EVERY time you board a flight at KL International Airport, you are quietly leaving behind the protective blanket that has been keeping you safe your entire life.
That blanket is the Earth's atmosphere, and at cruising altitude, the universe has some rather uninvited things to send your way.
Does flying on a plane actually expose you to significant radiation?
Verdict:
TRUE, BUT...
Commercial aircraft cruise at altitudes of between 7,000 and 12,000 metres, well above most of the atmospheric shielding that protects people on the ground from cosmic radiation.
Cosmic radiation consists of high-energy particles originating from outside the solar system, including from distant supernovae, as well as charged particles released by the sun.
When these particles collide with molecules in the Earth's atmosphere, they produce secondary particles, some of which reach the ground as background radiation.
At cruising altitude, significantly more of this radiation reaches passengers and crew because most of the atmospheric buffer has been left behind.
According to the US Centres for Disease Control and Prevention, the amount of radiation received during a flight depends on three main factors: the duration of the flight, the altitude, and how far the route is from the equator.
The Earth's magnetic field deflects cosmic radiation most effectively at the equator and least effectively near the poles, meaning that polar and high-latitude routes receive considerably more radiation than equatorial ones.
This is actually good news for Malaysian travellers.
Flights departing from Kuala Lumpur to regional destinations such as Bangkok, Jakarta or Singapore operate close to the equator and receive radiation dose rates two to three times lower than equivalent flights on higher-latitude routes, according to the US-based Health Physics Society.
A research paper published in the journal Space Weather estimated that a transequatorial flight between Colombo and Jakarta resulted in a total effective radiation dose of just 9.7 microsieverts, compared with 60 microsieverts for a transatlantic Paris to New York flight and 82 microsieverts for a transpolar Beijing to Chicago route.
For context, a single dental X-ray delivers approximately 10 microsieverts of radiation.
The longer the flight and the higher the latitude, the greater the exposure, meaning a Malaysian travelling to London on a high-altitude route will receive a more meaningful dose than someone flying to Bali for the weekend.
A 2025 review published in ScienceDirect, examining cosmic radiation and airline passengers, found that while the risks for occasional passengers were minimal, flight crew members warranted careful monitoring due to their cumulative exposure over time.
The Australian Radiation Protection and Nuclear Safety Agency confirmed that large studies of pilots and cabin crew had shown no detectable association with an increased risk of cancer that could be attributed to radiation exposure from flying.
For the average Malaysian who boards a plane a handful of times a year, the additional radiation dose is a small fraction of the natural background radiation a person receives annually from the ground, food and building materials regardless of whether they fly at all.
The CDC notes that cosmic radiation already accounts for approximately 11% of a person's total annual exposure to natural radiation sources, whether they fly or not.
For frequent flyers logging many long-haul hours annually, cumulative exposure does become more meaningful and is treated as an occupational health consideration in several countries.
To give that some scale, 1,000 microsieverts make up one millisievert, and the European Union sets a maximum annual limit of six millisieverts for aircrew on the most demanding long-haul routes, which is the equivalent of clocking up roughly 1,000 hours in the air, or flying a distance greater than twice the gap between the Earth and the Moon.
For pregnant travellers and crew, international guidance recommends that total additional radiation exposure during pregnancy be kept below one millisievert, a level that research suggests poses no significant increase in risk.
The radiation from flying is real, measurable and well-documented, but for the occasional passenger boarding at KLIA, authorities and researchers consistently describe the dose as posing no adverse health effects.
Sources:
1. https://www.cdc.gov/radiation-
2. https://www.cdc.gov/niosh/
4. https://www.sciencedirect.com/
5. https://pmc.ncbi.nlm.nih.gov/
6. https://pmc.ncbi.nlm.nih.gov/
7. https://hps.org/ate_faq/
8. https://agupubs.onlinelibrary.
