Linalyl formate

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

to GLP

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2015

Report date:

2015

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Linalyl formate

EC Number:

204-120-6

EC Name:

Linalyl formate

Cas Number:

115-99-1

Molecular formula:

C11H18O2

IUPAC Name:

linalyl formate

impurity 1

Reference substance name:

Linalyl acetate

EC Number:

204-116-4

EC Name:

Linalyl acetate

Cas Number:

115-95-7

Molecular formula:

C12H20O2

IUPAC Name:

1,5-dimethyl-1-vinylhex-4-en-1-yl acetate

impurity 2

Reference substance name:

Linalool

EC Number:

201-134-4

EC Name:

Linalool

Cas Number:

78-70-6

Molecular formula:

C10H18O

IUPAC Name:

3,7-dimethylocta-1,6-dien-3-ol

Test material form:

liquid

Details on test material:

Identification:Linalyl formate
Chemical name: 3,7-dimethyl-1,6-octadien-3-yl formate
EC No.: 204-120-6
CAS No.: 115-99-1
Physical state/Appearance: Clear colorless liquid

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

At 0 and 24 hours from fresh media and at 24 and 48 hours from old media.

Test solutions

Details on test solutions:

In the range-finding test Daphnia magna were exposed to a series of nominal test concentrations of 0.10, 1.0, 10 and 100% v/v saturated solution.
Based on the results of the range-finding test the following test concentrations were assigned to the definitive test: 10, 18, 32, 56 and 100% v/v saturated solution.

Preparation of the saturated solution employed shorter stirring times than the conventional 24 hours in order to minimise degradation/hydrolysis of the parent ester. A media preparation trial show the maximum linayl formate concentration was achieved using a saturated solution method of preparation at an initial loading rate of 50 mg/L, sonicated for a period of 15 minutes prior to the removal of any undissolved test item by filtration through a 0.2 μm Sartorius Sartopore filter (first approximate 1 liter discarded) to give a nominal test concentration of approximately 28 mg/L. Analysis of the freshly prepared test solutions showed a main peak (RT 3.5 mins) corresponding to the parent ester but also two minor peaks with shorter retention times (approximately 2.7 and 3.4 mins) indicating that there had been some degradation/hydrolysis during preparation of the solutions. The primary degradation of the test item is believed to be due to hydrolysis of the ester functional group to give the corresponding alcohol (linalool) and carboxylic acid (formic). This is supported by the water solubility determination of linalyl formate where hydrolysis/degradation of the test item was also observed and where the chromatogram of a linalool marker standard gave a retention time common to one of the degradant peaks.

Test organisms

Test organisms (species):

Daphnia magna

Study design

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Test conditions

Test temperature:

Temperature was maintained at 19 to 20 °C throughout the test. The water temperature was recorded daily throughout the test using a Hanna Instruments HI 93510 digital thermometer.

pH:

The pH of the prepared media was 7.9 ± 0.3 and stored at approximately 21 ºC. The pH was measured daily using a Hach Flexi handheld meter

Dissolved oxygen:

The dissolved oxygen concentration at the end of the test is ≥3 mg/L in the control and test vessels. The dissolved oxygen concentration was measured daily using a Hach Flexi handheld meter

Salinity:

No (freshwater)

Nominal and measured concentrations:

Range finding test: Nominal test concentrations of 0.10, 1.0, 10 and 100% v/v saturated solution

Definitive test: Nominal test concentrations of 10, 18, 32, 56 and 100% v/v saturated solution; 0-Hour measured test concentrations: 0.46, 0.79, 1.4, 2.4, 4.4 mg/L

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

2.4 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 95% CL: 1.9 - 3.1 mg/L

Effect concentrations 2

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

1.4 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

mobility

Effect concentrations 3

Duration:

48 h

Dose descriptor:

LOEC

Effect conc.:

2.4 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

In accordance with the tiered approach for selecting an appropriate exposure regime for unstable and volatile substances (OECD, 2000), a closed semi-static system was used with no headspace. Under such conditions it is considered appropriate to base the effect results on the mean measured concentrations of fresh solutions. This gave a 48-hour EC50 of 2.4 mg/L.

Evaluating data using time-weighted mean measured concentrations to give a “worse case” analysis of the data is not appropriate. A decline in measured test concentration was observed in the old or expired test media at 24 and 48 hours (3% to 8% of the initial measured concentrations). The chromatograms for the 24 hour old samples showed that the two minor peaks seen in the 0 hour samples (see "Details on Test Solutions") had significantly increased indicating that hydrolysis/degradation of the parent ester had progressed during the exposure period. The rapid decline in measured concentrations means that effects based on time-weighted mean measured concentrations are unrealistically low and not in-line with the expected trend based on log Kow when compared with linalyl esters that are degraded less rapidly (see Table in "Any other information on results incl. tables"). Usually within classes of chemicals a trend of increasing aquatic toxicity is observed with increasing log Kow. Thus linalyl isobutyrate is expected to be most toxic, followed by linalyl propionate and then linalyl formate. However, the EC50 values based on time-weighted mean measured concentrations are 1.1, 2.2 and 0.77 mg/L respectively. The correct trend is observed for linalyl isobutyrate and linalyl propionate, which are degraded at similar rates (56-68% and 52-71% initial after 24 hours) but not for linalyl formate, which is degraded much more quickly. Furthermore, experimental evidence indicates that all the linalyl esters are primarily degraded via hydrolysis to the common degradant (linalool) and corresponding carboxylic acid, which are less toxic than the parent esters. The latter is supported by available data on the ECHA website for linalool (EC201-134-4), formic acid (EC200-579-1), propionic acid (EC201-176-3) and isobutric acid (EC201-195-7). Therefore, no degradation products are formed that would lead to linalyl formate exhibiting higher acute toxicity to daphnia than either linalyl isobutyrate or linalyl propionate. In contrast EC50 values based on mean measured concentrations of fresh solutions, which are 1.4, 2.8 and 2.4 mg/L respectively, more closely reflect the expected trend based on log Kow and are justified based on the exposure regime of closed semi-static renewal with no headspace.

References
OECD 2000, Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures. OECD Environmental Health and Safety Publication. Series on Testing and Assessment. No. 23. Paris 2000.

Results with reference substance (positive control):

A positive control used potassium dichromate as the reference item at concentrations of 0.32, 0.56, 1.0, 1.8 and 3.2 mg/L.
Exposure conditions for the positive control were similar to those in the definitive test.
Analysis of the immobilization data by probit analysis using linear maximum likelihood regression at 24 and 48 hours. All analysis was carried out using the ToxRat Professional computer software package (ToxRat):

The 24 h EC50 was 1.1 mg/L .
The 48 h EC50 was 0.75 with 95 % confidence limits of 0.69 - 0.82 mg/L.
The NOEC was 0.56 mg/L and the LOEC was 1.0 mg/L.

The No Observed Effect Concentration is based upon less than 10% immobilization at this concentration.
The results from the positive control with potassium dichromate were within the normal range for this reference item.

Any other information on results incl. tables

Comparison of acute daphnia results for linalyl esters where all studies were conducted under the same conditions and by the same laboratory (all data owned by the Lead Registrant).

 

Substance Name	Linalyl formate	Linalyl propionate	Linalyl isobutyrate
CAS Number	115-99-1	144-39-8	78-35-3
EC Number	204-120-6	205-627-5	201-108-2
Molecular Formula	C11H18O2	C13H22O2	C14H24O2
Partition coefficient N-Octanol/water (Log Kow)	3.7	4.9	5.5
Short-term Daphnia toxicity
48h EC50(mg/L), based on mean measured concentrations of fresh solutions (24 hour renewal)	2.4	2.8	1.4
48h EC50(mg/L), based on time-weighted mean measured concentrations	0.77	2.2	1.1
% of the initial measured concentration after 24 hours	3-8%	52-71%	56-68%

 

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

In a guideline study, conducted according to GLP, Linalyl Formate was found to have an EC50 (48 hr) (average initial measured test concentrations) of 2.4 mg/L.