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Toxicity and Health Effects of Ortho-chloro-benzylidene-malononitrile (CS gas)



The CS gas has repeatedly been used as a tear gas by police forces during manifestations and riots, in Europe, in the United States and elsewhere. Our study is aimed to examine toxicity and health effects on humans of CS gas, following the people exposure to CS gas in Valsusa (Italy), during the 2011-2015 period. The claims that the CS gas is not toxic are counterbalanced by many findings by recent studies, showing many toxic effects, especially in case of misuse of the gas, or in weak and sensitive subjects. Adoption of the precaution principle seems, in this case, recommendable. The use of CS gas by police forces for riot control should therefore be abandoned, substituted by other countermeasures.
© by PSP Volume 26 No. 1/2017, pages 151-155 Fresenius Environmental Bulletin
Massimo Zucchetti*, Raffaella Testoni
Dipartimento di Energia, Politecnico di Torino Corso Duca degli Abruzzi, 24, 10129 Torino, Italy
The CS gas has repeatedly been used as a tear
gas by police forces during manifestations and riots,
in Europe, in the United States and elsewhere. Our
study is aimed to examine toxicity and health
effects on humans of CS gas, following the people
exposure to CS gas in Valsusa (Italy), during the
2011-2015 period. The claims that the CS gas is not
toxic are counterbalanced by many findings by
recent studies, showing many toxic effects,
especially in case of misuse of the gas, or in weak
and sensitive subjects. Adoption of the precaution
principle seems, in this case, recommendable. The
use of CS gas by police forces for riot control
should therefore be abandoned, substituted by other
CS gas, toxicity, health effects, tear gas.
The chemical product ortho-chloro-
benzylidene-malononitrile (the so-called CS gas), is
chemically synthesized by reacting two chemicals
compounds: 2-clorobenzaldeide and malononitrile.
CS gas has repeatedly been used as a tear gas by
police forces during manifestations and riots, in
Europe, in the United States and elsewhere.
Our study is aimed to examine toxicity and
health effects on humans of CS gas, given our
observation of side effects cases due to exposure of
Italian people participating to manifestations since
2001 up to the present days.
The immediate effects of the gas on humans
occur at low concentrations and depend on the
irritating action to the skin and mucous membranes.
The first target organs are represented by eyes:
intense tearing due to irritation of the mucous
membrane, blepharospasm, conjunctivitis,
periorbital edema, burning, and pain. CS is
commonly classified as a non-lethal weapon to
control the riots. However, CS gas has proven to
have toxic side effects, which are currently studied
in toxicology.
According to Amnesty International, after
exposure in riots in Genoa 2001 (Italy), many
persons have filed a formal complaint,
accompanied by medical reports, claiming to suffer
long-term effects (damage to lungs, throat and skin)
due to exposure to gas CS. Similar reports are
available from other exposed people in Valsusa
(Italy) manifestations during 2011-2015.
In weak subjects, literature reports damage to
the lungs, and in some cases, effects on heart and
liver have been reported too. The potential damage
to internal organs, as well as gastrointestinal
symptoms, was evidenced by accidental exposures
reported in literature. Concerning the eyes, the
increase in intraocular pressure may onset acute
glaucoma in susceptible individuals.
As far as respiratory apparatus is concerned,
usual effects are represented by irritation of the
upper airways that are clinically manifested as nasal
congestion and runny nose: those effects are usually
reversible and disappear within a short time if the
exposed person moves to breath clean air and
washes himself and his/her clothes with fresh water.
In some cases, irritating effects may extend distally
and cause laryngitis, tracheitis, bronchial irritation
and cough with copious phlegm. In severe cases
laryngitis may result in laryngospasm and irritation
of the lower airways, namely ARDS (Acute
Respiratory Distress Syndrome). In medical
literature, numerous cases of prolonged cough and
breathing difficulties for several months are also
reported. Concerning skin, contact with the gas skin
causes burning sensation that usually subsides
quickly: the contamination of the clothes can
prolong the effects and, in case of prolonged
exposure, can lead to real burns. For
gastrointestinal tract, effects usually stem from the
contamination of food and beverage, and depend on
the irritation of the mucous membranes and lead to
symptoms such as nausea, vomiting, loss of
appetite, diarrhea, and abdominal pain. More
serious effects, such as acute liver disease
(hepatitis), have also been reported occasionally.
Finally, there is some however disputed -
evidence from recent studies of carcinogenic and
mutagenic effects of CS. They identify the
mechanism that underlies the toxic action of CS,
namely the formation of cyanides. The carcinogenic
© by PSP Volume 26 No. 1/2017, pages 151-155 Fresenius Environmental Bulletin
mechanism of CS is not based on the interaction of
the compound with DNA, but directly on the
apparatus of mitotic cells, causing chromosomal
The effectiveness of CS in crowd control
comes from its property as a skin and mucous
membrane irritant and extremely serious tear
maker, even at low doses. Conjunctivitis and
concomitant blepharospasm, burning and pain are
typical. These symptoms are exacerbated in hot or
humid environment. CS is commonly micronized
and mixed with an antiagglomerant or treated with
a water repellent silicone (known formulations as
CS1 and CS2, respectively): in those cases, it can
remain active for days or weeks when dusted on the
The use of tear gas in recent situations of civil
unrest shows that exposure to the weapon is
difficult to control and this weapon is seldom
incorrectly used. Severe traumatic injuries from
exploding tear gas grenades and toxic damage were
documented. In addition, the available toxicological
data are still uncertain regarding this agent’s
possibility to cause long-term pulmonary,
carcinogenic and reproductive effects. However,
published in vitro tests showed o-
chlorobenzylidenemalononitrile to be both
mutagenic and clastogenic.
The widespread use of tear gas agents
naturally raises the question of their safety.
Unfortunately, the nature of its application makes
analytical epidemiological investigation of exposed
persons difficult. In general, the authors of early
(70’s and 80’s) review articles have found out that,
if used properly, the harmful effects are transient
and of no consequence in the long run [1-3].
The question arises on the effects of tear gas
when improperly used. In our community survey,
performed in the recent years (2011-2015) in
Valsusa (Italy) [4], we had repeated accounts of
police forces firing tear gas directly into crowd
gatherings and enclosed spaces such as rooms and
People who find themselves close to
exploding tear gas grenades, may not unfrequently
sustain penetrating trauma from plastic fragments,
which is exacerbated by the presence of chemical
tear gas. Many individuals sustain blistering skin
burns from direct contact with the tear gas powder.
There have been several stories of people that
experienced more severe toxic injuries requiring
medical care and, in some cases, hospitalization.
Our survey on the Val Susa community
discovered some common symptoms, including
coughing and shortness of breath, among
respondents and their children, which persisted for
weeks after the exposure. The medical doctors
noted that patients with asthma and chronic
obstructive pulmonary disease who were exposed to
tear gas seldom showed deterioration of lung
function, some in a serious degree that required
medical treatment and hospitalization. We were
particularly impressed by the lack of information
available to the local community on the effects of
tear gas.
As reported above, many studies between
volunteers have noted that, in most cases, the
removal from exposure to the CS determines fairly
rapid recovery with cessation of all symptoms
within a short time.
Toxicology studies by inhalation [5, 6] at high
levels of exposure CS, however, have demonstrated
its ability to cause fatal chemical pneumonitis and
pulmonary edema. In situations where high levels
of exposure have occurred, those effects, as well as
heart failure, hepatocellular damage and death, have
been reported in adults. [5-8]. A child exposed to
CS in a house where police fired CS containers to
subdue a mentally disturbed adult developed severe
pneumonia requiring steroid therapy, oxygen,
antibiotics, and 29 days of hospitalization [9].
The concentration of the respiratory tract of
CS that would be lethal to 50% of healthy adults
was estimated to be of 25000-150000 mg/m3 per
minute, based on animal studies [10]. When
detonated outdoors, a CS grenade generates a cloud
of 6 to 9 m in diameter, in the center of which a
concentration of 2000-5000 mg / m3 can be
produced, with concentrations quickly decreasing
with distance [11]
If detonated in an enclosed space or in groups,
however, you could expect much higher levels of
exposure. In addition, chemical weapons are
generally been noted to be notoriously uneven in
their dispersion [12].
Oral toxicology studies [13-14] have noted the
ability of CS to cause severe gastroenteritis with
perforation. Metabolic studies indicate that CS
absorbed is metabolized to cyanide in peripheral
tissues. However, the actual possibility of exposure
to CS levels causing significant generation of
cyanide at the tissue level is controversial: to
breathe the massive quantities, necessary to
generate cyanide, serious lung injury may prevent
this occurrence. However, this argument ignores the
ingestion of chemical tear gas that can occur with
pharyngeal deposition of compounds CS, not
completely dispersed and swallowing of respiratory
© by PSP Volume 26 No. 1/2017, pages 151-155 Fresenius Environmental Bulletin
Burns due to contact and the development of
skin sensitization with allergic contact dermatitis
have been described in a series of experimental and
observational studies on animals and humans [15-
19]. This is in line with many skin burns
encountered during our investigation in Val Susa.
Symptoms of prolonged cough and shortness
of breath that were reported in our survey of the Val
Susa community: they suggest that this effect may
have occurred because of exposure to CS.
The potential damage to internal organs, as
well as gastrointestinal symptoms, was evidenced
by an accidental exposure reported in [20]. The
laryngeal and bronchial obstruction is demonstrated
for example in [21]. Some studies have associated
exposure to the CS with miscarriages, see for
instance [22].
In the study [23], it was established that the
CS chemical agent had no carcinogenic effects
mediated by DNA damage. However, the study in
[24] affirms that the carcinogenic mechanism of CS
is not based on the interaction of the compound
with DNA, but directly on the apparatus of mitotic
cells, causing chromosomal aberrations. The agent
CS can alkylate sulfhydryl groups and, possibly,
DNA [25-26]. As such, it is potentially genotoxic.
Some researchers have shown CS to be mutagenic
on salmonella cells [26] and mice [27]. The CS
agent has been found to suppress the non-specific
esterase activity in mouse skin sebaceous glands
[28-29]: this property was suggested to be used as a
screening test for the carcinogenic potential of
chemicals [29]. A study [30] showed the
carcinogenicity of CS in mice.
From the toxicological point of view, there is
a great need for more epidemiological and
laboratory research that illuminate the health
consequences of exposure to full tear gas
compounds such as CS. The possibility of health
consequences in the long term, such as the
formation of cancer, reproductive effects, and lung
disease is particularly worrying in view of the
multiple exposures suffered by demonstrators and
non-demonstrators too in some areas of civil unrest.
The development of tolerance of CS, a
phenomenon that has been confirmed in studies on
human volunteers [31] has probably increased the
length and intensity of the exposure held by some
We also believe, however, that the evidence
already assembled on the misuse of tear gas, as well
as its toxicology, arise the question whether its
further use may be tolerated under any conditions.
We recognize that it is not enough for health
professionals to study and simply refuse as
"clinically unacceptable" any mode of riot control.
As with many dangers, for example, asbestos, toxic
industrial emissions, radiation, there is an important
role for scientists: study, document, analyze and
report on these risks and to advise the government
on what is acceptable and what does not lead to an
acceptable risk.
At a time when the world has recently seen
the recurrence of the use of CS, this time in the
Middle East, it is also noteworthy that, in 1969, on
the occasion of the General Assembly of the United
Nations, 80 countries voted for prohibit the use of
any chemical warfare, including tear gas, by
applying the Protocol of Geneva.
The technical paper presented at the Public
Prosecutor's Office Court of Genoa , as informative
part and attached to the file - complaint "Syndrome
Genoa " June 15, 2002 , titled "Malononitrile - CS :
mutagenicity data" , signed by Prof. Nicola Lopresti
(University of Pisa) and other researches, shows, on
a scientific basis and based on experimental data,
that a substance like CS could be classified by the
European Commission (Dangerous Substances
Directive 675/148/CEE) in Class 3, namely:
"substances presenting positive results in the most
revealing mutagenicity assays , for which no
relevant in vivo data are available. Substances of
this type represent a danger to humans because of
their possible mutagenic effects.
Exposure to Genoa in 2001 was massive but
single. Instead, two exposure situations are
particularly dangerous as regards Valsusa:
- For operators of the police forces, CS gas
is a working tool and the contact could have
continued, long-term effects unknown today,
especially in those backside officials and agents not
wearing masks.
- For the protesters of the Susa Valley, there
is the same scenario of repeated exposure.
Exposures in the 2011-2016 five-year period have
been some tens.
Prolonged exposure could transform both the
police agents and the protesters in a group of
highly-exposed subjects to CS gas, potentially
causing unexpected effects due to repeated
Concerning legal aspects, the Italian Law is
actually not clearly treating this case. Under the bill
April 18, 1975, # 110 (Supplementary to the current
regulations for the control of small arms,
ammunition and explosives), Article 1 states that
© by PSP Volume 26 No. 1/2017, pages 151-155 Fresenius Environmental Bulletin
"For the purposes of criminal laws, the public
security and other laws or regulations on weapons
are weapons of war of every kind that , by their
strong potential for offense, are or may be intended
for the modern armament of the troops at home or
abroad for the use of war and the bombs of any type
or parts of them , aggressive chemicals, deadly
contraptions of war of any kind , bottles or
wrappers explosive or incendiary". This ranks the
CS gas as weapons of war in the third category, i.e.
"chemical weapons".
As for its use in war, the "Convention on the
Prohibition of the Development, Production,
Storage and Use of Chemical Weapons and on their
Destruction" signed at European Union level, in
Paris January 13th , 1993, and adopted in Italy in
1995 and entered into force on April 29th 1997,
prohibits the use of CS gas in any war scenario.
Unfortunately, no explicit statement about the use
of CS gas for riot control by police forces is added
to this prohibition. CS gas is part of the equipment
of the Italian police forces since 1991.
In conclusion, the claims that the CS gas is not
toxic are counterbalanced by many findings by
recent studies, showing many toxic effects,
especially in case of misuse of the gas, or in weak
and sensitive subjects. Adoption of the precaution
principle seems, in this case, recommendable. The
use of CS gas by police forces for riot control
should therefore be abandoned, substituted by other
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[13] Gaskins, JR, Hehir, RM, McCaulley, DR,
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© by PSP Volume 26 No. 1/2017, pages 151-155 Fresenius Environmental Bulletin
[22] Howard H. et al, (1989) Tear Gas: Harassing
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the American Medical Association, August 4,
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Military Actions. Somerville, Mass. USA.
Received: 29.06.2016
Accepted: 26.09.2016
Massimo Zucchetti
Dipartimento di Energia, Politecnico di Torino
Corso Duca degli Abruzzi, 24 10129 Torino, Italy
... The following reagents were used in the synthesis reaction of o-chlorobenzylidene malononitrile: o-chlorobenzaldehide (C 7 H 5 ClO, CAS Registry Number 89-98-5, MW 140 g/mol, Thermo Scientific, 97% purity), malononitrile (C 3 H 2 N 2 , CAS Registry Number 109-77-3, MW 66 g/mol, Sigma-Aldrich, 99% purity) and diethylamine (C 4 H 11 N, MW 73 g/mol, CAS Registry Number 109-89-7, Sigma-Aldrich, 99.5% purity) as a catalyst. o-Chlorobenzylidene malononitrile was synthesized in-house via a condensing reaction between o-chlorobenzaldehide and malononitrile (Figure 1), in the presence of diethylamine [33][34][35][36]. ...
Full-text available
The removal yield of organic substances present in water depends on the environmental conditions, on the chemical composition of the water and on the chemical substance dissolved in the water, which constitutes the substrate of the metabolic activities of the microalgae that use these substances in the biochemical reactions of cellular enzyme complexes. o-Chlorobenzylidene malononitrile (CS, to use its military designation) was synthesized in-house, for research purposes, by a condensing reaction between o-chlorobenzaldehide and malononitrilein the presence of diethylamine. The detection, identification and confirmation of o-chlorobenzylidenemalononitrile (coded CBM in this experimental study) was performed using gas chromatography–mass spectrometry (GC-MS) and the purity of CBM was 99%. The biodegradation capacity in the samples that contained the biological suspension, after 24 h and 96 h of incubation, was determined via GC-MS analysis, and no evidence of the presence of CBM or some metabolites of CBM was detected. In the parallel samples, a hydrolysis process of CBM at room temperature, without biological treatment, revealed two main metabolites, malononitrile and o-chlorobenzaldehyde, respectively. This study is focused on evaluating the biodegradation capacity of o-chlorobenzylidene malononitrile in the presence of a biological material, culture of Chlorella sp., in comparison with a classical hydrolysis process. The tests performed indicate that the suspension of Chlorella sp. consumed the entire amount of CBM and metabolites from the analyzed samples. The tests prove that the biological material can be used to decontaminate the affected areas.
... For determination of the concentration/effect relationship of CBM, the points indicating inhibition between 0 and 100% were taken into account [31,32]. ...
Full-text available
Toxic substances used as chemical weapons present a number of particularities that affect the surrounding environment, having a wide range of action by disrupting the ecological balance: they may infect soil or air, or form aerosols through smoke or toxic fog. Such substances can have a long duration of action, from minutes to weeks, which is why they are used in military attacks. This study evaluated the toxicological character of o-chlorobenzyliden malonitrile (CBM) in order to study the toxicity limit of this substance using microbiological cultures of Saccharomyces sp., Chlorella sp., Lactobacillus sp. and Paramecium sp., which were used to determine their rate of growth in the presence of different concentrations of o-chlorobenzyliden malonitrile and their ability to respond to this toxic stimulus.
... The immediate effects of CS Gas on humans occur at low concentrations and cause irritating action on the skin and mucous membranes. The first target organs are the eyes: intense tearing due to irritation of the mucous membrane of the eye membrane, blepharospasm, conjunctivitis, periorbital edema, burning and pain [8]. ...
Full-text available
Toxicological characterization and global assessment of the toxicity of some chemicals used in the specific technique of the defense and public order system (e.g. o-chlorobenzylidene manolonitrile which enters the composition of the CS gas) is especially useful for environmental protection. Based on the results obtained, the toxicological characterization (acute lethal toxicity) and the harmful potential of some toxic substances, individual or in mixture, against euythermal sweet fish are established. The tests performed aim to change the behavior of the species studied in the presence of chlorobenzylidene manolonitrile, a substance used in the technique of defense and public order system. The tests established the toxicity values of acute lethal concentration LC50 and serve to further determine the maximum allowable concentration that inhibits the development of normal fish fauna in contaminated waters. The test results allow the toxicological characterization and measurement of the acute lethal toxicity of an inhibitor, in order to make more efficient its elimination from the contaminated environment.
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CS tear gas has long been described as harmless. Its use has been justified as being less lethal and causing less damage than other law enforcement techniques. However, as soon as it was first introduced in civilian use, there were cases of death and serious concerns in the population, health effects were documented throughout its use. Negative effects on health, both acute and more or less in the long term, are obvious and officially well known by the military and the police. The number of studies recommending restriction, control, training or guidelines of use of these gases are numerous, and scientists studying combat gases like CS gas have always worried about their effects on health especially in weaker populations such as children, elderly, people suffering from pathologies, or people exposed to very high doses. In particular, people exposed to high doses are undoubtedly targets of choice, who will suffer more or less serious bodily and often psychological damage. CS gas triggers an irritant effect that can cause irreparable damage to skin, lungs, eyes, cardiovascular system, gastrointestinal system. Its carcinogenicity is still debated but biochemical evidence suggests that it may have a mutagenic effect. The immediate health effects of cyanide anion are well documented: irritant effects on the eyes, skin, respiratory tract, damage to the cardiovascular system and central nervous system (leading to headaches, dizziness, a great fatigue…). On a longer term, cyanide anion can worsen these attacks and also affect the endocrine system (thyroid). Currently, carcinogenicity is still under discussion, but biochemical studies suggest that it may have mutagenic or even epigenetic activity. Many cases of death have been described but have always been contested or concealed. In addition, during dispersion of tear gas and during its metabolism after absorption in the body, cyanide is released, causing symptoms described by some toxicologists and doctors as vertigo or loss of consciousness. The context of chronic exposure to low doses of cyanide in relation to repeatedly use of CS tear gas has been discussed in this paper. Such exposure is a major risk factor for brain, liver, kidneys, eyes, gastrointestinal system. General effects affecting the whole body and weakening general health of the population are expected from massive chronic exposure. Chronic elevation of thiocyanate levels in blood, as is the case in smokers, can have health consequences as well. During its distribution in the organism and then during its metabolization, two cyanide Anion Molecules (CN-) are released from a CS tear gas molecule. It seems in fact logical that two cyanide anion molecules are formed, from the malononitrile group which is in fact made up of two nitrile functions (an organic group, having a cyanic function, linked to a carbon atom, R-C≡N). Acute effects of cyanide are well described: mainly dizziness or fainting. In the case of longterm exposure to low doses of cyanide, released by metabolization from CS tear gas, due to repeated use of that chemical weapon, effects such as great fatigue are discussed in this bibliographic work. Such an Exposure, impacting essential constituents of the organism is a major risk factor for the brain, the liver, the kidneys, the eyes, the gastrointestinal system, the cardiovascular system, the thyroid ... Overall, all of these serious toxic effects, affecting living organisms, undeniably have a significant impact on populations in repeated contact with high concentrations of CS gas. A permanent increase in the level of Thiocyanate in the blood, the main biological marker of Cyanide, as is the case in smokers, can also have long-term effects on health, as characteristic of a high level of Cyanide (extreme fatigue, neurological or endocrine disorders ...). The increase in the use of these so-called "less lethal" chemical weapons, in increasingly important proportions and without specific regulation, leads to a risky exposure for equipped personnel, demonstrators, and exposed population living in the neighborhood. In addition, the much less studied environmental effects are certainly not negligible. Some states or countries are beginning to give exposure guidelines, such as New Jersey in the United States, which requires thiocyanate testing after exposure, and recommends liver and kidney check-up. In Quebec, authorities demand that work surfaces be washed, fruits and vegetables also, filters and hoods used in houses or food establishments, as well as filters for refrigeration systems in cold rooms changed, and directives concerning businesses and inhabitants of exposed districts are very strict. So why are such recommendations not applied worldwide? With the Increase in the use of CS gas during demonstrations (Figure 44), it becomes urgent that the governments making use of CS gas take binding decisions going in the direction of the protection of public health, which can only follow the direction of the recommendations of the Organization for the Prohibition of Chemical Weapons (OPCW) and certain Non Governmental Organizations (NGOs).
The aim of this study was to determine whether o-chlorobenzylidene malononitrile ( CS) exhibits any genotoxic activity towards Salmonella or mammalian DNA in vivo. CS was synthesized with a [14C]-label at the benzylic carbon atom. It was administered i. p. at a dose Ievel of 13 mg/kg (1 mCi/kg) to young adult male rats. Liverand kidney DNA was isolated after 8, 25, and 75 h. The radioactivity was at (liver, 8 and 75 h) or below (all other samples) the Iimit of detection of 3 dpm. Therefore, a possible binding of CS to DNA is at least 105 times lower than that of the strong hepatocarcinogen aflatoxin B1, and 4,000 tim es lower than that of vinyl chloride. In contrast to this Iack of DNA binding, but in agreement with the chemical reactivity of CS, a binding to nuclear proteins could be detected with specific activities ranging between 50 and 121 dpm/mg for liver and between 3 and 41 dprnlmg for kidney. Protein binding could weil be responsible for its pronounced cytotoxic effects. es was also tested in the Ames Salmonella/microsome assay. Strains TA 1535, TA 1537, TA 1538, TA 98, and TA 100 were used with or without pre-incubation. Only with strain TA 100 and only without pre-incubation, a doubling of the number of revertants was detectable at the highest dose Ievels used, 1,000 and 2,000 !lg CS per plate. With pre-incubation of TA 100 with CS, a slight increase of the number of revertants was seen at 100 and 500 !lg per plate, and a subsequent fall below control values at 1,000 A check for the number of surviving bacteria revealed a strong bacteriotoxicity of the higher doses of es so that the calculated mutation frequencies, i.e., the oumber of revertants per number of surviving bacteria, increased with doses up to 500 !J.g. This toxicity could be counteracted in part by the addition of increasing amounts of rat liver microsomes. In the view of these results, and taking into account the rare and low exposure of man, it is concluded that CS will not create a risk for the induction of point mutations or of carcinogenic processes mediated by DNA binding.
Tear gas has gained widespread acceptance as a means of controlling civilian crowds and subduing barricaded criminals. The most widely used forms of tear gas have been o-chlorobenzylidenemalononitrile and ω-chloroacetophenone. Proponents of their use claim that, if used correctly, the noxious effects of exposure are transient and of no long-term consequences. The use of tear gas in recent situations of civil unrest, however, demonstrates that exposure to the weapon is difficult to control and indiscriminate, and the weapon is often not used correctly. Severe traumatic injury from exploding tear gas bombs as well as lethal toxic injury have been documented. Moreover, available toxicological data are deficient as to the potential of tear gas agents to cause long-term pulmonary, carcinogenic, and reproductive effects. Published and recent unpublished in vitro tests have shown o-chlorobenzylidenemalononitrile to be both clastogenic and mutagenic. Sadly, the nature of its use renders analytic epidemiologic investigation of exposed persons difficult. In 1969, eighty countries voted to include tear gas agents among chemical weapons banned under the Geneva Protocol. There is an ongoing need for investigation into the full toxicological potential of tear gas chemicals and renewed debate on whether their use can be condoned under any circumstances. (JAMA. 1989;262:660-663)
In studies in rats, chloroacetophenone (CN) and o-chlorobenzylidenemalononitrile (CS) produced severe gastroenteritis, with deaths generally occuring within two days after a single dose, Laboratory and commercial preparations containing more than 4% W/V CN produced permanent corneal injury, while a laboratory preparation containing 10% W/V CS produced no corneal injury. Washing eyes with water shortly after instillation of lacrimators reduced conjunctival swelling. CN applied to rabbit skin usually produced purpura and necrotic eschar; CS occasionally produced eschar without purpura. Washing exposed skins with water or soap and water, at Intervals up to 30 minutes after exposure, provided little benefit. Dermal recovery was substantially complete at five weeks.
Eighteen chemicals were tested for their mutagenic potential in the L5178Y tk+/− mouse lymphoma cell forward mutation assay by the use of procedures based upon those described by Clive and Spector [Mutat Res 44:269–278, 1975] and Clive et al [Mutat Res 59:61–108, 1979]. Cultures were exposed to the chemicals for 4 hr, then cultured for 2 days before plating in soft agar with or without trifluorothymidine (TFT), 3 μg/ml. The chemicals were tested at least twice. Significant responses were obtained with benzofuran, benzyl chloride, bromodi-chloromethane, butylated hydroxytoluene, chlorendic acid, o-chlorobenzalmalo-nitrile, 1,2,3,4-diepoxybutane, dimethyl formamide, dimethyl hydrogen phosphite, furfural, glutaraldehyde, hydroquinone, 8-hydroxyquinoline, and resorcinol. Apart from bromodichloromethane, butylated hydroxytoluene and dimethyl hydrogen phosphite, rat liver S9 mix was not a requirement for the activity of any of these compounds. Chemicals not identified as mutagens were water, tert-butyl alcohol, pyridine, and witch hazel.
The comparative acute toxicity of two peripheral sensory irritant materials, 1-chloroacetophenone (CN) and 2-chlorobenzylidene malononitrile (CS), has been investigated in several species of small mammal using solutions in polyethylene glycol 300 for intravenous, intraperitoneal and oral administration, and as pure aerosols for inhalation exposure. Additionally, the comparative potency for inducing primary contact dermatitis was studied. CN and CS were found to be about equitoxic by intravenous and intraperitoneal injection, but CS was significantly less toxic by the oral and inhalation routes and less likely to cause non-lethal tissue damage than CN.
A case of death resulting from the indiscriminate use of the tear gas compounds CN and CS has been presented and briefly discussed.
Sebaceous gland non-specific esterase activity was suppressed following application to mouse skin of 2 electrophilic alpha beta-unsaturated compounds, o-chlorobenzylidenemalononitrile and beta-nitrostyrene, but not by three others.