Every day, somewhere in the cosmos, a star explodes. The Universe is crackling with supernova explosions. Dying stars spray their debris far and wide, accelerating some of their atoms to nearly light speed. Together, all these supernovas create a swarm of detritus, zipping to and fro through the Milky Way, which we call "cosmic rays."
Cosmic rays are a form of radiation. They are a melange of subatomic particles such as protons, the stripped-down nuclei of atoms, and high-energy photons. They are ever-present, 24/7, and there is no way to avoid them.
What Are Cosmic Rays?
Cosmic rays penetrate the walls of spacecraft with ease, posing a health risk to astronauts. A single cosmic ray can disable a satellite if it hits an unlucky integrated circuit. Cosmic rays also cause "air showers" of secondary particles when they hit Earth's atmosphere, spraying us on the ground with cosmic rays of less intensity than astronauts absorb.
Many people don't know this, but airplanes absorb a lot of cosmic rays. Flying 30,000ft to 40,000 ft high, they are much closer to space than we are on the ground below. The walls of aircraft are no better at stopping cosmic rays than the skin of NASA spacecraft. Our measurements show that cosmic rays dose rates inside typical commercial jets are 30 to 60 times greater than sea level.
How Do They Get Into My Airplane?
Energetic cosmic rays can crash through DNA like little atomic cannonballs, causing complex breaks called "clustered DNA damage." Cosmic rays can also heat and ionize tissue, upsetting the local thermal and electrical balance of biological systems.
Our species grew up on Earth's surface, not flying 40,000 feet high where secondary cosmic rays are increasingly intense. Human cells may not have evolved to fully repair the damage caused by this radiation.
Researchers have known these facts for decades. The International Commission on Radiological Protection (ICRP) has classified pilots as occupational radiation workers. During a typical polar flight from Chicago to Beijing, for instance, members of the flight crew can receive a whole body exposure equivalent to two chest x-rays. Multiplied over the course of a career, this can cause problems such as increased risk of cancer and possibly cataracts.
Passengers are affected, too. A 100,000 mile frequent flyer accumulates about 20 chest x-rays, regardless of the latitude of their flights. Even during a single flight across the continental USA, passengers absorb a whole body dose approximately equal to a modern dental X-ray.
No one knows for sure how these doses affect travelers. Comparing airline radiation to medical radiology is a bit like comparing apples and oranges. When you get an x-ray in a dentist's office, for example, the radiation is confined to a small area of your body (the jaw) and a small interval of time. When you fly from LA to Boston, the radiation permeates your entire body, touching organs unaffected in the dentist's office. On the bright side, aviation radiation is spread out over hours instead of seconds, giving your cells more time to repair the damage.
How Do Cosmic Rays Affect Us When We Travel?
An increasing body of research is revealing the impact that cosmic radiation has on everything from clouds and lightning to cardiac arrhythmias in the general population.
Our latest measurements show that cosmic rays in Earth's atmosphere are intensifying, with an increase of more than 18% since 2015.
None of us at Rads on a Plane are medical doctors, nor are we offering medical advice. Instead, we are astrophysicists, computer scientists, and communicators. Our job, as we see it, is to gather true information about aviation radiation and to share it with you. It's up to you to decide what it means for your health.
All of us involved in this project continue to travel on planes without fear of immediate effects from the exposure we receive onboard. However, the more we have learned about the radiation environment "up there", the more we have become mindful of our accumulated doses--and thoughtful of other travelers such as pregnant women who may be more vulnerable than we are.
Rads On A Plane Helps You Take Control of Your Own Exposure to Radiation