Dangerous advice

The true but somewhat less catchy title would be "Why I think the public promotion of a threshold for harm from radiation is a bad idea." 

Radiation causes a fear in the public that few other hazards can come close to. Biological hazards like the normal flu sweep through populations and kill literally millions and no one bats an eyelid. A coal mine collapsing in China killing 30 might not even be the headline story of the evening news but a radiation leak that might kill someone over a 30 year window is a worldwide screaming headline story for months.

Fukushima's radiation leak which killed no one occurred immediately after a Tsunami which killed over 15,000 people. Yet it was the radiation leak that got the lion's share of media attention. An already devastated people had their worst and most illogical fears "confirmed" not by facts but by a sensationalist media storm. The exposed were even paraded as a faux case study in the dangers of nuclear power to the world. "Look the nuclear safety experts were wrong, we may have to evacuate the northern hemisphere" was the message screamed by one article. It is immediately obvious that this is daft to almost everyone with even the slightest training in radiation science but the fact it is utter bollocks is pretty much irrelevant when it comes to the public1

Frankly the public perception of radiation is so skewed it cannot be easily fixed at least not for older generations. The cold war apocalypse-based imagery, Chernobyl hysteria promoted by scientifically illiterate campaign groups and the ever present lurking human fear of cancer are not something that a snappy educational video will solve. The hard precise language of science and specifically radiation physics and epidemiology does not help. In any case that modern science comprehensively shows something to be wrong is only relevant if you listen to science. Most people don't.

Telling someone that "an accident increased their lifetime cancer risk by 1%" maybe the truth (it is for someone exposed to 100 mSv of radiation) but different people feel very differently about receiving such a statement. A medical Oncologist might feel:
Phew, that doesn't really affect my lifetime odds of cancer.
but the average member of the public will feel:
AH! They INCREASED my chance of CANCER!
Jump forward 15 years into the future to when the victims of our imaginary exposure hear they have cancer. I guarantee you both would believe their accidental exposure caused their cancer, regardless of their own training or others pointing out that this is highly unlikely. Everyone who gets cancer who lived near Chernobyl "knows" their cancer was caused by the accident no matter what comparisons with other areas might suggest. Basically when it comes to our own, and the health of our families, you generally find humans are not the most logical of beings. If you think you or an educational scheme can change this let me be blunt you are wrong.

Those dispensing advice relating to radiation have a tricky job, they have to be both right and reassuring to combat inherent illogical fears. Being precisely right is crucial as any uncovered mistake no matter how minor will immediately seriously damage the public's confidence in all your statements. But reassuring is also important as the public is very poorly educated about radiation and many opponents (e.g. anti-nuclear folk) take every opportunity to shout scary misinformation and chances to counter this are few and far between. Still if I had to choose between being technically precise and giving comforting but vague assurance I would go with the precise truth. Mostly this is because as a medical scientist I am against lying to, or withholding the truth from, the public even if it is for their benefit2.

I cannot, in good faith, state there is no risk from low doses of radiation. The precise truth is that the risk is negligible or, should you prefer, that no one has definitively demonstrated any risk increase. It's basic PR that in any well publicized debate you should not voluntarily hold a well-defined position that has a genuine chance of being toppled by new hard evidence. This is especially true when the debated issue is pointless. Publically arguing whether a 10 mSv exposure increases cancer risk from 33% to 33.1% or not is simply daft. The corrections due to lifestyle on the 33% figure might be +/-5%, genetics maybe +/-20%, etc. You might think by arguing about the possible nonexistence of a small risk you are publically promoting how safe radiation is but actually all the public hears is scientists arguing amongst themselves. You are freely gifting the infamous if-they-can't-even-agree-amongst-themselves-why-should-we-listen-to-them effects3 to opponents.

Is it really that bad to say the risk is negligible? After all nothing is totally safe (e.g. you think that food you ate earlier is 100% safe?). 

So why did UNSCEAR advise a threshold limit? It is true that their threshold of 100 mSv is the minimum value the evidence suggests at which the risk-dose model that UNSCEAR promotes (the LNT) definitely applies but assuming 99 mSv is a safe level is another matter. Now to be fair this is not what UNSCEAR's report actually states but it is an idea that has been around a while and the proposers were certain to use the report as justification. I personally do not believe UNSCEAR members could not have predicted or not expected this usage. I think they accepted it  on the basis that it is an easier message to sell to the public. I understand this but it is risky.

If an exposure of 99 mSv is accepted as harmless then for cost reasons we will tend towards that value. Of course people and engineering will attempt to keep it down and operate safety factors but the economic reality is that the lower the dose (ie the better the shielding and handling) the more expensive the facility or mishap clean-up will be. Would you spend another $100 million to improve shielding if your models suggest the current would limit radiation to spikes giving a 95 mSv exposure in an accident?

Let us consider what would then happen if data on a large population exposed to 90 mSv became available. We could calmly reassure the exposed by extolling the 100 mSv threshold model right "Don't worry there will be no effect from this dose". But effects at 100 mSv are known so it is very possible that a currently unobservable effect at 90 mSv would be seen in a large exposed population. Now let me be very clear. The effect would be tiny but the ramifications of this discovery would be massive. The public who had been placated by the threshold model would turn on the advisers. "SCIENTISTS LIED TO YOU!" would be the crux of most articles. Revising the threshold or meekly stating "that is what the data said" would be next to useless in restoring public confidence. It would probably be the most devastating PR hit to radiation research and nuclear power since the effects of the atomic bombing of Japan were revealed to the public.

Of course all this could also happen at lower limits but it would take longer and it's hard to imagine a situation where you would not get forewarning by first seeing effects at higher, thou still under 100mSv, doses4. Even a panicky public won't care about a reduction in a safety factor. It all comes down to a very simple point. If taking X or more of something is definitely bad and the effect of taking less than X is essentially unknown then I for one would rather set the recommended limit as low as is reasonable rather than at X. Especially if being wrong is going to have me damned by the public and destroy all confidence in a field I think is important for humanity.



  1. I am not calling the public stupid they are just untrained and (often) uninterested in how radiation "works"
  2. This is why I do not think medical doctors should prescribe placebos like homeopathy.
  3. This effect is immensely damaging to a cause and a powerful tool for those who work to oppose scientific positions.
  4. Some make very good cases that we already have seen these in some studies.