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Flying and Health: Cosmic Radiation Exposure for Casual Flyers and Aircrew

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The scientific evidence does not indicate an increase in health risk from exposure to naturally occurring cosmic radiation while flying.


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Introduction

People travelling in aircraft may be exposed to more ionising radiation than they would be exposed to on the ground. The increased exposure occurs because the Earth’s atmosphere provides less protection from cosmic radiation at the typical cruising altitudes of commercial aircraft, which are usually between 7 000 and 12 000 metres.

What is cosmic radiation?

All living organisms are exposed to ionising radiation on a continuous and daily basis. It is in the food we eat, the air we breathe and the buildings we live in. This type of exposure is referred to as background radiation. The two main sources of background radiation include radioactive materials, such as uranium in the natural environment and cosmic radiation from outer space. There is considerable variation in the background radiation levels throughout the world. The world average is 2.4 mSv per year and the average Australian background radiation dose is around 2 mSv each year.

Sources and exposures

Cosmic radiation is mainly in the form of particles from outer space. Some contribution also occurs from the sun, together with solar particle events. Solar particle events are rare occurrences that can result in higher exposures for short periods of time. The earth’s atmosphere offers considerable protection from cosmic radiation, such that at ground level only small exposures occur. Because Australia has the lowest elevation of any continent, background cosmic radiation at ground level is low.

As altitude increases, the cosmic radiation component increases. The important part of a flight from an overall cosmic radiation exposure perspective is the period of flight cruising, typically involving altitudes between 7 000 and 12 000 metres.

Latitude – the distance from the equator – also has an influence on the cosmic radiation exposure level. Exposures increase the further the flight path is away from the equator.

What are the health effects for casual flyers and aircrew?

Large studies involving the health of pilots and aircrew have shown no detectable association with an increased risk of cancer that might be expected to arise from radiation exposure. Exposures of aircrew to cosmic radiation are typically less than a quarter of the occupational dose limit of 20 mSv per year – around 1.8 mSv per year for those involved in domestic routes, and around 4 mSv per year for those involved in international flight routes. These figures are similar to those experienced by aircrew in other countries.

It is also possible for people who fly very frequently, for example 10-20 hours per week on long haul flights to approach and exceed a 1 mSv per year dose.

For pregnant travellers and aircrew, the Australian and international guidance is that the unborn child should be treated in broad terms as a member of the public. The public dose limit is 1 mSv. Radiation exposure to the unborn child of less than 1 mSv above background levels will not lead to a significant increase in risk associated with radiation-related health effects. The table below provides some indication of doses for a number of routes and also indicates flying hours and number of flights taken to achieve a 1 mSv dose.

Hours Exposure for Effective Dose of 1 millisievert
Altitude (ft) Altitude (m) Hours at latitude 30° S (1) Hours at equator (2)
27,000 8,230 510 1,330
30,000 9,140 380 980
33,000 10,060 300 750
36,000 10,970 240 600
39,000 11,890 200 490
42,000 12,800 170 420
45,000 13,720 150 380
48,000 14,630 140 350
Source(s): (1) CARI-6 model - Averaged over a complete Solar Cycle
(2) Effects of Cosmic Radiation on Aircrew – Herbert R Meyer

 

Route Estimates Dose/Flight (µSv) Flights for 1 mSv
Darwin-Perth 16 62
Perth-Broome-Darwin 8 131
Darwin-Singapore 9 107
Frankfurt-Singapore 39 25
Melbourne-Johannesburg 71 14
Melbourne-Singapore-London 65 15
London-Singapore-Melbourne 42 23
Sydney-Buenos Aires 68 15
Buenos Aires-Sydney 80 13
Data provided by Capt Ian Getley and adapted for presentation
1 mSv = 1000 µSv

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