7.1. Initial actions

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The role of the health sector in eliminating the sources of contamination depends on the scenario. If the event occurs in a factory, for instance, controlling the leak is the responsibility of the company and the relevant response agencies (fire department, hazardous materials experts). If there is an external release, however, the health sector is appropriately involved in detecting the incident, identifying the origin and nature of the contamination, and stopping the exposure (for example, by withdrawing products from the market). It should also participate in defining possible courses of action to impede the spread and decontamination, restrict access to relevant areas, protect people, and assess possible short- and long-term health threats.

a. Decontamination: This consists of eliminating the hazardous substances from victims, responders, protective equipment, and anything else involved at the site of a chemical incident, so as to prevent the substances from migrating to clean areas. Knowing what chemical agent is responsible for the contamination makes more effective action possible, and also facilitates proper medical care. WISER is a system designed to assist first responders in hazardous material incidents. WISER provides a wide range of information on hazardous substances, including substance identification support, physical characteristics, human health information, and containment and suppression advice.

b. Control access areas: The most common way of organizing the response to an incident of this type includes the following elements:

  • Exclusion zone (hot): This extends to quite a distance from the site of the incident to prevent primary contamination of people and materials. No decontamination or care of victims is conducted here except for evacuation.
  • Reduced contamination zone (warm): This is the area around the hot area. It includes corridors where victims, responders, and equipment are decontaminated. There is a risk here of secondary contamination from objects and individuals coming from the hot zone.
  • Support zone (cold): This area should be entirely free from contamination. Contaminated victims and response personnel should be decontaminated before entering it. The command post and coordination activities are also centered here.

Access to the different areas should be strictly controlled, and should be limited to the smallest possible number of people. Read more about these issues in the International Atomic Energy Agency's Manual for First Responders to a Radiological Emergency.

c. Protection of staff: The use of personal protective equipment is an effective way to reduce exposure, but usually only responders have access to it.

For populations exposed to airborne contamination, two principal options are available: on-site sheltering and evacuation. On-site sheltering can be people’s own homes with the windows, doors, and any ventilation or air conditioning systems closed off until there is notification that the danger has passed. However, the effectiveness of such arrangements depends to a great extent on the airtightness of the dwellings as well as the duration of the exposure. For that reason, the most common choice is evacuation to a contamination-free area.

Table 7 lists some criteria to consider in deciding whether to evacuate or aim for on-site refuge. The primary consideration in evaluating risk is twofold: the intensity and duration of exposure.

When to evacuate

Evacuation is the best option when…
  The area has not been exposed, but still may be.
  The probable duration of exposure is such that the protection offered by sheltering could be insufficient.
  The chemical agents have been extensively dispersed, and contamination is persistent.  
  The chemical has not been identified, but is suspected of being dangerous.  
  The chemical substance is highly hazardous.  
  The concentration in the air will be dangerous for a prolonged period.  
  There is a risk of explosion.  
  The number of people to evacuate is relatively small.  

The decision to authorize return after an evacuation depends on the availability of environmental monitoring data that confirm that the area is again safe and that essential services can be provided.

Return can also be contingent on some level of restriction or on precautions regarding secondary contamination (such as contamination of food, crops, or water as a consequence of the primary contamination). In such cases, measures must be taken to ensure emergency supplies.