1,1,2,3,4,4-hexafluorobuta-1,3-diene

Endpoint summary

Description of key information

As 1,1,2,3,4,4-hexafluorobuta-1,3-diene is a gaseous substance at ambient temperature, only the inhalation route could be evaluated. Dose-dependent acute toxicity effects and mortality were observed in rats exposed for 4 -hours (whole body) to nominal concentrations of 1.8, 6.2, and 20.0 mg/L and observed for 14 days post-exposure. Clinical signs included laboured respiration and wheezing at the highest concentrations, and a subdued appearance was noted in all groups during exposure. Contrary to the two other treatment groups, here were no histopathological findings in the animals of the low concentration group.

Under the conditions of this study the LC50 of the test substance was estimated to be 4.418 mg/L or ca. 667 ppm for male and female rats

Key value for chemical safety assessment

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:

16-DEC-1992 to 03-MAY-1993

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

well documented, despite some missing details

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: EPA guidelines for acute toxicity testing

Version / remarks:

no further details

Deviations:

not specified

GLP compliance:

yes

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River (UK) Limited (Margate, Kent / UK)
- Age at study initiation: no data available
- Weight at study initiation: 154 to 418 g
- Fasting period before study: no data available
- Housing: in a semi-barrier maintained animal room, in suspended poly-propylene cages with detachable stainless steel tops and bottoms
- Diet: ad libitum (except during the 4-h exposure period), Rat and Mouse (Modified) No. 1 Diet SQC Expanded (Special Diets Services Limited, UK)
- Water: ad libitum (except during the 4-h exposure period), domestic mains quality drinking water
- Acclimation period: no data available

ENVIRONMENTAL CONDITIONS
- Temperature: 18 to 21°C
- Humidity: 30 to 59%
- Air changes: 15 to 20 per hr
- Photoperiod: 12 hrs dark / 12 hrs light (07:00 - 19:00)

IN-LIFE DATES: no data available; only the delivery dates were reported (08-OCT-1992, 29-OCT-1992, and 05-JAN-1993 for 3 batches of 5 males and 5 females).

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

air

Remarks:

filtered compressed air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: no data available
- Exposure chamber volume: 100-L all glass exposure chamber
- Method of holding animals in test chamber: during exposure to the test item the animals were confined within stainless steel mesh compartments within the exposure chamber.
- Source and rate of air: flow rate of 25 L/min (see in Table 1 below in “any other information on materials and methods incl. tables”)
- Method of conditioning air: no data available
- System of generating test atmosphere: the test item was generated as a vapour, by direct mixture of the test gas with filtered compressed air. The gas flow from the cylinder was controlled by a regulator and flow meter. The gas line was connected to a glass "T" piece through which passed a stream of filtered air. The test gas/air mixture was then ducted to the inlet port of the exposure chamber. The required concentration within the exposure chamber was maintained by finely regulating the gas and air flow rates (using rotameters). Chamber air flow was monitored continually using flowmeters and the values were recorded at 30-min intervals.
- Treatment of exhaust air: following a "single pass" through the exposure chamber the contaminated air was extracted from the chamber and then exhausted to the external atmosphere.
- Temperature, humidity, pressure in air chamber: 25°C, 25 to 61% humidity (see in Table 1 below in “any other information on materials and methods incl. tables”)

VEHICLE
- Composition of vehicle: Filtered compressed air
- Justification of choice of vehicle: the test substance is a gas

Analytical verification of test atmosphere concentrations:

no

Duration of exposure:

4 h

Concentrations:

1.8, 6.2, and 20.0 mg/L for groups 3, 2 and 1, respectively (nominal concentrations)

No. of animals per sex per dose:

5 per sex and per group

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: all animals were observed during exposure for signs of any adverse reactions to treatment; any clinical signs noted were recorded at 30-min intervals. Surviving animals were also observed immediately after exposure, for the first 1-2 h post-dosing and thereafter at least once and normally twice daily during the subsequent 14-d observation period.
All rats were weighed immediately before dosing and surviving animals were also weighed on days 2, 3, 4, 7, 10 and 14 post-exposure.
- Necropsy of survivors performed: yes; all animals sacrificed in extremis or found dead, and any animals surviving at the end of the 14-d observation period were subjected to a macroscopic post-mortem examination. Surviving animals were sacrificed by carbon dioxide asphyxiation. Each rat was examined externally prior to opening the abdominal and thoracic cavities. Any gross lesions observed were recorded. The respiratory tract was subjected to detailed macroscopic examination for signs of irritancy or local toxicity. All organs were examined in situ.
- Other examinations performed: the lungs of each animal were removed and weighed to allow calculation of lung/body weight ratio.

Statistics:

The LC50 was estimated using probit analysis. Due to the limited fractional mortality, Berkson's modification was used to calculate the probit values and hence no confidence intervals could be reported.

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

4.418 mg/L air (nominal)

Based on:

test mat.

Exp. duration:

4 h

Remarks on result:

other: converted value: ~667 ppm

Sex:

female

Dose descriptor:

LC50

Effect level:

3.34 mg/L air (nominal)

Based on:

test mat.

Exp. duration:

4 h

Remarks on result:

other: converted value: ~504 ppm

Sex:

male

Dose descriptor:

LC50

Effect level:

5.442 mg/L air (nominal)

Based on:

test mat.

Exp. duration:

4 h

Remarks on result:

other: converted value: ~821 ppm

Sex:

male/female

Dose descriptor:

LC0

Effect level:

1.8 mg/L air (analytical)

Based on:

test mat.

Exp. duration:

4 h

Remarks on result:

other: converted value: ~271 ppm; no mortality observed.

Mortality:

All animals of group 1 (i.e., 20 mg/L) died: one female was found dead in the exposure chamber at the end of dosing, and a further 3 females died immediately after dosing. All remaining animals died within 1 h after exposure.
All females and one male of group 2 (i.e., 6.2 mg/L) were killed in extremis on day 1 following exposure. One male was found dead on day 2, and a second male was killed in extremis on day 4.
No death occurred in the group 3 (i.e., 1.8 mg/L).

Clinical signs:

other: During exposure, animals of groups 1 and 2 (i.e., 20.0 and 6.2 mg/L) showed slow, laboured respiration, whereas the respiration of animals from group 3 (i.e., 1.8 mg/L) was slightly slow. All groups were also subdued during exposure to the test item. A s

Body weight:

Body weight was markedly decreased in the 3 males of group 2 which survived either to day 4 or throughout the 14-d observation period.
Body weight gain for animals of group 3 was normal.

Gross pathology:

All animals from group 1 showed dark liver and distended or fluid-filled stomach and intestines. The lungs were also dark and either mottled or enlarged.
Abnormal findings in premature decedents of group 2 (3/5 males and 5/5 females) included dark or mottled liver and lungs, pale or mottled kidneys, distended stomachs, darkened spleen and fluid in the trachea. No abnormalities were noted in the 2 surviving males.
With the exception of a mottled kidney in one male, no significant abnormalities were noted in animals of group 3 at necropsy.

Other findings:

- Organ weights: values of lung/body weight ratio were considered to be within normal limits for all surviving animals.

Table 3: mortality results

concentration (mg/L)	Males	Females
20	5/5	5/5
6.2	3/5	5/5
1.8	0/5	0/5

Table 4: Body weight (mean ± standard deviation)

Group/Concentration (mg/L)		Predose	Day 2 p-e	Day 3 p-e	Day 4 p-e	Day 7 p-e	Day 10 p-e	Day 14 p-e
1 (20.0)	Males	389 ± 29 g	-	-	-	-	-	-
	Females	279 ± 27 g	-	-	-	-	-	-
2 (6.2)	Males	403 ± 12 g	341 ± 11 g	332 ± 16 g	323 ± 24 g	356 ± 9 g	377 ± 2 g	403 ± 4 g
	Females	264 ± 12 g	-	-	-	-	-	-
3 (1.8)	Males	211 ± 11 g	226 ±  14 g	231 ± 14 g	240 ± 15 g	271 ± 17 g	295 ± 19 g	321 ± 21 g
	Females	182 ± 17 g	185 ± 18 g	186 ± 17 g	191 ± 17 g	203 ± 19 g	211 ± 20 g	224 ± 22 g

p-e = post-exposure

Interpretation of results:

Category 3 based on GHS criteria

Conclusions:

The combined LC50 of the test item (males and females) was estimated to be 4.418 mg/L, i.e. 667 ppm (males: 5.442 mg/L, or 821 ppm; females: 3.340 mg/L, or 504 ppm).

Executive summary:

The acute inhalation toxicity of the test item was investigated in accordance with OECD 403 and EPA guidelines and in compliance with GLP.

Groups of 5 male and 5 female Sprague-Dawley rats were exposed by whole-body inhalation to a vapour of the test substance in compressed filtered air at the nominal concentrations of 1.8, 6.2 and 20.0 mg/L for a single 4-hour period. Following exposure, animals were retained without treatment for 14 days. Clinical observations and body weights were recorded throughout the study and at the end of the 14-d observation period. Animals were then killed and given a gross examination post-mortem.

All animals of group 1 (i.e., 20 mg/L) died within 1 h after exposure. All females and one male of group 2 (i.e., 6.2 mg/L) were killed in extremis on day 1 following exposure. One male was found dead on day 2, and a second male was killed in extremis on day 4. No death occurred in the group 3 (i.e., 1.8 mg/L).

A subdued appearance was noted for all groups during exposure to the test item. Respiration was slow and laboured for animals of groups 1 and 2, and slightly slow for animals of groups 3. In group 2, observations noted included a subdued, hunched appearance with piloerection and laboured respiration also noted to be wheezing in females. The eyes of some animals were either closed or half-closed. The majority of the surviving males continued to show a hunched, subdued appearance on day 2, as well as slightly laboured respiration and piloerection. The remaining 2 males appeared normal on day 7 and throughout the remainder of the 14-day observation period. Rapid respiration was recorded for the majority of animals from group 3 immediately after exposure, as well as a subdued appearance. All animals appeared normal approximately 1-2 h after exposure and throughout the 14-d observation period.

All animals from group 1 showed dark liver and distended or fluid-filled stomach and intestines. The lungs were also dark and either mottled or enlarged.

Abnormal findings in premature decedents of group 2 included dark or mottled liver and lungs, pale or mottled kidneys, distended stomachs, darkened spleen and fluid in the trachea. No abnormalities were noted in the 2 surviving males. With the exception of a mottled kidney in one male, no significant abnormalities were noted in animals of group 3 at necropsy.

Body weight was markedly decreased in the 3 males of group 2 which survived either to day 4 or throughout the 14-d observation period, while body weight gain for animals of group 3 was normal. Values of lung/body weight ratio were considered to be within normal limits for all surviving animals.

Under the conditions of this study the LC50 of the test substance was estimated to be 4.418 mg/L or ca. 667 ppm for male and female rats, therefore the test substance is classified as Acute Toxicity Category 3 (H331) according to the classification criteria of Regulation (EC) No. 1272/2008 (CLP / EU GHS).

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LC50

Value:

4 418 mg/m³ air

Quality of whole database:

Results obtained from a well documented study performed according to standardised methodology. The study showed dose-dependent toxicity.

Justification for classification or non-classification

Under the conditions of this study the LC50 of the test substance was estimated to be 4.418 mg/L or ca. 667 ppm for male and female rats, therefore the test substance is classified as Acute Toxicity Category 3 (H331) according to the classification criteria of Regulation (EC) No. 1272/2008 (CLP / EU GHS).