Pug: Don't bother arguing with me about this. Make no mistake, you
will lose.
But cancer is a disease that is very much dependent on your environment, and isn't affected by one thing but rather a combination of unnatural things that take their toll over time.
That's not how cancer develops from radiation exposure. That particular risk is usually modeled with the linear hypothesis, which basically assumes that one person receiving a dose of 100 REM will yield on average as many new cancers as ten people getting 10 REM. (The linear hypothesis is known to be wrong for radiation exposure, but they use it anyway because it errs on the side of caution. See "radiation hormesis," in particular.)
Not one of these factors will give you cancer, but many of these over a period of time can trigger something wrong -- but that also depends on the human body as some have more resistance.
"Cancer" is a discrete event in which one particular cell develops a mutation causing uncontrolled growth. Whatever specific cause triggers the mutation, is the cause of that cancer. (Immunocompromised patients also have an "increased risk" of cancer, not because such a mutation is more likely to happen in them, but because their immune systems are less likely to respond. In theory they should get cancer at the same rate as the rest of us, and then have a poorer course and outcome; but in practice they're also at an increased risk of developing a malignant tumor that their immune systems fail to respond to and so
do get more cancers than the rest of us.)
Something like X-rays aren't meant to be fired at you every day. Most people are likely to need not more than three X-rays in a lifetime. My uncle lives in Virginia and air travels every other day, and is just an example. But if this comes to pass, in one week he'd already have had more X-Rays than most of us would have in a lifetime.
These are a good deal less powerful than medical X-rays; they don't penetrate skin very well at all (meaning that the only real risk is skin cancer); and X-rays and worse are raining down on you from space all the time. (They also come from the ground, seawater, granite rocks, and your own body, to name a few common sources. Also, most natural radiation exposure is in the spectrum of gamma rays, which are like X-rays except a) worse and b) more able to penetrate internal organs.) Also, flying on an airplane automatically exposes you to a relatively large dose of radiation.
Now that's just medical X-rays that aren't really that high in volume. I am just wondering, how'd the come up with that stat? How do you measure what has caused the cancer?
Probably by examining patient histories, and correlating the frequency of medical X-rays with the frequency of cancers. (Chances are they also controlled for any confounds they could identify.)
