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Professor Fraunfelder’s editorial (1) contains several misconceptions
and these basically derive from its title “Is CS gas dangerous?” CS is a
solid at room temperatures and thus cannot be described as a “gas”. When
used for riot control purposes, it is dispersed as a microparticulate
cloud produced by a pyrotechnic device. CS has a very low aqueous
solubility and is in fact hydrolysed to inactive products. Thus in order
to deploy CS as a spray, a non-aqueous solvent needs to be used – methyl
isobutyl ketone {MIBK} in the case of the British police sprays. MIBK is
an industrial degreasing agent, which will remove lipid from the skin
causing reddening, scaling, blistering and peeling as well as irritation
of the eyes and respiratory tract. In the chemical industry the use of
skin and eye protection is advised when handling MIBK (2) yet,
paradoxically, the British police are trained to spray this chemical
directly into a person’s face. Their delivery device is not an aerosol
akin to that dispensing hair lacquer but really should be described as a
“squirt can” from which a stream of liquid is released similar to
windscreen de-icer.
The physico-chemical properties of CS are of importance when
considering the management of contaminated subjects. They should be
advised to stay in the open air, ideally with their face into the wind and
any contaminated clothing should be removed. With regard to treating
ocular exposure, irrigation with removal of any solid fragments, is to be
recommended because CS is hydrolysed to inactive products and “blow
drying” will not cause any CS to evaporate and may contaminate the medical
facility through blowing residual CS away from clothing.
Whilst there is much research which conforms the safety of CS when
used at low concentrations [1 part per 100,000,000] as a microparticulate
cloud for riot control purposes [3], experimental studies have
demonstrated ocular damage following the application of high
concentrations of CS to the eye, especially when applied in solution. [4].
There are also case reports of significant ophthalmological sequelae [5]
and I have personally seen many cases, which are still sub judice of
damage following the use of CS incapacitant both in subjects and in police
constables, which has health and safety at work implications
The key issue with regard to the safety of CS, is not CS toxicity per
se but that of its formulation.
Yours sincerely,
Peter J Gray MA FRCS FRCOphth DMCC
Ophthalmologist
SOUTH PETHERTON, Somerset, TA 13 5 BD
[I have no competing interests]
1/. Fraunfelder FT. Is CS gas dangerous? BMJ 2000; 320:458-9
2/. Methyl isobutyl ketone Health & Safety Guide, World Health
Organization, Geneva, 1991
3/. Report of the enquiry into the Medical and Toxicological aspects
of CS, part II, Command Paper 4775, Her Majesty’s Stationary Office,
London, 1971
4/. Ballantyne B, Gazzard MF, Swanston DW, & Williams P. The
Ophthalmic Toxicology of o-Chlorobenzylidene Malononitrile (CS). Archives
of Toxicology 1974; 32: 149-168
5/. Petersen KK, Schroder HM & Eiskjaer SP. CS-taregasspray som
skadevoldende middel. Ugeskrift for Laeger 1989; 151: 1388-1389
CS gas is not CS spray - formulation is important
Sir
Professor Fraunfelder’s editorial (1) contains several misconceptions
and these basically derive from its title “Is CS gas dangerous?” CS is a
solid at room temperatures and thus cannot be described as a “gas”. When
used for riot control purposes, it is dispersed as a microparticulate
cloud produced by a pyrotechnic device. CS has a very low aqueous
solubility and is in fact hydrolysed to inactive products. Thus in order
to deploy CS as a spray, a non-aqueous solvent needs to be used – methyl
isobutyl ketone {MIBK} in the case of the British police sprays. MIBK is
an industrial degreasing agent, which will remove lipid from the skin
causing reddening, scaling, blistering and peeling as well as irritation
of the eyes and respiratory tract. In the chemical industry the use of
skin and eye protection is advised when handling MIBK (2) yet,
paradoxically, the British police are trained to spray this chemical
directly into a person’s face. Their delivery device is not an aerosol
akin to that dispensing hair lacquer but really should be described as a
“squirt can” from which a stream of liquid is released similar to
windscreen de-icer.
The physico-chemical properties of CS are of importance when
considering the management of contaminated subjects. They should be
advised to stay in the open air, ideally with their face into the wind and
any contaminated clothing should be removed. With regard to treating
ocular exposure, irrigation with removal of any solid fragments, is to be
recommended because CS is hydrolysed to inactive products and “blow
drying” will not cause any CS to evaporate and may contaminate the medical
facility through blowing residual CS away from clothing.
Whilst there is much research which conforms the safety of CS when
used at low concentrations [1 part per 100,000,000] as a microparticulate
cloud for riot control purposes [3], experimental studies have
demonstrated ocular damage following the application of high
concentrations of CS to the eye, especially when applied in solution. [4].
There are also case reports of significant ophthalmological sequelae [5]
and I have personally seen many cases, which are still sub judice of
damage following the use of CS incapacitant both in subjects and in police
constables, which has health and safety at work implications
The key issue with regard to the safety of CS, is not CS toxicity per
se but that of its formulation.
Yours sincerely,
Peter J Gray MA FRCS FRCOphth DMCC
Ophthalmologist
SOUTH PETHERTON, Somerset, TA 13 5 BD
[I have no competing interests]
1/. Fraunfelder FT. Is CS gas dangerous? BMJ 2000; 320:458-9
2/. Methyl isobutyl ketone Health & Safety Guide, World Health
Organization, Geneva, 1991
3/. Report of the enquiry into the Medical and Toxicological aspects
of CS, part II, Command Paper 4775, Her Majesty’s Stationary Office,
London, 1971
4/. Ballantyne B, Gazzard MF, Swanston DW, & Williams P. The
Ophthalmic Toxicology of o-Chlorobenzylidene Malononitrile (CS). Archives
of Toxicology 1974; 32: 149-168
5/. Petersen KK, Schroder HM & Eiskjaer SP. CS-taregasspray som
skadevoldende middel. Ugeskrift for Laeger 1989; 151: 1388-1389
Competing interests: No competing interests