Zero risk or Negligible Risk

One of the gripes that pro-nukes have about SNT is that it accepts the no-perfectly-harmless-dose hypothesis.¹ These people think the public is too stupid to understand that there is no practical difference between negligible risk and zero risk. They are wrong. All of us accept negligible risks every time we walk out the door.

Figure 1. Lucy and the meaning of the word negligible

In the Peanuts comic strip, Lucy is counting the stars. But she realizes she can't see the teeny-weeny ones. She's too far away. So she grabs a chair and stands on it to get closer. Her logic is impeccable. But everyone gets the joke, even Charlie Brown; and everyone who gets that joke understands the meaning of the word negligible.

If you don't accept the no-perfectly-harmless-dose premise, you must argue that there is a threshold below which there is absolutely zero harm. You have just painted yourself into a corner whence there is no escape. You have set up a false dichotomy. Either there is such a threshold or LNT. The LNTers pounce on this. They don't defend LNT. They can't . That would require claiming 1000 mGy received all at once produces the same harm as 1 mGy per day for a 1000 days. That would require claiming we can't repair low dose rate radiation harm. Nobody is that stupid. Rather they attack the concept of a threshold as unproven and unprovable, putting a nearly impossible burden on the thresholder.

They ask the thresholder exactly where is this magic threshold? What is that dose? Give me a number! If the thresholder declines to give them a number, he has lost the debate. If he comes up with a number, he is asked: what is so special about that number such that a tiny bit below that number, radiation is perfectly harmless, while a tiny bit above that number radiation is harmful? He can't say. He has lost the debate. By his own rules, we are left with LNT.

In addition, our thresholder has set off all sorts of psychological alarm bells. People instinctively know there is no activity that has absolutely zero risk. Even the most beneficial nutrient or drug will sometimes cause harm. Even the best vaccine will occasionally kill. Why is this guy insisting on absolutely zero harm? He must think I have good reason to be very worried about radiation. And he must think I'm none too bright. I'm not buying this snake oil.

A threshold is not only impossible to defend, it is completely unnecessary. The problem is not that people won't accept negligible risk. The problem is people do not think the risk associated with radiation dose rates to the public produced by a nuclear power plant release is negligible. Our job is not to convince people that there is zero risk; but rather to convince people that any risk from nuclear power plant releases is eminently acceptable in return for the benefits.

We do that by:

1. Pointing out radiation is natural and ubiquitous. It is everywhere. Is it pointless to talk about something being radioactive. You are radioactive. Your dog is radioactive. The only question is how radioactive. This means we must get quantitative when it comes to radiation.

2. Outlining the range of background radiation rates, which runs from 0.003 mGy/d to 0.16 mGy/d. Higher in spots, such as radon spas. We have no evidence of increased cancer incidence in high dose rate areas. Keep everything in terms of daily dose rates. Dose without an exposure period is meaningless. In this context, the relevant exposure period is the repair period.

3. Going over the examples where people have been exposed to far higher than background dose rates. We see no increase in cancer incidence, until we get into the range of 20 mGy/day or higher, even when that daily dose is repeated for thousands of days. We don't say there is absolutely no harm. Rather we say, if there is any harm, it is so small we can't reliably detect it. A risk that you cannot detect is hardly a risk at all.

4. Even in a release as large as Fukushima, no member of the public was exposed to 20 mGy/d for even one day nor would they have been, if there had been no evacuation.

In return, for this negligible risk, we could have zero pollution, very low CO2, 24/7 electricity for 3 cents per kilowatt hour. This would both push almost all fossil out of power generation and make humanity wealthier. These twin effects will increase health and longevity far in excess of the loss in life expectancy associated with an occasional release, which loss in most releases will be undetectable. It's the nuclear plant that isn't built that kills.

1. This is usually phrased ``no-perfectly-safe-dose". But that's useless wording. What's “safe" it a subjective judgement. I may think jumping out of an airplane with a parachute is safe. My wife may differ. We are both right.