By J. E. Hinners, MD MPH
Maybe you are heading home from a Thanksgiving weekend at the grandparents’ house. Maybe you are booking your upcoming Christmas flight back home. Maybe you work as part of an airline crew. Or maybe you are simply just a frequent flyer.
In any case, the question might cross your mind at some point:
What kind of radiation health risks does commercial air travel pose?
Here’s a summary:
Airport security scanners
It’s easy to be conscious of airport security scanners as a radiation source, because they’re visibly obvious, and we seem to wait forever in lines just to have a close encounter with them. By “airport security scanners” here, I am referring to the full-body x-ray backscatter system used by the TSA.
But actually, airport scanners are a much lesser source of radiation than time spent in-flight.
The skin dose of radiation from a single-pose, two-sided scan in a man who is 5’10” has been found to be 40.4 nGy; the effective dose was found to be 11.1 nSv. This effective dose is roughly equivalent to naturally occurring radiation exposure during just 12 seconds of time spent on a typical flight.
The American National Standards Institute/Health Physics Society sets the standard yearly dose limit at 250 μSv. In order for an individual to exceed the yearly dose limit via airport security scans, that person would have to go through more than 22,500 scans per year.
So perhaps our bigger question should be…
What is our exposure to radiation during the flight, itself?
Radiation exposure on flights occurs due to cosmic radiation from the sun, which only makes up 9% of radiation sources. Other sources are also naturally occurring, such as certain food sources. And still many other sources are man-made: CT scans, x-rays, etc.
Flight radiation dose differs according to the particular flight and depends on several flight factors:
- Duration: the longer the flight, the more radiation
- Latitude of flight route: the closer to either the North or South Poles, the more radiation
- Altitude: the higher the altitude, the more radiation
- Current solar activity: some conclude that flights occurring between 8am-5pm (times of sun exposure) receive higher radiation exposure than night flights (while this conclusion is logical, some others disagree with this statement, and so far there is limited supporting data, to my knowledge)
- Weather and environmental conditions: solar storms and regional nuclear disaster sites appear to increase radiation exposure in-flight
- Seattle–>Portland: 0.03
- Los Angeles–>Honolulu: 0.26
- New York–>Chicago: 0.39
- London–>New York: 0.51
- Tokyo–>New York: 0.55
- Athens–>New York: 0.63
- Paris–>Buenos Aires: 3 (lowest measured dose rate)
- Paris–>Tokyo: 9.7 (highest measured dose rate)
One man demonstrates the variability of radiation exposure on planes by bringing his “gamma scout” Geiger counter with him on his many air travels. He seems to get a picture of his gamma scout reading on every flight and train route through many different countries.
This website cracks me up – I can just imagine him making it to the Eiffel Tower for the first time but missing the scenery because he’s looking at his gamma scout reading. To be honest, this is probably something I would do if I had a gamma scout.
What is the standard human radiation dose limit?
The National Council on Radiation Protection and Measurements (NCRP) spells out a standard set of recommended radiation dose limits for varying scenarios–for the average adult down to the case of “inadvertent irradiation of a clandestine stowaway in a cargo container” (thank goodness they covered that scenario, too…). So while there are many various standard limits, based on the individual and circumstances, here are several key dose limits:
- Dose limit for average adult, general public: 0.1 rem (1 mSv) total effective dose equivalent (TEDE) annually
- Dose limit for pregnant women: 0.5 rem (5 mSv) over the duration of the entire pregnancy
- Occupational dose limit for adults: 5 rem (0.05 Sv) TEDE annually
- Occupational dose limit for minors (under 18): 10% of the above dose limit for adults
How much radiation are average adults typically exposed to every year?
The U.S. Nuclear Regulatory Commission estimates that the average American receives a yearly radiation dose of 0.62 rem (620 mrem)–most of which comes from radon background exposure in the air; this yearly dose appears to cause no human harm. Those who would be more at risk for greater radiation exposure in-flight would be airline crew personnel rather than the average adult passenger.
How much radiation are airline crews typically exposed to every year?
In one study quite a while back in 1998 (unfortunately, I’ve not found more recent reports as of yet, so figures may have changed)–average annual cosmic ray dose for airline crews were as follows:
- Cabin crews: 2.27 mSv (for 673 block hours)
- Long-distance flight captains: 2.19 mSv (for 568 block hours)
The only flight crews that would exceed the NCRP radiation dose limit guidelines would be those flying many hours while pregnant (such as 100 hours per month) who also flew primarily on the highest dose-rate flight routes (such as some of the global flight routes listed above).
Flight crew health risks associated with radiation exposure?
Since flight crews have a much greater exposure to cosmic radiation in-flight relative to the average adult passenger, they are often the subjects of studies looking to establish health risk associations with in-flight radiation.
I don’t intend to flesh out a full review of the literature here on this topic. But overall, there have been some mixed results.
A few interesting studies about flight crew health risks (some of them conflicting):
- Twice the incidence of melanoma skin cancer in pilots and cabin crew compared to the general population
- Overall cancer risk was not elevated in flight crews
- Malignant melanomas, skin cancer, and breast cancer incidence appeared elevated in flight crews
- Brain cancer risk in flight crews appeared elevated in one German cohort
- Cardiovascular mortality risks appeared very low in flight crews
- Cockpit crew had low overall disease mortality (including from cancer and cardiovascular diseases) compared to the general population
- Aircraft accident mortality was highly elevated in cockpit crew
- Malignant melanoma incidence was increased in cockpit crew
- Non-chronic lymphocytic leukemia was not elevated among cockpit crew
- Central nervous system mortality was elevated in cockpit crew
- Flight attendants had fewer deaths (including cancer) relative to the general U.S. population
- NO elevation in breast cancer and melanoma incidence among flight attendants compared to the general population
- Average flight attendant job-related cosmic radiation exposure was low
- Deaths from HIV were 16 times higher among male flight attendants compared to the general population of men
- Suicide deaths were 1.5 times higher among flight attendants compared to the general population
- Alcoholism among flight attendants was 2.5 times higher than that among the general population
- Deaths from aircraft, water, and rail accidents were 3.5 times higher among flight attendants relative to the general population.
Some takeaway points from what’s been discussed so far:
- Airport security scanners are less of a radiation health risk than time spent in-flight
- The average frequent flyer generally does not tend to exceed the recommended NCRP radiation dose limit
- The average flight crew member generally does not tend to exceed the recommended NCRP radiation dose limit
- Flight crew members most at risk of exceeding the recommended dose limits are pregnant women who fly many hours and primarily on high radiation-dose flight routes
- If you want to minimize your air travel radiation exposure, here are some things you can do:
1) Fly less often.
2) If you’re still scared of the airport security scanner after the multitude of assurances available above, you can see if you can opt for the security “pat-down” rather than the scanner at your airport.
3) Fly over shorter distances or choose a series of short connecting flights rather than one long flight (short flights tend to be lower in altitude).
4) Opt for flight routes that don’t travel over the North or South Poles.
5) Consider flying at night rather than during the day.
6) And possibly choose your flight seat in the middle portion of the flight cabin rather than the very front or very back of the cabin where radiation exposure has been reported to be higher in one study.
7) Generally strengthen your body for best managing radiation exposure through healthy diet, exercise, and other lifestyle choices.
Bon voyage! And if you’re aching to bring out your inner nerd, check out some Geiger counters to add to your Christmas wish list!