How much radiation is dangerous?

Chart of the day.

As I noted earlier, radiation levels at Japan's Fukushima power station have reached 400 millisieverts (mSv) per hour. The chart below (posted by @ gakuranman) helps put this figure into perspective. A typical chest X-ray, for instance, involves exposure of about 0.05 mSv, while a stomach X-ray involves 0.6 mSv. The annual amount of natural radiation is roughly 2 mSv; the current limit for nuclear industry employees is 20 mSv per year.

According to the World Nuclear Association, 100 mSv a year is the lowest level at which any increase in cancer is clearly evident; absorption of more than 500 mSv can depress white blood-cell levels. A single dose of 1,000 mSv causes radiation sickness such as nausea and vomiting; a single dose of 5,000 mSv would kill about half of those receiving it within a month.

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Following the Chernobyl disaster in 1986, those exposed to levels greater than 350 mSv were relocated. In Japan, the government has ordered everyone within 30 kilometres of the danger zone to stay indoors, and has imposed a no-fly zone around the power station. The US navy's 7th Fleet, stationed 100 miles offshore, has retreated after 17 crew members were treated for radiation exposure.

George Eaton is political editor of the New Statesman.

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Andy Burnham's full speech on attack: "Manchester is waking up to the most difficult of dawns"

"We are grieving today, but we are strong."

Following Monday night's terror attack on an Ariana Grande concert at the Manchester Arena, newly elected mayor of the city Andy Burnham, gave a speech outside Manchester Town Hall on Tuesday morning, the full text of which is below: 

After our darkest of nights, Manchester is today waking up to the most difficult of dawns. 

It’s hard to believe what has happened here in the last few hours and to put into words the shock, anger and hurt that we feel today.

These were children, young people and their families that those responsible chose to terrorise and kill.

This was an evil act. Our first thoughts are with the families of those killed and injured. And we will do whatever we can to support them.

We are grieving today, but we are strong. Today it will be business as usual as far as possible in our great city.

I want to thank the hundreds of police, fire and ambulance staff who worked throughout the night in the most difficult circumstances imaginable.

We have had messages of support from cities around the country and across the world, and we want to thank them for that.

But lastly I wanted to thank the people of Manchester. Even in the minute after the attack, they opened their doors to strangers and drove them away from danger.

They gave the best possible immediate response to those who seek to divide us and it will be that spirit of Manchester that will prevail and hold us together.

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