Australian Clinical Guidelines for Radiological Emergencies - September 2012

External Contamination

Page last updated: 07 December 2012

External radiation does not cause external contamination - the rays/particles either pass straight through the body or are absorbed and deposit their energy. Contamination can only occur if particulate radioactive materials come into contact with clothing, skin, or body tissues. The most likely way for this to occur is if dust or bomb debris becomes contaminated and is deposited onto persons nearby.

The amount of contamination by radioactive material on a person’s body indicates the amount of ongoing exposure to radiation. Heavy contamination suggests a high total dose of radiation is likely to be absorbed.

    Surface contamination by material on clothes, hair or skin can be measured using external detectors, although these may not detect all kinds of radiation emitted by a radioactive substance.

    The principle of radiological decontamination is to remove particles from the person without dispersing them into the atmosphere or onto previously clean surfaces. This is a lot more difficult than it sounds, and staff will have to practise regularly if they are to have any chance of success. An indicator substance, such as a dye or coloured powder, can be used in training to show staff just how easy it is to transfer contamination from one surface to another.

    The following sections give guidance on decontamination equipment and procedures. Each hospital should develop their own protocols in consultation with local health authorities and emergency services.

    Requirements

    Whether on-site or offsite, for mass decontamination or individual, the general requirements for decontamination are the same:
    • Detection and monitoring equipment
    • Protection for equipment, staff and site
    • Replacement clothing for patient
    • Waste containment
    Detection equipment is used to assess the level and location of contamination, which may be localised to small, circumscribed areas. At the very minimum, it will include a Geiger-Müller counter (for beta and gamma radiation) and an alpha probe (for alpha radiation). It is advisable to have disposable covers for the detection probes, especially the alpha probe, to prevent contamination and loss of function.

    Monitoring is done via personal dosimeters (for all decontamination staff), and, if available, an area detector.

    Protective equipment aims to prevent the spread of contamination around the decontamination site and to staff and surfaces. In a hospital setting, it is preferable to carry out decontamination outside the building to minimise the risk of contaminating the interior. For decontamination of non-ambulatory patients, which may have to be carried out in the ER or triage area, protection may be provided by applying temporary coverings to floors, benches doors and essential equipment.

    All decontamination staff will require protective clothing: hats, masks, gowns, boots, aprons and gloves. Eye protection is advisable. A second pair of gloves allows for rapid change between patients or replacement if contamination occurs.

    Replacement clothing of some sort will be required for patients following decontamination. Depending on the ambient temperatures and cultural factors, this may be anything from a simple disposable shift to a full-length coverall and blankets.

    Waste containment is essential to prevent the spread of contaminated particles. All contaminated clothing, dressings and protective garments must be bagged and tagged. Any water used for washing or for cleansing wounds must be collected. Water collected from a mass decontamination site should, ideally, be contained in a holding tank; however, it is unlikely that the amount of radiation in the water will constitute a significant hazard to the sewer system, particularly in comparison with the effect of rain or fire-fighting liquids at the incident site.

    Procedures

    At assessment, patients are deemed to be contaminated or clean. Clean patients do not require decontamination. Given the length time and manpower that assessment takes (especially for alpha particles), it may be deemed expedient in a mass casualty incident to assume that all patients with dust or shrapnel are contaminated, and defer individual assessment to the post-decontamination line.

    Patients should be divided into ambulatory and non-ambulatory decontamination lines. Ambulatory patients can go through mass decontamination units (dedicated or improvised), while non-ambulatory patients will have to be decontaminated by teams, probably close to the receiving hospital. A detailed protocol for decontamination of non-ambulatory patients is included in the chapter on hospital management.

    Decontaminating patients is relatively straightforward in comparison with chemical decontamination, as there is no vapour hazard. Removal of the outer layers of clothing will account for approximately 80% of contamination, and washing exposed skin and hair with ordinary soap and water will account for another 10-15%. Removal of particles from wounds and body crevices such as the ears and nostrils may require a little more effort. Care must be taken to remove clothing in a fashion that does not create aerosols of contaminated particles, and all discarded clothing should be bagged. Contaminated personal effects may be suitable for cleaning or may have to be discarded.

    Care must be taken to provide mass decontamination in a manner that is suitable for the climate and the culture. In particular, it is advisable to have the disrobing, showering and dressing facilities screened from the outside, and to provide same-sex supervisors in each section.

    Emergency cases. There may be occasions, particularly in an incident involving explosives, when contaminated patients require immediate treatment. In these cases, treatment should not be delayed until decontamination has taken place, but care should be taken to minimise the spread of contamination as much as possible, by covering the patients during transport, minimising the number of exposed corridors and rooms, and covering doors, door handles and essential equipment with plastic or tape. Inside the OT, the usual no-touch rules and clothing should be sufficient to protect surgical teams, but additional precautions must be taken to assess any foreign material for radiation and to collect potentially-contaminated run-off.