Oxacycloheptadecan-2-one

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The read-across source chemical oxacyclohexadecan-2-one and the target chemical oxacycloheptadecan-2-one are structural homologues of each other, with the only difference between the two being one additional carbon atom in the cyclic aliphatic chain (C15 and C16, respectively). Considering a very long aliphatic chain in both substances, the presence of additional carbon atom (CH2 moiety) in oxacycloheptadecan-2-one is not expected to influence its (eco)toxicological properties in comparison to oxacyclohexadecan-2-one. Therefore read-across from oxacyclohexadecan-2-one to oxacycloheptadecan-2-one is considered to be justified.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Both substances are mono-constituent substances of high purity (details on purity are provided in the confidential sections of the robust study summaries) and do not contain toxicologically relevant impurities which could influence their toxicological behavior.

3. ANALOGUE APPROACH JUSTIFICATION
The read-across source chemical oxacyclohexadecan-2-one and the target chemical oxacycloheptadecan-2-one are structural homologues of each other, with the only difference between the two being one additional carbon atom in the cyclic aliphatic chain (C15 and C16, respectively). Considering a very long aliphatic chain in both substances, the presence of additional carbon atom (CH2 moiety) in oxacycloheptadecan-2-one is not expected to influence its (eco)toxicological properties in comparison to oxacyclohexadecan-2-one. This is confirmed by the available data on both substances (see data matrix) which confirm nearly identical physico-chemical and (eco)toxicological properties for all endpoints. There are no additional functional groups present in oxacyclohexadecan-2-one which may influence its toxicity. Both substances have comparable physico-chemical properties, i.e. high log Pow (> 4) and poor water solubility (< 1 mg/L), thus their behavior in the aquatic environment is expected to be comparable. Therefore read-across from oxacyclohexadecan-2-one to oxacycloheptadecan-2-one is considered to be justified.

4. DATA MATRIX (data on oxacyclohexadecan-2-one taken from its dissiminated REACH dossier available on the ECHA website):

Substance Oxacycloheptadecan-2-one Oxacyclohexadecan-2-one
Molecular formula C16H30O2 C15H28O2
Molecular weight 254.4 240.38 g/mol
Melting point 35 °C 34.6 °C
Boiling point 265-275 °C 325 °C
Water solubility 0.103 mg/L 0.34 mg/L
Log Pow 7.3 5.79
Vapour pressure <= 0.053 Pa at 25 °C 0.085 Pa at 25 °C
Acute oral toxicity LD50 > 5000 mg/kg bw LD50 > 5000 mg/kg bw
Acute dermal toxicity LD50 > 5000 mg/kg bw LD50 > 5000 mg/kg bw
Skin irritation Read-across Not irritating
Eye irritation Not irritating Not irritating
Skin sensitization Read-across Not sensitizing
Repeated dose toxicity NOAEL > 1000 mg/kg bw/day NOAEL > 1000 mg/kg bw/day
Reproductive toxicity NOAEL > 1000 mg/kg bw/day NOAEL > 1000 mg/kg bw/day
Developmental toxicity NOAEL > 1000 mg/kg bw/day NOAEL > 1000 mg/kg bw/day
Toxicity to fish 96-h LC50 > solubility limit EC50 > solubility limit
Toxicity to daphnia Read-across 48-h EC50 > 0.17 mg/L
Toxicity to algae 72-h ErC50 > 0.004 mg/L 72h ErC50 > 0.47 mg, 72h ErC10 = 0.42 mg/L

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 0.17 mg/L

Basis for effect:

mortality

Remarks on result:

other: read-across from Pentadecan-15-olide

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

14 December 2012 - 04 March 2013

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Version / remarks:

2004

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Version / remarks:

2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

- Melting point: 34.6°C
- Measured solubility in pure water: 0.3 mg/L at 20°C

Analytical monitoring:

yes

Details on sampling:

- Concentrations: control and all test concentrations
- Sampling method: 200 mL (fresh sample solutions probably taken from the bulk solution, and used sample solutions from pooled replicates)
- Sample storage conditions before analysis: samples were analysed on the day of receipt (but it is unclear if this is the same day

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: preparation of a saturated solution (direct addition to test medium) - The test item was melted at 40°C, an amount of 1125 mg weighed onto a glass slide and the slide suspended in 22.5 L of reconstituted water (nominal loading rate = 50 mg/L). The medium was stirred by magnetic stirring at such rate to form a vortex in the water column. The stirring was stopped after 47 hours and the mixture allowed to stand for 1 hour. A wide bore glass tube, covered at one end with Nescofilm was submerged into the vessel, sealed end down, to a depth of approx. 5 cm from the bottom of the vessel. A length of Tygon tubing was inserted into the glass tube and pushed through the Nescofilm seal. Microscopic inspection of the water column showed no micro-dispersions or undissolved test item to be present. The aqueous phase was removed by mid-depth siphoning (first 75-100 mL were discarded) to give the 100% saturated solution (WAF). Aliquots (20, 64, 200 and 640 mL) of the 100% saturated solution were added to test vessels and made up to a final volume of 2 L to give test concnetrations of 1.0, 3.2, 10 and 32% (v/v) of the saturated solution. Test medium for the renewal after 24 hours was prepared from the above mentioned mixture (saturated solution): after removal of sufficient volume of the aqueous phase, stirring was resumed for a further 23 hours followed by a 1 hour standing period. Removal of the aqueous phase and subsequent dilutions were performed as described above. To minimize possible photolytic degradation, all test item preparation was performed under laboratory safety lighing/shielded from light. To minimize losses due to volatilization, stirring was performed in a completely filled and sewaled vessel.
- Controls: test medium without test item
- Evidence of undissolved material: no - the saturated olutions prepared at a loading rate of 50 mg/L showed no micro-dispersions or undissolved test item on microscopic inspection.
- Other: Prior to use the test medium was aerated until the dissolved oxygen concentration was approximately air-saturation value.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Daphnia magna
- Source: in-house laboratory culture, 1st instar D. magna
- Feeding during culture:
* Food type: mixture of algal suspension (Desmodesmus subspicatus) and Tetramin® flake food suspension
* Frequency: daily
- Feeding during test: no
- Age at study initiation: young daphnids with an age of < 24 hours

ACCLIMATION
- Acclimation period: no

METHOD FOR PREPARATION AND COLLECTION OF EARLY INSTARS OR OTHER LIFE STAGES:
Adult daphnia were maintained in 150 mL glass beakers containing Elendt M7 medium in a temperature controlled room maintaining the water temperature at 20 °C. The lighting cycle was controlled to give a 16 hours light and 8 hours darkness cycle with 20 minute dawn and dusk transition periods. Culture conditions ensured that reproduction was by parthenogenesis. Gravid adults were isolated the day before initiation of the test, such that the young daphnids produced overnight were less than 24 hours old. These young were removed from the cultures and used for testing.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

250 mg/L as CaCO3

Test temperature:

19-21°C

pH:

fresh solutions: 7.9 - 8.1
used solutions: 7.8 - 8.1

Dissolved oxygen:

fresh solutions: 9.0 - 9.8 mg O2/L
used solutions: 8.6 - 9.5 mg O2/L

Nominal and measured concentrations:

- Nominal concentrations: 0 (control), 1.0, 3.2, 10, 32 and 100% (v/v) of a saturated solution prepared at a loading rate of 50 mg/L (based on range-finding study).
- Measured concentrations (TWA): n.d., 0.0013, 0.0044, 0.008, 0.024 and 0.17 mg/L.

Recovery at 24h: n.a., 0, 13.0, 16.9, 15.4 and 38.8%
Recovery at 48h: n.a., 0, 0, 0, 1.3 and 55.6%

Time-weighted mean measured test concentrations were used to calculate effect parameters in view of a decline in test concentration during 24 hours, and in order to give a “worst case” analysis of the data.

Details on test conditions:

TEST SYSTEM
- Test vessel: conical flasks (probably glass)
- Fill volume: approximately 160 mL (test vessels were completely filled and sealed)
- Aeration: no
- Renewal rate of test solution: yes, after 24 hours
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: reconstitueted water (ISO medium)
- Culture medium different from test medium: yes - culture medium: Elendt M7
- Intervals of water quality measurement: water temperature, pH and dissolved oxygen concentrations were recorded daily

OTHER TEST CONDITIONS
- Adjustment of pH: yes; where needed, pH was adjusted to pH 7.8 ± 0.2
- Photoperiod: no (test performed in the dark)

EFFECT PARAMETERS MEASURED
Mobility at 24 and 48 hours

RANGE-FINDING STUDY
- Test concentrations: not reported
- Results used to determine the conditions for the definitive study: yes

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 0.17 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat. (dissolved fraction)

Basis for effect:

mobility

Remarks on result:

other: no toxic effects at saturation

Details on results:

- Mortality of control: no
- Other adverse effects control: no
- Effect concentrations exceeding solubility of substance in test medium: yes
- Other: Relative to initial [%] (calculated by the reviewer) ranged from 13.0 - 38.8 % during the first renewal period (no data for the lowest test concentration), and 1.3 - 55.6% in the second renewal period (only for 32% dilution and 100% saturated solution).

Individual pH, temperature and dissolved oxygen values remained within acceptable limits throughout the duration of the study.

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Dose-response test: yes (test concentrations: 0.32, 0.56, 1.0, 1.8 and 3.2 mg/L)
- EC50: 0.45 mg/L (95% CI: 0.42 - 0.48 mg/L)

Validity criteria fulfilled:

yes

Remarks:

see 'Overall remarks'.

Conclusions:

The test substance is not acutely toxic to Daphnia magna at saturation in test medium. The EC50 is >0.17 mg/L, based on time-weighted mean measured concentrations.

Executive summary:

The acute toxicity of the test substance to the freshwater invertebrate Daphnia magna was investigated in a study according to OECD TG 202 and in compliance with GLP criteria. A saturated solution was prepared in test medium at a loading rate of 50 mg/L by stirring for 47 hours, followed by a 1 hour settling period and siphoning off the clear solution. Test organisms were exposed for 48 hours (with renewal after 24 hours) to the following test solutions: an untreated control (test medium only), 1.0%, 3.2%, 10% and 32% (v/v) dilutions of the 100% saturated solution, and the 100% saturated solution. 4 replicates with 5 daphnids were tested for each treatment group. Test concentrations were analytically determined with a validated GC-FID method. Since test concentrations in used solutions were not found to remain within 80 -120% of initial measured concentrations, time-weighted mean measured concentrations were calculated. TWA mean measured concentrations in the 0.1, 3.2, 10 and 32% dilutions and the 100% saturated solution were 0.0013, 0.0044, 0.008, 0.024 and 0.17 mg/L, respectively. Daphnids were observed for immobilisation after 24 and 48 hours in all treatment groups. In absence of adverse effects, the EC50 was concluded to be >0.17 mg/L based on TWA mean measured concentrations. The substance is not acutely toxic to Daphnia magna at saturation in test medium.

Description of key information

No data on the short-term toxicity of Oxacycloheptadecan-2 -one is available. Read-across is performed to the close structural analogue Pentadecan-15 -olide (CAS# 106 -02 -5).

For Pentadecan-15 -olide the acute toxicity to Daphnia magna was investigated in a study according to OECD TG 202 and in compliance with GLP criteria. A saturated solution was prepared in test medium at a loading rate of 50 mg/L by stirring for 47 hours, followed by a 1 hour settling period and siphoning off the clear solution. Test organisms were exposed for 48 hours (with renewal after 24 hours) to the following test solutions: an untreated control (test medium only), 1.0%, 3.2%, 10% and 32% (v/v) dilutions of the 100% saturated solution, and the 100% saturated solution. 4 replicates with 5 daphnids were tested for each treatment group. Test concentrations were analytically determined with a validated GC-FID method. Since test concentrations in used solutions were not found to remain within 80 -120% of initial measured concentrations, time-weighted mean measured concentrations were calculated. TWA mean measured concentrations in the 0.1, 3.2, 10 and 32% dilutions and the 100% saturated solution were 0.0013, 0.0044, 0.008, 0.024 and 0.17 mg/L, respectively. Daphnids were observed for immobilisation after 24 and 48 hours in all treatment groups. No adverse effects were observed. Therefore, the 48 -h EC50 was concluded to be in excess of the substance solubility which is determined at >0.17 mg/L under the conditions of the test.