Acrylonitrile

Endpoint summary

Description of key information

The acute toxicity dataset for acrylonitrile is extensive and is reviewed in the EU RAR (2004) and Sapphire Group report (2004).  The results of a guideline-comparable study in the rat show an acute oral LD50 value of 81 (62 -107 mg/kg bw).  In contrast to the results of earlier studies, a modern guideline-compliant study of dermal toxicity in the rat reports an LD50 value of >200 mg/kg bw. In a modern, guideline-comparable study the acute inhalation (4 -hour) LC50 of acrylonitrile in the rat was calculated to be 2.05 mg/L.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Reference 1

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Qualifier:

according to guideline

Guideline:

other: the EU RAR summarises a large number of studies of various experimental designs

Principles of method if other than guideline:

Several oral toxicity studies are reviewed; studies were performed in various species and to different experimental designs.

GLP compliance:

not specified

Remarks:

: non-GLP published studies

Test type:

other: the EU RAR summarises a large number of studies of various experimental designs

Limit test:

no

Species:

other: studies were performed in various species

Strain:

other: studies were performed in various species

Sex:

male/female

Route of administration:

oral: gavage

Vehicle:

unchanged (no vehicle)

Doses:

The EU RAR summarises the findings of a number of studies; the dose levels used are not reported for all studies

No. of animals per sex per dose:

Not reported

Control animals:

not specified

Details on study design:

Studies investigates the single dose oral (gavage) toxicity of acrylonitrile.

Statistics:

LD50 values were calculated by Probit analysis.

Preliminary study:

Not reported

Sex:

male

Dose descriptor:

LD50

Effect level:

81 mg/kg bw

95% CL:

62 - 107

Remarks on result:

other: CF Nelson Rats

Sex:

not specified

Dose descriptor:

LD50

Effect level:

25 - 186 mg/kg bw

Remarks on result:

other: various species

Sex:

not specified

Dose descriptor:

LD50

Effect level:

25 - 48 mg/kg bw

Remarks on result:

other: Mice

Sex:

not specified

Dose descriptor:

LD50

Effect level:

50 - 85 mg/kg bw

Remarks on result:

other: Guinea pig

Sex:

not specified

Dose descriptor:

LD50

Effect level:

72 - 186 mg/kg bw

Remarks on result:

other: Rat

Sex:

not specified

Dose descriptor:

LD50

Effect level:

93 mg/kg bw

Remarks on result:

other: Rabbit

Mortality:

In the study with CF Nelson rats, all rats died within 24 hours of administration.

Clinical signs:

other: In the study with CF Nelson rats, no significant clinical signs were observed.

Gross pathology:

Lethal doses in guinea pigs (50 or 100 mg/kg) casued dilation of the right ventricle, congestion of the coronary blood vessels, hepatic and splenic congestion and inflammation of the intestinal mucosa. Oral administration resulted in rapidly developing adrenocortical haemorrhagic necrosis (apoplexy). Duodenal ulcerogenic effects of acrylonitrile have been reported in rats, that were markedly enhanced by pretreatment of the rats with the mixed function oxidase inducers polychorinated biphenyl (PCB), Arochlor 1254 or phenobarbital. Gastrointestinal haemorrhage has also been reported. The severity of the bleeding was independent of the route and was dose and time dependent. The gastric lesions were associated with a decrease in glutathione content of the stomach. Focal superficial necrosis of the liver in association with haemorrhagic gastritis was reported following administration at 150 mg/kg bw in drinking water.

Other findings:

Target organs of acute oral toxicity include the endocrine system, lung, brain, stomach and duodenum.

It is suggested that necrosis of the liver and adrenals is due to peroxidative damage induced by acrylonitrile.

Interpretation of results:

Category 3 based on GHS criteria

Conclusions:

The results of the acute oral toxicity studies with acrylonitrile are consistent with the current CLP classification.

Executive summary:

The EU RAR (2004) reviews the available data on the acute oral toxicity of acrylonitrile. Oral LD50 values for various species are reported to be in the range 25 -186 mg/kg bw with a species sensitivity of mouse>guinea pig>rabbit and rat. The results of a guideline-comparable study in the rat show an acute oral LD50 value of 81 (62 -107) mg/kg bw.

Clinical signs resulting from acute acrylonitrile administration have been examined in a number of different species and have been to found to vary very little. The clinical signs can be divided into four stages. Immediately after administration the animal goes through an excitatory phase, with agitation and lacrimation. A tranquil phase follows and cholinergic symptoms, such as salivation, lacrimation, urination and defecation occur. Next there is a convulsive phase in which the animal undergoes clonic seizures. The terminal stage preceding death is a paralytic phase in which the animal is immobile. The clinical signs indicate that the action of acrylonitrile is that of a typical nitrile, with toxic action probably due to a cleavage of the molecule to produce hydrogen cyanide, which is one of the key mediators of toxicity. However, as with any nitrile, there is a complex interplay of a number of factors that affect the outcome of acrylonitrile toxicity. These include the rate of cyanide liberation and detoxification, the dose level, the route of administration, the species of animal and the presence of other bioreactive sites within the molecule.

Summary of oral LD50 values reported in the EU RAR (2004)

LD50	Species
81 mg/kg bw	CF Nelson Rats
25-186 mg/kg bw	various species
25-48 mg/kg bw	Mice
50-85 mg/kg bw	Guinea pig
72-186 mg/kg bw	Rat
93 mg/kg bw	Rabbit

Reference 2

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Published mechanistic study reporting acute LD50 values

Qualifier:

no guideline followed

Principles of method if other than guideline:

Dixon’s up and down method

GLP compliance:

no

Remarks:

published study

Test type:

up-and-down procedure

Limit test:

no

Specific details on test material used for the study:

Not reported

Species:

rat

Strain:

Wistar

Sex:

female

Route of administration:

oral: gavage

Vehicle:

not specified

Details on oral exposure:

Rats were gavaged with acrylonitrile

No. of animals per sex per dose:

6-8 rats were used in total

Control animals:

not specified

Key result

Sex:

female

Dose descriptor:

LD50

Effect level:

95.1 mg/kg bw

Based on:

test mat.

95% CL:

>= 81.7 - <= 110.6

Remarks on result:

other:

Remarks:

An acute oral LD50 of 95.1 (81.7 -110.6) mg/kg bw is reported.

An acute oral LD50 of 95.1 (81.7 -110.6) mg/kg bw is reported.

Interpretation of results:

Category 3 based on GHS criteria

Conclusions:

An acute oral LD50 of 95.1 (81.7 -110.6) mg/kg bw is reported.

Executive summary:

The oral LD50 of acrylonitrile was investigated preliminary to mechanistic investigations. 6 -8 female Wistar rats were administered acrylonitrile by gavage according to Dixon’s up and down method. An acute oral LD50 of 95.1 (81.7 -110.6) mg/kg bw is reported. This value is consistent with other data.

Reference 3

Endpoint:

acute toxicity: oral

Type of information:

other: review

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Qualifier:

according to guideline

Guideline:

other: the review summarises the results of various studies of different experimental design

Principles of method if other than guideline:

The review by The Sapphire Group summarises the results of various studies of different experimental design

GLP compliance:

no

Remarks:

: review of various published studies

Test type:

other: review of published data

Limit test:

no

Species:

other: the review summarises the results of various studies in different species

Strain:

other: various

Sex:

male/female

Route of administration:

oral: gavage

Vehicle:

not specified

Doses:

The review summarises the results of various studies of different experimental design

No. of animals per sex per dose:

Various

Control animals:

not specified

Sex:

not specified

Dose descriptor:

LD50

Effect level:

>= 25 - <= 186 mg/kg bw

Remarks on result:

other: Values reported for all species investigated

Sex:

not specified

Dose descriptor:

LD50

Effect level:

>= 25 - <= 48 mg/kg bw

Remarks on result:

other: Values reported for the mouse

Sex:

not specified

Dose descriptor:

LD50

Effect level:

>= 50 - <= 85 mg/kg bw

Remarks on result:

other: Values reported for the guinea-pig

Sex:

not specified

Dose descriptor:

LD50

Effect level:

93 mg/kg bw

Remarks on result:

other: Value reported for the rabbit

Sex:

not specified

Dose descriptor:

LD50

Effect level:

>= 72 - <= 186 mg/kg bw

Remarks on result:

other: Values reported for the rat

Sex:

male

Dose descriptor:

LD50

Effect level:

81 mg/kg bw

95% CL:

>= 62 - <= 107

Remarks on result:

other: Value from a guideline-comparable rat study

Reported oral LD50 values for acrylonitrile for various species lie in the range of 25 to 186 mg/kg bw.  The mouse appears to the most sensitive species, followed by the guinea-pig, rabbit and rat. No data are available for the dog. The results of a guideline-comparable rat study report a value of 81 (62 -107) mg/kg bw.

Interpretation of results:

Category 3 based on GHS criteria

Conclusions:

Reported oral LD50 values for acrylonitrile for various species lie in the range of 25 to 186 mg/kg bw.  The results of a guideline-comparable rat study report a value of 81 (62 -107) mg/kg bw. Findings are consistent with the current CLP classification of acrylonitrile.

Executive summary:

This 2004 review by The Sapphire Group summarises the data available for the acute oral toxicity of acrylonitrile in various species.

 

Reported oral LD50 values for acrylonitrile for various species lie in the range of 25-186 mg/kg bw.  The mouse appears to the most sensitive species, followed by the guinea-pig, rabbit and rat; no data are available for the dog. The results of a guideline-comparable rat study report a value of 81 (62 -107) mg/kg bw. Findings are consistent with the current EU classification of acrylonitrile (R25).

 

The clinical signs resulting from acute acrylonitrile administration have been examined in a number of different species and have been to found to vary little between species. The clinical signs following acute exposure to acrylonitrile have been divided into four stages. Immediately after administration, the animal goes through an excitatory phase; the eyes water, and the animal becomes agitated. A tranquil phase follows and cholinergic symptoms, such as salivation, lachrymation, urination, and defecation occur, and may be a true cholinergic response since atropine was reported to block the effect. Application of acrylonitrile an isolated guinea pig ileum caused vigorous contractions that were blocked by atropine. Next, there is a convulsive phase in which the animal undergoes clonic seizures. The terminal stage preceding death is a paralytic phase in which the animal is immobile. These clinical signs indicate that the action of acrylonitrile is that of a typical nitrile, with toxic action probably due to a cleavage of the molecule to produce hydrogen cyanide, which is one of the key mediators of the toxicity. However, as for any nitrile, there is a complex interplay of a number of factors that affect the outcome of AN toxicity. These include the rate of cyanide liberation and detoxification, the dose of cyanogen, the route of administration, the species of animal, and the presence of other bioreactive sites within the molecule.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

81 mg/kg bw

Quality of whole database:

The EU RAR (2004) reviews the available data on the acute oral toxicity of acrylonitrile. Oral LD50 values for various species are reported to be in the range 25 -186 mg/kg bw with a species sensitivity of mouse>guinea pig>rabbit and rat. The results of a guideline-comparable study in the rat show an acute oral LD50 value of 81 (62 -107) mg/kg bw.

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Reference 1

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

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

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.

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.

Preliminary study:

Not applicable.

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

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

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.

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

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.

Reference 2

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

Non-standard acute inhalation toxicity study investigating the efficacy of potential antidotes; various exposure times are investigated

GLP compliance:

no

Remarks:

: published study

Test type:

other: non-standard study investigating the efficacy of potential antidotes

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male

Route of administration:

inhalation: vapour

Type of inhalation exposure:

not specified

Vehicle:

other: unchanged (no vehicle)

Analytical verification of test atmosphere concentrations:

no

Duration of exposure:

>= 10 - <= 180 min

Concentrations:

350 ppm (1406 mg/m3); 950 ppm (2055 (mg/m3); 1100 ppm (2380 mg/m3); 1600 ppm (3461 mg/m3); 2400 ppm 5192 mg/m3); 2600 ppm (5624 mg/m3); 3000 ppm (6490 mg/m3)

No. of animals per sex per dose:

3 (650, 950, 1100, 1600, 2400, 2600 ppm) or 6 (3000 ppm)

Control animals:

no

Details on study design:

6 groups of 3 rats were exposed to acrylonitrile vapour at various concentrations for periods of between 10 and 180 minutes. A further group of 6 rats was exposed to 3000 ppm for 30 minutes.

Statistics:

Probit analysis was used to determine the LC50

Preliminary study:

Not reported

Sex:

male

Dose descriptor:

LC50

Effect level:

5.74 mg/L air

Exp. duration:

0.5 h

Remarks on result:

other: Calculated (Probit)

Sex:

male

Dose descriptor:

LC50

Effect level:

3.41 mg/L air

Exp. duration:

1 h

Remarks on result:

other: Calculated (Probit)

Sex:

male

Dose descriptor:

LC50

Effect level:

2.03 mg/L air

Exp. duration:

2 h

Remarks on result:

other: Calculated (Probit)

Sex:

male

Dose descriptor:

LC50

Effect level:

1.21 mg/L air

Exp. duration:

4 h

Remarks on result:

other: Calculated (Probit)

Sex:

male

Dose descriptor:

LC50

Effect level:

0.89 mg/L air

Exp. duration:

6 h

Remarks on result:

other: Calculated (Probit)

Mortality:

See table below

Clinical signs:

other: No details

Body weight:

No details

Gross pathology:

No details

Other findings:

No details

Mortality

Acrylonitrile concentration (mg/L)	Exposure time	Mortality
1.406	3h	1/3
2.055	2h	1/3
2.380	2h	3/3
3.461	0.5h	0/3
5.192	10 min	0/3
5.624	0.5h	1/3
6.490	0.5h	6/6

Interpretation of results:

Category 3 based on GHS criteria

Conclusions:

The 4 -hour LC50 is calculated to be 1.21 mg/L.

Executive summary:

In this study, male Wistar rats (3 or 6/group) were exposed (whole body) to acrylonitrile vapour in an acute inhalation toxicity for periods of up to 3 hours. Using the results of this study, the EU RAR calculates LC50 values using Probit analysis. LC50 values were calculated to range from 0.89 mg/L (6 -hour exposure) to 5.74 mg/L (30 -minute exposure). The 4 -hour LC50 was calculated to be 1.21 mg/L. Given the exposure conditions in this study (i.e. whole-body) and the likely extensive dermal absorption of acrylonitrile, a contribution of dermal exposure to the overall toxicity observed cannot be excluded.

Reference 3

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

Acute 4 hour inhalation toxicity study in the rat and other species.

GLP compliance:

no

Remarks:

: study pre-dates GLP

Test type:

standard acute method

Limit test:

no

Species:

other: rats, guinea pigs, rabbits, cats, dogs and monkeys.

Strain:

not specified

Sex:

not specified

Details on test animals or test system and environmental conditions:

Various specieis: whole body exposure assumed

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Remarks:

[assumed]

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

Whole body exposure is assumed, given the age of the study and the species investigated.

Analytical verification of test atmosphere concentrations:

not specified

Duration of exposure:

4 h

Concentrations:

Various expousre concentrations were used

No. of animals per sex per dose:

16 rats per expousre concentration

Control animals:

not specified

Preliminary study:

Not applicable

Sex:

not specified

Dose descriptor:

LC50

Effect level:

7.88 mg/L air

Exp. duration:

0.5 h

Remarks on result:

other: rat

Sex:

not specified

Dose descriptor:

LC50

Effect level:

4 mg/L air

Exp. duration:

1 h

Remarks on result:

other: rat

Sex:

not specified

Dose descriptor:

LC50

Effect level:

2.03 mg/L air

Exp. duration:

2 h

Remarks on result:

other: rat

Sex:

not specified

Dose descriptor:

LC50

Effect level:

1.03 mg/L air

Exp. duration:

4 h

Remarks on result:

other: rat

Sex:

not specified

Dose descriptor:

LC50

Effect level:

0.69 mg/L air

Exp. duration:

6 h

Remarks on result:

other: rat

Body weight:

No information.

Gross pathology:

No information.

Other findings:

.

Toxicity of acrylonitrile vapour in rats exposed for 0.5 to 8 Hours

 

Exposure Time (hrs)	Exposure Conc. (ppm)	Mortality (%) During Exposure	Total Mortality (%)	Effects
0.5	2445 1490 1270 665	0 0 0 0	0 0 0 0	Marked; slight residual effects to 24 hrs Marked; no residual effects in 24 hrs Marked; no residual effects in 24 hrs Moderate transitory effects
1	2445 1490 1270 665	0 0 0 0	81 25 0 0	Deaths in 4 hrs; slight effects at 24 hrs in survivors Deaths in 4 hrs; slight effects at 24 hrs in survivors Marked effects; slight effects at 24 hrs; normal at 48 hrs Marked transitory effects
2	1260 595 305	0 0 0	100 6 0	Fatal; deaths within 4 hrs Marked transitory effects Slight transitory effects
4	635 315 130	50 25 0	100 31 0	Fatal Marked; no effects in survivors at 24 hrs slight transitory effects
8	320 270 210 135 90	94 44 6 0 0	94 44 6 0 0	Fatal Marked; no effects in survivors at 24 hrs Marked transitory effects Moderate transitory effects Slight discomfort

Nonlethal effects included initial rapid respiration followed by rapid shallow breathing; prior to death animals

exhibited slow, gasping respiration Toxicity of AN Vapour In Dogs Exposed for 4 Hours

 

Exposure Concentration (ppm)	Gender	Effects
30	F F F F	Slight salivation by end of exposure period; no other effects Slight salivation by end of exposure period; no other effects Slight salivation by end of exposure period; no other effects Slight salivation by end of exposure period; no other effects
65	F F	Severe salivation; weak by end of exposure Coma by end of exposure; died at 8 hrs
100	M F F	Severe salivation during exposure; full recovery within 24 hrs Convulsions at 2.5 hrs; coma by end of exposure; partial paralysis of hind legs for 3 days Convulsions at 2.5 hrs; coma by end of exposure; full recovery within 48 hrs
110	F M F	Coma at end of exposure; dead at 4.5 hrs Coma at end of exposure; dead at 3 days Coma at end of exposure; food refusal for 10 days; slowly recovered
165	F M	Convulsions at 2 hrs; dead at 3 hrs of exposure Coma from end of exposure to death at 4 hrs.

Toxicity of acrylonitrile vapour in guinea pigs exposed for 4 hours

 

Exposure Conc. (ppm)	Mortality (%) During Exposure	Total Mortality (%)	Effects
100 265 575 1160	0 0 25 13	0 0 63 100	Slight to no effect Slight transitory effect; reduced feed consumption for 4 days Ocular and nasal irritation during exposure; delayed death (3-6 days) probably from pulmonary edema 5 Dead within 1.5 hrs post exposure; 2 dead at 18 hrs

 

Interpretation of results:

Category 3 based on GHS criteria

Conclusions:

The 4-hour LC50 of acrylonitrile in the rat was calculated to be 1.21 mg/L under the conditions of this study.

Executive summary:

The authors exposed groups of rats, guinea pigs, rabbits, cats, dogs and monkeys for varying periods of time to different expousre concentrations of acrylonitrile vapour. In rats, 100% mortality was within 2 -6 hours of exposure to 635 ppm. Responses included initial stimulation of respiration followed by rapid shallow respiration. Above a concentration of 300 ppm, rats started exhibiting signs of ocular and nasal irritation. Rats exposed to any concentration of acrylonitrile exhibited flushing (reddening) of the skin, nose, ears, and feet. Prior to death, the rats were gasping and convulsing. Gross pathology findings of dead rats revealed bright red lungs of abnormal consistency and dark red blood. Rats which survived exposure exhibited no residual effects. Exposure 315 ppm for 4 hours resulted in 31% mortality and exposure to 635 ppm produced 100% mortality. LC50 value for the rat are calculated to be 7.55 mg/L (0.5-hour exposure), 4.00 mg/L (1-hour exposure), 2.03 mg/L (2-hour exposure), 1.03 mg/L (4 -hour exposure) and 0.69 mg/L (6 -hour exposure).

Reference 4

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

no guideline followed

Principles of method if other than guideline:

Acute inhalation toxicity in the rat; single concentration, 1 hour exposure.

GLP compliance:

no

Remarks:

: published study

Test type:

standard acute method

Limit test:

yes

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

5 male and 5 female young adult Sprague-Dawley rats

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Analytical verification of test atmosphere concentrations:

not specified

Duration of exposure:

1 h

Concentrations:

Rats were exposed to a single concentration of 1008 ppm (equivalent to 2240 mg/m3).

No. of animals per sex per dose:

5 rats per sex (single exposure concentration)

Control animals:

no

Preliminary study:

Not reported

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 1 008 ppm

Exp. duration:

1 h

Remarks on result:

other: No mortality at this exposure level equivalent to 2240 mg/m3

Mortality:

No mortality occurred.

Clinical signs:

other: Shallow and rapid breathing, decreased activity, nasal discharge, salivation, lacrimation and coma (3/10 rats).

Body weight:

No information.

Gross pathology:

No information.

Other findings:

Rats fully recovered within 5 minutes when exposed to fresh air.

There was no mortality in this study. Clinical signs noted included shallow and rapid breathing, decreased activity, nasal discharge, salivation, lacrimation and coma (3 of 10 animals). Based on these observed clinical signs the CNS was indicated to be a target organ. The extremities of all animals appeared red after 37 minutes of exposure. However animals recovered fully within 5 minutes when exposed to fresh air.

Interpretation of results:

study cannot be used for classification

Conclusions:

The 1-hour acute inhalation LC50 of acrylonitrile in the rat was calculated to be >1008 ppm.

Executive summary:

10 young adult male and female Sprague-Dawley rats were exposed (whole body) to acrylonitrile at a concentration of 1008 ppm (equivalent to 2250 mg/m3) for 1 hour to determine the acute inhalation toxicity. No deaths occurred. Clinical signs included shallow and rapid breathing, decreased activity, nasal discharge, salivation, lacrimation and coma (3/10 rats). Based on the clinical signs, the authors concluded that the CNS was a target organ. Based on the results of this study, the 1 hour inhalation LC50 of acrylonitrile in the rat under the conditions of this study was >1008 ppm (>2240 mg/m3).

Reference 5

Endpoint:

acute toxicity: inhalation

Type of information:

other: review of published studies

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Qualifier:

according to guideline

Guideline:

other: various studies are reviewed, with different experimental designs

Principles of method if other than guideline:

The EU RAR summarises the results of a number of 4-hour acute inhalation toxicity studies with acrylonitrile. Studies are of different designs and were performed in various species.

GLP compliance:

no

Remarks:

: review of older, published studies

Test type:

other: the EU RAR (2004) reviews the extensive dataset on the acute inhalation toxicity of acrylonitrile.

Species:

other: various species were used in the reviewed studies

Strain:

other: various

Sex:

not specified

Details on test animals or test system and environmental conditions:

Various

Route of administration:

inhalation

Type of inhalation exposure:

not specified

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

No further information

Analytical verification of test atmosphere concentrations:

not specified

Duration of exposure:

>= 0.5 - <= 8 h

Remarks on duration:

Studies are of variable duration and employed different durations of exposure

Concentrations:

No information available

No. of animals per sex per dose:

No information available

Control animals:

not specified

Details on study design:

Acute 4 hour inhalation toxicity tests

Statistics:

No information available

Preliminary study:

Not applicable

Sex:

not specified

Dose descriptor:

LC50

Effect level:

300 - 1 210 mg/m³ air

Exp. duration:

4 h

Remarks on result:

other: All species investigated

Sex:

not specified

Dose descriptor:

LC100

Effect level:

560 mg/m³ air

Exp. duration:

4 h

Remarks on result:

other: Rabbit

Sex:

not specified

Dose descriptor:

LC0

Effect level:

270 mg/m³ air

Exp. duration:

4 h

Remarks on result:

other: Rabbit

Sex:

not specified

Dose descriptor:

LC100

Effect level:

1 380 mg/m³ air

Exp. duration:

4 h

Remarks on result:

other: Rat

Sex:

not specified

Dose descriptor:

LC100

Effect level:

1 380 mg/m³ air

Exp. duration:

4 h

Remarks on result:

other: Cat

Sex:

not specified

Dose descriptor:

LC0

Effect level:

196 mg/m³ air

Exp. duration:

4 h

Remarks on result:

other: Monkey

Sex:

not specified

Dose descriptor:

other: LC25

Effect level:

1 250 mg/m³ air

Exp. duration:

4 h

Remarks on result:

other: Guinea-pig

Sex:

not specified

Dose descriptor:

other: LC33

Effect level:

240 mg/m³ air

Exp. duration:

4 h

Remarks on result:

other: Dog

Sex:

not specified

Dose descriptor:

LC0

Effect level:

63 mg/m³ air

Exp. duration:

4 h

Remarks on result:

other: Dog

Mortality:

Delayed mortality (25%) was observed in guinea pigs exposed to 575 ppm (1250 mg/m3), as a result of lung oedema occurrring 3-5 days following exposure.

Gross pathology:

Marked lung congestion was seen in all species except guinea pigs, in which the lungs were pale in colour and gave a frothy exudate on sectioning.

Other findings:

The sensitivity of species to acrylonitrile inhalation decreases in the order mouse, guinea pig and rat.

The LC50 values reported for a range of species following a 4-hour inhalation exposure lie in the concentration range of 300-1210 mg/m3.

Interpretation of results:

Category 3 based on GHS criteria

Conclusions:

The results of the studies summairsed in the EU RAR are consistent with the current CLP classification.

Executive summary:

The EU RAR summarises and reviews the extensive dataset available for the acute inhalation toxicity of acrylonitrile. The LC50 values after a 4 -hour exposure lie in the concentration range of 300-1210 mg acrylonitrile/m3, with a relative species sensitivity of species to acrylonitrile inhalation decreases in the order mouse>guinea pig>rat.

Reference 6

Endpoint:

acute toxicity: inhalation

Type of information:

other: review of published studies

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Qualifier:

according to guideline

Guideline:

other: the review covers a large number of published studies of acute inhalation toxicity

Principles of method if other than guideline:

The 2004 review by The Sapphire Group review and summarises the available data on the acute inhalation toxicity of acrylonitrile.

GLP compliance:

no

Remarks:

: the review covers generally older, published studies

Test type:

other: summary of published data

Limit test:

no

Species:

other: the results of various studies in a number of species are summarised

Strain:

other: various

Sex:

male/female

Route of administration:

inhalation: vapour

Type of inhalation exposure:

not specified

Vehicle:

other: unchanged (no vehicle)

Analytical verification of test atmosphere concentrations:

not specified

Duration of exposure:

>= 10 - <= 240 min

Concentrations:

The reviewed studies used various exposure concentrations.

No. of animals per sex per dose:

Various

Control animals:

not specified

Preliminary study:

None

Sex:

not specified

Dose descriptor:

LC50

Effect level:

>= 300 - <= 1 210 mg/m³ air

Exp. duration:

4 h

Remarks on result:

other: all species

Sex:

not specified

Dose descriptor:

LC50

Effect level:

200 mg/m³ air

Exp. duration:

4 h

Remarks on result:

other: dog

Sex:

not specified

Dose descriptor:

LC50

Effect level:

300 mg/m³ air

Exp. duration:

4 h

Remarks on result:

other: mouse

Sex:

not specified

Dose descriptor:

LC50

Effect level:

990 mg/m³ air

Exp. duration:

4 h

Remarks on result:

other: guinea pig

Sex:

not specified

Dose descriptor:

LC50

Effect level:

>= 470 - 1 210 mg/m³ air

Exp. duration:

4 h

Remarks on result:

other: rat

The LC50 values reported for a range of species following a four hour inhalation exposure are noted to be in the concentration range 300 -1210 mg/m3.  Inhalation studies provided approximate 4 -hour LC50 values of of 200 mg/m3 in the dog, 300 mg/m3 hr in the mouse and 990 mg/m3/4 hr in the guinea pig.

In rats, the data of Dudley et al (1942) and Appel et al (1981) provide a 4 -hour LC50 of 1030 -1210 mg/m3/4 hr, although a lower value of 470 mg/m3 was reported by Knobloch et al (1971).

Dudley & Neal (1942) also investigated the individual susceptibility of a range of species (rats, guinea pigs, rabbits, cats, dogs, and monkeys) to varying concentrations of acrylonitrile.  The results indicated that rabbits were moderately susceptible, with exposure to a level of 260 ppm (560 mg/m3) for four hours causing 100% mortality in four to five hours, while a level of 135 ppm produced marked, but transitory effects. Rats and cats were noted to be of about equal susceptibility, 100% mortality being observed in rats within two to six hours of exposure to 635 ppm (1380 mg/m3) acrylonitrile and in cats within 1.5 hours of exposure to 600 ppm (130 mg/m3). Exposure of two monkeys to 90 ppm (196 mg/m3) produced only slight transitory redness of the face, genitalia, and extremities; with full recovery in 12 hours.  Delayed mortality (25%) was observed in guinea pigs exposed to a level of 575 ppm (1250 mg/m3), mortality occurring as a result of lung oedema three to five days following exposure. In general, guinea pigs appeared to be less sensitive to acrylonitrile than rats following inhalation exposure, but yet the lethality in both species after administration by other routes is comparable. This could be due to the lower respiratory volume per kg body weight of guinea pigs . The dog was shown to be the most sensitive species. Exposure to 110 ppm (240 mg/m3) was fatal in two out of three dogs exposed, while a four-hour exposure to a level of 100 ppm resulted in convulsions followed by coma in two out of three dogs. One of these dogs recovered completely within 48 hours while the other showed partial paralysis of the hind legs for three days. The third dog exposed to 100 ppm showed severe salivation during the test, but recovered fully within 24 hours. At an exposure level of 29 ppm (63 mg/m3) for four hours, signs of toxicity in dogs were confined to slight salivation at the end of the test. The authors also investigated the protective effects of sodium nitrite, thiosulphate and methylene blue. Sodium nitrite was shown to be the most effective of the three antidotes in delaying the onset of symptoms of acrylonitrile toxicity and reducing the severity of the effects in rats and rabbits, although it had no such protective effect in guinea pigs. The authors suggest that it is likely that acrylonitrile was metabolised to cyanide, as postulated for other nitriles.

 

The same authors also investigated the effect of increasing exposure levels of AN and increasing duration of exposure, from 0.5 to 8 hours, in rats. Their results are summarised below:

Concentration acrylonitrile (mg/m3)	Exposure period (h)	Rats exposed (#)	Mortality
5300	0.5	16	-
3230	0.5	16	-
2750	0.5	16	-
1440	0.5	16	-
5300	1	16	12
3230	1	16	4
2750	1	16	-
1440	1	16	-
23730	2	16	16
1440	2	16	1
660	2	16	-
1380	4	16	16
680	4	16	5
280	4	16	-
690	8	16	15
590	8	16	7
460	8	16	1
290	8	16	-
200	8	16	-

Appel et al (1981) administered lethal doses of acrylonitrile to male Wistar rats by different routes of application (ip, gavage and inhalation) in order to observe the effect of potential antidotes on the acute toxicity of AN. Inhalation exposure for 30 minutes to 3000 ppm (6490 mg/m3) proved to be lethal in all six rats examined. The results from the Dudley & Neal (1942) and Appel et al (1981) were used to establish LC50 values for the rat, using the method of Probit Analysis (Finney, 1971):

Concentration acrylonitrile (mg/m3)	Exposure period (h)	Rats exposed (#)	Mortality
1406 (650)	3	3	1
2055 (950)	2	3	1
2380 (1100)	2	3	3
3461 (1600)	0.5	3	-
5192 (2400)	10 minutes	3	-
5624 (2600)	0.5	3	1
6490 (3000)	0.5	6	6

 

 The LC50 value for inhalation of AN obviously decreases with increasing exposure time, the LC50 values after four hours of exposure are in the concentration range 1030-1210 mg/m3, as shown by these two independent studies. The consistency between the results for the two studies should be noted, particularly considering the time gap of approximately 40 years between them.

Exposure (h)	LC50 (mg/m3)
	Dudley et al (1942)	Appel et al (1981)
0.5	7880	5740
1	4000	3410
2	2030	2030
4	1030	1210
6	690	890

Vernon et al, in a study carried out in 1985 and reported in the Journal of the American College of Toxicology in 1990, exposed a group of ten young adult Sprague-Dawley rats (five of each sex) to a concentration of 1008 ppm (2240 mg/m3) for one hour. There was no mortality. Clinical signs noted included shallow and rapid breathing, decreased activity, nasal discharge, salivation, lacrimation and coma (3/10 animals). Based on these observed clinical signs, the CNS is indicated to be a target organ. The extremities of all animals appeared red after 37 minutes of exposure. However, animals recovered fully within five minutes when exposed to fresh air. The acute inhalation (rat) LC50 was calculated to be >1,008 ppm (2,240 mg/m3). With respect to lethality in other species following inhalation exposure, the LC50 for dogs following a four hour exposure has been estimated from the data of Dudley and Neal (1942) to be 200 mg/m3 (90 ppm), while exposure to 580 to 670 mg/m3 (267 to 309 ppm) was fatal for three rabbits within two to three hours.

Interpretation of results:

Category 3 based on GHS criteria

Conclusions:

The results of the studies summarised in the review are consistent with the current CLP classification, specifically the 4-hour rat LC50 values of 1030 and 1210 mg/m3 reported by Dudley et al (1942) and Appel et al (1981).

Executive summary:

LC50 values reported for a range of species following a four hour inhalation exposure are in the concentration range of 300-1210 mg/m3.  The results of the studies summarised in the review are consistent with the current EU classification, specifically the 4-hour rat LC50 values of 1030 and 1210 mg/m3 reported by Dudley et al (1942) and Appel et al (1981).

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LC50

Value:

2 050 mg/m³ air

Quality of whole database:

A recent, guideline-compliant study is supported by older and largely non-standard data

Acute toxicity: via dermal route

Link to relevant study records

Reference

Reference 1

Endpoint:

acute toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

no guideline followed

Principles of method if other than guideline:

Topical application with occlusion, single dose for 4 hours.

GLP compliance:

not specified

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

not specified

Sex:

male/female

Details on test animals or test system and environmental conditions:

10 rats.

Type of coverage:

occlusive

Vehicle:

unchanged (no vehicle)

Details on dermal exposure:

topically applied acrylonitrile with occlusion.

Duration of exposure:

4 hours.

Doses:

200mg/kg.

No. of animals per sex per dose:

10 rats total, no further information available.

Control animals:

not specified

Details on study design:

No further information.

Statistics:

None reported.

Preliminary study:

Not applicable/no information

Key result

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 200 mg/kg bw

Based on:

test mat.

Remarks on result:

other: Deaths 1/10 at 200 mg/kg bw

Mortality:

1 mortality occurred.

Clinical signs:

other: Slight oedema seen in 3 rats 24 hours following exposure.

Gross pathology:

No information.

Other findings:

No information.

No further information.

Interpretation of results:

Category 4 based on GHS criteria

Conclusions:

1 rat died following 4 hours occluded topical application of acrylonitrile (200 mg/kg bw). Slight oedema was observed in 3 of the surviving rats 24 hours following exposure.

Executive summary:

1 rat (out of 10) died following 4 hours occluded topical application of acrylonitrile (200 mg/kg bw). Slight oedema was observed in 3 of the surviving rats 24 hours following exposure.

Reference 2

Endpoint:

acute toxicity: dermal

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

Investigation of acute dermal toxicity following the application of a single occlusive dose applied to intact rabbit skin

GLP compliance:

not specified

Remarks:

: published study

Test type:

standard acute method

Limit test:

no

Species:

rabbit

Strain:

not specified

Sex:

male

Details on test animals or test system and environmental conditions:

15 young adult male rabbits

Type of coverage:

occlusive

Vehicle:

unchanged (no vehicle)

Details on dermal exposure:

Single dose of 200 mg/kg bw occlusively applied to intact skin.

Duration of exposure:

24 hours

Doses:

200 mg/kg bw

No. of animals per sex per dose:

15 males, single dose level

Control animals:

not required

Preliminary study:

Not applicable/no information

Sex:

male

Dose descriptor:

LD50

Effect level:

< 200 mg/kg bw

Sex:

male

Dose descriptor:

LD100

Effect level:

200 mg/kg bw

Mortality:

100% mortality was seen ithin the the first 24 hours

Clinical signs:

other: None noted.

Gross pathology:

No information.

Other findings:

No further information.

The acute dermal LD50 of acrylonitrile to rabbits was found to be <200 mg/kg bw, indicating that acrylonitrile can readily penetrate the skin.

Interpretation of results:

Category 3 based on GHS criteria

Conclusions:

The acute dermal LD50 of acrylonitrile to rabbits was found to be <200mg/kg bw.

Executive summary:

A single dose of 200 mg/kg bw acrylonitrile was occlusively applied to the intact skin of male rabbits for 24 hours. 100% mortality occurred within the first 24 hours. The acute dermal LD50 of acrylonitrile in the rabbit was found to be <200 mg/kg bw after 24 hours exposure, indicating that acrylonitrile can readily penetrate the skin.

Reference 3

Endpoint:

acute toxicity: dermal

Type of information:

other: secondary source

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Qualifier:

no guideline followed

Principles of method if other than guideline:

The report contains the summarised results of a number of acute dermal toxicity studies in various species.

GLP compliance:

not specified

Test type:

standard acute method

Limit test:

no

Species:

other: summarised results from studies in a range of species

Strain:

not specified

Sex:

not specified

Type of coverage:

not specified

Vehicle:

not specified

Duration of exposure:

No information.

Doses:

No information.

No. of animals per sex per dose:

No information.

Control animals:

not specified

Details on study design:

No information.

Preliminary study:

Not applicable/no information.

Sex:

not specified

Dose descriptor:

LD50

Effect level:

148 - 693 mg/kg bw

Remarks on result:

other: LD50 values reported for all species

Dermal LD50 values for various species are reported to be in the range 148 -693 mg/kg bw. Rats are stated to be the most sensitive species.

Interpretation of results:

other: data not sufficient for classification

Remarks:

Criteria used for interpretation of results: EU

Conclusions:

Dermal LD50 values for various species are reported to be in the range 148 -693 mg/kg bw. Rats are stated to be the most sensitive species.

Executive summary:

The BUA document summarises the available dermal toxicity data. Dermal LD50 values for various species are reported to be in the range 148 -693 mg/kg bw. Rats are stated to be the most sensitive species.

Reference 4

Endpoint:

acute toxicity: dermal

Type of information:

other: review of available data

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Qualifier:

no guideline followed

Principles of method if other than guideline:

The EU RAR summarises the data available on the acute dermal toxicity of acrylonitrile.

GLP compliance:

no

Remarks:

: summaries of non-GLP published studies

Test type:

standard acute method

Limit test:

no

Species:

other: studies in various species (guinea pig, rat and rabbit) are summarised

Strain:

not specified

Sex:

not specified

Type of coverage:

not specified

Vehicle:

not specified

Duration of exposure:

No information available

Doses:

No information available

No. of animals per sex per dose:

No information available

Control animals:

not specified

Details on study design:

No information available

Statistics:

No information available

Preliminary study:

Not applicable

Sex:

not specified

Dose descriptor:

LD50

Effect level:

260 - 690 mg/kg bw

Remarks on result:

other: Guinea pig

Sex:

not specified

Dose descriptor:

LD50

Effect level:

148 - 282 mg/kg bw

Remarks on result:

other: Rat

Sex:

not specified

Dose descriptor:

LD50

Effect level:

226 mg/kg bw

Remarks on result:

other: Rabbit

Mortality:

No information available

Clinical signs:

other: No information available

Gross pathology:

No information available

Other findings:

No information available

Dermal LD50 values for various species were in the range of 148-693 mg/kg body weight, with the rat reacting most sensitively (BUA, 1995). In a study by Vernon et al. (1969) a single dose of 200 mg/kg was applied occlusively to the intact skin of 15 young adult male rabbits for an exposure period of 24 hours. This study resulted in death of all animals within the first 24 hours, with no clinical signs being noted. The acute dermal LD50 of acrylonitrile in this study was <200 mg/kg. This indicates that acrylonitrile can readily penetrate the skin.

Interpretation of results:

Category 2 based on GHS criteria

Conclusions:

The results of the relevant rat studies indicate that the current CLP classification of acrylonitrile is appropriate.

Executive summary:

The EU RAR summrises the available acute derma toxiciity data for acylonitrile. Dermal LD50 values for various species were in the range of 148-693 mg/kg body weight, with the rat reacting most sensitively (BUA, 1995). In a study by Vernon et al. (1969) a single dose of 200 mg/kg was applied occlusively to the intact skin of 15 young adult male rabbits for an exposure period of 24 hours. This study resulted in death of all animals within the first 24 hours, with no clinical signs being noted. The acute dermal LD50 of acrylonitrile in this study was <200 mg/kg. This indicates that acrylonitrile can readily penetrate the skin.

Reference 5

Endpoint:

acute toxicity: dermal

Type of information:

other: review of published data

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The 2004 review by The Sapphire Group contains summaires of the available acute dermal toxicity data for acrylonitrile. The review was subject to independent peer review.

Qualifier:

no guideline followed

Principles of method if other than guideline:

The review summarises the available acute dermal toxiicty studies, which are of varing experimental design

GLP compliance:

no

Remarks:

: older published studies

Test type:

other: the review summarises the available acute dermal toxiicty studies

Limit test:

no

Species:

other: various

Strain:

other: various

Sex:

not specified

Type of coverage:

not specified

Vehicle:

not specified

Duration of exposure:

Various study designs are reported, including a 24-hour occlusive exposure in rabbits.

Doses:

Various study designs are reported

No. of animals per sex per dose:

Various study designs are reported

Control animals:

not required

Sex:

male/female

Dose descriptor:

LD50

Effect level:

>= 148 - <= 693 mg/kg bw

Remarks on result:

other: Values for all species

Sex:

male

Dose descriptor:

LD50

Effect level:

< 200 mg/kg bw

Remarks on result:

other: Rabbit

Sex:

male

Dose descriptor:

LD100

Effect level:

200 mg/kg bw

Remarks on result:

other: Rabbit

Dermal LD50 values for various species were in the range of 148 to 693 mg/kg bw with the rat reported to be most sensitive.

Executive summary:

The Sapphire Group reviewed the available acute dermal toxicity data for acrylontrile. Dermal LD50 values for various species were in the range of 148 to 693 mg/kg bw with the rat reacting most sensitively (BUA, 1995). In a study by Vernon et al. (1969), a single dose of 200 mg/kg bw was applied occlusively to the intact skin of 15 young adult male rabbits for an exposure period of 24 hours. This study resulted in death of all animals within the first 24 hours, with no clinical signs being noted. The acute dermal LD50 of acrylonitrile in this study was <200 mg/kg bw.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

200 mg/kg bw

Quality of whole database:

A recent, guideline-compliant study is supported by older and largely non-standard data.

Additional information

Overview

The dataset for acute toxicity is extensive and has been reviewed and summarised in the EU RAR (2004) and also by The Sapphire Group (2004); summaries of these reviews are therefore also included for completeness.

 

Signs of acute toxicity

The signs of toxicity resulting from acute acrylonitrile administration have been examined in a number of different species and have been to found to vary very little. The clinical signs following acute exposure to acrylonitrile can be divided into four stages. Immediately after administration the animal goes through an excitatory phase, with agitation and lacrimation. A tranquil phase follows and cholinergic-type symptoms, such as salivation, lacrimation, urination and defecation occur. These signs may reflect a true cholinergic response or may occur through an indirect mechanism. Next there is a convulsive phase in which the animal undergoes clonic seizures. The terminal stage preceding death is a paralytic phase in which the animal is immobile. The clinical signs indicate that the action of acrylonitrile is that of a typical nitrile, with a toxic action probably due to a cleavage of the molecule to produce hydrogen cyanide, which is one of the key mediators of the toxicity. However, for any nitrile, there is a complex interplay of a number of factors that affect the outcome of acrylonitrile toxicity. These include the rate of cyanide liberation and detoxification, the dose level, the route of administration, the species of animal and the presence of other bioreactive sites within the molecule.

 

Acute oral toxicity 

Rao et al (2013) report an LD50 of 95.1 (81.7 -110.6) mg/kg bw in female Wistar rats. The available data on acute oral toxicity have been summarised in the EU RAR (2004) and Sapphire Group report (2004) and are also presented here for completeness. The EU RAR (2004) reports oral LD50 values for various species in the range 25 -186 mg/kg bw. The sensitivity of various species to orally administered acrylonitrile is noted to decrease in the order mouse>guinea pig>rabbit and rat. The results of a guideline-comparable study in the rat show an acute oral LD50 value of 81 (62 -107 mg/kg bw). .

LD50	Species
81 mg/kg bw	CF Nelson Rats
25-186 mg/kg bw	various species
25-48 mg/kg bw	Mice
50-85 mg/kg bw	Guinea pig
72-186 mg/kg bw	Rat
93 mg/kg bw	Rabbit

Oral LD50 values (EU RAR, 2004)

The Sapphire Group report also notes oral LD50 of 25-86 mg/kg bw (summarised below).

LD50	Species
25-186 mg/kg bw	All species
25-48 mg/kg bw	Mouse
50-85 mg/kg bw	Guinea pig
93 mg/kg bw	Rabbit
72-186 mg/kg bw	Rat
81 (62-107) mg/kg bw	Rat

Oral LD50 values (Sapphire Group, 2004)

Acute inhalation toxicity 

In a modern GLP and OECD 403-compliant study (Kiplinger, 2005), the 4 -hour LC50 of acrylonitrile in the rat was calculated to be 964 ppm (males), 920 ppm (female) and 946 ppm (males and females combined). These LC50 values are equivalent to 2.09, 2.00 and 2.05 mg/L respectively. Vernon et al (1990) report a 1-hour LC50 of >1008 ppm (2.24 mg/L) in the rat. No mortality occurred in this study. Clinical signs were considered to indicate the CNS as a target organ; signs of toxicity were reversible within 5 minutes of exposure termination. Appel et al (1981) report a 1-hour LC50 value of 1578 ppm (3.42 mg/L) and a 4-hour LC50 value of 557 ppm (1.21 mg/L) in the rat.

 

Summary of rat mortality from Appel et al (1981)

Acrylonitrile concentration (mg/L)	Exposure time	Mortality
1.406	3h	1/3
2.055	2h	1/3
2.380	2h	3/3
3.461	0.5h	0/3
5.192	10 min	0/3
5.624	0..5h	1/3
6.490	0.5h	6/6

 

Dudley & Neal (1942) exposed groups of rats, guinea pigs, rabbits, cats, dogs and monkeys to acrylonitrile for different time periods and varying concentrations. 100% mortality occurred in rats within 2-6 hours of exposure to 635 ppm acrylonitrile. 100% mortality occurred in rabbits within 4-5 hours of exposure to 260 ppm acrylonitrile, exposure to 135 ppm produced marked but transitory effects. 100% mortality occurred in cats within 1.5 hours of exposure to 600 ppm acrylonitrile, 4 hours exposure to 90 ppm caused slight transitory redness of the face and genitalia in monkeys; the animals were fully recovered after 12 hours.

Summary of rat mortality from Dudley & Neal (1942)

Acrylonitrile concentration (mg/L)	Exposure time (h)	Mortality
5.33	0.5	0/16
3.23		0/16
2.75		0/16
1.44		0/16
5.30	1.0	12/16
3.23		4/16
2.75		0/16
1.44		0/19
2.73	2.0	16/16
1.44		1/16
0.66		0/16
1.38	4.0	16/16
0.68		5/16
0.28		0/16
0.69	8.0	15/16
0.59		7/16
0.46		1/16
0.29		0/16
0.20		0/16

The EU RAR summarises and reviews the extensive dataset on the acute inhalation toxicity of acrylonitrile. LC50 values for 4 -hour exposure periods are in the range 300-1210 mg acrylonitrile/m3. The sensitivity of species to acrylonitrile inhalation toxicity is noted to be in the order mouse>guinea pig>rat.

Endpoint	Concentration (mg/L)	Exposure time	Species
LC50	0.30-1.21 mg/m³	4 h	All species
LC100	0.56 mg/m³	4 h	Rabbit
LC0	0.27 mg/m³	4 h	Rabbit
LC100	1.38 mg/m³	4 h	Rat
LC100	1.38 mg/m³	4 h	Cat
LC0	0.196 mg/m³	4 h	Monkey
LC25	1.25 mg/m³	4 h	Guinea-pig
LC33	0.24 mg/m³	4 h	Dog
LC0	0.063 mg/m³	4 h	Dog

Data from the EU RAR (2004)

The document also provides a reanalysis of the results from the studies of Dudley & Neal (1942) and Appel et al (1981), calculating LC50 values using Probit analysis (Finney, 1971). The values (shown below) are noted to be consistent with each other. The Sapphire Group review (2004) reports LC50 values for a range of species following a four hour inhalation exposure in the concentration range of 300-1210 mg/m3.  The results of the studies summarised in the review are consistent with the current EU classification, specifically the 4-hour rat LC50 values of 1030 and 1210 mg/m3 reported by Dudley & Neal (1942) and Appel et al (1981).

 Calculated LC50 values for the studies of Dudley & Neal (1942) and Appel et al (1981)

Exposure duration (h)	Calculated LC50 value (mg/L)
	Dudley & Neal (1942)	Appel et al (1981)
0.5	7.88	5.74
1	4.00	3.41
2	2.03	2.03
4	1.03	1.21
6	0.69	0.89

Data from the EU RAR (2004)

Acute dermal toxicity

 A modern, guideline-compliant study (SNF, 2005) reports an acute dermal LD50 value in the rat of >200 mg/kg bw: one out of ten animals died at this dose level and slight oedema was apparent in three survivors. In contrast to the results of the previous study, Vernon et al (1990) report a dermal LD50 in the rabbit of <200 mg/kg bw. In this study, a single dose of 200 mg/kg bw was applied occlusively to the intact skin of 15 young adult male rabbits for an exposure period of 24 hours. This study resulted in death of all animals within the first 24 hours, with no clinical signs being noted. The BUA report (1995) notes dermal LD50 values for various species in the range of 148 to 693 mg/kg bw with the rat reported to be most sensitive. The EU RAR (2004) and Sapphire Group report (2004) notes also note dermal LD50 values of 148 -282 mg/kg bw in the rat, 226 mg/kg bw in the rabbit and 260 -690 mg/kg bw in the guinea pig.

 

Acute toxicity by other routes of exposure 

The EU RAR (2004) reports LD50 values for acrylonitrile administered via the subcutaneous, intraperitoneal or intravenous routes to rats, guinea pigs, hamsters, mice and rabbits. The values for these routes of administration are noted to be broadly similar to those for oral administration.

 

LD50 values for other routes of exposure

LD50 value	Species	Exposure route
47-50 mg/kg bw	Mouse	Intraperitoneal
65-100 mg/kg bw	Rat	Intraperitoneal
25-50 mg/kg bw	Mouse	Subcutaneous
35 mg/kg bw	Mouse	Subcutaneous
60 mg/kg bw	Hamster	Subcutaneous
80-96 mg/kg bw	Rat	Subcutaneous
100 mg/kg bw	Rat	Subcutaneous
130 mg/kg bw	Guinea pig	Subcutaneous
69 mg/kg bw	Rabbit	Intravenous
72 mg/kg bw	Guinea pig	Intravenous

Values reported in the EU RAR (2004)

Justification for classification or non-classification

Acrylonitrile is listed in Annex VI of the CLP Regulation (1272/2008/EC) with classification in Acute Toxicity Category 3, H301: Toxic if swallowed, H311: Toxic in contact with skin and H331: Toxic if inhaled. The available data are consistent with this harmonised classification and no change is proposed.

The acute toxicity data for acrylonitrile were reviewed in detail in the EU Risk Assessment Report (2004). The following summary is based largely on the EU RAR, supplemented by literature reviews conducted in 2014 and, more recently, in March 2017. 

 

Acute oral toxicity

Following oral dosing, the mouse appears to be the most sensitive species, with oral LD50 values ranging from 28-48 mg/kg bw. The reported range in the guinea pig is 50-85 mg/kg bw, an oral LD50 of 93 mg/kg bw is reported in the rabbit, while in the rat the range of reported LD50 values is 72 -186 mg/kg bw (EU RAR, 2004). Vernon et al., in a study carried out in 1969 but reported in the Journal of the American College of Toxicology in 1990, orally dosed four groups of 5 young adult male CF Nelson rats with 50, 100, 200 and 400 mg/kg bw acrylonitrile and observed them for 14 days. All deaths occurred during the first 24 hours with no significant clinical signs being observed; the acute oral LD50 was calculated to be 81 (62 -107) mg/kg bw. Rao et al. (2013) report an acute 24 hour LD50 of 95.1 mg/kg bw in female Wistar rats. The acute oral LD50 of acrylonitrile is lower in mice than in rats, as would be expected based on the comparative metabolism. The oral LD50 in mice was reported by Tullar (1947) to lie between 25-48 mg/kg bw, as summarised in WHO (1983).  Tanii & Hashimoto (1984) reported similar values of 27 and 38 mg/kg bw. These values, however, appear artificially low. Ghanayem et al. (2002) dosed mice with 20 mg/kg bw/d on five days per week for 2 years without any observable cyanosis.  Leonard (1981) also dosed mice with 30 mg/kg bw and found no lethality. Tanii (1989) administered mice 60 mg/kg bw and observed 80% mortality, but susbsequently administered 79 mg/kg bw without lethality. Data indicate that mice excrete a higher percentage of administered acrylonitrile as thiocyanate (and hence appear to metabolise more acrylonitrile to cyanide) than rats or humans (EU RAR, 2004). Reported oral LD50 values for acrylonitrile in various species lie in the range 25 -186 mg/kg bw (GDCh/BUA, 1995).  No human data are identified. For classification purposes, the rat LD50 values were chosen because the rat is the preferred species for classification. Furthermore the lower values in mice are not considered to be more relevant to humans based on comparative metabolism.

 

Comparison with the CLP criteria

The available rat oral LD50 values for acrylonitrile are in the range of 72 -186 mg/kg bw. These values are within the boundaries for CLP Category 3 (50 – 300 mg/kg bw).

Acute dermal toxicity

Dermal LD50 values for various species are in the range 148 -693 mg/kg bw, with the rat being the most sensitive species (BUA, 1995). In a study by Vernon et al. (1969) a single dose of 200 mg/kg bw was applied to the intact skin of 15 young adult male rabbits and occluded for an exposure period of 24 hours. This study resulted in death of all animals within the first 24 hours, with no clinical signs being noted. The acute dermal LD50 of acrylonitrile in this study was therefore <200 mg/kg bw.  Roudabush et al. (1965) reported an LD50 for the rabbit of 226 mg/kg bw. In a more recent rat study (SNF, 2005), acrylonitrile administered topically with occlusion at a dose level of 200 mg/kg bw for 4 hours resulted in 10% mortality (1 of 10 rats). Human data also indicate a potential for systemic toxicity following dermal exposure to acrylonitrile.

 

Comparison with the CLP criteria

The available dermal LD50 values for acrylonitrile are in the range 148 -693 mg/kg bw. The majority of studies (including the most reliable modern and guideline-compliant study) indicate classification in Catgeory 3 (LD50 values of 200 -1000 mg/kg bw).

Acute inhalation toxicity

The LC50 values reported for a range of species following a 4-hour inhalation exposure lie in the concentration range of 0.3 -1.21 mg/L. Dudley & Neal (1942) investigated the susceptibility of rats, guinea pigs, rabbits, cats, dogs and monkeys to a single 4-hour exposure to varying concentrations of acrylonitrile. The results indicated that rabbits were moderately susceptible; exposure to 260 ppm (0.56 mg/L) for 4 hours caused 100% mortality in 4 -5 hours, while a level of 135 ppm produced marked but transitory effects. Rats and cats were of about equal susceptibility, 100% mortality being observed in rats within 2–6 hours of exposure to 635 ppm (1.38 mg/L) and in cats within 1.5 hours of exposure to 600 ppm (1.30 mg/L). Exposure of two monkeys to 90 ppm (0.196 mg/L) produced only slight transitory effects. Delayed mortality (25%) was observed in guinea pigs exposed to a level of 575 ppm (1.25 mg/L) as a result of lung oedema 3 -5 days following exposure. In general guinea pigs appeared to be less sensitive than rats following inhalation exposure, but the lethality in both species after administration by other routes is comparable.  Dudley & Neal (1942) report that the dog was the most sensitive species. Exposure to 110 ppm (0.24 mg/L) acrylonitrile was fatal in 2 out of 3 dogs exposed, while a 4-hour exposure to a level of 100 ppm resulted in convulsions followed by coma in 2 out of 3 dogs. One of these dogs recovered completely within 48 hours while the other showed partial paralysis of the hind legs for 3 days. The third dog exposed to 100 ppm acrylonitrile showed severe salivation during the test but recovered fully within 24 hours. At an exposure level of 29 ppm (0.063 mg/L) for 4 hours, signs of toxicity in dogs were confined to slight salivation.  With regard to the acute lethality of aceylonitrile in animals, dogs appeared to be the most sensitive species following exposure via inhalation but the dataset for dogs is limited.  At least some of the species variability in the toxic response to acrylonitrile may be a function of the cyanide metabolite and activity levels of rhodanese. It is reported that dogs have relatively low concentrations of rhodanese and rats have relatively high concentrations; overall species variability was about 3 -fold. Data from studies of rats provide the most extensive evaluation of exposure durations and the best definition of dose response.  A total of seven rat studies were identified that contain information useful for calculating the 4 -hour or 1 -hour LC50 of acrylonitrile.

Human data also demonstrate the potential for systemic toxicity following inahalation exposure to acrylonitrile.

Comparison with the CLP criteria

The whole body inhalation 4-hour LC50 values reported for acrylonitrile vapour in the rat range from 150 -557 ppm, with the best documented study reporting a value of 557 ppm.  A well-documented GLP Guideline nose-only 4 -hourr vapour inhalation study reported an LC50 value of 946 ppm.  Values from the best available studies are therefore in CLP Category 3. (500 -2500 ppm)