Quite a bit has been written about the lethality or otherwise of the radiation doses received by the workers at the stricken Fukushima power plants.
In his latest Interpreter post, Richard Broinowski has stated that 'From all informed reports, some of the heroes who worked in the plant desperately trying to remediate damage have received [lethal] doses from gamma radiation and will die'.
Here are a couple of contrary views: The maximum reported whole body dose to any worker as a result of the incidents is around 170 mSv (millisieverts). This is beyond general occupational limits of 50 mSv in any one year, but well below the recommended limit for intervention in emergency situations, which is 500 mSv.
No workers have suffered radiation sickness, although those workers who have been exposed to over 100 mSv in a short period are likely to incur a 1% increase in overall lifetime cancer risk.
The website of the United Nations Scientific Committee on the effects of Atomic Radiation (UNSCEAR), says that direct health effects (radiation burns or sickness) do not appear until the dose is around 1,000 mSv, and doses become lethal somewhere between 1,000 and 10,000 mSv (individuals vary in susceptibility to radiation, so there is no single threshold). 170 mSv is well below any of these thresholds.
Richard's statement that 'Among the many thousands of civilians who have received small radiation doses in Fukushima, Iwate and Miyagi Prefectures, some, according to the best informed of nuclear physicians, will probably die sooner or later from one radiation-induced cancer or another' also bears closer examination.
While it is true that radiation protection principles are predicated on the linear no-threshold model, it is instructive to compare that model with the actual results from the Chernobyl accident. Chernobyl was a much more serious accident than Fukushima, and much more serious than Fukushima could ever have been. In particular, doses to exposed civilian populations were significantly greater than is the case with Fukushima. What do extensive investigations by UNSCEAR conclude?
Apart from the dramatic increase in thyroid cancer incidence among those exposed at a young age, and some indication of an increased leukaemia and cataract incidence among the workers, there is no clearly demonstrated increase in the incidence of solid cancers or leukaemia due to radiation in the exposed populations. Neither is there any proof of other non-malignant disorders that are related to ionizing radiation. However, there were widespread psychological reactions to the accident, which were due to fear of radiation, not to the actual radiation doses.
The last sentence is important; it is the fear of radiation, rather than radiation itself, which has caused possibly the most widespread health consequences. Given that, we need to be very careful about spreading exaggerated and unscientific fears about the health effects of the low doses of radiation being experienced in Japan.
Don Higson, Fellow of the Fellow of the Australasian Radiation Protection Society has this to say:
'Ziggy Switkowski (SMH News Review, April 2-3, 2011) says "radiation-induced illnesses [at the Fukushima nuclear plant] have struck fewer than 20 emergency workers". Actually, it is fewer than 3. To be precise, two of three workers who ignored the readings of their radiation monitors and got their feet wet while wading in contaminated water. Their feet were burned by beta radiation, which could be nasty but is unlikely to be life threatening. The third worker was wearing gum boots, which protect against beta radiation but not against gamma radiation.
Altogether, a total of less than 20 workers have received radiation doses in the range 100 to 180 mSv. To put this into perspective, a dose of up to 30 mSv could be incurred from a CT scan. There is no chance of radiation sickness unless exposures reach about 1000 mSv.
Doses in the range 100 to 180 mSv cause a small risk of developing cancer after 20 or more years if the dose is incurred instantaneously (as in the atomic bomb explosions at Hiroshima and Nagasaki). If the dose is spread over a period of time, the risk is lower and less certain. About 25% of the population dies from cancer whether accidentally exposed to radiation or not. This rate might be increased by an additional one percent (say from 25% to 26%) for the more highly exposed workers at Fukushima'.
And finally, you can read George Monbiot's response to his critics.
Photo by Flickr user Dancing Arethusa.