Dear Mark: Happy New Year, and Flight Crews, Radiation, and Cancer

Dear_Mark_Inline_PhotoBefore I get to the questions, Happy New Year, everyone! We have some exciting announcements and daily posts coming throughout January designed to help you successfully tackle this coming year (and any future ones you experience) along with some great giveaways, so stay tuned this week.

For today’s Dear Mark, I’m answering just one question. It concerns an article I posted in yesterday’s Weekend Link Love about the radiation exposure flight crews experience. They receive more radiation than people who work next to nuclear reactors, which sounds really dangerous. Won’t all that radiation result in higher cancer rates?

Let’s take a look:

Hi Mark,

Regarding the article about flight crews being exposed to more radiation than any other profession, does this translate into higher cancer rates?

The atmosphere is teeming with cosmic rays from outer space. Few reach us here on the Earth’s surface, but up in the air it’s a different story. Your average member of an air crew will receive about three times as much radiation each year as your average landlubber does.

Here’s the article

So they’re getting considerably more radiation than everyone else. Are flight crew members even at a higher risk for cancer? Maybe, depending on the sex, the study, and the cancer. In one study of female flight attendants, breast cancer and melanoma were the biggest risks. In another, male crew members had slightly increased risks for melanoma and all-cause mortality while female members had slightly increased risks for breast cancer and reduced all-cause mortality and mortality from all cancers. Another study found that female flight attendants reported 34% more reproductive cancers than the general population.

Okay, there are some increase and some decreases. But let’s focus on the increases. Is the radiation the cause?

They do get more radiation than anyone else, and high dose radiation can and does cause cancer.

But that’s not all they get. They also subject their bodies to consistently inconsistent circadian inputs. They whizz all over the world, crossing time zones. They’re often active at night, if their bodies can even identify “night.”

The two cancers that keep popping up—breast and melanoma—have established relationships to circadian arrhythmia. The ability of our skin to resist the damaging effects of UV rays is severely degraded when sleep or circadian rhythms are disturbed. And there are dozens of studies linking breast cancer to shift work, sleep disturbances, nighttime light exposure, and other things that either cause or reflect circadian misalignment.

My guess is that the circadian arrhythmia of plane work is more of a primary cause.

There’s also the lack of sun exposure.

As I’ve shown in a previous post, too little sunlight may be as bad for melanoma risk as too much sunlight. Sun gives us vitamin D, which has the ability to turn pre-cancerous skin cells into benign skin cells, repair UV damage, and prevent the formation of skin cancer. If you’re sitting inside an airport or an airplane for most of your work day, you aren’t producing any vitamin D from sun exposure.

But I don’t think the radiation is having much of an effect. In one study that found an increased risk of skin cancer in pilots, they were unable to link the increased risk to increased exposure to cosmic radiation. Although the authors maintain the “influence of cosmic radiation on skin cancer cannot be entirely excluded,” I find it far more likely that circadian misalignment and perhaps sun deficiency are the culprits. 

What’s really ironic is that the low level doses of radiation flight crews receive may be protective. This is the hormesis hypothesis, which posits that low doses of otherwise harmful stimuli provoke an adaptive response that results in net benefits to health. Most people can think of hormetic stressors like polyphenols (antioxidants are actually pro-oxidants that compel our endogenous antioxidant systems to work better), fasting (going without food trains us to burn body fat), exercise (damages your muscles, which come back stronger than before), but radiation is another one.

That’s probably surprising to you. Radiation is supposed to be dangerous at any dose, just less dangerous at lower doses. Turns out that the old paradigms of radiation toxicity are probably wrong as an absolute anyway.

Linear paradigm: The toxicity of radiation proceeds linearly in a dose-response fashion.

Threshold paradigm: There’s a certain amount of radiation that we can safely tolerate, after which the toxicity increases linearly.

Hormesis paradigm: Some radiation is healthier than none. Too much is really bad.

Imagine if the hormesis hypothesis is true. That would mean it’s conceivable that protecting the flight crews from radiation exposure would increase their risk of cancer. I’m not saying it’s true. We need more data. I’m just saying I wouldn’t be surprised if it were.

All this is a roundabout way of saying not to worry about flying. And if you are a flight attendant or pilot, perhaps you should worry, just not for the reasons you were thinking.

Oh, and get your sleep, sun, and daytime natural light. Wear blue blocking shades after dark and cut down on the electronics usage.

Take care. Have a great year. I can’t wait to tackle it with you all.


TAGS:  dear mark, toxins

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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22 thoughts on “Dear Mark: Happy New Year, and Flight Crews, Radiation, and Cancer”

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  1. Sleep and getting some sun are something I want to do more of this year. I travel extensively and want to rest and enjoy the sunlight a little more than I do. I do turn off all electronic devices several hours before bed. Happy New Year everyone.

  2. Wow, lots to absorb here. I’m not going to worry about the little bit of radiation I’m exposed to when flying…the benefits of travel and new experiences are so worth it. But the whole circadian rhythm thing is really interesting…I’ve really been working on improving mine. I’m trying to avoid looking at my phone when I go to bed (this is tough for me) and maybe it’s time to break out my ugly orange goggles again. Thanks for the great info!

  3. A couple of years ago I got a cat scan of my brain (no jokes, they did find one LOL). I later found out it was the equivalence of something like 300 X-rays at one time. I initially freaked out, but what’s done is done. I take a spoonful of chlorella every day, some studies indicate that it protects the body against radiation and removes radioactive particles from the body. There is also some evidence that a combination of lemon balm, ginkgo biloba and spirulina can mitigate the affects of radiation. I also take curcumin, cycle in a medicinal mushroom blend, and just started taking nicotinamide riboside, which supposedly helps with DNA repair.

    1. Radiation is cumulative and exposure should therefore be avoided whenever possible. Unfortunately, the medical profession has long had a cavalier attitude toward this fact. Researchers at U. Penn have found that ordinary flax seed can mitigate harmful effects of radiation in mice, both before and after exposure. Don’t know if it works for humans. You might want to read up.

      1. Thanks for the tip Shary, I will research that right away! I do take a tablespoon of ground flax seed every day to help with PSA levels, so maybe I got lucky and someone up there was helping me out LOL. I do agree with your assertion 100%. – George

  4. “But I don’t think the radiation is having much of an effect. In one study that found an increased risk of skin cancer in pilots, they were unable to link the increased risk to increased exposure to cosmic radiation.”

    Every been in a cockpit? It’s flooded with sunlight. Pilots don’t just wear those expensive aviators for fun. I’d suggest elevated skin cancers are due to the sunlight exposure at higher altitude which would have an effect on the ratios of UVA, B and C received. Man did not evolve at 40,000 feet.

    1. I found Mark’s POV very thought provoking: I tend to agree that the deleterious effect of disturbed circadian rhythm is going to be pretty significant for frequent flyers. There is a significant body of research now to back this up. I also tend to agree that the quite mild ‘background cosmic radiation’ effect is probably hormetic, ie overall beneficial (see: and ).

      However, I can also envisage there being an additional deleterious effect of sunlight in the cockpit: the glass will filter out the UVB rays (which are the ones responsible for Vitamin D synthesis), but it will not filter out the deeper penetrating, more harmful UVA rays (which are related to melanomas). Having had a cancerous growth removed from my face last year, I wish there was a sunscreen product available here in the UK which had a relatively low level of UVB protection (to allow for Vitamin D synthesis) whilst at the same time providing a very high level of UVA protection to protect against melanomas/ long term skin damage. Bearing in mind of course that I would have to self-regulate my time in the sun, and get out of the sun before starting to turn pink.. I only learned last year that the level of UVA protection shown on the bottle is actually proportionate to the SPF (UVB) protection factor – hence if you buy an SPF 10 sunscreen product with an ‘ultra’ UVA protection, then the absolute UVA protection is not very high since it is related to the low level of UVB protection. Not sure if that holds true in the USA too?

    2. High quality aircraft glass (as found on Airliners) – the windshields are especially thick – UV proof, but not enough. Some pilots actually wear sunscreen – the sunglasses are to reduce glare and block UV, and they also look cool.

  5. Hi
    Won’t we have the 21-days Primal Blueprint this summer on Vimify?

    Thanks and happy new year

  6. Mark, this post sorely disappointed me. I consider you fairly unbiased and thoughtful when it comes to your research. But I have a major problem with how you and the wellness community completely discount the dangers of unprotected UV exposure (a KNOWN carcinogen). Yes, a little sunshine is good for you, but too many people use the vitamin D excuse to overdo it. You max out your vitamin D production in about 10-15 minutes of incidental sun exposure – which you can get on forearms running errands – anything beyond just damages your DNA (look up cyclobutane pyrimidine dimers). I usually say a tan is your skin crying for help — it truly represents DNA damage. Are you really telling me you don’t believe that pilot’s increase in skin cancers is related to being tens of thousands of miles closer to the sun and UV radiation, and is instead related to their disturbed sleep pattern??? Come on, I think that is being foolish to the detriment of the health of your readers. Sure, circadian rhythms are important, but it seems to be you are ignoring the obvious in order to protect some flawed logic about UV exposure.

    And your quoting of the article regarding skin cancers in pilots was incorrect. It directly states that “The relative risk of skin cancers increased with the time since first employment, the number of flight hours, and the estimated radiation dose.” Your misquoting and redirecting makes me question if you can unbiasedly evaluate something that goes against your beliefs. To date, I believed that you could!

    Why the huge defense of the sun??? Let’s just acknowledge that it’s good for mood and circadian rhythms to get a little sunshine and play outside. Yes, you get vitamin D production but it’s limited to the first 10 minutes. Use PROTECTION! I literally diagnose a skin cancer in my office EVERY day.

    I apologize for getting a little smart, but let me just say this. This love affair of getting sun without protection gives me great job security. I can’t argue with people who vehemently quote vitamin D synthesis or the dangers of sunscreen- no amount of science can convince them otherwise. But eventually I see many of them in my office when they want laser to reverse their sunspots and wrinkles or to cut out their skin cancers.

    Sorry for the rant. I am a big fan otherwise!

    Jackie Dosal, MD
    Board Certified Dermatologist

    1. Dr. Dosal, just in case you did not already know about this, for your patients that work outdoors, in addition to standard protection techniques, you might want to consider recommending they take an astaxanthin supplement daily. There is compelling evidence it greatly helps protect against sun damage.

    2. Are you really telling me you don’t believe that pilot’s increase in skin cancers is related to being tens of thousands of miles closer to the sun and UV radiation, and is instead related to their disturbed sleep pattern???

      Planes generally fly no higher than 40,000 feet, ( i fly a lot so going on my own experience)
      40,000 ft = 7.5757576 miles.

      1. I think what Jackie meant was: “flying tens of thousands of miles at 40,000ft”. She seems a very educated woman (+1 to her very intelligent comment above by the way) and I’m sure does not imagine that an aeroplane cruises at an altitude of 10,000 miles+. We would be in space at an altitude 62 miles…

    3. I’ve flown a number of small planes, with glass roof canopies, and believe me, you will get sunburned. Even the super thick Airline windshields let through UV, they designed them primarily for strength – new regulations may see string UV filtering become a requirement. Airline pilots have been known to apply sunscreen as a norm.

  7. Just finished reading “Why we sleep” by Matthew Walker. Everything you wish to know about the power of sleep, circadian rhythms, NREM AND REM. For us (personally) it’s the final piece in the jigsaw of health and fitness. To quote from one of his chapters “I was once fond of saying sleep is the third pillar of good health, alongside diet and exercise. I have changed my tune. Sleep is more than a pillar: it is the foundation on which the other two health bastions sit. Take away the bedrock of sleep or weaken it just a little and careful eating or physical exercise become less than effective”.
    Diet and exercise are negotiable to an extent – if we want that piece of cheese cake or miss a session at the gym it’s not going to have a significant long term impact. Sleep (as M Walker discusses) is non negoitiable.
    A must read and certainly one for a podcast Mark

  8. Just to add that in reference to your article and again I quote from Matthew Walkers book:
    “Stirred by the strength of accumulating evidence, Denmark recently became the first country to pay worker compensation to women who had developed breast cancer after years of night shift work in government sponsored jobs such as nurses and air cabin crew. Other governments – Britain for example – have so far resisted similar legal claims…….despite the science”.
    Radiation may have some effect but disruption to your own natural sleep rhythm appears to be the major cause.
    According to M Walker companies like Nike and Google now allow employees to time their daily work hours to match their individual circadian rhythms and their respective night owl and morning lark chronotype nature. They also have “nap pods” where employees can indulge in sleep throughout the work day.
    I doubt very much weather these companies are taking a soft approach as they are as shrewd as they are profitable.

  9. I’m a Flight attendant, and am also wondering about the WiFi we have on the planes now, and how that is affecting us health wise.

    1. It’s not. At all. Good lord, you have a hundred times higher dose and duration in your own home. Further, the energy levels of cosmic rays, UV, and UHF (phone, wifi) are very wide.


    1. Dr M
      In my journals…including the JNM…the LNT is gasping its last. It is not quite dead but expert opinion is substantially in the upper hand. My RSO is the President of Assoc of Medical Health Physicists…..she and I toss this around a lot she has rejected it. The LNT infrastructure and regulations is being dismantled to some degree . For radiation workers there are still regulations and neither the NRC ior FDA in a position to join the rolling stone too far. If you wish I can dig around link you to the articles and discussion.

      I oversee the radiation safety for human subjects research in PET for the University, along with the RSC. Absolute risk of cancer for subjects is not calculated for the Informed Consent documents because it’s impossible to know. the language is so vague as to be , IMO, not terribly “informative”.

      Here is a start

      There is a phenomenon of hormesis.

      Professor of Radiology