A few days after the devastating 8.9 magnitude earthquake and tsunami that hit Japan, the Japanese government has announced that radiation from the quake-stricken Fukushima Daiichi nuclear power plant has reached harmful levels after a third blast occurred at the plant earlier today. The readings at the site rose beyond safe limits- 400 millisieverts per hour (mSv/hr), compared to the average person’s exposure of 3mSv in a year. Residents within a 30km radius have been told to evacuate or stay indoors.
A fake text message (purporting to come from BBC) that warned of nuclear radiation hitting other parts of Asia circulated around Asian countries today, causing panic across Asia- and of course, Hong Kong was not exempt. Patients and friends alike asked questions in fear- What should one take as a precaution? What happens if the radiation does come this far? Do we really stay indoors and keep the home airtight?
And with American nuclear expert Joseph Cirincione saying that even the United States could be affected if a complete meltdown occurs, it’s hard not to panic.
What we do know:
- Experts say even small radiation doses, as low as 100 millisieverts, can slightly raise cancer risk
- Leukemia is the most common radiation-induced cancer
- Other cancers including that of the thyroid, lung, skin, breast and stomach may take years to develop
How much radiation is too much?
- 2 mSv/yr (millisieverts per year)- Typical background radiation experienced by everyone (average 3 mSv in North America)
- 9 mSv/yr- radiation exposure by airline crew flying the New York-Tokyo polar route
- 20 mSv/yr- Current average limit for nuclear industry employees and uranium miners
- 50 mSv/yr- Former routine limit for nuclear industry employees. It is also the dose rate which arises from natural background levels in several places in Iran, India and Europe
- 100 mSv/yr- Lowest level at which any increase in cancer is clearly evident. Above this, the probability of cancer occurrence increases with dose
- 350 mSv/lifetime- Criterion for relocating people after Chernobyl accident (1986 nuclear power plant disaster in Ukraine)
- 1,000 mSv single dose- Causes radiation sickness such as nausea and decreased white blood cell count, but not death
- 5,000 mSv single dose- Would kill about half of those receiving it within a month
SOURCE: World Nuclear Association