Butyl propionate

Short-term toxicity to aquatic invertebrates

Administrative data

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2005

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Although the study was conducted according to OECD TG 202, EU Method C.2 and EPA 797.1300 and in accordance with the Principles of Good Laboratory Practice (GLP), the difference between the measured analytical concentrations and nominal concentrations were in excess of ±50%.

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

reference to same study

Cross-reference 2

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2005

Report date:

2005

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OTS 797.1300 (Aquatic Invertebrate Acute Toxicity Test, Freshwater Daphnids)

Deviations:

no

Principles of method if other than guideline:

not applicable

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Butyl propionate

EC Number:

209-669-5

EC Name:

Butyl propionate

Cas Number:

590-01-2

Molecular formula:

C7H14O2

IUPAC Name:

butyl propanoate

Details on test material:

- Name of test material (as cited in study report): UCAR n-butyl propionate
- Physical state: transparent colourless liquid
- Analytical purity: 99.7%
- Lot/batch No.: 369856

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
not applicable

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 0 (water control), 5.44, 9.07, 15.1, 25.2, 42.0, and 70.0 mg/L
- Sampling method: Replicate test solutions as well as the mixing cell were sampled for analytical confirmation on days 0 and 2 of the study. To assess analytical method precision and solution homogeneity, three additional samples were taken on day 0 from representative 5.44 and 70.0 mg/L test solutions and analyzed along with the day 0 samples

Test solutions

Vehicle:

no

Details on test solutions:

For the definitive test, two replicate test vessels were prepared in laboratory dilution water (LDW) at each nominal exposure concentration of 5.44, 9.07, 15.1, 25.2, 42.0, and 70.0 mg/L. In addition, two replicate vessels of control water (LDW with no test material added and referred to as water control) were prepared. Vessels were replenished on a regular intermittent cycle (approximately every 45 minutes) with test solutions delivered from a flow-through proportional diluter, which was fortified from a glass vessel filled with undiluted test material.

Test organisms

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: water flea
- Strain: Daphnia magna
- Source: in- house cultures initially obtained from New England Bioassay, Inc., Manchester, Connecticut.
- Age at study initiation (mean and range, SD): Daphnid instars less than 24- hours old from a laboratory-reared culture were used as the test organisms.
- Method of breeding: Rearing conditions were as follows: illumination (cool-white fluorescent) 2050 ± 350 lux; 16-hour light/8- hour dark photoperiod; temperature 20 ± 2°C. Daphnids were fed a mixed diet of Pseudokirchneriella subcapitata, a freshwater green alga (formerly known as Selenastrum capricornutum) and YCT (yeast, Cerophyll, and trout chow suspension) five times weekly. The day before instars were needed for testing, stock tanks with daphnids, which have had at least three broods, were removed from the incubator. The instars were separated from adults by gently lifting the screened insert from the 2-L stock tank, releasing instars through the nylon mesh screen while retaining the adult daphnids. The screened insert containing adult daphnids were then placed in another stock tank that contained daphnid water (LDW). The original solution with instars was poured through a metal sieve into another stock tank. The instars collected on the sieve were discarded, and the original solution was poured back into the initial stock tank. The corresponding screened insert holding adult daphnids was then put back in place. This procedure was repeated the day the study was set to collect < 24-hour old instars for use in the study.

Study design

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Post exposure observation period:

not applicable

Test conditions

Hardness:

Hardness (as CaCO3) was 71 and 79 mg/L in the control water and highest test level, respectively

Test temperature:

20 ± 1°C

pH:

pH ranged from 7.6-7.9

Dissolved oxygen:

Dissolved oxygen levels ranged from 7.9-8.9 mg/L (89-100% oxygen saturation) over the 48-hour exposure period.

Salinity:

not applicable

Nominal and measured concentrations:

Nominal test concentration - 0 (water control), 5.44, 9.07, 15.1, 25.2, 42.0, and 70.0 mg/L
Measured test concentration - The mean measured concentrations were less than the lowest level quantified of 0.906 mg/L for the water control and 3.09, 5.56, 10.4, 17.2, 33.5, 49.1 mg/L for the treatment solutions.

Details on test conditions:

TEST SYSTEM
- Test vessel: The test vessels were 600-mL Pyrex beakers, each containing approximately 500 mL of control or test solution. Each vessel contained a Nitex (Tetko, Elmsford, New York) screen-covered glass protrusion exit port at approximately the 500 mL graduation mark to allow for the overflow of test solution during each cycle of the diluter. All vessels were loosely covered and uniquely labeled for identification purposes.
- Type of flow-through (proportional diluter): An intermittent- flow proportional diluter system was used to maintain constant exposure concentrations during the 2-day (48- hour) study period. This system is designed to deliver up to six test concentrations, a vehicle control, and a water control. The diluter was
calibrated so that the concentration of the test substance in each treatment below the high concentration was approximately 60 percent of that in the next higher treatment level. The diluter operated as follows: a precision dosing system (Hamilton Company, Reno, Nevada MICROLAB 500 system) delivered a designated amount of test material from a glass vessel to the mixing chamber where it was mixed with lab dilution water and then distributed to toxicant cells. The mixing chamber was equipped with a recirculating pump that facilitated dissolution and mixing of the test material. When the diluter cycled, the test substance from each toxicant cell blended with water from its respective water cell and flowed into mixing/splitting chambers. Silicone delivery tubes with glass capillary
tube exit ports from these chambers provided approximately 100 mL of test solution to each of four replicate test vessel locations of which two were utilized. The mixing/splitting chambers were randomly positioned on the diluter. The test vessels were positioned under these chambers on one tier, side-by-side, in a water trough. A thermostatic temperature controller maintained a water temperature of 20 ± 1°C in the trough. Diluter and laboratory lighting provided a 16-hour light/8- hour dark transitional photoperiod during testing. The diluter was calibrated prior to test initiation and averaged 6.3 volume turnovers in the test aquaria each 24- hour period during exposure.
- No. of organisms per vessel: 10 daphnids/vessel
- No. of vessels per concentration (replicates): 2 vessels/replicate
- No. of vessels per control (replicates): 2 vessels/replicate

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The laboratory dilution water (LDW) was Lake Huron water supplied to The Dow Chemical Company by the City of Midland Water Treatment Plant. The water was obtained from the upper Saginaw Bay of Lake Huron near Whitestone Point and was limed and flocculated with ferric chloride. The water was pumped to the laboratory prior to treatment for municipal use. Before use in the laboratory, the water was sand- filtered, pH-adjusted with gaseous CO2, carbon-filtered, and UV- irradiated. Refer to attachments for further details.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Immobility was observed in th daphnids exposed

TEST CONCENTRATIONS
- Range finding study: In the probe study, one replicate of ten daphnid per dose level was exposed to nominal concentrations of 0 (water control), 15.6, 25.9, 43.2, 72.0, 120, and 200 mg/L, over a 48-hour flow-through exposure period. Flow-through conditions were used due to the volatility of n-butyl propionate in aqueous solution. Following 48-hours of exposure, daphnid immobility was observed in 40%, 30%, and 70% of the daphnid at the 15.6, 25.9, and 43.2 mg/L test levels, respectively and in 100% of the daphnid at the 72.0 mg/L and above test levels; no immobility was observed in the water control. No changes in behavior or physical appearance were observed in water control or test levels.
Analytical chemistry confirmation of test solution concentrations ranged from approximately 61% to 84% during the exposure. The test concentrations within their respective test levels remained relatively consistent over the exposure period indicating that equilibrium of the test solution concentrations had been reached and that the lower percent of target concentrations (£ 84%) observed during the exposure may have been due to the volatilization of the test material from aqueous solution. Based on this preliminary information, the following target (nominal) concentrations for the definitive test were selected: 0 (water control) 5.44, 9.07, 15.1, 25.2, 42.0, and 70.0 mg/L.
- Results used to determine the conditions for the definitive study: yes

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

18.5 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 15.0-22.7 mg/l

Effect concentrations 2

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

5.56 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

No changes in daphnid behavior or appearance were observed at any test level during the study. Following 24 hours of exposure, immobility was observed in 15%, 60%, 40%, and 55% of the daphnids at the 10.4, 17.2, 33.5, and 49.1 mg/L test levels, respectively. At test termination (48-hours of exposure), immobility was observed in 20%, 60%, 65%, and 100% of the daphnids at the 10.4, 17.2, 33.5, and 49.1 mg/L test levels, respectively. No immobility was observed at the 5.56 mg/L and below test levels or in the water control during the conduct of the study.

Under the conditions of the study, the 48-hour LC50 of UCAR n-butyl propionate to Daphnia magna was 18.5 mg/L, with a 95% confidence interval of 15.0-22.7 mg/L and the 48-hour NOEC was 5.56 mg/L and was determined based on the highest exposure concentration tested exhibiting no daphnid immobility or change in behavior or appearance.

Results with reference substance (positive control):

not applicable

Reported statistics and error estimates:

An appropriate U.S. EPA computer program was used to calculate the 24- and 48-hour EC50 values (the concentrations estimated to immobilize 50 percent of the daphnids after 24 and 48 hours of exposure, respectively) and corresponding 95% confidence intervals, when possible. Two statistical methods were available: Probit Program, Version 1.5, U.S. EPA, 1994 and Trimmed Spearman-Karber (TSK) Program, Version 1.5, U.S. EPA, 1994. The order of preference used to select the method for reporting EC50 values is Probit analysis followed by trimmed Spearman-Karber. However, the appropriateness of a given method is determined by the concentration-response data, e.g., the number of concentrations resulting in immobility between 0 and 100 percent. The NOEC was determined based on biological interpretation of the data and/or the highest concentration tested exhibiting no daphnid immobility.

Any other information on results incl. tables

Results from the day 0 analysis, as the average of measured concentrations from two replicate test solutions per dose level, ranged from 59.2 to 87.6% of the target concentrations. The day 2 measured concentrations were 54.2 to 71.7% of target from the average of two replicate test solution values per dose level. A study average was also calculated for each dose level by averaging the day 0 and day 2 average measured concentrations. The study average values ranged from 56.8 to 79.8% of target concentrations. The lower percent of target concentrations observed was likely due to the volatility of the test material under the test conditions (@ 20°C). However, the measured test concentrations within their respective test levels remained consistent over the exposure period and indicated that equilibrium of the test solution concentrations had likely been achieved.

 

Samples collected from the mix cell (target concentration of 70.0 mg/L) on days 0 and 2 of the study afforded measured concentrations of 64.7 and 55.7 mg/L, respectively. None of the analyses of the LDW controls exhibited a peak eluting at the retention time of n-butyl propionate at a concentration exceeding the lowest level quantified (LLQ) equivalent to 0.906 mg n-butyl propionate/L LDW.

 

The variability associated with the analytical method as well as solution homogeneity was assessed on day 0 of the study. Four replicate samples were collected from representative 5.44 and 70.0 mg/L test solutions. Four repeated measurements (4 samples x 1 injection/sample) resulted in percent relative standard deviation (RSD) values of 2.77 and 4.27% for the low and high-test levels, respectively. The GC/FID instrumentation exhibited a linear response over the concentration range extending from 0.23 to 43 mg n-butyl propionate/L diluent. The LLQ was set at 0.906 mg n-butyl propionate/L LDW based on the concentration of the lowest standard analyzed on day 2 multiplied by the dilution factor.

 

Dissolved oxygen levels ranged from 7.9-8.9 mg/L (89-100% oxygen saturation) over the 48-hour exposure period. Temperatures measured from on day 0 and 2 from the individual test vessels and continuously from a surrogate vessel remained a constant 20°C and therefore within 20± 1°C  throughout the study. The pH ranged from 7.6-7.9 and the light intensity ranged from 739-950 lux.

Water quality parameters such as hardness, alkalinity, conductivity, and residual chlorine were measured from the day 0 control water and the highest test level. Hardness (as CaCO3) was 71 and 79 mg/L in the control water and highest test level, respectively. Alkalinity (as CaCO3) was 42 mg/L in both the control water and highest test level. Conductivity was 169 and 165mmhos/cm in the control water and highest test level, respectively. Residual chlorine was <10 ppb (instrument’s limit of detection) in both solutions measured.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of the study, the 48-hour LC50 of UCAR n-butyl propionate to Daphnia magna was 18.5 mg/L, with a 95% confidence interval of 15.0-22.7 mg/L and the 48-hour NOEC was 5.56 mg/L and was determined based on the highest exposure concentration tested exhibiting no daphnid immobility or change in behavior or appearance.

Executive summary:

The study was conducted with two groups of ten daphnids exposed to nominal test concentrations of 0 (water control), 5.44, 9.07, 15.1, 25.2, 42.0, 70.0 mg/L, over a 48-hour flow-through exposure period. Observations were made at 24 and 48 hours for daphnid immobility (inability to swim within 15 seconds after gentle agitation of the test container) and any changes in behavior or appearance.

 

All replicate test solutions were sampled for analytical confirmation of n-butyl propionate concentrations on days 0 and 2 of the study. The collected samples were analyzed by gas chromatography with flame ionization detection (GC/FID). Test solution concentrations (average of measured concentrations from two replicate test solutions per dose level) ranged from 59.2 to 87.6% of the targe t concentrations on day 0 and 54.2 to 71.7% of target on day 4. The study average values ranged from 56.8 to 79.8% of target concentrations. The lower percent of target concentrations observed was likely due to the volatility of the test material under the test conditions (@ 20°C). However, the measured test concentrations within their respective test levels remained consistent over the exposure period and indicated that equilibrium of the test solution concentrations had been reached. The mean measured concentrations for the study were less than the lowest level quantified of 0.906 mg/L for the water control and 3.09, 5.56, 10.4, 17.2, 33.5, and 49.1 mg/L for the treatment solutions.

 

No changes in daphnid behavior or appearance were observed at any test level during the study. Following 24 hours of exposure, immobility was observed in 15%, 60%, 40%, and 55% of the daphnids at the 10.4, 17.2, 33.5, and 49.1 mg/L test levels, respectively. At test termination (48-hours of exposure), immobility was observed in 20%, 60%, 65%, and 100% of the daphnids at the 10.4, 17.2, 33.5, and 49.1 mg/L test levels, respectively. No immobility was observed at the 5.56 mg/L and below test levels or in the water control during the conduct of the study.

 

Under the conditions of the study, the 48-hour LC50 of UCAR n-butyl propionate to Daphnia magna was 18.5 mg/L, with a 95% confidence interval of 15.0-22.7 mg/L and the 48-hour NOEC was 5.56 mg/L and was determined based on the highest exposure concentration tested exhibiting no daphnid immobility or change in behavior or appearance.