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A person living at sea level receives a small radiation dose from cosmic radiation. The dose varies with latitude and altitude but the variability across Ireland in extremely small. Air crew and airline passengers receive an additional dose from cosmic radiation. For passengers and aircrew, the dose received depends on the frequency of flights and the routes flown.
The Earth is continuously being bombarded by high energy radiation from the sun (solar radiation) and the solar system (galactic radiation). The collective term for these forms of radiation is cosmic radiation.
Cosmic radiation is absorbed by the Earth’s atmosphere. Below an altitude of 15,200 metres, the intensity and power of cosmic radiation diminishes rapidly. Flying at high altitude increases the radiation exposure. The intensity of cosmic radiation is also influenced by the earth’s magnetic field, which can deflect the particles. Deflection is greatest at the equator and least at the poles where cosmic radiation can penetrate deeper into the atmosphere.
Because cosmic radiation increases with altitude and latitude, air travel, and in particular air travel near the poles, results in an additional radiation dose. Higher doses are associated with long-haul, flights to North America and trans-polar routes to the far-east. Lower doses are associated with short-haul flights to Europe.
Air crew who fly exclusively below 8000 metres are unlikely to receive radiation doses in excess of 1 millisievert (mSv) per year – the radiation dose limit for the public as specified by the law.
Air crew who fly above 8000 metres will receive higher doses from cosmic radiation. Aircraft operating above 15,200 metres are required under Civil Aviation JAR-OPS regulations to be equipped with cosmic radiation detection and measurement equipment.
Airline operators are required by law to carry out an evaluation of the likely exposure of air crew to cosmic radiation. The evaluation must:
Where the evaluation shows that any air crew are liable to receive doses in excess of 1 mSv in any 12 month period, the operator must:
Any Air crew liable to receive cosmic radiation doses in excess of 6 mSv in a year would be classified as ‘Category A workers’ and must be provided with additional levels of protection, including:
The assessment of each individual air crew dose is made by combining route dose with crew roster data. Route dose estimates can be calculated using computer programs specifically designed for that purpose. Computer programmes such as EPCARD and CARI-6 are specifically designed to calculate route dose, and these programmes are recognised by the EPA.
When a pregnancy is declared by a female crew member, steps must be taken to prevent that individual becoming exposed to more than 1 mSv during the remainder of the pregnancy.
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