Higher exposure near the poles
Editorial review 2026
The atmospheric shield
The layers of air in the atmosphere provide protection against cosmic radiation that decreases with altitude and depends on the route taken. For commercial aircraft flying at an altitude of 10 km, the dose received varies between 0.005 mSv/h and 0.007 mSv/h depending on whether the route avoids or flies over the poles. At an altitude of 18 km, the dose is approximately doubled. For an astronaut living on a space station at an altitude of 400 km, the dose rate is between 0.030 and 0.040 mSv per hour, so that seven days in orbit are enough for the astronaut to be exposed to the annual dose of natural radioactivity at ground level (4.5 mSv). © SCK.CEN
The shortest route from New York to Hong Kong passes over the North Pole. In March 2001, two American airlines inaugurated a transpolar route connecting these two cities. A Chinese airline was expected to follow. As crews and passengers travelling on these polar routes are exposed to additional radiation, the American press reported concerns expressed by scientists and unions representing pilots, stewards and flight attendants.
The importance of the poles is due to the fact that the Earth is a large magnet. The magnetic field surrounding it deflects some of the cosmic rays that bombard it. This magnetic shield combines with the layers of the atmosphere to provide protection from radiation, except at the two weak points in its armour: the North and South Poles. A traveller taking a polar route from New York to Hong Kong therefore receives a dose of 0.100 millisievert (mSv), three times greater than the dose received by a passenger on a Los Angeles–Tokyo flight, which is only slightly shorter.
The radiation comes mainly from the Sun, located in the Earth’s cosmic neighbourhood. The doses received therefore depend on solar activity, which follows an 11-year cycle. The Sun experiences periods of eruptions which, like earthquakes, are classified according to their magnitude. Flying over the pole should be avoided during high-magnitude storms. An aircraft that had taken such a route on the day of the strongest eruption recently recorded would have exposed its passengers to ten times the 0.100 mSv received during an ordinary flight.
Solar eruptions and the Northern Lights
Solar eruptions are gigantic cataclysms that eject large numbers of high-energy cosmic particles into space. The shield formed by the magnetic field surrounding the Earth prevents these particles from reaching its surface, except near the poles. During solar eruptions, showers of cosmic particles received in regions such as Scandinavia produce magnificent Northern Lights. For air travel, these predictable episodes of intense radiation should be avoided.
© NASA
Airlines operating these routes take precautions and change their routes in the event of a solar storm. The American Space Center continuously monitors the Sun’s activity. It provides a summary for the coming week, predicts activity for the next 24 hours and issues warning bulletins in the event of a major eruption.
Travellers even have free access, via the Internet, to a program that calculates the millisieverts received from one airport to another. The calculation does not take solar eruptions into account, as their influence can be neglected outside polar routes.
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