Flying and health: Cosmic radiation exposure for casual flyers and aircrew

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?

Cosmic radiation mainly consists of large high energy particles (protons and nuclei) that originate from outside our solar system and even from other galaxies, with some contribution from our sun. When they strike the earth’s atmosphere, they interact and create secondary particles, some of which reach the earth’s surface. This type of exposure is referred to as background radiation, and forms one of the two main sources of background radiation.

What is the exposure to cosmic radiation?

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. At altitude, cosmic radiation exposure increases. Therefore during flights, which typically involve flying at altitudes between 7 000 – 12 000 metres, cosmic radiation exposure is increased.

Cosmic radiation exposure also increases with increased latitude (distance from equator). Therefore flights that are distant from the equator or over the poles receive more cosmic radiation exposure.

Solar particle events are rare occurrences that can result in higher exposures for short periods of time.

What are the health effects for casual flyers?

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. It is possible for people who fly very frequently, for example 10-20 hours per week on long haul flights, to approach and exceed a 1 millisievert (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 an unborn child of less than 1 mSv above background levels will not lead to a significant increase in risk due to radiation. It should be noted that 1 mSv above background is a very conservative limit for the public and unborn children, it is well below any exposures that have proven health consequences.

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.