November 13, 2012
Why Fukushima Death Toll Projections Are Based on Junk Science
Mark Lynas takes on the faulty science behind new study
Original post here.
The media is abuzz with the first study attempting to quantify expected cancer deaths which may result from Fukushima. Written by Ten Hoeve and Mark Jacobson from Stanford University, the paper 'Worldwide health effects of the Fukushima Daiichi nuclear accident' is published in the journal Energy and Environmental Science (free PDF copy).
I will say upfront that I think the study is worse than useless. Jacobson (Hoeve is a former PhD student of his) is a long-time anti-nuclear and pro-renewables advocate, and (as I show below) clearly has an agenda to raise further fears about the health impacts of Fukushima and nuclear power in general. However, in this deeply flawed paper he succeeds only in illustrating some of the absurdities in current radiological protection models, and that one thing we know for sure - even if those absurdities are ignored - is that the evacuation killed more people than the accident.
The Hoeve and Jacobson (H&J) paper uses an atmospheric transport model (which is not really intended for this purpose) to attempt to quantify the worldwide movement of radionuclides released by Fukushima. Here they all are in the image below, circulating around the entire Northern Hemisphere and looking appropriately scary. (Note however that even the strong colours indicate infinitesimal amounts of additional radiation, far below normal background everywhere outside Japan.)
H&J then plug the deposition of these radionuclides into a grid-model of populations and apply a risk coefficient taken from the EPA. This is where things get really hairy. The risk coefficient depends on the assumption of LNT (linear no-threshold), which hypothesises that the linear dose-response relationship demonstrated at high levels of radiation exposure (the higher the dose, the greater the health impact) can also be assumed to exist at much lower levels. This is problematic for all sorts of reasons, not least that there is no convincing evidence for it, and much more to contradict it.
Hardly anyone I meet in the nuclear community these days still believes in LNT. Indeed, the International Commission on Radiological Protection (ICRP) in its Publication 103 (2007) specifically states:
The collective effective dose quantity is an instrument for optimisation, for comparing radiological technologies and protection procedures, predominantly in the context of occupational exposure. Collective effective dose is not intended as a tool for epidemiological risk assessment, and it is inappropriate to use it in risk projections. The aggregation of very low individual doses over extended time periods is inappropriate, and in particular, the calculation of the number of cancer deaths based on collective effective doses from trivial individual doses should be avoided.
H&J avoid the need to heed this instruction by cherry-picking an older ICRP reference from 2005, and using the EPA approach which is no longer the world standard. As the Health Physics Society explains in non-scientific language anyone can understand:
...the concept of collective dose has come under attack for some misuses. The biggest example of this is in calculating the numbers of expected health effects from exposing large numbers of people to very small radiation doses. For example, you might predict that, based on the numbers given above, the population of the United States would have about 40,000 fatal cancers from background radiation alone. However, this is unlikely to be true for a number of reasons. Recently, the International Council on Radiation Protection issued a position statement saying that the use of collective dose for prediction of health effects at low exposure levels is not appropriate. The reason for this is that if the most highly exposed person receives a trivial dose, then everyone's dose will be trivial and we can't expect anyone to get cancer. [my emphasis]
The HPS illustrates this commonsensical statement with the following analogy:
Another way to look at it is that if I throw a 1-gram rock at everyone in the United States then, using the collective dose model, we could expect 270 people to be crushed to death because throwing a one-ton rock at someone will surely kill them. However, we know this is not the case because nobody will die from a 1-gram rock. The Health Physics Society also recommends not making risk estimates based on low exposure levels.
Unfortunately the entire supposed value of the H&J paper involves taking precisely this invalid approach, assessing below-trivial doses to very large populations in order to come up with an outcome where some people die of cancer. Even so, the number is not very big, no doubt to Jacobson's intense disappointment. All told, H&J can only come up with 130 "worldwide excess mortalities", mostly in Japan, although between 0 and 6 fatalities are supposed to happen in the US also - despite the infinitesimal extent of Fukushima-derived radiaoactive contamination there. This is about as inappropriate a use of the LNT model - which was designed only as a precautionary approach to occupational exposures - as it is possible to have.
Even though I think these figures are junk science, it is worth putting them in context. Let's suppose that we were to accept H&J's calculations at face value. How bad will Fukushima then have been? There are 130 deaths every 7 hours currently due to outdoor particulate air pollution (3.7 million annually, according to UNEP), many from coal-burning power stations which are the main alternative to nuclear for baseload electricity production in most of the world. That's more than three Fukushimas every day. An additional two million die every year due to indoor air pollution, mostly because they don't have access to electricity.
The H&J paper rather strangely then goes on to extrapolate deaths from a hypothetical Fukushima-equivalent accident at Diablo Canyon nuclear power station in California. Clearly this case is picked to try to scare North Americans, and Jacobson is hoping to get a higher expected death toll because the radioactive release from Diablo Canyon would likely drift towards Los Angeles rather than being swept out to sea as happened after the accident in Japan. (Plus, Diablo Canyon is in a tectonically-active area, so more potentially scary.) Even so, the death toll is still disappointingly low, at 156 (11-1570, lowest to highest probabilities). Cue a few concluding sentences about how 1.5% of reactors ever built have blown up, that "the risk of a meltdown is not small" therefore:
The risks and consequences of a meltdown must be considered along with other impacts, risks, costs, and benefits of nuclear power, discussed elsewhere, in comparison with other electric power sources in deciding the future direction of worldwide energy policy.
In conclusion, I don't like to go in for ad hominem stuff, but the background of Mark Jacobson must be noted here. Jacobson is perhaps best known for a fantastical paper (PDF) published in Scientific American which proposed that all the world's energy should be generated from wind, water and sun by 2030. This has been critiqued in too many places for me to link to here (although Barry Brook over at BNC perhaps did it best), but suffice to say that it depends on a build-out of 4 million large wind turbines and 90,000 massive solar plants, and is, well, impractical to say the least. An earlier paper claimed that nuclear power must be carbon intensive because of all the burning buildings that would result from the inevitably-ensuing large-scale nuclear war.
This is not the perspective of an objective energy scientist, but of an anti-nuclear campaigner pursuing an ideological agenda. If there is still any lingering doubt about Jacobson's lack of objectivity, check out his TED debate with Stewart Brand under the heading 'Does the world need nuclear energy?'
But I want to end on a different note, with a look at how real people actually did suffer and die as a direct result of the Fukushima accident - not because of the radiation itself, but because the fear of radiation led to a hurried evacuation of vulnerable people from hospitals and care homes. A paper in The Lancet describes the sorry mess that resulted:
Medical personnel did not accompany the patients during transportation. Bed-ridden patients were laid down on the seats, wrapped in protective gowns. During transportation, some patients suffered trauma by falling from the seats of the vehicles.
Evacuation continued late into the night. As the situation at the damaged plant became more volatile, the evacuation became more rushed and patients were transported by police vehicles as well. The vehicles were packed full, not only with patients but also with residents who had missed the chance to evacuate on their own. Late at night on March 14, patients were required to leave the buses because admitting hospitals or facilities could not be found and the vehicles were required elsewhere. Eventually, the patients were temporarily housed at a meeting room of the Soso Health Care office in Minamisoma city, with no heaters or medical supplies. Many had to wait for more than 24 h before reaching admitting facilities.
27 patients with severe medical problems such as end-stage renal failure or stroke were transported more than 100 km to Iwaki city. At least 12 of them were confirmed dead at 0300 h on March 15, ten of whom seemed to have died in the vehicles during transportation. Later, it was reported that more than 50 patients died either during or soon after evacuation, probably owing to hypothermia, dehydration, and deterioration of underlying medical problems.
And the next sentence is the key:
In the Fukushima Daiichi Nuclear Power Plant accident, there were no deaths related to radiation or the explosion of the reactors. However, the evacuation of these patients was accompanied by loss of life.
As Chernobyl showed, fear of radiation is a far greater risk than radiation itself in the low doses experienced by the affected populations after both accidents. Unfortunately work by Jacobson and other anti-nuclear campaigners (in academia, environmental groups and elsewhere) will make this fear worse, and harm people's health accordingly. I hope they are aware of this.