the threat of chemical weapons
DESCRIPTION
The Threat of Chemical Weapons. Tokyo 1995 - Aum Shinrikyo. 27 June 1994 – Aum Shinrikyo sect released sarin in the central Japanese city of Matsumoto in response to a court case. Killed 7 and harmed 200. Role of Aum Shinrikyo not recognised at the time. - PowerPoint PPT PresentationTRANSCRIPT
The Threat ofChemical Weapons
Tokyo 1995 - Aum Shinrikyo
• 27 June 1994 – Aum Shinrikyo sect released sarin in the central Japanese city of Matsumoto in response to a court case. Killed 7 and harmed 200. Role of Aum Shinrikyo not recognised at the time.
• 20 March 1995 - Aum members released sarin in a co-ordinated attack on five trains in the Tokyo subway system, killing 12 commuters, seriously injuring 54, and affecting 980 more. More than 5000 presented themselves to hospital during the day.
• 5 May 1995 - burning paper bag discovered in a toilet in Shinjuku station in Tokyo, the busiest station in the world. Revealed to be a hydrogen cyanide device “which, had it not been extinguished in time, would have released enough gas into the ventilation system to kill 20,000 commuters”.
Sarin in Tokyo
• ~ 1L Sarin placed in plastic bags on floor of trains. Punctured with sharpened umbrella tips before Aum people walked off train.
• However, volatility of sarin is low and very little was aerosolised.
Shoko Asahara
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Sarin in Tokyo
• ~ 1L Sarin placed in plastic bags on floor of trains. Punctured with sharpened umbrella tips before Aum people walked off train.
• However, volatility of sarin is low and very little was aerosolised.
• Only 4 deaths with 4 of the attacks despite hundreds of people being exposed. 2 of the deaths occurred in cleaners removing bags.
• In 5th attack, a passenger identified the cause of the noxious substance and kicked it out of the door onto a crowded platform. ? aerosolised or contacted skin; 4 people died on platform.
Shoko Asahara
Chemical weapon attacks on civilians
• In 1995, the world was poorly prepared for chemical weapon attacks on civilian populations. This was despite the 1988 attack on the Iraqi kurdish village of Halabja which killed ~5,000 of the town’s 50,000 civilian population.
• The trains in Tokyo were attacked over about 30 mins. Some of the contaminated trains kept running for hours, further affecting commuters.
• It took hours for the fact that it was a chemical attack to be recognised and then even longer to recognise the causative agent.
• Hopefully, we are much better prepared in the UK today . . .
Edinburgh - one lovely summer’s night
• 03.00 in A&E. Late shift has just gone home. Pretty quiet.
• Red phone goes off. Incident in a disco in town – small explosion, some smoke. Scores of people down quickly. Maybe 60, 70 people.
• Paramedics have arrived on scene but people are already heading to hospital in private vehicles. They should be with you soon.
• Hmmmmmm……
• Do we know what to do, or what chemical it might be, if this has been a chemical attack?
The first car arrives outside …
• Three people apparently unconscious. One very agitated sweaty driver. Other cars approaching.
• Should the injured come into A&E or be treated outside . . . . . ?
• You start running through in your head all that you know about chemical weapons ……
Current major CW threat agents
Blistering Agents (vesicants)• Sulphur mustard*• Nitrogen mustard
• Lewisite (also Mustard/Lewisite Mixture)
Nerve Agents• G agents : GB (sarin)*, GD (soman)*, GF • V agents : VX*, R-33 (Russian V agent)
• GA (tabun)* (developing nations)
Lethal Industrial Gases• Phosgene
• Hydrogen Cyanide ?*
Riot control chemicals (CS) New agents
Globally, sulphur mustard and GB are the greatest threat
LCt50 (est) LD50 percutaneously mg.min m-3 (mg per 70 kg man)
VX 10-30 * 5-10GD 50-70 350 GB 100 1700GA 135-400 1000Lewisite 1 1200-1500 ~3500Sulphur mustard 1500 (>~100**) 4500 (>~0.1**) Phosgene 3000 N/AHCN 5000 N/A
The toxic hazard will be dependent on the volatility (for inhalation) and persistency (for skin) of the agent
(* when aerosolised) (** effective doses)
Toxicities by inhalation and skin contact
Dissemination
• As shown in Tokyo, the full effectiveness of chemical weapons can only be realized if they are dispersed so that they are delivered to individual people
• One can achieve this by breaking the bulk agent into vapour [for inhalation], tiny particles/aerosols or liquid droplets [skin & mucosal contact], or in rare cases powder [inhalation]
• One good method for dispersing chemical weapons is through combining them with explosives. Therefore, chemical injuries are likely to be combined with injuries from explosives.
• Adding a thickener to liquids increases persistence, adhesiveness and difficulty of decontamination
Volatility of CW agents
B.Pt. (oC) Volatility at 25oC (mg per m3)
Phosgene 8 >1,000,000 (Non-Persistent)
Water 100 ~150,000
GB (sarin) 158 22,000
Lewisite 196 3900
GD (soman) 198 3900
Sulphur mustard 217 910 (Intermediate)
GF 239 680
GA 247 490
Nitrogen mustard 257 110
VX 300 9 (Persistent)
Approach to diagnosis
• Could this be cyanide?
Rapid onset of symptoms after inhalational exposureCirculatory collapse, seizures, respiratory arrest
Normal secretions, pupils. No fasciculation** High lactate >10 mmol/L **
Hydrogen cyanide – chemical asphyxiant
• Colorless, highly flammable gas or highly volatile bluish-white liquid. Odor of almonds but some cannot smell it. Gas lighter than air, so disperses quickly.
• Inhibits cytochrome oxidase.
• High [-CN] = immediate tachypnoea, gasping, then seizures, cardiovascular collapse. More moderate [-CN] = dizziness, headache, agitation, confusion. Coma, seizures if prolonged.
• Rapid decontamination of liquid CN essential.
• High flow oxygen, supportive care; measure blood lactate.
• Specific antidote: dicobalt edetate or Na nitrite + thiosulphate. Not required if the patient is breathing normally and fully conscious five minutes after removal from source. Cyanide unlikely if lactate normal.
Approach to diagnosis
• Could this be cyanide?
• Could this be an organophosphorus nerve agent?
Rapid onset of symptoms after inhalational exposureCollapse, seizures, respiratory difficulty & arrest
Excessive secretions & sweat, miosis. Maybe fasciculations.
But slower onset after skin exposure (eg VX)Localised fasciculations at site of skin exposure
Organophosphorus nerve agents
• Colorless to brown fluids at room temp. Some have fruity odour. Variable volatility –> spray and aerosol. Vapours heavier than air.
• Highly toxic; inhibit acetylcholinesterase. Single drop on skin can kill.
• Cause cholinergic syndrome – respiratory failure (loss of central drive, NMJ dysfunction, direct lung effects), cardiovascular shock, seizures. Sweat, secretions, miosis, fasciculations. Poor vision.
• Rapid decontamination of liquid nerve agent essential. High flow oxygen, suction, airway support/intubation.
• Urgent use of specific antidotes: atropine (antimuscarinic), pralidoxime (AChE reactivator), diazepam.
• **Beware nosocomial contamination**
Antidotes for OP nerve agents
• Atropine 1-3 mg bolus, repeated every 5-10 min (possibly in doubling doses) to improve cardio-respiratory function
• Pralidoxime 30 mg/kg over 30 min, then infusion of 8 mg/kg/min [Adult = 2g loading dose, then 0.5 g/hr]
• Diazepam 10 mg bolus for agitation
• It is essential that pralidoxime is given early, before ‘ageing’ has occurred. Combipen allows pre-hospital antidote administration.
Approach to diagnosis
• Could this be cyanide?• Could this be an organophosphorus nerve agent?
• Could this be Lewisite?
Rapid onset of burns and blistering within minutes of exposureBlepharospasm, tearing eyesCough, burning throat pain
Lewisite – vesicant/irritant
• Arsenical compound - chlorovinyl dichloroarsine
• Colorless and odorless. However, impurities are yellow or brown liquid with a distinctive odor (~geraniums). Heavier than air.
• Affects skin, eyes, respiratory system (+/- systemic arsenical effects)
• Rapid absorption through clothes and skin, and after inhalation
• Immediate clinical effects. Severity increases with dose, exposure time, hot humid conditions. Liquid worse than gas.
• Rapid decontamination essential. Specific antidote: BAL dimercaprol
Approach to diagnosis
• Could this be cyanide?• Could this be an organophosphorus nerve agent?• Could this be Lewisite?
• Could this be mustard?
Burns and blistering, tearing eyes, cough and throat pain usually begin 2-12 hrs after exposure
Sulphur mustard – vesicant
• Sulphur compound - 1,5-dichloro-3-thiapentane. First used 1917
• Colorless and odorless. However, impurities are yellow/brown liquid with a distinctive odor (~mustard/horseradish). Heavier than air.
• Affects skin, eyes, respiratory system, (bone marrow)
• Rapid absorption through clothes and skin, and after inhalation
• Although tissue damage starts immediately, clinical effects are usually delayed. Latent period 1-24 hrs; then evolve over hrs/days. Severity increases with dose, exposure time, hot humid conditions.
• Rapid decontamination essential. No antidote. Mortality 3-4% - aim is to incapacitate
Clinical effects of sulphur mustard
Approach to diagnosis
• Could this be cyanide?• Could this be an organophosphorus nerve agent?• Could this be Lewisite?• Could this be mustard?
• Could this be phosgene?
Immediate onset of eye and skin irritationRapid or delayed respiratory symptoms (dyspnoea, laryngospasm)Nausea, chest pain, hypotension
Phosgene – lung irritant
• Colorless gas or white cloud at room temp. First used WWI 1915. May smell of musty hay/mown grass. Difficult to detect.
• Heavier than air. Degrades slowly.
• Not highly water soluble so reaches alveoli. Reacts with tissue water to produce hydrochloric acid
• Immediate irritant effect – watering eyes, blepharospasm, N&V, wheeze, chest pain, haemolysis. Rarely early death.
• After 2-72 hr latent period, patients develop pulm’ oedema, shock, ARDS. Can be precipitated by exercise. Outcome not predicted by dose/initial SxSx
• Rx - High flow oxygen, bronchodilators, supportive care. Decontaminate.No specific antidote
Approach to diagnosis (HPA)
• Could this be cyanide?• Could this be an organophosphorus nerve agent?• Could this be Lewisite?• Could this be mustard?• Could this be phosgene?
• Could this be chlorine or another irritant gas?
Immediate onset of eye and skin irritationRapid onset of choking, coughing, wheeze
Chlorine – lung irritant
• Green-yellow gas or clear amber fluid. First used WWI 1915. Smells of bleach/swimming pools. Highly reactive, explosive. Easily detected.
• Heavier than air. Degrades slowly.
• Highly water soluble - most effects in upper airway. Alveolar effects less common. With tissue water, produces hydrochloric & hypochlorous acids
• Immediate upper airway irritant effect – coughing, choking, wheeze, dyspnoea, N&V. With large exposures, acidosis. Chemical pneumonitis, pulmonary oedema, ARDS may be delayed.
• Stinging eyes, blepharospasm, erythema. Frostbite after contact with compressed liquid gas.
• Rx - High flow oxygen, bronchodilators, supportive care. Decontaminate.No specific antidote
Organophosphorus pesticides as weapons
• Important but little discussed. Freely available and cheap to buy
• Toxic - 3500 mg of methyl parathion might kill a 70 kg adult by dermal exposure, cf 1700 mg for sarin.
Very low volatility: chlorpyrifos 3 mPa Low risk of nosocomial contamination or explosive dispersionSmelly but this is likely due to solvents coformulantsSolvents much more volatile: toluene 3 kPa (6 log difference)
• Likely weapon use would be via contaminated water or food, as occurs throughout south Asia on a regular basis.
• Contaminated flour in bread - hundreds of patients with no links appearing at multiple hospitals
Threat of chemical weapons
• ?Not likely but, if a chemical weapon is used, things will move fast. You and the department will need to be up to speed.
• The scenario was very loosely based on a CS explosion that occurred in a UK disco, bringing many people to A&E
• Immediate chemical problems are cyanide and the nerve agents. Patients will die within minutes. Patients who make it to hospital are likely to be survivors or the worried well.
• Mustard and Lewisite will kill few people but cause major chaos and overload medical facilities
• Chlorine [and phosgene] are unlikely to kill many people but they will again cause chaos.