Cyanogen chloride

Endpoint summary

Description of key information

Summary:

There is only limited information (animal and human data) on the acute toxicity of ClCN available. The available results listed below can be used as rough basis for the assessment. In the absence of further animal data, it can be assumed that chlorcyan has a similar toxicity as hydrogen cyanide.

The main intake pathway for cyanogen chloride proceeds via the respiratory tract. Chlorcyan is moderately soluble in water (25 cm3 of the gas/ml water at 20 degrees C) and hydrolyzed to form cyanic acid and hydrochloric acid. Because systemic effects have occurred after exposure of both humans and also in animal experiments and these effects are similar to a poisoning with HCN, absorption of the intact noxa, which has been deposited on the mucous membranes of the respiratory tract, is to be presumed. No data is available on the penetration of the gas through the intact skin. Because symptoms of irritation to the skin were registered following chronic exposure of workers (see "Chronic toxicity"), it can be concluded that the substance reacts with corresponding constituents of the skin. During this, HCN can be released which is effectively absorbed through the skin. Until information to the contrary is available, skin, absorption should therefore be assumed. Under conditions encountered in practice, intake by the gastrointestinal pathway is not relevant.

Main toxic effects

Acute:

Severe irritation to the eyes and airways, lung damage, neurotoxic effects, gastrointestinal complaints. Although the toxicological database for chlorcyan is small, it allows the conclusion to be drawn that the noxa (partially used as a constituent of poison gas in World Wars I/II) combines a very severe potential to irritate and to cause systemic effects. Concentrations > 20 ppm irritate the eyes, 40 ppm causes blepharospasm and intense lacrimation [2].

Skin:

Neither experience nor animal experiments are available on acute skin irritation through contact with the gas. Therefore, it is also impossible to assess the dermal toxicity. However, this would be important in order to assess the risk which would exist in an accidental situation when a highly contaminated area were entered with an escape mask only. To be on the safe side, a high dermal toxicity should be expected.

Inhalation:

For inhalative exposure, 20 ppm was reported to be the concentration limit which can be tolerated by humans for the maximum of 1 minute [1]. The pungent odor is already perceptible from 1 ppm upwards. [3]. Because at this concentration massive tissue damage or systemic effects are not to be expected in cases of short-term exposure, the substance was added to the infamous "Zyklon B" as a warning substance (and as a polymerization inhibitor). 40 ppm chlorcyan in the air one breathes leads to severe irritation to the eyes (see above), sight defects and tussive irritation. High exposures (no details given) additionally caused dizziness and nausea. In older experiments on various animal species, the period of time was detected in which certain concentrations cause death. At 100 ppm, 20 and 37 minutes were required for dogs and rats, respectively, at 340 ppm these periods lay below 10 minutes. Poisoning symptoms resulted from a combination of toxic pulmonary edema and disturbances to the cellular respiration due to the cyano group. This diagnosis was supported by the fact that only 8 % of dogs survived when they were exposed to 920 - 1440 ppm for 1 - 2 minutes. By comparison, when amyl nitrite (antidote against cyanide) and oxygen were applied after this exposure, 77 % of the animals survived. Dogs recovered after inhaling 0.05 mg/L (20 ppm) for 20 min. Those inhaling 0.3 mg/L (120 ppm) for 8 min exhibited severe injury but they recovered [1].

In mice, inhalation of 0.2 mg/L (80 ppm) cyanogen chloride for 5 min was tolerated by some animals; 0.3 mg/L (120 ppm) for 3.5 min was fatal to some animals. [5].

Cyanogen chloride has caused marked irritation of the respiratory tract with hemorrhagic exudate from the bronchi and trachea, and pulmonary edema. A concentration of approximately 500 ppm (1.0 mg/L) for 3 minutes was fatal to the mouse; 120 ppm (0.3 mg/L) for 3.5 minutes was fatal to the cat; 48 ppm (0.12 mg/L) for 6 hours was fatal for a dog; a goat exposed at 1000 ppm (2.5 mg/L) for 3 minutes died after 70 hours; and a concentration of 1200 ppm (3.0 mg/L) was fatal to the rabbit.

Results [4]:

- LC50 rat, inhal = 5400 mg/m3 (3 min)

- LC50 mouse, inhal = 3000 mg/m3 (0.5 min)

- LC50 rabbit, inhal = 6000 mg/m3 (7 min)

- LC50 guinea pigs, inhal = 5500 mg/m3 (2 min)

- LC50 cat, inhal = 6000 mg/m3 (1 min)

- LC50 cat, oral = 6000 mg/m3

- LC50 dog, inhal = 3800 mg/m3 (1 min)

References:

[1] DFG: Toxikologisch-arbeitsmedizinische Begründungen von MAK-Werten; Verlag Chemie]

[2] W.M. Grant, J.S. Schuman: Toxicology of the eyes; 4th Edition, Charles C Thomas Publisher, Springfield, Illinois; 1993

[3] American Conference of Governmental Industrial Hygienists "Documentation of the threshold limit values and biological exposure indices (2006)

[4] Lewis, R.J. Sr. (ed) Sax's Dangerous Properties of Industrial Materials. 11th Edition. Wiley-Interscience, Wiley & Sons, Inc. Hoboken, NJ. 2004., p. 1022-1023

[5] Bingham, E.; Cohrssen, B.; Powell, C.H.; Patty's Toxicology Volumes 1-9 5th ed. John Wiley & Sons. New York, N.Y. (2001)., p. 4:1397

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Based on fhe results of the available study on rats, cyanogen chloride is classified as follows:

- Acute toxicity, Cat. 1

- H300+H310+H330: Fatal if swallowed, in contact with skin or if inhaled.