I fly a lot.
I remember when I first started travelling significantly, on one flight a woman sitting next to me told me of her worries about the radiation she would be exposed to during the long flight.
The thought lingered in my mind for a few seconds, but I never thought any more of it.
Until a friend posed this question over dinner a few nights ago…
Methodology
I looked at radiation doses using data from radiologyinfo.org (via The Guardian) and compared it to findings from a number of studies investigating radiation exposure during commercial airline flights.
Results
Radiation dosages
Let’s start by looking at radiation guidelines, and set some points of reference to make this data more quantifiable.
| Event | Radiation reading, millisievert (mSv) |
|---|---|
| Single dose, fatal within weeks | 10,000 |
| Typical doseage recorded in those Chernobyl workers who died within a month | 6,000 |
| Single does which would kill half of those exposed to it within a month | 5,000 |
| Single doseage which would cause radiation sickness, including nausea, lower white blood cell count. Not fatal | 1,000 |
| Accumulated doseage estimated to cause a fatal cancer many years later in 5% of people | 1,000 |
| Max radiation levels recorded at Fukushima plant yesterday, per hour | 400 |
| Exposure of Chernobyl residents who were relocated after the blast in 1986 | 350 |
| Recommended limit for radiation workers every five years | 100 |
| Lowest annual dose at which any increase in cancer is clearly evident | 100 |
| CT scan: heart | 16 |
| CT scan: abdomen & pelvis | 15 |
| Dose in full-body CT scan | 10 |
| Natural radiation we’re all exposed to, per year | 2 |
| CT scan: head | 2 |
| Spine x-ray | 1.5 |
| Radiation per hour detected at Fukushimia site, 12 March | 1.015 |
| Mammogram breast x-ray | 0.4 |
| Chest x-ray | 0.1 |
| Dental x-ray | 0.005 |
The scientific unit of measurement for whole body radiation dose, called “effective dose,” is the millisievert (mSv).
Most routine x-rays expose us to very low levels of radiation. A dental x-ray exposes a patient to 0.005 mSv. Putting this into context, the lowest annual dose at which any increase in cancer is clearly evident is 100 mSv, or 20,000 dental x-rays.
Radiation exposure during flying
| Route | mSv per 100 block hours | mSv per 1 hour |
|---|---|---|
| Seattle to Portland | 0.03 | 0.0003 |
| New York to Chicago | 0.39 | 0.0039 |
| Los Angeles to Honolulu | 0.26 | 0.0026 |
| London to New York | 0.51 | 0.0051 |
| Athens to New York | 0.63 | 0.0063 |
| Tokyo to New York | 0.55 | 0.0055 |
Based on studies, the radiation dose rate on 6 typical commercial airline flights at an altitude of 35,000 feet varies between 0.0003 mSV and 0.00055 per hour (mean average = 0.0004 msv). It is important to note that radiation dose levels represent a complex function of duration of flight, latitude, and altitude.
That said, assuming the average flight times from the route data from my post: The Worlds Shortest Commercial Flight. 2 Minutes to Fly 3 Kilometres, the graph and table below show estimated radiation exposure for the 38 longest (by time) routes.
| Rank (mSv) | From | To | Distance km | Scheduled duration | Radiation dose (mSv) |
|---|---|---|---|---|---|
| 1 | Auckland | Doha | 14,524 | 17:35:00 | 0.0070 |
| 2 | Auckland | Dubai | 14,203 | 17:15:00 | 0.0069 |
| 3 | Dallas/Fort Worth | Sydney | 13,804 | 16:55:00 | 0.0068 |
| 3 | San Francisco | Singapore | 13,593 | 16:55:00 | 0.0068 |
| 5 | Johannesburg | Atlanta | 13,582 | 16:40:00 | 0.0067 |
| 6 | Dubai-International | Los Angeles | 13,420 | 16:35:00 | 0.0066 |
| 7 | Abu Dhabi | Los Angeles | 13,502 | 16:30:00 | 0.0066 |
| 7 | Jeddah | Los Angeles | 13,409 | 16:30:00 | 0.0066 |
| 9 | Doha | Los Angeles | 13,367 | 16:25:00 | 0.0066 |
| 10 | San Francisco | Singapore | 13,593 | 16:20:00 | 0.0065 |
| 10 | Dubai-International | Houston-Intercontinental | 13,144 | 16:20:00 | 0.0065 |
| 10 | Dallas/Fort Worth | Hong Kong | 13,072 | 16:20:00 | 0.0065 |
| 10 | Abu Dhabi | Dallas/Fort Worth | 12,962 | 16:20:00 | 0.0065 |
| 10 | Doha | Houston-Intercontinental | 12,951 | 16:20:00 | 0.0065 |
| 10 | Dubai-International | Dallas/Fort Worth | 12,940 | 16:20:00 | 0.0065 |
| 10 | Doha | Dallas/Fort Worth | 12,764 | 16:20:00 | 0.0065 |
| 17 | Abu Dhabi | San Francisco | 13,128 | 16:15:00 | 0.0065 |
| 18 | New York | Guangzhou | 12,878 | 16:05:00 | 0.0064 |
| 18 | New York | Guangzhou | 12,878 | 16:05:00 | 0.0064 |
| 18 | Johannesburg | New York | 12,825 | 16:05:00 | 0.0064 |
| 18 | Mumbai | Newark | 12,565 | 16:05:00 | 0.0064 |
| 22 | New York | Hong Kong | 12,983 | 16:00:00 | 0.0064 |
| 22 | New York | Hong Kong | 12,983 | 16:00:00 | 0.0064 |
| 22 | New York | Hong Kong | 12,983 | 16:00:00 | 0.0064 |
| 22 | Newark | Hong Kong | 12,980 | 16:00:00 | 0.0064 |
| 26 | Houston-Intercontinental | Taipei | 12,776 | 15:55:00 | 0.0064 |
| 26 | Mumbai | Newark | 12,565 | 15:55:00 | 0.0064 |
| 28 | Dubai-International | San Francisco | 13,041 | 15:50:00 | 0.0063 |
| 28 | Newark | Hong Kong | 12,980 | 15:50:00 | 0.0063 |
| 28 | Boston | Hong Kong | 12,827 | 15:50:00 | 0.0063 |
| 28 | Los Angeles | Melbourne | 12,748 | 15:50:00 | 0.0063 |
| 28 | Los Angeles | Melbourne | 12,748 | 15:50:00 | 0.0063 |
| 28 | Los Angeles | Melbourne | 12,748 | 15:50:00 | 0.0063 |
| 34 | Toronto | Hong Kong | 12,569 | 15:35:00 | 0.0062 |
| 35 | Toronto | Hong Kong | 12,569 | 15:30:00 | 0.0062 |
| 35 | Toronto | Hong Kong | 12,569 | 15:30:00 | 0.0062 |
| 35 | New York | Taipei | 12,566 | 15:30:00 | 0.0062 |
| 38 | New York | Taipei | 12,566 | 15:20:00 | 0.0061 |
The mean average mSv for the 38 longest flights by time, with durations between 15:20 and 17:35, is 0.0064 mSv. Put another way, just under 6.5% of the radiation you would receive from a chest x-ray. The longest flight by time, Auckland to Doha at 17 hours 35 minutes, exposes passengers to and estimated 0.007 mSV, which is about 0.32% of the average radiation you would be exposed to each year naturally.
Frequent flyers
In 2017, business traveler Tom Stuker became the world’s most frequent flyer, logging 18,000,000 miles (28,968,192 km) of air travel on United Airlines over the last 14 years — that’s 722.8 times (51.6 times per year) around the world (assuming 40,075 km equatorial circumference of earth)!
Assuming an average flight speed (550 mph), Stuker’s 18,000,000 miles would translate into 32,727 hours (2337.6 hours per year) of flight time or 212 mSv (15.12 mSv per year) of radiation. About the same as a CT scan of your abdomen and pelvis each year.
Most pilots typically log under 1,000 hours per year so airline workers would have risk levels about half that of Stuker’s (less than 7.5 mSv per year).
tl;dr
Even if you’re a frequent flyer, the risk from radiation to your health is low. Pilots are exposed to no more than 7.5 mSv per year, equivalent to 75 chest x-rays, well below the lowest annual dose at which any increase in cancer is clearly evident (100 mSv).