996

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Comparable to guideline study conducted in compliance with GLP regulations

Principles of method if other than guideline:

The procedure described in this test method is based on ASTM's "Microbiological Inhibition Testing Procedure," and is a modification of the standard five day biochemical oxygen demand (BOD) analysis. The test measured the threshold inhibition concentration of the test substance to a mixed microbial inoculum by measuring the oxidation change over various concentrations of the test substance and comparing this to the oxidation change of an easily degradable substance such as D-glucose. The threshold inhibition concentration is defined as the lowest concentration of the test substance which produces a reduction in biochemical oxidation.
This test uses the measurement of dissolved oxygen (DO) utilization as an indicator of microbial oxidation in a closed test system. If the test substance is inhibitory, oxygen utilization will decrease at higher concentrations of test substance.

Marks PJ (1973). "Microbiological Inhibition Testing Procedure," Biological Methods for the Assessment of Water Quality, ASTM STP 528, American Society for Testing and Materials, pp. 221-226.

GLP compliance:

yes

Analytical monitoring:

yes

Vehicle:

no

Details on test solutions:

BOD dilution water was the test medium. One batch of dilution water was prepared and aerated with compressed air through a gas dispersion tube to bring the DO of the water to approx. 9.0 mg/L. One batch of the water was used for test substance EA, and their control.

Test organisms (species):

activated sludge, domestic

Details on inoculum:

Activated sludge was collected on 29 February 1996 from the Downingtown Regional Water Pollution Control Center in Downingtown, Pennsylvania. This facility receives predominately domestic waste. The sludge was aerated overnight prior to use in this study. The sludge was screened through a 2 mm sieve. On the same day the total suspended solids (TSS) was determined to be 3247 mg/L. A portion of the sludge was added to a semi-continuous activated sludge (SCAS) unit and diluted with tap water to obtain a TSS concentration of approx. 2500 mg/L. The unit was aerated at a rate adequate to maintain solids in suspension. On 01 March 1996 approximately 40 mL of sludge was collected from the SCAS unit and diluted 1:10 with BOD dilution water. The diluted sludge was used as the microbial inoculum.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

20.0 - 20.1 °C

Nominal and measured concentrations:

Nominal: 0.1, 1.0, 5.0, 10, 15, 20, 100, 300, 500, and 800 mg active/L

Details on test conditions:

The appropriate amount of test substance stock solution was added to the BOD bottles . The bottles were then filled with approximately 100 mL, of BOD dilution water. A five milliliter aliquot of the inoculum was added to each bottle followed by six milliliters of D-glucose stock solution. The bottles were then filled completely (300 mL) with BOD dilution water, and the initial dissolved oxygen (DO) concentration was measured in each bottle.
Any volume lost from insertion of the DO probe was replaced with BOD dilution water and each bottle was capped and placed in an incubator in the dark at 20 ± 0.2°C for three days.
A final DO concentration was measured after the three day incubation period.


TEST SYSTEM
- Test vessel:
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: 300 mL BOD bottles
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

other: Threshold inhibition concentration

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

After the incubation period, the DO was measured in each bottle. The residual DO concentrations were plotted against the testing concentrations and the threshold inhibition concentration of the test substance was determined. When the line representing the test substance intercepts the line representing D-glucose and continues to increase with testing concentration, the point of interception is called the threshold inhibition concentration. The threshold inhibition concentration of EA was greater than 100 mg active/L.

Measured TOC of the stock solution: 0.57 mg C/mg active

There was a difference between theoretical and measured TOC of 5 %.

Final nominal concentration [mg active/L]	Replicate	Initial DO [mg O2/L]	Final DO [mg O2/L]
Dilution water control	1	9.1	9.0
Dilution water control	2	9.1	9.0
D-glucose control	1	9.1	5.6
D-glucose control	2	9.1	5.6
TS 0.1	1	9.1	5.4
TS 0.1	2	9.1	5.4
TS 1.0	1	9.1	5.4
TS 1.0	2	9.1	5.3
TS 5.0	1	9.1	5.2
TS 5.0	2	9.1	5.1
TS 10	1	9.1	4.7
TS 10	2	9.1	4.8
TS 15	1	9.1	4.0
TS 15	2	9.1	4.2
TS 20	1	9.1	3.5
TS 20	2	9.1	3.7
TS 100	1	9.0	2.4
TS 100	2	9.0	2.6
TS 300	1	8.5	6.4
TS 300	2	8.5	6.7
TS 500	1	8.9	7.0
TS 500	2	8.9	7.2
TS 800	1	9.3	7.9
TS 800	2	9.3	7.9

Validity criteria fulfilled:

yes

Description of key information

The inhibition of the degradation activity of activated sludge is not anticipated when Ethyl acrylate is introduced into biological treatment plants in appropriately low concentrations.
EC10 > 100 mg/L (domestic activated sludge, BOD test)

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

100 mg/L

Additional information

Concerning acute toxicity of ethyl acrylate towards aerobic microorganisms, a study conducted by Roy F. Weston Inc. for BAMM is available (BAMM, 1996). The test procedure was based on ASTM's "Microbiological Inhibition Testing Procedure," and was a modification of the standard five day biochemical oxygen demand (BOD) analysis. The test measured the threshold inhibition concentration of the test substance to a mixed microbial inoculum by measuring the oxidation change over various concentrations of the test substance and comparing this to the oxidation change of an easily degradable substance such as D-glucose. The threshold inhibition concentration was defined as the lowest concentration of the test substance which produces a reduction in biochemical oxidation. Activated sludge originated from the Downingtown Regional Water Pollution Control Center in Downingtown, Pennsylvania. This facility receives predominately domestic waste. Effect values after 72 hrs exposure were: EC10 > 100 mg/L.

In a static acute toxicity test with Nitrosomonas spec. the inhibition of ammonia consumption was used as criterion for toxic inhibition of Nitrosomonas (Blum & Speece 1991). The seed bacteria for the nitrifying enrichment culture were obtained from the mixed liquor of an activated sludge plant treating meat-packing, rendering and hide-curing waste-water (Initial biomass concentration: 450 mg/L VSS). The IC50 based on nominal concentrations equaled 47 mg/L after 24 hrs exposure.

In addition, several studies on the inhibition of anaerobic microorganisms by ethyl acrylate are available (Lin Chou W et al. 1978, Blum & Speece 1991).

Taking all these test results into consideration, inhibition of the degradation activity of activated sludge in a WWTP is not anticipated when the substance is introduced in appropriately low concentrations in WWTPs.