Even if a study existed that found them 100% safe, here's the thing about science: the later discovery of a missing fact or understanding about some small unknown behavior can change EVERYTHING. But then you are left with people who simply flout the original study for political reasons or ignorance. Happens in every field.
This is also why modern nuclear power plant design seem so safe. And then something they didn't factor in shows up, or someone takes a sloppy shortcut in building or regulations that wasn't accounted for and suddenly there's no way to undue the damage (and no way to stop the failure).
If they won't let TSA agents wear dosimeters, well then you'd have to be a moronic zombie to become a TSA agent and work around these machines. And that's predictably who is left working there. But hey you can sue for lack of benefits when you are dying of cancer, only to be told on your deathbed that you fall within the range of people who get cancer anyway, couldn't be the machine.
I'd say "stop flying" but of course these machines are now in portable versions in vans and they can just drive down a street and expose everyone to it, opt-in or not (this really exists, it's not tinfoil hat paranoia http://google.com/search?q=backscatter+vans ).
Thirty years of use and demonstrable, well-documented lack of increased cancer rates in the users. That's why it's irresponsible to use them for political reasons. Or are you among those people who think they make you more secure?
I would be less worried about proving them safe ex ante than maintaining the safety of those around them. Regular monitoring for leakage and exposure would be a great start. The reason gate agents are not allowed to wear monitors is political. If there is any problem found I think it that workplace rule should be considered malicious.
Okay, so once in 1,000 years isn't enough. I'll buy that, especially where an accident's effect can last for up to a century.
So, how about once in 10,000 years? Once in 100,000 years? That's on the level of meteor strikes, and I can't think of any power plant that could withstand those.
I think that "never" is as impractical as "two years from now."
I'd call it safe if it only failed when it no longer mattered - if your power plant does not contain the nuclear waste in case of collision with the moon, it's a non issue, because there is nobody left alive to matter.
This is also why modern nuclear power plant design seem so safe. And then something they didn't factor in shows up, or someone takes a sloppy shortcut in building or regulations that wasn't accounted for and suddenly there's no way to undue the damage (and no way to stop the failure).
If they won't let TSA agents wear dosimeters, well then you'd have to be a moronic zombie to become a TSA agent and work around these machines. And that's predictably who is left working there. But hey you can sue for lack of benefits when you are dying of cancer, only to be told on your deathbed that you fall within the range of people who get cancer anyway, couldn't be the machine.
I'd say "stop flying" but of course these machines are now in portable versions in vans and they can just drive down a street and expose everyone to it, opt-in or not (this really exists, it's not tinfoil hat paranoia http://google.com/search?q=backscatter+vans ).