Not only is this not Chernobyl – even Chernobyl was not Chernobyl
Radiation near the reactors rises to 2-3 millisievert/hour during planned venting operations from the damaged cores, but workers are pulled back ahead of these. In general their exposure rates are much lower, permitting them to keep doing shifts inside the plant for months if need be – though as soon as the situation is downgraded from a lifesaving operation to one intended merely to save equipment, which could be quite soon, the annual exposure limit will probably be cut to 100 millisievert. So far only one worker is known to have surpassed this reduced level, which is the point at which – should large numbers of people be exposed – a slightly higher cancer risk later in life becomes measurable.
The main risk to the Fukushima workers is from ordinary fires and explosions, of the same sort which have been seen all across the stricken region, which have so far injured 14 people on site but killed none. The quake itself did kill one nuclear worker (at a different powerplant, Fukushima Daini) who was in a crane cab when it struck, and two others have been missing since the tsunami hit. Nobody has been hurt at any nuclear site since last Tuesday.
Outside the plant, radiation levels are being monitored at many locations by a variety of Japanese and international agencies. Thus far the highest reported level was a dose rate of 0.16 millisievert/hour picked up by an IAEA team at the edge of the 20km evacuation zone yesterday, widely reported under scaremongering headlines but nonetheless insignificant. Such a level would have to be sustained for a month continuously before any increased cancer risk occurred. Readers should also bear in mind that this increased risk would be a tiny fraction of a single percentage point; ie you have say a 25 per cent chance of dying of cancer one day anyway, varying mainly on such factors as whether you smoke. If that IAEA reading of radiation somehow stayed steady (it cannot, as most of the isotopes causing it have short half-lives) and you remained outdoors at that location continuously for at least a month, your cancer chance would then be 25.0001 per cent or similar.
There is no indication that the IAEA reading was anything more than a brief spike. Japanese monitoring teams also reported a brief rise in levels to 0.05 millisievert/hour at one location near the plant.
In summary, no radiation levels of any public-health concern have been detected beyond the plant fence.
There also exists the related issue of food contamination, which has also stoked huge levels of public fear in the last 48 hours or so since initial sampling results became available. Again, however, absolutely nothing of any concern has been revealed so far, though the Japanese government has bowed to the hysteria and instituted a precautionary, temporary ban on spinach and kakina (another leafy vegetable) from four provinces. The government has also requested, though not required, that milk from Fukushima province should not be shipped.
Chief cabinet secretary Yukiyo Edano, announcing the measures, stated yesterday that it was perfectly safe to consume the named products, in which very low levels of radioactive iodine and caesium had been found.
This seems very credible. Based on experience from Chernobyl the only possible public danger is that from the radioactive isotope iodine-131. Children and young adults who ingested small amounts of this in milk during the weeks following the Chernobyl incident subsequently had a very slightly enhanced risk of thyroid cancer even though they had never been exposed to dangerously high radiation levels: this was because the body, especially if one's diet is low in salt, takes up iodine and concentrates it in the thyroid gland.
Colossal amounts of iodine-131 were hurled high into the atmosphere when the Chernobyl core melted down, burst open, blew up and then burned while molten and open to the sky for days on end. It's now thought that some 18 million youngsters across the region consumed dangerously contaminated milk as a result, containing iodine levels thousands of times higher than those seen now in Japan, and that as a result their chance of getting cancer increased from say 25 per cent (or whatever it would normally have been) to 25.02 per cent. Death rates didn't rise correspondingly as thyroid cancer can normally be cured.
This remains the only radiological effect of the Chernobyl disaster on people outside the plant itself, though so many scare stories were and still are circulated about it that one will still be subjected to a barrage of abuse for saying so. It is now an officially acknowledged fact that the great bulk of medical damage to the public after Chernobyl resulted from mass panic and associated psychological stress, not from the accident itself.