Disinfectant Spraying Aboard Aircraft

The requirement to spray the passenger cabin (and luggage hold) of certain aircraft is laid down by the International Health Regulations (IHR) and overseen by the World Health Organisation (WHO). Each national Government is responsible for implementing the regulations.

The purpose of the IHR is to ‘ensure the maximum security against the international spread of diseases’. Part of these security measures is the hygiene and disinfection of aircraft, and the WHO publishes a ‘Guide to Hygiene and Sanitation in Aviation’ which describes the procedures that should be followed to ensure compliance with the relevant parts if the IHR. Since responsibility for the enforcement of the regulations lies with national governments, and there is, as usual, some room for flexibility in interpreting the rules, it follows that each national government may insist on slightly different procedures and degrees of rigour. These differences may be exaggerated at times when specific risks are seen to be present, since different governments might take a different view about how seriously to take the risk.

Disinfection of aircraft falls into several categories:

Firstly, when a passenger suffering from a serious infectious disease has been carried, there is a requirement to disinfect the aircraft. This is usually done by filling the interior of the aircraft with a bactericidal / viracidal gas for a few hours (after the passengers have left!) and then allowing this to disperse before the aircraft is used again. Ethylene oxide is commonly used for this purpose, used with carbon dioxide as a ‘carrier’. However, it is accepted that, in most cases, it will not be known that a passenger was infected with a serious illness until a few days later, when this sort of disinfection is unlikely to be useful or practicable.

Secondly, a bactericidal / viracidal agent should be used for the routine daily cleaning of aircraft in service, and should be added to the chemicals used in the on-board toilets. The agents commonly used for this routine cleaning are sodium hypochlorite solution (‘Milton’), or a solution of formaldehyde. Generally, a more thorough spray- or gas-based disinfection (as above) will be carried out at each regular servicing of the aircraft. This would include the use of insecticides as well as bactericidal / viracidal chemicals.

Thirdly, IHR regulations do not only cover the spread of infection from person to person, but also the spread of disease by insects or animals (e.g. mosquitoes, cockroaches). Therefore, in certain circumstances, there is a requirement to spray aircraft passenger cabins with insecticide. This will usually be done on routes to and from specific destinations, although this can change if a national government perceives a special risk at a particular time. Since insects can be carried on clothing and luggage, this insecticide treatment must be carried out when the passengers and their belongings are ‘sealed’ in the aircraft.

Lists of destinations / routes where spraying can be expected are available on most airline websites but are subject to change by local governments and port authorities if they perceive a particular risk.

Some airlines instruct their staff to make an announcement ‘shortly before’ spraying (the timescale is not defined); the policy of other airlines is not to make a formal announcement, but to ‘respond to passenger queries’. I imagine that the lack of announcement (or lack of time to respond to it) is designed to avoid passenger objections - by the time you realise what’s happening, it’s too late. Since no individual passenger would be permitted to avoid being sprayed, and failure to spray could result in the aircraft being refused permission to land, this would appear to be a considerable obstacle.

The most common insecticide used for aircraft cabin spraying (in the presence of passengers) is d-phenothrin, a synthetic pyrethroid.

Pyrethrum is a natural insecticide originally derived from the chrysanthemum plant; man-made synthetic chemicals of a similar structure have been developed over the years, and are widely used as household and garden insecticides as well as commercially. Pyrethroids are not organophosphates or organochlorines, and are generally regarded as ‘safer’ insecticides; hence their household use. Unlike the other groups of insecticides, they are not considered to have a cumulative or delayed effect because they are metabolised and excreted by the body. They break down quickly in the environment, and do not spread about much (in soil, for example). However, they are neurotoxins - it is their poisonous effect on insect and mammal nerves that makes them work. Symptoms of overdosage include tremor, nausea, excessive salivation, excitability and paralysis. They are also known to cause skin irritation / burning, possibly with rashes or urticarial wheals (nettlerash), sneezing, watery eyes and wheeze (bronchospasm).

These chemicals are not particularly water-soluble and are therefore usually ‘carried’ in an alcohol-based solvent such as paraffin, designed to evaporate off quickly so that surfaces are not left damp (the pesticide residue is left behind).

An aerosol delivery system will also require a propellant - usually a hydrofluorocarbon compound (used in refrigeration and air-conditioners).

As is often the case, if your chemical detoxification pathways are working well, and you are not specifically sensitive to these chemicals, and are otherwise generally healthy, you probably won’t notice any particular adverse effects from being sprayed. Any symptoms you do get would be mild and transitory - settling down without any treatment. However if you are specifically sensitive to these chemicals you might expect the symptoms to be more severe, and perhaps require some treatment (maybe an antihistamine for the skin symptoms, possibly a puff of your inhaler for the wheeze). If you suffer from multiple chemical sensitivity, with impaired detoxification and increased sensitivity, then you will undoubtedly be more severely affected, with more persistent symptoms.

Air travel is always going to be difficult for the chemically-sensitive person. The chemicals outgassing from the fittings and furnishings of the passenger cabin are considerable, and must be added to those given off by the passengers themselves (including perfumes etc) and the smell of aviation fuel. The chemicals used in cleaning will often also contain degreasers and fragrance, as well as the actual disinfecting agent. The insecticides used, although reckoned to be the ‘safest’ available, are designed to be persistent. If you fly to an area where insecticide spraying is required, you will not be able to avoid it. Even if you avoid flying on routes where spraying is not known to be done, you may be caught out if local rules are implemented at particular times, and the aircraft you are flying in may well have been sprayed recently, either in-flight or at a scheduled service.

Tips to reduce exposure might include:

• Choose a ‘non-spray’ route with an airline that does not fly long-haul to ‘spray’ destinations - their aircraft are less likely to have residual chemical load.
  
• Take a mask and be prepared to use it quickly
  
• If you have arranged to use oxygen on the flight, make sure you use it during spraying and for a while afterwards.
  
• Wear long-sleeved clothing to reduce the area of skin available to absorb spray chemicals.
  
• As always, use a multivitamin / mineral supplement to improve detoxification / chelation of chemicals.
  
• Don’t wear contact lenses on the flight.
  
• Keep a set of clothing for ‘flying only’ and change after the flight (clothing will retain insecticides).
  
• If your flight back to the UK from a long-haul destination will be ‘sprayed’ (due to UK regulations), you might find a flight to another European destination will not (if they interpret the rules differently). You can then get a short-haul flight from Europe to the UK.

Further information:

British Airways http://www.britishairways.com/travel/healthdisinsect/public/en_us

World Health Organisation http://www.who.int/csr/ihr/en/

Pyrethroids http://www.inchem.org/documents/ehc/ehc/ehc96.htm

Author: John Collard, Clinical Director, Allergy UK- October 2005