Occupational exposure: Emergency workers and helpers
Emergency exposure situations require prompt action in order to avoid or reduce adverse consequences. Uncertainty surrounding the ionising radiation types and exposure pathways is likely, particularly in the early stages of an emergency exposure situation. This factsheet is intended to provide an overview of the relevant terminology and concepts that will help protect emergency workers and helpers from exposure to ionising radiation during an emergency.
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Your priorities in an emergency, as an emergency worker, are to regain control of the situation, mitigate consequences and save lives while ensuring your own safety. When an emergency involves a source of ionising radiation, it is termed an emergency exposure situation. In these situations exposure to ionising radiation must be considered, therefore normal occupational dose limits are no longer appropriate, and guidance values are applied (ARPANSA RPS G-3).
Internal exposure to ionising radiation occurs when radioactive material is inhaled, ingested or enters into the bloodstream (e.g. through wounds). Internal exposure continues until the radionuclide either decays or is excreted from the body. In some cases, treatments can be administered to assist the body’s natural excretion processes.
External exposure can occur in two ways:
- Contamination: when radioactive material is deposited on skin or clothes through immersion or airborne contaminants such as dust, liquids or aerosols. External contamination can often be removed from the body by simply removing contaminated clothing and washing exposed areas.
- Irradiation: from being in close proximity to a radioactive source. Moving away from the source, limiting time spent near the source or increasing shielding between you and the source will reduce your exposure.
There is no firmly established scientific evidence of harm for doses below 100 mSv. As such, there will be no observable health effects when applying the occupational exposure limits, the guidance values or the national reference level to emergency workers and helpers. There may be a small increase in cancer risk for doses above 100 mSv when received in a short period.
Acute radiation syndrome (ARS) can occur if a very high level of exposure is delivered over a short period. Symptoms can include nausea and vomiting, and in extreme cases, death can occur. The onset of these symptoms ranges from hours to weeks, depending on the dose received. The threshold for ARS is approximately 1000 mSv. Pregnant and breastfeeding workers should be excluded from emergency response activities. Health risks associated with exposure to ionising radiation are provided in RPS F-1 (ARPANSA 2014).
Figure 1: Radiation health effects at different exposure levels
At the onset of an emergency exposure situation, the type and magnitude of ionising radiation exposure is unknown, and there is little scope to apply occupational dose limits. In the absence of dose limits, a national reference level of 50 mSv applies to emergency workers and helpers when responding to an emergency exposure situation. In emergency exposure situations, the dose guidance value of up to 500 mSv may be applied under circumstances in which the expected benefits to others clearly outweigh the emergency worker’s own health risks. These response actions should only occur on a voluntary basis, where the emergency worker understands and accepts the health risks and should not be undertaken by helpers. During the later stages of an emergency when the situation is under control, normal occupational dose limits should be applied. These are defined in RPS C-1 (ARPANSA 2016). As more information comes to hand through monitoring or assessment, it may change the required response.
Table 1: National reference level and guidance values for emergency workers and helpers in an emergency exposure situation
|50 mSv||National reference level||Applied to most emergency workers and all helpers in an emergency exposure situation|
|100 mSv||Guidance value||Applied to emergency workers involved in preventing a large collective dose|
|500 mSv||Guidance value||Applied to emergency workers involved in urgent protective actions – including life-saving, and prevention of serious injury or development of catastrophic conditions|
Personal Protective Equipment (PPE) is one of the most effective ways to reduce radiation exposure in an emergency, particularly respiratory protection to avoid internal exposure. Suitable protective clothing, i.e. chemical, biological and radiological (CBR) suits, will prevent external contamination. Coupled with appropriate monitoring, withdrawal guidance and the application of the basic radiation safety principles (minimise time, maximise distance and use of shielding) will minimise doses.