Airplane in sun

Pilots are Exposed to the Equivalent of 75 Chest X-Rays per Year

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

Download data.

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

Download data.

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.

Radiation Doses (mSv) for 38 Longest Flights by Time (2017)

Download chart.

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

View calculations.

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).

Footnotes

  1. Data sources + data used in this post.
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