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Air travel has become, for a privileged few in the world, almost routine.

The procedure of flying is so uniform and recognisable, almost habitual, that people have made terrible, terrible comedy shows about it.

What you may not be aware of is the increased exposure to radiation up in and above the clouds.

We fly up significantly closer to the outer limits of the earth's atmosphere while cruising at 39,000 feet, and up there we are far more likely to come into contact with cosmic atomic particles.

When we're on the ground, we're less likely to come into contact with these, due to the magnetic field surrounding our planet.

As Nasa says of these particles:

Particles with sufficient energy, however, can penetrate both Earth’s magnetosphere and atmosphere, where they collide with molecules of nitrogen and oxygen. These collisions cause the high-energy particles to decay into different particles through processes known as nucleonic and electromagnetic cascades.

If you could see the particles from the airplane window, you would notice them clustering in a region above the plane.

The density of the atmosphere causes the decay to happen predominantly at a height of 60,000 feet, which creates a concentrated layer of radiation particles known as the Pfotzer maximum.

The rate of radiation exposure means that airline crew members are classified as "radiation workers" due to their continued exposure to cosmic rays.

Eddie Semones, a radiation health officer at Nasa, toldBusiness Insider:

Cosmic rays are not a significant exposure risk on the ground.

You actually get more exposure from the Earth’s natural radioactive material than from galactic cosmic rays.

Radiation dose rates increase with altitude and latitude and can vary from hour to hour. (Picture: NASA/NAIRAS)

This is also the reason Nasa doesn't permit astronauts to spend more than a year in orbit. The space agency does not want to boost their lifetime risk for cancer more than an extra three per cent.

However, as the CDC details:

There are no official dose limits for aircrew in the United States.

Meanwhile, the Council of the European Union adopted a directive limiting aircrew exposure to cosmic radiation in May 1996, implemented from May 2000.

The International Commission on Radiological Protection recommends crew members not be exposed to more than 20 millisieverts (mSv) per year, while the general public should receive less than 1 mSv per year. The annual exposure for aircrews is an estimated 3 mSv.

Nasa studied cosmic radiation further in January 2017, taking measurements between 26,000 and 120,000 feet above the Earth.

The results were published in the journal Space Weather, and will be used to improve space weather models, like the Nowcast of Atmospheric Ionizing Radiation for Aviation Safety, or NAIRAS, model, which predicts radiation events. These are, in Nasa's words:

Used by commercial pilots to know when and where radiation levels are unsafe, allowing rerouting of aircraft in the affected region when necessary.

You can calculate your exposure on a given flight, using a tool by the Federal Aviation Administration.

Still looking forward to your summer holiday?

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