Undecanal

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2018-12-11 to 2018-12-21

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Version / remarks:

adopted April 2004

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Samples were taken in the fresh media at the start of the exposure and at the renewal of the test solutions (0 and 24 hours) as well as in 24-hours old media at the renewal and at the end of the exposure (24 and 48 hours).

Vehicle:

no

Details on test solutions:

A saturated solution with a nominal loading of 10 mg/L of the test item was freshly prepared with sterile demineralized water in a closed glass flask before the start of the exposure (at day 0) and before the renewal of the test solutions (at day 1). An appropriate volume of the test item (the density of 0.828 g/cm3 at 20 °C was taken into account) was placed by pipette onto the water surface and the bottle was closed with the screw cap. The headspace in the glass flask was minimized. The test item solution was stirred with a magnetic stirrer at approximately 1100 rpm for 1 hour at room temperature. After completion of stirring, the water phase (saturated solution) was removed by siphoning from the center of the water body after a short settling period not exceeding 10 minutes. The test item solution was checked via laser beam (Tyndall effect) for undissolved test item (formation of an emulsion). A positive Tyndall effect was observed in the saturated solution. After measurement of the Tyndall effect, the components of the dilution water were added to the saturated solution. The saturated solution was used as the highest concentration level and as a stock solution for the preparation of further dilution levels by dilution with dilution water. The test solutions after addition of the nutrients and dilution were colourless and clear. Additionally, pure Elendt medium always exhibits a slight Tyndall effect. Therefore, the Tyndall effect in this study was considered not relevant.
The preparation method for the saturated solution was based on results of a preliminary experiment outlined within the attached illustration under the heading "17.1 1st Stability Test in Demineralized Water". It was a compromise between the aim of obtaining saturation level and keeping the reaction product undecanoid acid as low as practically possible.

Test organisms (species):

Daphnia magna

Details on test organisms:

Test system: Daphnia magna STRAUS, obtained from continuous laboratory cultures.
Reason for the selection of the test system: Daphnia magna is the preferred species in accordance with the test guidelines and is bred at the test facility.
Origin: Institut für Wasser-, Boden- und Lufthygiene (WaBoLu), 14195 Berlin, Germany;
Breeder: Noack Laboratorien GmbH, Käthe-Paulus-Str. 1, 31157 Sarstedt, Germany;
Culture: In glass vessels (2 - 3 L capacity) with approximately 1.8 L culture medium, at 20 +/- 2 °C, 16 hours illumination, light intensity of max. 1500 lx;
Culture medium: Elendt M4, according to OECD 202, Annex 3 (2004), was used.
Feeding of the culture stocks: The daphnids are fed at least 5 times per week ad libitum with a mix of unicellular green algae, e.g. Pseudokirchneriella subcapitata and Desmodesmus subspicatus. The algae are cultured at the test facility.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Post exposure observation period:

No

Hardness:

Total hardness [mg CaCO3/L]
0h: 306;
24h: 272

Test temperature:

During the test period, the temperature in the incubator was 19.5 - 20 °C.

pH:

pH range over all concentration groups during the study (0 h to 48 h): 7.34 to 8.77

Dissolved oxygen:

Oxygen concentration range over all concentration groups during the study (0 h to 48 h): 7.72 mg/L to 8.55 mg/L

Salinity:

n.a.

Conductivity:

Dilution Water at the Start of the Exposure and at the Renewal (0 and 24 hours; without daphnids) [μS/cm]:
0 h: 644
24 h: 635

Nominal and measured concentrations:

The saturated solution and a further four dilution levels prepared out of the saturated solution in a geometric series with a separation factor of 2 by dilution of the saturated solution with sterile dilution water were tested as follows:
6.25 - 12.5 - 25.0 - 50.0 - 100% of the saturated solution.
This corresponded to the time weighted mean measured concentrations of 214 – 390 – 918 – 1915 – 3820 μg/L.
Dilution water without test item incubated under the same conditions as the test groups served as the control.

Details on test conditions:

See IUCLID section "Any other information on materials and methods incl. tables" below.

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

1 459 µg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

other: n-undecanal and n-undecanoic acid

Basis for effect:

mobility

Remarks on result:

other: 95% Cl: 1213 – 1643 µg/L

Duration:

48 h

Dose descriptor:

EC10

Effect conc.:

1 033 µg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

other: n-undecanal and n-undecanoic acid

Basis for effect:

mobility

Remarks on result:

other: 95% Cl: 841 – 1355 µg/L

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

2 516 µg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

other: n-undecanal and n-undecanoic acid

Basis for effect:

mobility

Remarks on result:

other: 95% Cl: 1923 – 3802 µg/L

Details on results:

See IUCLID section "Any other information on results incl. tables" below.

Results with reference substance (positive control):

The percentage of immobility for the reference item potassium dichromate (SIGMA-ALDRICH, batch number MKBV0900V, purity 99.0%, CAS RN 7778-50-9) was determined over 24 hours of exposure from 2018-12-04 to 2018-12-05 with the following results:

EC50 (24 h; immobility)= 2.03 mg/L (95% CI: 1.00 - 4.00 mg/L)

The respective confidence limits were empirically derived from the observation data as follows: The highest concentration level without any effect (EC0) and the lowest concentration level causing 100% immobilization (EC100) were used as confidence limits.

The result is within the valid range.

Reported statistics and error estimates:

Dose response modelling was performed using four parameter logistic equation i.e. sigmoidal dose-response with variable slope.
The following equation was applied:
Y=Bottom + (Top-Bottom)/(1+10^((LogEC50-X)*HillSlope))
 
Reported parameters for goodness of fit are the following (48 h exposure):
 
R^2 (goodness of fit - between 0 and 1, the closer to 1 the better): 0.9663
 
Standard deviation of residuals, Sy.x = [(sum over all squared residuals)/(n-k)]^0.5, n-k being degrees of freedom (16):
Sy.x = 9.354;
Replicates test for lack of fit: the scatter of replicates for Xi is quantified by SD_replicates, the SD_lack of fit quantifies how close the curve approaches the mean of replicates. F compares these values: F= (SD_lack of fit / SD_replicates)^2. The p-value gives the probability of finding the F value under the presumption that all scatter is Gaussian (i.e. the model correct). A small p-value indicates that the model is wrong.
SD_replicates: 9.661;
SD_lack of fit: 0.03195;
Discrepancy (F): 1.094E-05;
P value: 0.9974;
 
Conclusion:
The model fit is very well (high goodness of fit) and the replicates test for lack of fit confirms a good fit of the model: the scatter of replicates (moderate SD) is acceptabel and compared to SD_lack of fit considerably higher (very low F-value), indicating a very good fit. Correspondingly, confidence intervals for derived ECx values are acceptable.

Measured Exposure Concentrations during the Definitive Test

All concentration levels and the control were analytically verified via LC-MS/MS. Samples were taken in the fresh media at the start of the exposure and at the renewal of the test solutions (0 and 24 hours) as well as in 24-hours old media at the renewal and at the end of the exposure (24 and 48 hours). The test item concentrations and the corresponding degradation product (n-undecanoic acid) were determined. Details on analytical results are given in Tables 5, 6, and 7 within the illustration attached to this IUCLID endpoint study record.

Biological results:

The absolute numbers of immobile daphnids are presented in Table 4 within the attached illustration. The study was performed under semi-static conditions in a closed system without headspace.

The concentration-effect relationships after 48 hours of exposure is illustrated graphically in Figure 2 of the attached illustration. All effect concentrations (EC10 / 50 / 100) given are based on the summed up time-weighted mean measured concentrations of the test item and the degradation product Undecanoic acid.

EC₁₀-, EC₅₀- and EC₁₀₀-Values

		n-Undecanal + n-Undecanoic acid
Effect Concentrations	Test duration  [hours]	Time-weighted mean measured concentrations of the test item and its degradation product [µg/L]
EC10 (with confidence limits)	24	1809 (95% Cl: 889 – 3714)
	48	1033 (95% Cl: 841 – 1355)
EC50 (with confidence limits)	24	2516 (95% Cl: 1923 – 3802)
	48	1459 (95% Cl: 1213 – 1643)
EC100	24	> 3820
	48	3820

Additional Observations during the Definitive Test:

The tested concentration levels were colorless and visually clear throughout the exposure period. A positive Tyndall effect was observed in the saturated solution. The test solutions after addition of the nutrients and dilution were colourless and clear. Additionally, pure Elendt medium always exhibits a slight Tyndall effect. Therefore, the Tyndall effect in this study was considered not relevant.

Validity of the test

The study was performed according to OECD Guideline 202 (2004). The validity criteria were fulfilled:

- In the control group, no daphnids were immobilized or showed any signs of disease or stress, e.g. discoloration or unusual behavior such as trapping on the surface of the water, during the

48-hour test period (required: not more than 10% of the daphnids in the control).

- The dissolved O2 concentration in the 24-hours old media was ≥ 7.72 mg/L (required: ≥ 3 mg/L in the 24-hours old media) in all concentration levels and the control.

Validity criteria fulfilled:

yes

Conclusions:

OECD TG 202 (GLP), acute immobilisation test on Daphnia magna with n-Undecanal:
the 48 hours-EC50 for Daphnia magna was 1459 μg/L (95% confidence limits: 1213 – 1643 μg/L) based on the summed up time-weighted mean measured concentrations of the test item n-undecanal and the reaction product, n-undecanoic acid.

Executive summary:

For the test item n-undecanal an acute immobilization test with Daphnia magna (STRAUS) was performed according to OECD 202 (2004) compliant with GLP.

The study was conducted under semi-static conditions over a period of 48 hours with a saturated solution of the test item and a further four dilution levels in a geometric series with a separation factor of 2 (nominal concentrations 6.25 to 100% of the saturated solution, corresponding to the time-weighted mean measured concentrations 214 – 390 – 918 – 1915 – 3820 µg/L). Since for the test item a ready biodegradability was assumed, the test was carried out under sterile conditions (as far as possible) and in a closed system without headspace to prevent loss of the test item and contamination by bacteria.

The test item is a colorless and clear liquid with a water solubility of 0.012 g/L (20 °C). A saturated solution of the test item was prepared one hour before the start of the exposure (day 0) and one hour before the renewal of the test solutions (day 1). The saturated solution was used as the highest concentration level and as the stock solution for the preparation of all further tested concentration levels.

The tested concentration levels were colorless and visually clear throughout the exposure period. Twenty daphnids (divided into 4 replicates with 5 daphnids each) were exposed to each concentration level and the untreated control.

The test item concentrations and the corresponding degradation product (n-undecanoic acid) were analytically verified via LC-MS/MS in the fresh media at the start of the exposure and at the renewal of the test solutions (0 and 24 hours) as well as in the old media at the renewal and at the end of the test (24 and 48 hours) in all tested concentration levels and the control.

The measured concentration of the  test item n- undecanal in the fresh media (0 and 24 hours) were in the range of 110 µg/L to 2285 µg/L and in the corresponding old media (24 and 48 hours) 5.58 µg/L to 1664 µg/L. Additionally, the concentrations of the degradation product undecanoic acid were analyzed and calculated as n-undecanal concentrations by conversion with a factor of 1.094 (based on the ratio of the molar weights of the test item and its degradation product). The measured concentration of undecanoic acid given as n-undecanal equivalents in the fresh media (0 and 24 hours) were in the range of 106 µg/L to 2362 µg/L and in the corresponding old media (24 and 48 hours) < LOQ to 2298 µg/L.

Since the measured test item concentrations did not remain within ± 20% of the initially measured concentrations over time, the ECx-values are based on the summed up time-weighted mean measured concentrations of the test item n-undecanal and the degradation product undecanoic acid.

The validity criteria of the test guidelines were fulfilled.

The following 48 h effect concentrations were derived via dose-response modelling:

EC10 (48 h; mobility; time weighted mean measured): 1033 µg/L (95% Cl: 841 – 1355 µ/L)

EC50 (48 h; mobility; time weighted mean measured): 1459 µ/L (95% Cl: 1213 – 1643 µg/L)

Description of key information

OECD TG 202 (GLP), acute immobilisation test on Daphnia magna with n-Undecanal:

the 48 hours-EC50 for Daphnia magna was 1459 μg/L (95% confidence limits: 1213 – 1643 μg/L) based on the summed up time-weighted mean measured concentrations of the test item n-undecanal and the reaction product, n-undecanoic acid.  

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

1.46 mg/L

Additional information

In the reliable and valid key study (Noack, 2019) n-undecanal was tested for acute toxicity towards aquatic invertebrates in an immobilization test with Daphnia magna (STRAUS) performed according to OECD 202 (2004) compliant with GLP.

The study was conducted under semi-static conditions over a period of 48 hours with a saturated solution of the test item and a further four dilution levels in a geometric series with a separation factor of 2 (nominal concentrations 6.25 to 100% of the saturated solution, corresponding to the time-weighted mean measured concentrations 214 – 390 – 918 – 1915 – 3820 µg/L). Since for the test item a ready biodegradability was assumed, the test was carried out under sterile conditions (as far as possible) and in a closed system without headspace to prevent loss of the test item and contamination by bacteria.

The test item is a colorless and clear liquid with a water solubility of 0.012 g/L (20 °C). A saturated solution of the test item was prepared one hour before the start of the exposure (day 0) and one hour before the renewal of the test solutions (day 1). The saturated solution was used as the highest concentration level and as the stock solution for the preparation of all further tested concentration levels.

The tested concentration levels were colorless and visually clear throughout the exposure period. Twenty daphnids (divided into 4 replicates with 5 daphnids each) were exposed to each concentration level and the untreated control.

The test item concentrations and the corresponding degradation product (n-undecanoic acid) were analytically verified via LC-MS/MS in the fresh media at the start of the exposure and at the renewal of the test solutions (0 and 24 hours) as well as in the old media at the renewal and at the end of the test (24 and 48 hours) in all tested concentration levels and the control.

The measured concentration of the  test item n- undecanal in the fresh media (0 and 24 hours) were in the range of 110 µg/L to 2285 µg/L and in the corresponding old media (24 and 48 hours) 5.58 µg/L to 1664 µg/L. Additionally, the concentrations of the degradation product undecanoic acid were analyzed and calculated as n-undecanal concentrations by conversion with a factor of 1.094 (based on the ratio of the molar weights of the test item and its degradation product). The measured concentration of undecanoic acid given as n-undecanal equivalents in the fresh media (0 and 24 hours) were in the range of 106 µg/L to 2362 µg/L and in the corresponding old media (24 and 48 hours) < LOQ to 2298 µg/L.

Since the measured test item concentrations did not remain within ± 20% of the initially measured concentrations over time, the ECx-values are based on the summed up time-weighted mean measured concentrations of the test item n-undecanal and the degradation product undecanoic acid.

The validity criteria of the test guidelines were fulfilled.

The following 48 h effect concentrations were derived via dose-response modelling:

EC10 (48 h; mobility; time weighted mean measured): 1033 µg/L (95% Cl: 841 – 1355 µ/L)

EC50 (48 h; mobility; time weighted mean measured): 1459 µ/L (95% Cl: 1213 – 1643 µg/L)

Supporting data are available (BASF, 1990). Undecanal was tested in an acute Daphnia toxicity study according to EC Directive 79/831/EEC which is similar to OECD TG 202. The test material was undecanal with a purity of 65%, therefore the effect concentrations were recalculated on the basis of the given purity. The test item was dissolved using Cremophor RH 40 as vehicle at 100 mg/L. Starting from a stock solution of 100 mg/L, a dilution series was prepared. The following concentrations were tested: nominal (active ingredient): 0 (control), 0 (solvent control), 0.51, 1.01, 2.03, 4.06, 8.12, 16.25, 32.5, and 65 mg/L. No analytical verification of the test concentrations was performed and no provisions accounting for volatility were in place. Based on a Henry’s law constant of 64.3 Pa*m^3/mol, a decrease of the test item concentration can be expected over the test duration, but most animals died within the first 24 h of the test. The 48 -h EC50 was determined to be 3.85 mg/L based on test material and 2.5 mg/L based on active ingredient.

Concluding, the somewhat higher EC50 after 48 hs determined in the supporting study (2.5 mg/L; nominal) compared to the one determined in the key study (1.46 mg/L; measured) may be due to a) volatility of the test item; b) instability of the test item; and c) application of the test item with emulsifier which may alter bioavailablity, stability as well as volatility. Overall, despite the relevant draw-backs of the supporting study, results of key and supporting study are very close to each other increasing confidence in the key value for risk assessment derived from the valid key study.