2-butoxyethyl benzoate

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2016

Report date:

2016

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

2-butoxyethyl benzoate

EC Number:

226-685-8

EC Name:

2-butoxyethyl benzoate

Cas Number:

5451-76-3

Molecular formula:

C13H18O3

IUPAC Name:

2-butoxyethyl benzoate

Test material form:

other: liquid

Details on test material:

2-Butoxyethyl benzoate, Lot # 201303443-19; Purity 99.2 %

Specific details on test material used for the study:

Test Material Name: 2-Butoxyethyl benzoate
Chemical Name: 2-Butoxyethanol benzoate
Supplier, City, State (Lot, Reference Number): The Dow Chemical Company, Midland, Michigan (Lot # 201303443-19).
Purity/Characterization (Method of Analysis and Reference): The purity of the test material was determined to be 99.2% area (corrected for water) by gas chromatography with identification by nuclear magnetic resonance and gas chromatography mass spectrometry (Gobbi, 2014).
Test Material Stability Under Storage Conditions: The test material was determined to have two years of stability under ambient storage conditions (Wachowicz et al., 2015).

Sampling and analysis

Analytical monitoring:

no

Test solutions

Vehicle:

no

Test organisms

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Activated sludge was obtained from the Midland Municipal Wastewater Treatment Plant
(Midland, Michigan). This facility treats an excess of 3.0 x 106 gallons of wastewater
daily, of which > 90% is from domestic sources. Upon return to the laboratory, the
activated sludge was washed three times with tap water.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

30 min

Test conditions

Reference substance (positive control):

yes

Results and discussion

Effect concentrations

Key result

Duration:

30 min

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Any other information on results incl. tables

Initial Reaction Mixtures Rate (mg/L/hr) % Inhibition

Control (C1) 12.108 NA

Reference Mixture 1 (3 mg/L) 11.154 14.71

Reference Mixture 2 (10 mg/L) 9.072 30.63

Reference Mixture 3 (30 mg/L) 3.6 72.47

Test Mixture 1 (100 mg/L) 13.74 -5.07

Test Mixture 2 (100 mg/L) 11.67 10.76

Test Mixture 3 (300 mg/L) 9.294 28.93

Test Mixture 4 (300 mg/L) 9.27 29.11

Test Mixture 5 (1000 mg/L) 11.226 14.15

Test Mixture 6 (1000 mg/L) 10.968 16.13

Control (C2) 14.046 NA

Three hour reaction mixtures

Control (C1) 11.916 NA

Reference Mixture 1 (3 mg/L) 10.494 16.65

Reference Mixture 2 (10 mg/L) 7.548 40.05

Reference Mixture 3 (30 mg/L) 3.24 74.27

Test Mixture 1 (100 mg/L) 15.708 -24.76

Test Mixture 2 (100 mg/L) 16.518 -31.19

Test Mixture 3 (300 mg/L) 13.638 -8.32

Test Mixture 4 (300 mg/L) 13.614 -8.12

Test Mixture 5 (1000 mg/L) 10.704 14.99

Test Mixture 6 (1000 mg/L) 10.77 14.46

Control (C2) 13.266 NA

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The potential for 2-butoxyethyl benzoate to inhibit the respiration of municipal activated sludge was evaluated using the OECD 209 “Activated Sludge, Respiration Inhibition Test.” This study assessed the potential effect of a range of test chemical concentrations on measured activated sludge respiration rates following both 30 min. and three hour contact periods. The 2-butoxyethyl benzoate substance, at nominal concentrations of 100, 300, and 1000 mg/L did not show > 50% inhibition of the activated sludge respiration rate after either 30 min. or three hours contact times. Therefore, the 30 min and three hour EC50 values were determined empirically to be EC50 > 1,000 mg/L. A statistical comparison (ANOVA) of respiration rates at each test material concentration and contact time resulted in determination of no observed effect concentrations (NOEC) for 30 min. and three hours contact times of 300 mg/L and 1,000 mg/L, respectively.
Considering that these EC50 and NOEC concentrations are well above the measured water solubility limit of the test material (i.e., 106 mg/L at 20 °C), the 2-butoxyethyl benzoate substance is expected to have very low potential for adversely affecting biological wastewater treatment operations.

Executive summary:

The potential for 2-butoxyethyl benzoate to inhibit the respiration of municipal activated sludge was evaluated using the OECD Guideline 209 “Activated Sludge, Respiration Inhibition Test.” This test method assesses the potential effect of a range of test chemical concentrations on measured activated sludge respiration rates following a three-hour contact period. In this study, the potential impact on respiration rates was also evaluated after a 30 min. contact period, in consideration of the ready biodegradability and volatile properties of the test material. The 2-butoxyethyl benzoate substance, at nominal concentrations of 100, 300, and 1000 mg/L did not show > 50% inhibition of the respiration rate of the activated sludge after either 30 min. or three hours contact time.

Therefore, the 30 min and three hour EC50 values were determined empirically to be EC50 > 1,000 mg/L. A statistical comparison (ANOVA) of respiration rates at each test material concentration and contact time resulted in determination of no observed effect concentrations (NOEC) for 30 min. and three hours contact times of 300 mg/L and 1,000 mg/L, respectively. Further testing of potential impact of the test material on nitrifying activity of activated sludge was deemed to be unnecessary, because respiration of nitrifying bacteria represents a relatively small proportion of total activated sludge respiration, and very high concentrations of test material (above solubility limit) were necessary to impact total respiration. Considering that these EC50 and NOEC concentrations are well above the measured water solubility limit of the test material (i.e., 106 mg/L at 20 °C), the 2-butoxyethyl benzoate substance is expected to have very low potential for adversely affecting biological wastewater treatment operations.