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

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Before 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.

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