(E)-4-Ethoxy-1,1,1-trifluoro-3-buten-2-one (stabilized with BHT)

Endpoint summary

Description of key information

Acute toxicity via oral route: The acute oral LD50 of ETFBO was determined to be between 300 and 2000 mg/kg bwt in female Wistar rats.

Acute toxicity via inhalation route: The acute inhalation LC50 of ETFBO was determined to be between 0.056 and 0.084 mg/L in male and female Wistar rats.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

19 Sept.-06 Oct. 2006

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

The study was conducted according to an internationally recognised method, and under GLP. The substance is adequately characterised with its purity. Therefore full validation applies.

Qualifier:

according to guideline

Guideline:

OECD Guideline 423 (Acute Oral toxicity - Acute Toxic Class Method)

Version / remarks:

17 December 2001

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Certificate from 2004-08-19

Test type:

acute toxic class method

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Wistar outbred rat; Crl:(WI) WU BR obtained from Charles River, Germany.
- Females nulliparous and non-pregnant: Not specified in the report.
- Age at arrival: 7-8 weeks.
- Weight at study initiation: 154-172 g.
- Fasting period before study: Prior to dosing, the animals has fasted overnight. Approximately 4 hours after dosing, they had access to food again.
- Housing: A maximum of 6 animals per macrolon cage.
- Diet: Standard laboratory diet ad libitum. Each batch of this diet was analysed by the supplier (SDS Special Diets Services, Whitham, England) for the nutrients and contaminants and the results were kept available in the archives.
- Water: Tap water (N.V. Hydron Midden-Nederland) ad libitum .
- Acclimation period: 6 days.

ENVIRONMENTAL CONDITIONS
- Temperature: 22 +/- 3 °C
- Humidity: 40-70%. Upper limit occasionally up to 100%, because of wet cleaning of the animal room.
- Air changes: ca. 10 air changes/hour.
- Photoperiod: 12 hours light / 12 hours dark cycle.

IN-LIFE DATES:
- Start of study: 19/09/2006 (first group at 300 mg/kg and group at 2000 mg/kg) and 22/09/2006 (second group at 300 mg/kg).
- Termination of study: 06/10/2006.

Route of administration:

oral: gavage

Vehicle:

maize oil

Details on oral exposure:

DOSING
The animals were dosed with a 10 mL/kg body weight of a 30 or 200 mg/mL dilution of the test substance in maize oil in order to obtain the 300 and 2000 mg/kg bwt. The exact amount of the test substance to be dosed was calculated for each animal individually and administered by means of a syringe, equipped with an oral gavage.

CLASS METHOD
Rationale for the selection of the starting dose: The study was started with a dose level of 300 mg/kg body weight; which is the starting dose recommended in OECD 423 guideline when there is no information on the test substance.

Doses:

300 and 2000 mg/kg bwt.

No. of animals per sex per dose:

300 mg/kg bwt: 2 groups of 3 females; one being tested at the start of the study and the other being tested after having observed mortality in the 2000 mg/kg bwt dose level group.
2000 mg/kg bwt: 1 group of 3 females.

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days.
- Frequency of observations and weighing: All visible reactions to treatment were recorded, including type, severity, onset and duration. Observations were made within 1 hour and within 4 hours after dosing, and subsequently in surviving animals at least once daily throughout an observation period of 14 days. The body weight of each animal was recorded immediately before dosing on day 0, and on days 3, 7 and 14 of the study for the surviving animals.
- Necropsy of survivors performed: at the end of the observation period (on day 14), all surviving animals were killed with carbon dioxide and examined for external changes. Next, the abdominal and the thorax of each animal was opened and examined for gross pathological changes.

Statistics:

No

Key result

Sex:

female

Dose descriptor:

LD50

Effect level:

> 300 - < 2 000 mg/kg bw

Based on:

test mat.

Mortality:

300 mg/kg bwt: All animals survived.
2000 mg/kg bwt: All animals died.

Clinical signs:

300 mg/kg bwt: No clinical signs, other than transient piloerection in the first three animals dosed, were observed during the 14-day study period.
2000 mg/kg bwt: The animals generally showed sluggishness, blepharospasm, stretching, piloerection and increased respiratory frequency prior to their death.

Body weight:

300 mg/kg bwt: All animals gained weight during the 14-day study:
* Day 0: mean weight = 163 and 161 g for the first and second groups, respectively.
* Day 3: mean weight = 179 and 178 g for the first and second groups, respectively.
* Day 7: mean weight = 184 and 191 g for the first and second groups, respectively.
* Day 14: mean weight = 197 g for both groups.
2000 mg/kg bwt: All animals died within 24 hours after dosing:
* Day 0: mean weight = 160 g.

Gross pathology:

Examination at necropsy of the animals did not reveal distinct treatment-related gross alterations, other than one animal of the 2000 mg/kg bwt dose level which showed a stomach filled with liquid.

Body weight, mortality and clinical signs:

	Body weight (g)				Mortality	Clinical signs
	Day 0	Day 3	Day 7	Day 14
300 mg/kg bwt – 1^stgroup
1^stanimal	160	177	182	193	Alive	Transient piloerection (1h) in the three animals
2^ndanimal	158	174	178	192	Alive
3^rdanimal	172	187	191	207	Alive
300 mg/kg bwt – 2^ndgroup
1^stanimal	155	175	185	195	Alive	No clinical sign
2^ndanimal	163	180	197	202	Alive
3^rdanimal	165	180	190	193	Alive
2000 mg/kg bwt
1^stanimal	166	Found dead on day 1; terminal weight = 162			Dead	Sluggishness, stretched body position, blepharospasm, piloerection, increased respiratory frequency in 3 animals Coldness in 1 animal
2^ndanimal	161	Found dead on day 0; terminal weight = 160			Dead
3^rdanimal	154	Found dead on day 1; terminal weight = 166			Dead

Interpretation of results:

Category 4 based on GHS criteria

Conclusions:

The acute oral LD50 of ETFBO was determined to be between 300 and 2000 mg/kg bwt in female Wistar rats.

Executive summary:

The acute oral toxicity to female Wistar rats was investigated in a GPL-compliant study performed according to OECD test guideline 423 (acute toxic class method).

Two ETFBO dose levels were tested: 300 and 2000 mg/kg bwt. Two groups of three females were treated with the dose level of 300 mg/kg bwt, and one group of 3 females was treated with the dose level of 2000 mg/kg bwt. Route of administration was oral gavage using maize oil as vehicle. The observation period lasted 14 days following administration. All visible reactions to treatment were recorded, including type, severity, onset and duration. Observations were made within 1 hour and within 4 hours after dosing, and subsequently in surviving animals at least once daily throughout an observation period of 14 days. The body weight of each animal was recorded immediately before dosing on day 0, and on days 3, 7 and 14 of the study for the surviving animals. At the end of the observation period (on day 14), all surviving animals were killed with carbon dioxide and examined for external changes. Next, the abdominal and the thorax of each animal was opened and examined for gross pathological changes.

At the dose level of 300 mg/kg bwt, all animals survived, gained weight during the 14-day study and no clinical signs, other than transient piloerection in the first three animals dosed, were observed. At the dose level of 2000 mg/kg bwt, all animals died within 24 hours after dosing and generally showed the following clinical signs prior to their death: sluggishness, blepharospasm, stretching, piloerection and increased respiratory frequency. Examination at necropsy of the animals did not reveal distinct treatment-related gross alterations, other than one animal of the 2000 mg/kg bwt dose level which showed a stomach filled with liquid.

Under the conditions of this study, the acute oral LD50 value of ETFBO was thus determined to be between 300 and 2000 mg/kg bwt. According to the GHS criteria, ETFBO has to be considered as harmful if swallowed and has to be classified in category 4 for acute oral toxicity.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Quality of whole database:

A GPL-compliant study performed according to OECD test guideline 423 (acute toxic class method) is available. It is considered as fully reliable and the result is retained as key data.

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

23 Oct.-06 Nov. 2006

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

The study was conducted according to an internationally recognised method, and under GLP. The substance is adequately characterised with its purity. Therefore full validation applies.

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Version / remarks:

12 May 1981

Deviations:

no

Remarks:

The report mentions no deviation from the version of the guideline in place at that time, but some deviations from the study plan (see in the field "Any other information on materials and methods incl. tables").

GLP compliance:

yes (incl. QA statement)

Remarks:

Certificate from 2006-12-19

Test type:

concentration x time method

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: SPF-reared, Wistar WU rats (Crl:WI(WU, outbred) obtained from Charles River Deutshland, Sulzfeld, Germany.
- Females nulliparous and non-pregnant: Not specified in the report.
- Age at arrival: 6 weeks.
- Mean weight at study initiation: 264 g for males and 181 g for females.
- Fasting period before study: No information on fasting period before study, but information during exposure: no access to feed or water.
- Housing: Animals were first taken in their unopened shipping containers in a first animal room where they were kept in quarantine. After approval of the lot and raising of quarantine, they were moved to another animal room where rats were separated by sex and uniquely identified by ear tattoo. In this room, 5 to 6 males and 5 to 6 females were housed per cage (macrolon cage with bedding of wood shavings) under conventional conditions.
- Diet: Food was provided ad libitum, except during exposure. All rats were fed a commercially available rodent diet (Rat & Mouse No. 3 Breeding Diet RM3) from SDS Special Diets Services, Witham England. Each batch of this diet was analysed by SDS for the nutrients and contaminants and the results were kept available in the archives.
- Water: Water was provided ad libitum, except during exposure. Each cage was supplied with domestic mains tap-water suitable for human consumption. The water was given in propylene bottles, which were cleaned weekly and filled as needed. Results of the routine and periodical physical, chemical and microbiological examinations of drinking water were kept available in the archives.
- Acclimation period: 10 days or longer.

ENVIRONMENTAL CONDITIONS
- Temperature: 20 to 24 °C.
- Humidity: Frequently slightly above the 40-70% range, however generally not higher than 73%, except during short periods associated with cleaning activities.
- Air changes: ca. 10 per hour.
- Photoperiod: 12 hours light / 12 hours dark cycle.

IN-LIFE DATES
- Start of study: The study was started on 23/10/2006 with a pilot group of 1 male and 1 female which was exposed for 4 hours to a target limit concentration of 50 ppm. The day of exposure was named as day 0 of the study.
- Termination of study: The study was finished with the necropsy of the last animals on 06/11/2006.

Route of administration:

inhalation: vapour

Type of inhalation exposure:

nose only

Vehicle:

air

Remarks:

A stream of humidified air was used to transport the vapour to the inhalation chamber.

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Animals were exposed to the test atmosphere in a nose-only inhalation chamber, a modification of the chamber manufactured by ADG Developments Ltd., Codicote, Hitchin, Herts, SG4 8UB, United Kingdom. The inhalation chamber consisted of a cylindrical PVC column, surrounded by a transparent hood, and presenting 45 ports for animal exposure.
- Exposure chamber volume: ca. 70 L.
- Method of holding animals in test chamber: The animals were secured in plastic animal holders (Battelle), positioned radially through the outer hood around the central column. Male and female rats of each group were placed in alternating order. Only the nose of the rats protruded into the interior of the column.
- Source and rate of air / Method of conditioning air: The inhalation equipment was designed to expose rats to a continuous supply of fresh test atmosphere. The test material was passed using a motor-driven syringe pump (WPI Type SP22i, Wold Precision Instruments, Sarsota FL, USA) to a glass evaporator. A stream of humidified air, measured with a rotameter, was used to transport the vapour to the inhalation chamber. The resulting test atmosphere entered the exposure chamber at the bottom and was exhausted at the top. The mean airflow through the exposure chamber during exposure was 15.1 L/min.
- Method of particle size determination: Because the test material was generated as a vapour, particle size measurements were not carried out.
- Treatment of exhaust air: Not reported.
- Temperature in air chamber:
* Pilot exposure: 23.2 +/- 0.2 °C (range: 22.8-23.6 °C).
* Exposure A: 22.4 +/- 0.8 °C (range: 20.6-23.0 °C).
* Exposure B: 22.6 +/- 0.4 °C (range: 22.2-23.2 °C).
* Exposure C: 22.4 +/- 0.7 °C (range: 21.3-23.3 °C).
- Relative humidity in air chamber:
* Pilot exposure: 46 +/- 1% (range: 45-48%).
* Exposure A: 48 +/- 3% (range: 46-55%).
* Exposure B: 47 +/- 2% (range: 45-50%).
* Exposure C: 50 +/- 2% (range: 47-53%).
- Oxygen content in air chamber:
* Pilot exposure: 20.6%.
* Exposure A: 20.6%.
* Exposure B: 20.4%.
* Exposure C: 21.5%.

TEST ATMOSPHERE
- Brief description of analytical method used: The concentration of ETFBO in the test atmospheres was measured by total carbon analysis with a flame ionsation detector (RS55, Ratfisch, Germany). The response of the analyser was recorded on a chart recorder (Kip & Zonen, Delft, The Netherlands). Test atmosphere samples were passed to the total carbon analyser through a heated sample line (at ca. 80 °C). The mean response for each exposure was calculated by averaging values read every 5 minutes. The output of the total carbon analyser was calibrated in the range of 40-60 ppm on 19 October 2006 by sampling from 3 concentrations in duplicate: 40.8 and 41.6, 49.6 and 50.5, 60.8 and 60.8 ppm. The output of the total carbon analyser was calibrated in the range of 11-31 ppm on 24 October 2006 by sampling from 3 concentrations in duplicate: 10.8 and 11.4, 20.8 and 21.3, 31.2 and 31.3 ppm. The response Y of the analyser was related to the concentration X of the test material using linear regressions for each calibration. These relations were used to convert the readings of the total carbon analysers to test atmopshere concentrations of ETFBO.
- Samples taken from breathing zone: Test atmopshere samples were taken continuously from the exposure unit at the animals' breathing zone.

Analytical verification of test atmosphere concentrations:

yes

Remarks:

See above in the field "Details on inhalation exposure / TEST ATMOSPHERE / Brief description of analytical method used".

Duration of exposure:

>= 15 - <= 360 min

Remarks on duration:

Pilot exposure: 4 hours. Exposure A: 15, 30, 60, 120 and 240 min. Exposure B: 30, 45, 60, 90 and 135 min. Exposure C: 70, 105, 160, 240 and 360 min.

Concentrations:

Pilot exposure:
* Target concentration: 50 ppm.
* Actual concentration: 50.6 +/- 0.5 ppm.
Exposure A:
* Target concentration: 25 ppm.
* Actual concentration: 25.1 +/- 0.3 ppm.
Exposure B:
* Target concentration: 50 ppm.
* Actual concentration: 50.1 +/- 0.4 ppm.
Exposure C:
* Target concentration: 12.5 ppm.
* Actual concentration: 12.3 +/- 0.4 ppm.

No. of animals per sex per dose:

Pilot exposure (50 ppm): 1 male + 1 female.
Exposure A (25 ppm): 1 male + 1 female per exposure duration.
Exposure B (50 ppm): 1 male + 1 female per exposure duration.
Exposure C (12.5 ppm): 1 male + 1 female per exposure duration.

Control animals:

no

Details on study design:

- Duration of observation period following administration: 4 days.
- Frequency of observations and weighing:
* Behaviour, clinical signs and mortality: The rats were visually inspected just before exposure, for reactions to treatment during the exposure, shortly after exposure, and at least once daily during the observation period.
* Breathing pattern: Before exposure, shortly after exposure and 4 days after exposure, breathing pattern was monitored during 19 seconds/min for 10 minutes. Means of frequencies were calculated for 6 pre-exposure, 6 post-exposure (day 0) and 6 post-exposure (day 4). Changes in tidal volume, compared to pre-exposure values, were also determined from these recordings at these time points. RMV (Respiratory Minute Ventilation) were calculated by the product of frequency and tidal volume at each time point.
* Body weights: Body weights of the animals were recorded just prior to exposure (day 0) and on day 4.
* Pathology: Surviving rats were necropsied at the end of the 4-day observation period; they were killed by exsanguination from the abdominal aorta under pentobarbital anaesthesia. Animals in moribund conditions will also be killed in this way. All rats, including the deceased animals, were subjected to a post-mortem examination as soon after death as possible, with particular reference to any change in the respiratory tract. The lungs (including larynx and trachea) of surviving animals and animals killed in moribund condition were weighed. Samples of the nasal tissues of all surviving animals and all animals killed in moribund condition of groups A-C were preserved in a neutral aqueous phosphate-buffered 4% solution of formaldehyde (10% solution of formalin). The noses were decalcified using nitric acid. The lungs of these animals (after weighing) were infused with the fixative under ca. 15 cm water pressure to insure fixation. The tissues preserved were embedded in paraffin wax and were sectioned at 5 µm and stained with haematoxylin and eosin. Histopathological examination (by light microscopy) was performed on the nasal tissues and lungs of all surviving animals and all animals killed in moribund condition of groups A-C. The nose was examined at 6 levels and each lung lobe at 1 level.
- Necropsy of survivors performed: yes (see above).

Statistics:

It was tried (see in the section "Results and discussion / Mortality") to calculate the 4-h LC50 value using probit analysis (relationship between concentration, exposure duration and response), based on Finney (Finney D.J., Probit Analysis, Cambridge University Press, 1997).

Preliminary study:

- Behaviour, clinical signs and mortality: Shortly after exposure the two animals of the pilot study were sluggish and blepharospasm and piloerection were seen. The male animal of the pilot study was found dead on day 1 and the female animal in which mouth breathing and shortness of breath was seen, was subsequently sacrificed for humane reasons.

- Respiratory measurements: During exposure, breathing at a decreased rate (graded as slight) and laboured breathing (graded as slight) could be seen.

- Body weights: Although the male died on day 1 and the female was sacrificed on the same day, weight losts were observed for both animals on day 1 (male: day 0 = 240.7 g, day 1 = 218.4 g and female: day 0 = 171.4 g, day 1 = 159.6 g).

- Examinations at necropsy:
* Male:
Lungs: dark red discoloured.
Thorax: hydrothorax.
* Female:
Nose: encrustations.
Oral cavity: oedema under tongue, mandibles and saliva glands.
Thorax: hydrothorax
Lungs: haemorrhages on all lobes, tissue.

Sex:

male/female

Dose descriptor:

LC50

Effect level:

>= 8.2 - <= 12.3 ppm

Based on:

test mat.

Exp. duration:

4 h

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

>= 0.056 - <= 0.084 mg/L air

Based on:

test mat.

Exp. duration:

4 h

Remarks on result:

other: for conversion in mg/L, see in the field "Any other information on results incl. tables".

Mortality:

See the table named "Mortality Results" in the field "Any other information on results incl. tables".
Animals died or were killed in moribund condition after exposure to 50 ppm for one hour (or longer), after exposure to 25 ppm for two hours (or longer) and after exposure to 12.5 ppm for four hours (or longer). The response of males and females was comparable.
Although the mortality data seemed rather well behaved, probit analysis did not allow determination of the probit function and estimation of the LC50 for different exposure durations. The reason for that is the strict separation in the data between survivors and non-survivors, analogous to the situation that an LC50 value can not be estimated from 0% and 100% mortality rates only. The 4-hour LC50 was estimated to be between 8.2 and 12.3 ppm (for conversion in mg/L, see in the field "Any other information on results incl. tables"), the 1-hour LC50 was estimated to be between 37.5 and 50.1 ppm.

Clinical signs:

other: Exposure A: The animals were sluggish, this was graded as slight for the animals exposed during 15 or 30 minutes and moderate for the animals exposed for an hour and longer. Before death, the 3 animals found dead and the one sacrificed were sluggish and l

Body weight:

Except for animals that were exposed to 25 ppm during 15 minutes only and showed body weight gain in the 4 day observation period, all other animals showed appreciable weight loss during that period. The animals that were found dead or were sacrificed for humane reasons also showed appreciable body weight loss.

Gross pathology:

The main finding at necropsy was red discoloration of lungs and thymus. Sometimes the lungs were incompletely collapsed or there was haemorrhagic nasal discharge.

Other findings:

- Respiratory measurement: Shortly after exposure, the higher the product of concentration and duration had been, the lower breathing frequency and ventilatory flow were and although less obvious the higher tidal volume was. Four days after exposure, the higher the product of concentration and duration had been, the lower breathing frequency and the higher tidal volume was. Ventilatory flow (the product of breathing frequency and tidal volume) was, however, not related to the product of concentration and duration of exposure.
- Lung weights: Absolute and relative lung weights were increased. Most interestingly, the increase was significantly related to the product of exposure concentration and duration.
- Histopathology: Microscopic examination revealed clear histopathological changes in the nasal passages and lungs. Especially the respiratory epithelium in the nasal passages and lungs appeared to be a target for the test material. The olfactory epithelium in the nasal cavity and the alveoli in the lungs appeared quite resistant to damage, although prolonged exposure/high concentration also resulted in histopathological changes of the olfactory epithelium characterised by abrasion and/or vacuolation. The histopathological changes of the respiratory epithelium aggravated with increasing exposure time as well as increasing concentration of the test substance. The changes in the respiratory epithelium started with loss of the ciliae, subsequently the epithelium thickened, and after that it became flattened. Finally the epithelial cells came loose. In the most serious cases, the respiratory epithelium was completely lost, including the basal membrane, and the underlying tissue was also damaged. In most of the latter cases inflamrnatory reactions were also observed in the nasal cavity and lungs.

Mortality results:

Exposure	Concentration (ppm)	Duration (min)	Mortality outcome
A	25.1	15	No death
		30	No death
		60	No death
		120	Female: Deceased Male: Sacrificed for humane reasons
		240	Female: Deceased Male: Deceased
B	50.1	30	No death
		45	No death
		60	Female: Deceased Male: Deceased
		90	Female: Sacrificed for humane reasons Male: Deceased
		135	Female: Deceased Male: Deceased
C	12.3	70	No death
		105	No death
		160	No death
		240	Female: Deceased Male: Sacrificed for humane reasons
		360	Female: Deceased Male: Deceased

LC50 conversion from ppm to mg/L:

Concentration (mg/m3) = Concentration (ppm) x Molecular weight (g/mol) / 24.5 (L/mol)

Where:

24.5 L/mol = gas constant at 25 °C and 1013.25 hPa

Concentration (ppm) = 8.2 to 12.3 for the 4h-LC50 of ETFBO

Molecular weight (g/mol) = 168.11 for ETFBO

Concentration (mg/m3) = 8.2 to 12.3 x 168.11 / 24.5

Concentration (mg/m3) = 56.3 to 84.4

Concentration (mg/L) = 0.056 to 0.084

Interpretation of results:

Category 1 based on GHS criteria

Conclusions:

The acute inhalation LC50 of ETFBO was determined to be between 0.056 and 0.084 mg/L in male and female Wistar rats.

Executive summary:

The acute inhalation toxicity to male and female Wistar rats was investigated in a GPL-compliant study performed according to OECD test guideline 403 (concentration x time method).

The study started with a pilot group consisting of one male and one female which were exposed nose-only for 4 hours to a target limit concentration of 50 ppm ETFBO (actual concentration of 50.6 ppm). In the main study, three groups of five pairs of a male and a female were exposed nose-only for five different durations to three target concentrations:

* For the target concentration of 25 ppm (actual concentration of 25.1 ppm), the five durations were 15, 30, 60, 120 and 240 min.

* For the target concentration of 50 ppm (actual concentration of 50.1 ppm), the five durations were 30, 45, 60, 90 and 135 min.

* For the target concentration of 12.5 ppm (actual concentration of 12.3 ppm), the five durations were 70, 105, 160, 240 and 360 min.

ETFBO was generated as a vapour. After exposure, the animals were kept for an observation period of 4 days. Behaviour, clinical signs and mortality were recorded just before exposure, for reactions to treatment during the exposure, shortly after exposure, and at least once daily during the observation period. Respiratory measurements were performed before exposure, shortly after exposure and 4 days after exposure. Body weights of the animals were recorded just prior to exposure and on day 4. All rats were subjected to a post-mortem examination as soon after death with particular reference to any macroscopic and microscopic changes in the respiratory tract.

The animals exposed to ETFBO were sluggish in a generally concentration and duration dependent fashion. In addition, breathing abnormalities and blepharospasm were the most frequent other abnormalities seen. Except the animals exposed during only 15 minutes to 25 ppm, all surviving animals appreciably lost weight in the 4-day observation period. The main finding at necropsy was red discolouration of the lungs and thymus. The increase in relative lung weight was clearly related to the product of exposure concentration and duration. Microscopic examination revealed clear histopathological changes in the nasal passages and lungs. The changes aggravated with increasing duration and concentration of the exposure. Animals died or were killed in moribund condition after exposure to 50 ppm for one hour (or longer), after exposure to 25 ppm for two hours (or longer) and after exposure to 12.5 ppm for four hours (or longer). The response of males and females was comparable.

Under the conditions of this study, the acute inhalation LC50 value of ETFBO was determined to be between 8.2 and 12.3 ppm, corresponding to 0.056 and 0.084 mg/L. According to the GHS criteria, ETFBO has to be considered as fatal if inhaled and has to be classified in category 1 for acute inhalation toxicity.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Quality of whole database:

A GPL-compliant study performed according to OECD test guideline 403 (concentration x time method) is available. It is considered as fully reliable and the result is retained as key data.

Justification for classification or non-classification

Acute toxicity via oral route: The acute oral LD50 value of ETFBO was determined to be between 300 and 2000 mg/kg bwt. According to the GHS criteria, ETFBO has to be considered as harmful if swallowed and has to be classified in category 4 for acute oral toxicity.

Acute toxicity via inhalation route: The acute inhalation LC50 value of ETFBO was determined to be between 8.2 and 12.3 ppm, corresponding to 0.056 and 0.084 mg/L. According to the GHS criteria, ETFBO has to be considered as fatal if inhaled and has to be classified in category 1 for acute inhalation toxicity.