How much contamination would you find acceptable on your daughter’s teddy bear? Would you let her snuggle up at night with a bear that had been decontaminated to the industry standard – with low, but detectable counts? Does the bear mean so much to her that you’d want to get it back even with higher levels of contamination? Or would you insist on cleaning up every little bit of detectable radioactivity? And if not a teddy bear, how about the kitchen her dinner is cooked in, the living room carpet she lies on to watch TV, the classroom where she spends her days, or the silverware she eats with?
My guess is that virtually everyone reading this, no matter how where you stand on the biological effects of radiation exposure and no matter how cavalier you might be with your own radiation exposure, you’d hesitate to accept extra exposure to your kids. And it’s probably not a rational response; any more than any of our other concerns for our kids. I know I feel that way – if you’ve been reading this blog for any length of time you’ve most likely noticed that I am not overly concerned about low doses of radiation. At the same time, I have to admit that I’d have trouble telling my own daughter to snuggle up with her favorite (albeit lightly contaminated) Pooh bear.
This discrepancy is because there can be a disconnect between the head and the heart. I am utterly convinced that detectable contamination – say at the limit of 1000 decays per minute – would pose no threat to anyone; this is why it’s acceptable to release items with this level of contamination for unrestricted use. It would be good enough for me – but not for my girl.
So let’s think about the aftermath of a radiological emergency; one that’s spread contamination across a city, inside schools and businesses, and through homes and apartments. Cleanup will cost a fortune – maybe tens or hundreds of billions of dollars – and the more stringent the cleanup standards the more it’s going to cost. As a health physicist and a scientist I can crank out numbers to tell our elected and appointed officials how much radiation dose people will received from any level of contamination – and if they don’t believe me then I can run the numbers on a computer program such as RESRAD (for RESidual RADioactivity). But convincing an elected official – not to mention the workers, residents, and parents – to let people reoccupy an area that hasn’t been cleaned up to pre-emergency levels is going to be a hard sell.
So let’s think about the cost of every incremental bit of cleanup. Say that (in a hypothetical situation) contamination is evenly distributed and that contamination levels drop off proportionally with distance – doubling your distance from the center halves the contamination levels, tripling your distance reduces contamination by a factor of three, and so forth. Since the area of a circle is proportional to its radius this means that reducing contamination levels by a factor of two will increase the area to be cleaned up by a factor of four. So if the level of risk is directly proportional to the contamination levels, and if the cost of cleanup is proportional to the area cleaned up (both a bit on the simplistic side, but probably not too far off) then we can conclude that cutting your risk in half requires spending four times as much for remediation, and it’ll cost nine times as much to cut your risk by a factor of three. It’s not hard to see that costs skyrocket as we try to clean up to ever-lower levels – at what point do we stop cleaning up and decide to simply live with a little bit more contamination?
Ask a radio-phobe and the answer is obvious – clean up until all contamination is gone. A regulator would likely tell you to clean up until you meet the appropriate regulatory limits, and a scientist might answer that cleanup should proceed until the marginal reduction in risk is balanced by the increased cost. Which way will the decision go in an actual emergency? I honestly don’t know, and I don’t envy those who have to make such a decision.