Update on the Japanese Nuclear Accident

Just some updates in terms of doses, dose rates and IAEA nuclear event classification.

As you may have heard, on the 12th April, the category of the Japanese nuclear event has been upgraded to the highest ranking on the IAEA scale, level 7, the same as Chernobyl. However to put this in perspective, the total amount of radiation released from Japan is less than 10% of the total released from Chernobyl and a large portion of that is over/into the ocean, whereas Chernobyl was over land.

Gamma dose rates across the board show a decreasing trend. In all but one prefecture gamma is around background, with Fukushima dose rates outside the exclusion zone ranging from 0.1 to 20 uSv/h and displaying a downward trend.

Radioactive deposition levels have also significantly decreased showing a consistent downward trend.

In terms of total exposures to people, the highest exposure levels have (fairly obviously) been to emergency workers stabilising the reactors. Of the 70 odd workers, 28 have received exposures above 100mSv with no-one receiving doses above 250mSv. The two workers who had skin reddening from 1 Gy exposure to their feet received doses of around 170-180mSv. To put these doses in perspective, they equate to less than 1% increase in lifetime cancer risk. This is compared to the Japanese lifetime cancer risk of over 20% from normal everyday living.

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Japanese Nuclear Incident

Putting it all in perspective.

With all the media frenzy and hysteria I thought it timely to write a little on the Japanese nuclear power incident. The intent of this article is to hopefully clarify things for people who do not currently have an understanding of radiation, is based on my considered opinion and is not meant as an official statement. This article is in no way meant to downplay the seriousness of the situation in Japan as if the situation were to worsen, we could potentially see loss of some lives and contamination of the environment. However I would hope that we can put it in some perspective when considering the massive loss of life from the tsunami.

Firstly, what are the units used to measure radiation?

There are a number of units used to measure radiation. We measure radiation dose in Grays and Seiverts (further information can be found at ARPANSA ). The current unit used in the media reports and information put out by the Japanese Government is expressing doses and dose rates in Seiverts so that is the unit we will focus on. (Seivert is shortened to Sv)

The first clarification is the difference between dose and dose rates. Dose rate is a measure of how quickly you will develop radiation effects. Dose is a measure of the total effect received from the radiation. To better explain this I will use the analogy of drinking water. How quickly you drink a glass of water (do you gulp it down or do you sip it) is the drinking (dose) rate. So gulping may be 50 Litres per minute and sipping may be 0.5 Litres per minute. How much water you drink is like the 'dose'. So if I gave a 0.5 Litre glass of water to two people, one gulps and one sips, they both have different rates, but in the end they both drink the whole glass, so they both had the same 'dose'.

So how fast you drink is the 'dose' rate and how much you drink is the 'dose'. Radiation is similar to this. If there is one person receiving 100 milliSeiverts per hour (100 mSv/h) and one receiving 0.5 mSv/h, they are receiving vastly different dose rates! However if person one is only exposed for 5 minutes and person two is exposed for an entire day, they receive roughly the same total dose!

The next important point is the use of the term 'background radiation'. There is (always has been and always will be) some radioactive material in the ground around us, in the water we drink, in the food we eat and in the air we breathe. This has ALWAYS been there and was NOT put there by humans. It was there 10,000 years ago and will be there 10,000 years from now. So we are ALL - every single human, animal, blade of grass in the world - being exposed to some radiation every second of our lives. This is called BACKGROUND RADIATION. The amount of background radiation is different from one place on the planet to the next. You can literally walk 100m and measure different radiation levels from NATURAL sources. The amount of background radiation varies from around 0.15 microSv/h (0.00015 mSv/h, there are 1000 microSeiverts in 1 milliSeivert) up to 10 microSv/h. This means a total yearly BACKGROUND dose of 1.5 mSv up to 85 mSv.

So, what levels are being measured in Japan?

Well there was a short-term spike reported of up to 400 mSv/h. The important thing here is that this was a SHORT TERM spike, it was very localised and it was INSIDE the reactor grounds. This was NOT measured in a populated area! So if we go back to the water analogy, firstly you have to have someone to drink the water! Then it is not just a matter of how fast you are drinking, but also for how long! If a worker was exposed to this level of radiation for 10 minutes, they would receive less dose than some areas of the world receive as background. However this is still a very significant dose over such a short period of time.

The dose rates around the perimeter of the 30km evacuation zone have had some localised levels measured at around 100 microSv/h with most around 1 to 5 microSv/h.

There have been some news reports of "high radiation levels" in Tokyo. This is a very tricky statement. Yes, there have been some elevated levels that are "higher than normal" but calling them "high" may be somewhat misleading. Tokyo's normal background is somewhere around 0.15 microSv/h. There have been some reports of up to four times background. This is 0.6 microSv/h. Yes this is "higher" but is definitely not "high", as this is still much less than many other areas around the world (see above about natural background).

What are the potential health effects of radiation exposure?

Let us be honest, very high radiation doses (*note - doses NOT dose rates*) can potentially cause an increased likelihood of cancer, radiation sickness and in some extreme case, death. The doses needed for these effects are listed below. These are doses received from high dose rates. If the dose rates were lower you would need to receive even more!

• More than 200 mSv - Increased risk of cancer, some nausea potential spleen damage
• More than 500 mSv - Nausea, some hair loss, not fatal, potential bleeding of gums, some lung damage if the exposure is from breathing radioactive material
• More than 1,000 mSv - Onset of Acute Radiation Syndrome (historically called radiation sickness), sterility, low risk of death, potential radiation burns
• More than 5,000 mSv - Increased risk of death (probability 50%), radiation burns, cataracts of the eye
• More than 10,000 mSv - Fatal dose, death within 14 days

So, what are the likely effects of the doses rates and doses being (and likely to be) received in Japan?

• Some of the workers involved in trying to stabilise the situation will get sick and may lose some hair. With medical care they will make a full recovery, however they will have some increased likelihood of developing cancer.
• For people living on the boundary of the 30km exclusion zone, there may be a very slight increase in cancer rates, but this is not likely.
• For people living in Tokyo there will be NO noticeable health effects.
• NOONE will pass on any genetic defects from these exposures

So the net result - it is HIGHLY UNLIKELY that there will be any deaths occurring directly from the Japanese nuclear incident. It is possible (though not likely) that there will be a very slight increase in cancer rates among a VERY SMALL portion of the Japanese people.

WHAT IS WRONG WITH THIS PICTURE??

There are 6,400 + people who have died from the TSUNAMI. If even ONE person dies because rescuers cannot get to them due to the fear of the nuclear incident, that will be more than have died from the nuclear incident itself. THIS WILL BE A TRAGEDY!

On top of this no one has spoken about the GUARANTEED health issues that are going to occur due to the raging inferno that was the oil refinery/depot that went up in flames and spread toxic black smoke over populated areas. Or the issues caused by displacing people from their homes due to the cautionary (and completely correct) decision to evacuation people around the nuclear plant.

14 hospital patients have ALREADY died from the forced relocation, NOT from radiation exposure!

What does it mean for Australians?

It means that there is a lot to talk about, a lot of time on the TV but not much else. There is ABSOLUTLEY NO RISK to anyone in Australia, America or anywhere else outside Japan for that matter! What really saddens me is that the focus has been taken off the REAL disaster of the catastrophic earthquake and tsunami, that has taken the lives of over 6 thousand people, made tens of thousands more homeless and is forcing an entire nation towards starvation. Also do not forget that temperatures in Japan are dropping below zero in many places. While we all panic about the perceived risk from the nuclear incident, I unfortunately foresee the potential for more massive loss of life to starvation and cold. This is where our focus should be.

Article by:
Anthony O'Brien
Senior Radiation Consultant and Director
Radiation Professionals

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Past News Items for Radiation Professionals

Mar 2009: MRSA in a new office!: MRSA have just moved to new premises at 3/1862 Albany Hwy, Maddington. Please note this address for any future correspondence.

Nov 2008: Fixed Industrial Gauges: MRSA are pleased to now offer licensed radiation safety training courses for fixed gauges. These courses are recognised by the Radiological Council of WA. For further information please contact us

Oct 2008: New NORM Guidelines: The new federal NORM (Naturally Occurring Radioactive Material) guidelines have been released. This will impact a wide variety of industries that are not traditionally linked to radiation practices. For further information please contact us

Jul 2008: Oil and Gas courses Now Available: MRSA are happy to now offer radiation safety training courses for the oil and gas industry. For further information please contact us