Acrylonitrile

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

18th February to 9th June, 2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2005

Report date:

2005

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

GLP compliance:

yes (incl. QA statement)

Test type:

standard acute method

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Acrylonitrile

EC Number:

203-466-5

EC Name:

Acrylonitrile

Cas Number:

107-13-1

Molecular formula:

C3H3N

IUPAC Name:

prop-2-enenitrile

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

Crl:CD (SD) albino rats received in good health from Charles River, North Carolina. Rats were uniquely identified by ear tags. The acclimatisation period was a minimum of 7 days, during which the rats were observed twice daily for changes in general appearance and behaviour. The rats were also acclimated to restraint in the nose-only tubes prior to exposure initiation. Upon arrival, rats were housed in individual suspended wire cages. On the day of exposure they were placed in the restraint tubes in the animal room, transported to the exposure room, then returned to their home cages following exposure.

Rats were fed LabDiet 5002 (PMI Nutrition International, LLC) ad libitum. Municipal water was provided ad libitum. Food and water were withheld during exposure. No contaminants were present in the diet or water at sufficient concentrations to interfere with the study. The animal room was maintained on a 12 hour light/12 hour dark cycle. The room temperature was 22±3°C (actual 21.0-21.8°C), and relative humidity was 50±20% (actual 28.8-39.2%). Rats were approximately 8 to 12 weeks old at exposure initiation, and body weights ranged from 264 to 297g for males and from 242 to 264g for females. Acclimation to nose-only restraint tubes began on 21st February 2005, and experimental termination (gross necropsy) took place on 4th April 2005.

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

nose only

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

Exposures were conducted in a two-tiered conventional nose-only exposure system. Animals were restrained in nose-only tubes during exposure. Food and water were withheld during exposure. Exposure concentrations were recorded at least every 20-30 minutes during each exposure. Temperature and relative humidity were recorded using a probe. Oxygen content determination was measured during the pre-exposure method development pase.

The test article was held in a 250ml glass gas-washing bottle with a 50mm bottom fritted disc. The gas-washing bottle was enclosed in a containment cart heated to approximately 25°C so that the surface of the bottle was approximately 21°C. Compressed nitrogen was supplied to the base of the washing bottle to create the test article vapour. The vapour was passed through a dilution tee and diluted to the appropriate concentration using compressed air. The vapour then entered the nose only system. Dilution air flow rate ranged from 19 to 24 l/min.

Exposure concentrations were measured using gas chromatography. Samples were collected from the chamber using a sampling valve and sample loop. During each animal exposure the chamber was monitored for aerosol formation using an MIE light scattering aerosol photometer; no aerosol formation was observed in the exposures.

Analytical verification of test atmosphere concentrations:

yes

Remarks:

Gas chromatography

Duration of exposure:

4 h

Concentrations:

Nominal concentrations (ppm): 539, 775, 871, 1006, 1181 [equivalent to 1081, 1496, 1399, 1441 and 1925 mg/L]
Actual concentrations (ppm ± standard deviation): 539 ± 24.0, 775 ± 29.3, 871 ± 45.8, 1006 ± 67.8, 1181 ± 182.6.

The higher standard deviation value obtained at the 1181ppm exposure concentration was due to lower concentrations within the first 90 minutes of exposure due to a leak which was subsequently discovered and fixed.

No. of animals per sex per dose:

5 males and 5 females per concentration

Control animals:

no

Details on study design:

Groups of 5 male and 5 female rats were exposed to a single concentration of acrylonitrile vapour for 4 hours in a nose-only restraint tube. Rats were assigned to groups using a computerised randomisation procedure. The rats were selected based on body weight requirements and on the appearance of general good health. Individual body weights at randomisation were within ±20% of the mean for each sex.

Animals were observed for 14 days post-exposure. Each animal was observed for mortality at the approximate midpoint of exposure, immediately following exposure (day 0), and twice daily thereafter for 14 days. Clinical observations were made immediately following exposure (day 0) and daily thereafter for 14 days. Body weights were obtained immediately prior to exposure, and on post-exposure days 1, 7 and 14. All animals that died on study were weighed. Necropsy was performed on all animals. Animals surviving the post-exposure period were euthanased by intravenous injection of sodium pentobarbital solution. The major organ systems of the cranial, thoracic and abdominal cavities were examined for all animals.

Statistics:

LC50 values and slopes (with 95% confidence limits) were calculated by the method of Litchfield and Wilcoxon.

Results and discussion

Preliminary study:

Not applicable.

Effect levels

Effect levels 1

Sex:

male

Dose descriptor:

LC50

Effect level:

964 ppm

95% CL:

857 - 1 085

Exp. duration:

4 h

Remarks on result:

other: Equivalent to 2.09 mg/L

Effect levels 2

Sex:

female

Dose descriptor:

LC50

Effect level:

920 ppm

95% CL:

807 - 1 050

Exp. duration:

4 h

Remarks on result:

other: Equivalent to 2.00 mg/L

Effect levels 3

Sex:

male/female

Dose descriptor:

LC50

Effect level:

946 ppm

95% CL:

866 - 1 032

Exp. duration:

4 h

Remarks on result:

other: Equivalent to 2.05 mg/L

Mortality:

Mortality was 0/10, 0/10, 4/10, 7/10 and 9/10 rats for the 539, 775, 871, 1006 and 1181 ppm groups respectiively. One male and one female in the 1006 ppm group, and four males and three females in the 1181 ppm died during exposure. All other deaths were noted within 2 days of exposure.

Clinical signs:

other: In addition to the tabulated findings, animals in all groups were noted with red, brown and/or clear staining on various body surfaces following exposure. The authors report that these findings are typical for animals restrained in nose-only tubes for a 4

Body weight:

All surviving animals lost weight from study day 0 to 1, with the exception of 1 female in the 539ppm group (weight remained the same). All animals surpassed their initial (study day 0) body weight by study day 14.

Gross pathology:

A distended, gas filled jejunum was noted macroscopically for 1 female in the 871 ppm group that died early. A distended, gas-filled stomach was noted for 3 females in the 871 and 1006 ppm groups. 1 male and 1 female in the 1181 ppm group that died early were observed with dark red discolouration of the lungs. There were no other internal macroscopic findings for the animals found dead.

At scheduled necropsy, dark red discolouraion of the lungs was noted for 1 male in the 871ppm group. There were no other findings at the scheduled necropsy.

Other findings:

No other findings.

Any other information on results incl. tables

Clinical observations (number of animals with finding) made immediately following exposure.

	Group (ppm)
	539		775		871		1006		1181
Clinical Observation	M	F	M	F	M	F	M	F	M	F
Vocalisation upon handling	2	4	0	4	1	3	1	2	0	1
Tremors	1	0	3	3	4	5	2	4	1	1
Ataxia	0	0	1	0	4	3	2	4	1	1
Hypoactivity	0	0	0	1	0	1	2	0	0	0
Lunging*	0	0	0	0	0	0	1	0	0	0
Prostrate	0	0	0	0	0	0	1	0	0	0
Laboured respiration	0	0	0	1	3	4	2	4	1	0
Gasping	0	0	0	0	0	0	2	0	1	0

M = male, F = female

* noted as a sudden jump from the animal's original position.

Clinical observations (number of occurrences/number of animals) noted during the 14 day exposure period.

	Group (ppm)
	539		775		871		1006		1181
Clinical Observation	M	F	M	F	M	F	M	F	M	F
Vocalisation upon handling	1/1	1/1	0/0	0/0	3/3	0/0	0/0	1/1	0/0	0/0
Tremors	0/0	0/0	0/0	0/0	0/0	1/1	0/0	2/1	0/0	0/0
Ataxia	0/0	0/0	0/0	1/1	1/1	0/0	0/0	0/0	0/0	0/0
Hyperactivity	0/0	0/0	1/1	0/0	0/0	0/0	0/0	0/0	0/0	0/0
Hypoactivity	0/0	0/0	0/0	0/0	0/0	1/1	0/0	2/1	0/0	0/0
Laboured respiration	0/0	0/0	0/0	0/0	0/0	1/1	0/0	0/0	0/0	0/0
Gasping	0/0	0/0	0/0	0/0	0/0	1/1	0/0	0/0	0/0	0/0
Rales	0/0	0/0	0/0	0/0	1/1	1/1	0/0	1/1	0/0	0/0
Decreased defecation	0/0	0/0	1/1	1/1	4/4	3/3	0/0	2/1	0/0	0/0
Decreased urination	0/0	0/0	1/1	1/1	0/0	0/0	0/0	0/0	0/0	0/0

M = male, F = female

Applicant's summary and conclusion

Interpretation of results:

Category 3 based on GHS criteria

Conclusions:

The acute inhalation (4 -hour) LC50 of acryloniltrile in the rat was calculated to be 964 ppm (males), 920 ppm (female) and 946 ppm (males and females combined). LC50 values are equivalent to 2.09, 2.00 and 2.05 mg/L respectively.

Executive summary:

The acute inhalation toxicity of acrylonitrile in the rat was determined using a single 4 hour, nose-only exposure. The animals were 5 male and 5 female Crl:CD (SD) albino rats per concentration. The rats were exposed to acrylonitrile vapour at concentrations of 539, 775, 871, 1006 and 1181 ppm, at which mortality was 0/10, 0/10, 4/10, 7/10 and 9/10 animals, respectively. All deaths occurred within 2 days of exposure. Ataxia, laboured breathing, hypoactivity and gasping were noted immediately following exposure. Bodyweights decreased from Day 0 to Day 1 in all animals except 1 female in the 539 ppm group. Initial bodyweight was surpassed in all surviving animals by Day 14. Macroscopic findings noted in the 871 and 1006 ppm for animals that died were distended, gas-filled stomach and/or jejunum. For animals found dead in the 1181 ppm group, dark red discoloration of the lungs was observed . At the scheduled necropsy, dark red discoloration of the lungs was noted for one male in the 871 ppm group. There were no other gross findings at the scheduled necropsy of animals that survived.

Based on the results of this study, the LC50 of acrylonitrile was calculated to be 946 ppm when male and female albino rats were exposed to a nose-only acrylonitrile vapour for a single, 4-hour period.