A repeated dose study of the toxicity of inhaled 2-chlorobenzylidene malononitrile (CS) aerosol in three species of laboratory animal

Reevaluating tear gas toxicity and safety

Tear gases, or chemical demonstration control agents (DCA), were originally created as weapons that could severely disable or kill enemy troops. Though banned in war, these chemicals are still used in domestic policing. Here we review the available scientific literature on tear gas, summarizing findings from animal and environmental studies as well describing data from new human studies. We find a lack of scientific evidence supporting the safety of tear gas, especially regarding its long-term impacts on human health and the environment. Many of the available studies were published decades ago, and do not parse data by variables such as chemical type and exposure time, nor do they account for the diversity of individuals who are exposed to tear gas in real-life situations. Due to the dearth of scientific research and the misinterpretation of some of the available studies, we conclude that a serious reevaluation of chemical DCA safety and more comprehensive exposure follow-up studies are necessary.

Inhalation Toxicity of a Smoke Containing Solvent Yellow 33, Disperse Red 9 and Solvent Green 3 in Laboratory Animals

The repeated-dose inhalation toxicity of a smoke containing a mixture of three dyes was tested in female mice, rats and guinea pigs. The green component dye (Solvent Green 3) was retained in the lungs. Particularly in the rats marked collections of alveolar macrophages were found. In the same species several other adverse findings were noted: these included adenocarcinomas of the breast in the high-dose group and a dose-related incidence of biliary hyperplasia. Fatty change was noted in the livers of the test-group mice. A large proportion of the high-dose guinea pigs died during the exposure period, for which reason exposure was stopped early in that group, otherwise the guinea pigs were little affected. However, all test groups of all species showed reductions in growth during the exposure period.

Riot control agents: pharmacology, toxicology, biochemistry and chemistry

The desired effect of all riot control agents is the temporary disablement of individuals by way of intense irritation of the mucous membranes and skin. Generally, riot control agents can produce acute site-specific toxicity where sensory irritation occurs. Early riot control agents, namely, chloroacetophenone (CN) and chlorodihydrophenarsazine (DM), have been replaced with 'safer' agents such as o-chlorobenzylidene malononitrile (CS) and oleoresin of capsicum (OC). Riot control agents are safe when used as intended: however, the widespread use of riot control agents raises questions and concerns regarding their health effects and safety. A large margin exists between dosages that produce harassment and dosages likely to cause adverse health effects for modern riot control agents such as CS and dibenz[b,f]1 : 4-oxazepine (CR). Yet, despite the low toxicity of modern riot control agents, these compounds are not entirely without risk. The risk of toxicity increases with higher exposure levels and prolonged exposure durations. Ocular, pulmonary and dermal injury may occur on exposure to high levels of these substances, and exposure to riot control agents in enclosed spaces may produce significant toxic effects. Reported deaths are few involving riot control agents, and then only under conditions of prolonged exposure and high concentrations. Recently, concern has focused on the deaths resulting from law enforcement use of OC, a riot control agent generally regarded as safe because it is a natural product. As with other xenobiotics, not enough is known concerning the long-term/chronic effects of riot control agents. Clearly, there is considerable need for additional research to define and delineate the biological and toxicological actions of riot control agents and to illuminate the full health consequences of these compounds as riot control agents.

Comparative acute toxicity of o-chlorobenzylidene malononitrile (CS) and oleoresin capsicum (OC) in awake rats

Tear gases are largely used to control civil unrest. Their incapaciting effects involve eyes, skin and respiratory tract. This study was performed to compare acute respiratory effects of o-chlorobenzylidene malononitrile (CS), oleoresin capsicum (OC) and their respective solvents in awake rats, using an integrated system of nose-only exposure and multiple monitoring of breathing. Aerosols were generated by a Collison Nebulizer from the solutions held in tear gas sprays. The reduction of minute ventilation, observed during a 5 min exposure, was significantly more important with CS than with OC: minute ventilation represented 29+/-8 and 50+/-6% of pre-exposure minute ventilation respectively (P<0.05). The reduction of minute ventilation observed with CS and OC solvents alone was not significantly different from that observed with the tear gases themselves. The decrease in minute ventilation observed, between the second and the fifth minute of exposure, was of the same level for repeated exposure separated by 24 h. Time necessary to recover to 80% of pre-exposure minute ventilation was not significantly different between the two tear gases: 722+/-272 and 691+/-262 s for CS and OC respectively (NS). Histological analysis of the trachea, performed at the end of exposures, revealed an increase in mucus secretion after exposure to OC and cytoplasmic vacuoles in epithelial cells after exposure to CS. In the lungs, interstitial oedema was observed after exposure to OC and emphysema after exposure to CS.

Mutagenicity evaluation of riot control agent o-chlorobenzylidene malononitrile (CS) in the Ames Salmonella/microsome test

o-Chlorobenzylidene malononitrile (CS), a riot control agent, was evaluated for its possible mutagenic activity in the Ames Salmonella/mammalian microsome mutagenicity test. Five histidine-deficient (His-) mutant tester strains of Salmonella typhimurium--TA97a, TA98, TA100, TA102 and TA104--were used. The liquid preincubation procedure was used with metabolic activation (presence of S9 mixture) and without metabolic activation (absence of S9 mixture). For the experiments with metabolic activation, three different concentrations of S9 fraction (supernatant of Aroclor 1254-induced rat liver homogenate at 9000 g)--5%, 15% and 30% in S9 mixture--were used. Along with mutagenic activity, CS was also evaluated for cytotoxic activity in all the five tester strains of Salmonella typhimurium, both in the presence and absence of S9 mixture. The mutagenic and cytotoxic activities of CS were assessed by counting the His+ revertant colonies and by counting the microcolonies (His-, auxotrophs in the background lawn), respectively, and the respective mean values were compared with the relative negative (solvent) control. A dose range of 12.5-800 micrograms plate-1 for CS did not induce a mutagenic response either in the presence or absence of S9 mix. No change in the negative mutagenic response of CS has been observed even in the presence of an elevated level of S9 fraction in the S9 mix. A dose of 200 micrograms plate-1 for CS was found to be cytotoxic by decreasing the surviving cells as well as His+ revertant colonies; however, the effect was reduced in the presence of an elevated level of S9 fraction in the S9 mix.

2-Chlorobenzylidene malonitrile (CS) causes spindle disturbances in V79 Chinese hamster cells

Exposure of V79 Chinese hamster cells to 2-chlorobenzylidene malonitrile (CS), a chemical used as a sensory irritant for riot control, caused a concentration-dependent increase in the incidence of spindle disturbances. A C-mitotic effect with the appearance of C-metaphases, a metaphase block and the concomitant disappearance of ana-telophase figures were observed after a 3-h treatment. The results indicate that CS might induce aneuploidy in mammalian cells by interacting with the mitotic apparatus.

The repeated dose toxicity of a zinc oxide/hexachloroethane smoke

Mice, rats and guinea pigs were exposed to the smoke produced by ignition of a zinc oxide/hexachloroethane pyrotechnic composition, 1 h/day, 5 days/week, at three different dose levels, together with controls. The animals received 100 exposures except for the high dose guinea pigs, which underwent 15 exposures, because of high death rate during the first few days of exposure. The test material had very little effect on weight gain, but there was a high rate of early deaths in the top dose of mice. A variety of incidental findings was seen in both decedents and survivors, but organ specific toxicity was, with one exception, confined to the respiratory tract. The most important of these findings was a statistically significant increase in the frequency of alveologenic carcinoma in the high dose group mice (p less than 0.01) and a statistically significant trend in the prevalence of the same tumour over all dose groups and the controls. A variety of inflammatory changes was seen in the lungs of all species and some appeared to be treatment-related. Fatty change in the mouse liver was more common in the middle and high dose groups than the controls. The aetiology of the tumour incidence is discussed and it is pointed out that hexachloroethane and zinc, as well as carbon tetrachloride, which may be present in the smoke, may be animal carcinogens in appropriate circumstances. Carbon tetrachloride is a known human carcinogen.

Late inhalation toxicology and pathology produced by exposure to a single dose of 2-chlorobenzylidene malononitrile (CS) in rats and hamsters

Hamsters and rats exposed to single doses of CS were retained for up to 32 months, together with appropriate controls. Survival was unaffected and in no case was the incidence of histological changes significantly higher in the test animals than corresponding control animals. The overall incidence of neoplastic disease was similar in test and control animals. A high incidence of pituitary acidophil adenomas was detected in the female rats: these tumours were present both in control and test rats and it was concluded that they were probably the result of ad libitum feeding.

It was concluded that single doses of CS of 28 800 mg min m−3 administered during 1 hour or 18 000 mg min m−3 administered over 2 hours produced no long-term adverse effects in the two species studied.

2-Chlorobenzylmercapturic acid, a metabolite of the riot control agent 2-chlorobenzylidene malononitrile (CS) in the rat

Adult male Wistar rats administered i.p. with 2-chlorobenzylidene malononitrile (CS) excreted one mercapturic acid in urine. The amount of mercapturic acid determined gaschromatographically was about 4% of the dose (0.07 mmol/kg, n = 12). The structure of the mercapturic acid methylester was identified by t.l.c. and confirmed by synthesis and mass-spectrography. The acid appeared to be 2-chlorobenzylmercapturic acid [N-acetyl-S-(2-chlorobenzyl)-L-cysteine]. CS and some of its metabolites were also tested in the Ames Salmonella/microsome assay. Both mutagenic and toxic effects were measured with strain TA 100 as the indicator organism. No mutagenic effects were found with any of the tested substances. At dosages of CS, higher than 1,000 micrograms/plate a bacteriotoxicity was revealed.

Genotoxicity study of CS (ortho-chlorobenzylidenemalononitrile) in Salmonella, Drosophila, and mice. Failure to detect mutagenic effects

The lacrimatory agent CS was examined for genotoxic properties. In vitro, Salmonella typhimurium was exposed to CS at concentrations up to 1.5 mg per plate and reverse mutations were assayed. In vivo: male Drosophilae were fed with CS and sex-linked recessive lethal mutations in sperm cells were assayed using the Basc test. Further, mice were exposed to CS by oral or intraperitoneal administration; bone marrow erythrocytes were analysed for chromosomal mutations by means of the micronucleus test. All experiments failed to show a mutagenic activity of CS.