Infant radiation dose over 30 km from plant may be over 100 millisieverts

[thewiseguy]

The radiation dose received by one-year-old infants outside of a 30-kilometer radius of the Fukushima Daiichi nuclear plant since Saturday's explosion at the plant may have exceeded 100 millisieverts, a computer simulation conducted by the government showed Wednesday.

''There are some cases in which they could have received more than 100 millisieverts of radiation, even if they're outside the 30-kilometer radius and in the event that they spent every day outdoors since the explosion at the Fukushima nuclear plant,'' Chief Cabinet Secretary Yukio Edano told a news conference.

Haruki Madarame, chairman of the Nuclear Safety Commission of Japan, told reporters, ''The figure represents the level that one-year-old infants would have received and accumulated in their thyroids by midnight Wednesday since the explosion.''

Madarame said the radiation dose accumulated by adults outside the 30-km zone in their thyroids would be lower.

People exposed to a radiation dose of 100 millisieverts are required to take potassium iodide, Madarame said. An annual radiation dose of 100 millisieverts is believed to be associated with an increased risk of cancer.

http://english.kyodonews.jp/news/2011/03/80575.html

That is the equivalent of doing 2000 chest x-rays on a 1 year old infant.

[thereismore]

1. milli? not micro? If so, this is very serious. nt

[thewiseguy]

2. There currently is a 350 mSV/ lifetime limit

Not sure how that works for infants.

[Aerows]

3. If that is the case...

...then there is no way that the radiation levels that have been reported are accurate. I did a quick calculation on it, and that would put it at 416 µSv/ hr to come out with that level of contamination.

100,000 µSv ÷ 10 (days) ÷ (24 hours per day) = 416 µSv/ hr

I don't recall the levels ever being reported as being that high 30km from the plant, though I could be wrong.

Even now at the gates of the place it is reported as 470 µSv/ hr. So they are saying that even 30km away from the plant it is nearly as bad as it is at the gates of the facility?

[inademv]

4. Clearly they mean micro, not milli

That was a mistake that was made last week and never really corrected.

[FBaggins]

7. I don't think so.

They're not talking a whole-body dose here. They're estimating the worst-case scenario for an infant's thyroid dose if (s)he was out in the weather in the worst location for the entire crisis.

[inademv]

15. But that's still not in line

with the amount of radiation that the plant has been or reasonably could put out.

[FBaggins]

18. That would be true if they were talking about large areas.

But they're just running computer models on what the worst case overlap might be given the prevailing weather patterns.

Keep in mind that you can get dramatically different readings just a few hundred meters apart.


Another thing to consider is that they aren't talking about mSv/hr or even per day... they're talking about a total amount over more than ten days.

Lastly. Remember that effective dose takes a number of factors into account, including a weighting factor based on the sensitivity of the tissue in question (really high for an infant's thyroid).

[thewiseguy]

6. The article states that children do accumulate more radiation than adults

[FBaggins]

9. If it does, that's an error.

I think the correct statement would be that the same amount of exposure results in a higher effective dose in an infant.

[thewiseguy]

10. Here is what the article says:

Haruki Madarame, chairman of the Nuclear Safety Commission of Japan, told reporters, ''The figure represents the level that one-year-old infants would have received and accumulated in their thyroids by midnight Wednesday since the explosion.''

Madarame said the radiation dose accumulated by adults outside the 30-km zone in their thyroids would be lower.

[FBaggins]

14. That's what I thought. The DOSE is different.

Really its "effective dose" because that takes into account both body weight and what organs are impacted.

The child doesn't accumulate more "radiation", they get a higher dose with the same amount of radiation.

Thanks for the added info.

[FBaggins]

5. I think that's the potential thyroid dose if the child was outside this entire time.

And only for certain scattered areas, not just anywhere close to 30-km.

Having said that, this begins to approach a serious dose. It's one where potassium iodide is warranted.

The good news is that there are unlikely to be many infants who have hung around outside 24/7 since the earthquake that are close to 30 km from the plant.

There's a good chance that we'll see some increases in thyroid cancer down the road in this population, but after such an event, doctors are well trained to check for it and spot it early. It's easily treatable and very rarely malignant.

[Aerows]

12. Well, there is also the water.

Infants aren't supposed to drink it in Tokyo, so it certainly isn't going to be any better closer to the plant. I don't even know if some of those areas have running water, though, so maybe they weren't able to drink it.

[FBaggins]

16. I think their model is all-inclusive.

Infants aren't supposed to drink it in Tokyo

That's just a safety precaution. The level is technically higher than the standard, but we should keep in mind that that standard is what it allowable on an ongoing basis (IOW... the kid would be drinking it all year round).

Radioiodine has a pretty short half-life and is a fission product... so there won't be much more of it on the way (the plants stopped making the stuff days ago).

don't even know if some of those areas have running water, though, so maybe they weren't able to drink it.

I haven't seen recent reports, but right after the earthquake there were over a million people reported to have no access to clean water. That would certainly be a greater health risk than a few weeks of consuming water with radioiodine in the concentrations reported.

[Aerows]

17. That was what I meant...

...If it is all-inclusive, they are probably taking into account that people drank the water, too, so the radiation in just the air is likely not as high as I calculated. I would HOPE that is the case.

[Liberal_in_LA]

8. get out of there. everyone!

[Aerows]

11. If I had an infant in that area..

...I would certainly leave. I'd leave even if I had older children. There is just too much confusion with the way they are reporting radiation levels, and the fact that infants can't even drink the water in Tokyo tells me that this is much worse in the areas between Tokyo and the plant.

[Liberal_in_LA]

13. Me too! it's not worth the risk.