Japan earthquake - contamination & consequences outside Fukushima NPP

nikkkom

"one mili is ten micro"??!

joewein

That's a mistake, maybe by automated translation.

Japanese:
English:

NUCENG

I am not trying to stifle this discussion, but the bottle is clearly not related to the Earthquake or Fukushima. Should this be a new thread?

tsutsuji

It was a human mistake. Thanks Joewein for the correction. I don't mind moving talks on contamination unrelated to Fukushima to other threads.

nikkkom

It is somewhat related since this bottle wouldn't be found without large-scale dosimetric campaign induced by Fukushima disaster. How many more wonderful discoveries await us?

tsutsuji

Japan:
http://www3.nhk.or.jp/news/genpatsu-...nko_eikyo.html During a conference in Hamamatsu, nuclear accident minister Goshi Hosono said that he would build up a specialist team, whose mission will be to examine the effects on health of low radiations of the order of 20 mSv/year.

http://www3.nhk.or.jp/news/html/2011...622731000.html The Ministry of health's food safety commission held a meeting on 31 October. The provisional food safety levels will be revised with the goal of setting the maximum food exposure at 1 mSv/year from next April (instead of the present 5 mSv/year). Each food's new safety level will be decided within this year.

http://www.tokyo-np.co.jp/article/na...102000163.html The food safety commission received a report that considered that health effects can happen if the accumulated dose of internal exposure over one's life is 100 mSv or above. The maximum 1 mSv/year level for cesium was decided using references such as those of the codex alimentarius. 887, or 6% of the 14,536 food tests performed from July to September in Japan except Fukushima prefecture were above 100 Bq/kg (10% for Fukushima prefecture).

http://www.jiji.com/jc/c?g=soc_30&k=2011110300274 According to the ministry of Agriculture, there are 7200 tons of contaminated straw in 8 prefectures. If it is above 8000 Bq/kg it must be stored in special temporary storage facilities, but most of it is still stored on each farmer's land, as securing such storage space is a time consuming effort.

Tokyo:
http://www.asahi.com/national/update...111020738.html 0.01111 Bq/m³ of strontium 90 was measured in a 15 March air sample taken in Tokyo, Setagaya ward and reported to the Tokyo metropolis administration on 21 June.

Kanagawa:
http://www.jiji.com/jc/c?g=soc_30&k=2011110400425 12 Bq/kg of strontium 90 was measured in an earth sample, Zushi city announced on 4 November. The laboratory that made the measurement says it is reasonable to believe it came from Fukushima Daiichi.

http://news.kanaloco.jp/localnews/article/1111050004/ At Maioka park, Yokohama, 955 Bq/kg was found in shiitake mushrooms harvested and dried in October, and 2770 Bq/kg in those harvested in March and dried in April. 1.8 kg of the March harvest have been served in dishes.

http://mainichi.jp/area/kanagawa/new...40258000c.html 510 Bq/kg was found in tea grown in Yugawara, Kanagawa prefecture announced on 2 November. A tea shipment ban had been in force in 10 towns and villages since June, but in 9 of them, tests have always been below the 500 Bq/limit. The ban has been lifted in those 9 towns and villages except in Manazuru.

Chiba:
http://water-news.info/2103.html Ichihara Ecocement (Ichihara city) was ordered by the prefecture to stop effluents above 1000 Bq/kg flowing into Tokyo Bay, and the plant was stopped on 1 November. 1103 Bq/kg had been measured on 21 September and 1054 Bq/kg on 14 October.

http://www.yomiuri.co.jp/e-japan/chi...OYT8T00065.htm The prefecture took 5 seawater samples in Tokyo Bay up to 2 km away from the cement plant and announced on 4 November that no radiation had been detected.

http://www.chibanippo.co.jp/cn/news/national/63980 Fish samples will be tested to address the concerns of the nearby fish angling park which receives up to 300 visitors per day.

http://www.chibanippo.co.jp/cn/news/local/63749 A detailed survey of the Kashiwa Nedo district hotspot (the 270,000 Bq/kg one) was started on 2 November. Workers measured the surroundings' topography and took 20 earth samples. Sediment samples were also taken in the Ohorigawa river and in the Teganuma marsh. The results are expected for the end of November.

Ibaraki:
http://mytown.asahi.com/ibaraki/news...00001111040004 & http://mytown.asahi.com/ibaraki/news...00001111050002 A citizen group found 122,800 Bq/kg in a 6 October earth and sand sample from a concrete path between the main gate and the children building entrance in a school in Ryugasaki city. The city cleaned the path on 14 October, but samples taken near the path on 3 November had 11720 ~19050 Bq/kg (above the 8000 bq/kg standard that requires waterproofing and shielding measures). 228 locations in schools are above the city's 0.23 μSv/h standard. The mayor said "I have a child too. I will launch countermeasures not only as mayor but also as a parent".

http://mainichi.jp/area/ibaraki/news...40121000c.html The Tsukubamirai school board has decided not to serve to children the 7 kg of fresh shiitake mushrooms that had been planned for a 4 November school lunch menu. They had been harvested on 1 November in a farm's green house in Tsukubamirai city, and tested for radiation on 2 November, and 89 Bq/kg was found. The school board does not have a precise standard, but explains that it wants "to appease the parent's anxiety". Tsukubamirai city has two school lunch cooking centers. The school lunch food ingredients have been checked for radiations since the beginning of October and this is the first time that radioactive substances are detected.

http://mainichi.jp/area/ibaraki/news...40124000c.html Shiitake mushrooms grown outdoors in Omitama and Namegata had respectively 520 and 650 Bq/kg, Ibaraki prefecture announced on 2 November. The shipment ban issued in mid October is going on.

Tochigi:
http://mainichi.jp/area/tochigi/news...40183000c.html 1850 Bq/kg was found in kuritake mushrooms grown in Yaita city.

Gunma:
http://mainichi.jp/area/gunma/news/2...40095000c.html 3.3 Bq/kg found in raw milk from Naganohara village. The milk from Kawaba was below detection level (0.2 ~ 0.4 Bq/kg).

Niigata:
http://mainichi.jp/area/niigata/news...40248000c.html 24 prefectoral high schools etc. were checked and 19 hotspots of 0.31 ~ 1.1 μSv/h were found. The mud removed in one location had 50,000 Bq/kg . All 119 prefectoral middle and high schools will be checked by the end of this month.

Fukushima:
http://www.kfb.co.jp/news/index.cgi?n=201111052 The turnips, spinach and cabbages grown in Hosono and Kawauchi outside the planned evacuation zone can be distributed again, as the test results have been below detection level for 3 consecutive times. Turnips are allowed in the whole Fukushima prefecture, but in the central region, there is a requirement to remove leaves. The test results concerning 32 food products in 38 cities and villages released by the prefecture on 4 November were all below detection level or below the provisional safety limit.

http://www.yomidr.yomiuri.co.jp/page.jsp?id=49699 7% of babies and preschool children below 7 years old in Minamisoma have radiations in urines. The results that were announced cover 1532 children. It is the first part of a survey that will ultimately concern 3500 children. 93% are below the 20 Bq/l detection limit. The highest was 187 Bq/l. The accumulated doses over 70 years were calculated for all of the 104 children with radiations. 93 children between 20 and 30 Bq/l have a 0.054 ~0.058 mSv dose. The child with 187 Bq/l has 0.37 mSv.

http://www3.nhk.or.jp/news/html/2011...753271000.html The young children urine test is a response to the complaint that the internal exposure surveys conducted so far by Fukushima prefecture etc. have been checking only the older children who are able to keep a position in a "special equipment".

http://www.yomiuri.co.jp/e-japan/fuk...OYT8T00092.htm The dried kaki test results are 530 Bq/kg in Fukushima, 570 and 1230 Bq/kg in Minamisoma, which brings to 5 the number of cities or villages having a dried kaki shipment ban.

NUCENG

Oky Doky! At least here in the US, improper disposal of hazardous waste is already a criminal offense. From descriptions this is an old bottle. It will be difficult to find the person responsible, so after it is removed and cleaned up what lessons are to be learned and what will be done differently? If they find unexploded ordinance left over from WWII while searching for hotspots is that somehow related to Fukushima, the earthquake, or the tsunami? But if you believe this is linked to the accident, then go ahead and discuss it here. I'll admit, it is an interesting discovery that could happen in any country. So I would read it whether it is here or in a separate thread.

tsutsuji

http://www.japantimes.co.jp/text/nn20111109f1.html "the government has shifted the focus of its decontamination plan to areas with radiation readings, based on an annual accumulative amount, of between 20 millisieverts and more than 1 millisievert, with the goal of reducing the contamination by 50 to 60 percent over two years."

http://www3.nhk.or.jp/news/genpatsu-...entaisaku.html The Japanese government has released a decontamination manual for volunteers.On 13 November minister Goshi Hosono gave a hand to a group of 60 volunteers decontaminating houses in Date city, Fukushima prefecture.

http://www.youtube.com/watch?v=-Aqx45dUSXI video of Minister Hosono with the volunteers (the meeting before starting to work).

http://mainichi.jp/select/wadai/news...40071000c.html The helicopter maps have been released for Iwate, Yamanashi, Nagano, Shizuoka, Gifu, and Toyama prefectures.

http://radioactivity.mext.go.jp/ja/1...910_111112.pdf Iwate, Yamanashi, Nagano, Shizuoka, Gifu, and Toyama prefectures' helicopter maps.(37 pages).

Tokyo:
http://mainichi.jp/select/wadai/news...40036000c.html The Tokyo water agency has experimented a process using chlorine and activated carbon that enables to remove 40 to 60% of iodine. "If we had known it, we could have kept iodine below 100 Bq/l" (in March, instead of 210 Bq/l).

Chiba:
http://www.yomiuri.co.jp/national/ne...OYT1T00461.htm It was found that the company that was supposed to bury the 0.18 ~ 0.37 μSv/h (50 cm above ground) sand from school sandboxes in Kashiwa was instead storing it in the company premises with reuse in mind.

http://sankei.jp.msn.com/region/news...2580013-n1.htm 5 spots above 0.23 μSv/h (maximum 0.59) in one school in Ichihara.

Ibaraki:
http://sankei.jp.msn.com/region/news...2060000-n1.htm Log shiitake shipment is banned in Ibaraki city (outdoor and greenhouse) and in Ami (outdoors), bringing to 6 the number of towns in Ibaraki prefecture with a log shiitake restriction.

Kanagawa:
http://www.youtube.com/watch?v=moAeswWPyeQ (TBS) 2651 Bq/kg (above the 400 Bq/kg standard) in ashes from trees and grass from a park in Yokohama, distributed as fertilizer.

Shizuoka:
http://www.chunichi.co.jp/article/sh...302000003.html The shipment ban concerning dried shiitake produced in Izu city was lifted for the shiitakes harvested after 1 October.

Gunma:
http://mainichi.jp/area/gunma/news/2...40219000c.html Between 28 and 72 Bq/kg was found in mud in 6 sewage plants. Nothing detected in the other 5 plants.

http://mainichi.jp/area/gunma/news/2...40202000c.html 482 Bq/kg in deers. 337 Bq/kg in wild boars. Hunting is allowed again.

Tochigi:
http://mainichi.jp/area/tochigi/news...40337000c.html 517 Bq/kg in nameko mushrooms in Nikko city.

Fukushima:
http://www.yomiuri.co.jp/national/ne...htm?from=navlp 713 Bq/kg in dried kakis from Date city harvested in October.

http://sankei.jp.msn.com/affairs/new...3200033-n1.htm 700 Bq/kg in shiitake grown in vinyl houses in Kawamata. 84.5 kg in 845 packs had already been shipped. 95 packs have been recalled from the shops, the other packs are already sold.

http://video.jp.msn.com/watch/video/...36%7C%7C%7C%7C (TBS) 8300 Ha of agricultural land are above the 5000 Bq/kg limit.

http://www.yomiuri.co.jp/national/ne...OYT1T01048.htm Fukushima city's 20 kindergartens are requesting a compensation from Tepco because the number of pupils has diminished by 472 pupils.

SteveElbows

The IAEA published the final version of their report into remediation efforts. I haven't had the chance to read it in full yet.

http://www.iaea.org/newscenter/news/...nalreport.html

SteveElbows

Im reading it now. Suggestions I've read about so far are along the lines of:

Involve Universities/academia.

Extend the whole body counter measurements program to remedial workers after they have finished a days work.

Come up with some clear guidelines on what activity levels are suitable for landfill-type disposal.

Balance the psychological/economic impact against the actual real benefits from certain kinds of remedial work, and focus efforts on stuff that can make a real difference to exposure levels. Also consider how much radioactive waste some measures may produce, creating new problems that may exceed the benefits.

Dont label everything that comes from decontamination efforts as waste, you may be able to reuse some of it without exposing the public to unacceptable risk.

Try and educate the public into the importance of dose rates rather than just letting them focus on surface or volume concentration levels.

When you involve local people in decontamination efforts, make sure they are trained, and recognise that you will probably need specialists to do certain work.

Provide signs/other markings on the routes into the 'deliberate evacuation area', along with some instructions for the public (there are currently no signs on roads etc to mark the borders of this zone).

Decontaminating certain areas such as forests, or taking the level of decontamination beyond certain 'optimised levels', may involve time & effort that is not rewarded by an automatic drop in public exposure, and may create new problems by creating more stuff thats classified as radioactive waste.

There will be another airborne survey this month covering the entire Eastern part of Japan.

Praise for various data collection efforts, recommendation to formally describe the management of the collected data in a management plan.

Thats all I have time to look at today, having just reached page 34 where attention turns to agricultural land.

Luca Bevil

One question to you all (tsutsui san especially thx for the great painstaking work you ar edoing for us all).

is there an assessment of suicide cases among Fukushima evacuees as of today ?

tsutsuji

It does not answer your question about evacuees, but there are suicide statistics about Fukushima prefecture in general:
http://www.npa.go.jp/safetylife/seia...jisatsusya.pdf 2011 suicide statistics per prefecture and per month.
http://www.npa.go.jp/safetylife/seia...sunogaiyou.pdf page 8: 2010 monthly statistics per prefecture and per month.

I calculated the number of suicides in Fukushima prefecture from April to October and found 323 in 2011 versus 314 in 2010 (increase of 9 = +2.9%).
The number of suicides in Japan from April to October was 19269 in 2011 versus 18515 in 2010 (increase of 754 = +4%)

tsutsuji

http://www.asahi.com/national/update...111170270.html & http://www3.nhk.or.jp/news/html/2011...032781000.html The ministry of environment, in Tokyo, received a parcel from Fukushima prefecture containing contaminated earth (0.18 μSv/h according to NHK, maximum 0.6 μSv/h according to Asahi). It was found that the contaminated earth was later dumped by a ministry employee in an empty lot near his/her home in Saitama prefecture.

Tokyo:
http://mainichi.jp/select/wadai/news...40005000c.html During the two months that preceded the finding of the 2300 Bq/kg cow on 8 July, only 2 cows had been tested out of the about 2100 cows that were shipped to Tokyo metropolis.

http://eco.nikkeibp.co.jp/article/re...111118/109948/ Incinerators in Tokyo's 23 wards and in the Tama area are going process tsunami debris from Onagawa, Miyagi prefecture. The radiations are 440 Bq/kg (textiles) 220 Bq/kg (tatami mats) 100 Bq/kg (plastics), 77 Bq/kg (paper), 69 Bq/kg (wood). For the treatment of the debris from Miyako (Iwate prefecture), the standard was that ashes above 8000 Bq/kg should not be produced. Using a concentration factor of 33, that meant that the debris should not be above 240 Bq/kg.

Kanagawa:
http://www.yomiuri.co.jp/national/ne...OYT1T01356.htm Kanagawa prefecture's rainwater data for the 6 day period from 20 March to 1 April had errors. The largest error concerns the iodine radiation from 21 March 9 AM to 22 March 9 AM. The radiation was 9500 Bq/m³ which is 28 times as much as the 340 Bq/m³ value that had been reported then. It is a calculation mistake that was made at a time when personnel from other departments came for help. The mistake was reported to the Ministry of education and science on 13 May, but the ministry failed from immediately correcting the figures.

http://mainichi.jp/life/today/news/2...40106000c.html Tea samples from Manatsuru have been measured with 500, 360, and 290 Bq/kg. The shipment ban has been lifted.

Chiba:
http://mytown.asahi.com/chiba/news.p...00001111190002 A value below the 8000 Bq/kg ( 5100 Bq/kg = 2400 (Cs134) + 2700 (Cs137)) was found for the first time in the ashes from a mud incinerating facility in Abiko on 8 November. In the past values as high as 25000 Bq/kg had been found. 510 tons of 8000 Bq/kg and above ashes produced until October have to be stored in tents. When the values below 8000/kg are considered stable enough, the facility will start burying the ashes again. For the time being tent storage is going on.

http://www.tokyo-np.co.jp/article/ch....html?ref=rank An incinerating facility in Matsudo is going to try burning branches and grass again from 18 November to 28 November, limiting their quantity to 10% of the total and checking the ashes's radiation everyday. Branches and grass burning had been stopped as it was feared that the 8000 Bq/kg standard for ash burying would be exceeded.

http://mainichi.jp/area/chiba/news/2...40104000c.html 831 Bq/kg in outdoor grown shiitake mushrooms in Nagareyama. With Abiko and Kimitsu, this brings to 3 the number of cities in Chiba prefecture with above limit shiitake.

Saitama:
http://mainichi.jp/area/saitama/news...40257000c.html 1300 Bq/kg in one brand of Sayama tea. This brings to 112 the brands of tea above safety level among 1659 brands of tea tested in Saitama prefecture since September.

Gunma:
http://mainichi.jp/area/gunma/news/2...40209000c.html 2500, 900 and 870 Bq/kg in mud generated at 3 water processing facilities

Niigata:
http://mainichi.jp/area/niigata/news...40250000c.html Earth samples were taken in 38 areas in 17 cities and towns where the helicopter survey had found the highest contaminations. All areas are below 0.23 μSv/h. In the two areas above 10,000 Bq/m² in Uonuma city, the highest sample had 320 Bq/kg, which is below the ministry of agriculture's 5000 Bq/kg limit.　

http://mainichi.jp/area/niigata/news...40175000c.html Niigata prefecture wants to charge the national government with the cost of the disposal of contaminated waste above 100 Bq/kg instead of the 8000 Bq/kg value proposed by the national government. 100 Bq/kg is the value below which the law regulating nuclear power plant decommissioning allows to process nuclear waste in general waste processing facilities.

Yamagata:
http://mainichi.jp/area/yamagata/new...40092000c.html It has been decided that the "Yonezawa beef" brand name would be attributed only to beef with "no cesium detected (below 25 Bq/kg)", which is more severe than the government safety level of 500 Bq/kg. Beef where cesium is detected will be sold as "Grown in Yamagata" or "Grown in Japan".

Fukushima:
http://www.mhlw.go.jp/english/topics...ions111109.pdf One page listing the food shipment restrictions applying to Fukushima prefecture, updated on 9 November.

http://www3.nhk.or.jp/news/genpatsu-...0615_idou.html A survey of the mud at the bottom of rivers was performed in September. It was found that the mud is more highly contaminated downstream than upstream, which suggests that the contamination migrates toward river mouths. In Niidagawa river, 3200 Bq/kg was found upstream in Iitate village, and 13000 Bq/kg close to the mouth in Minamisoma. 28,000 Bq/kg was found in Manogawa river in Minamisoma, which is twice the value measured in May.

http://www3.nhk.or.jp/news/genpatsu-...700_josen.html A decontamination model work was started in Ookuma town (restricted zone). The plan is to decontaminate a 4.5 Ha zone near the town hall, including public facilities and 20 homes. In some places the radiation goes up to 20 μSv/h.

http://www3.nhk.or.jp/news/genpatsu-...ikaikuiki.html The Japanese government is studying the dispatch of military forces to perform decontamination tasks in the restricted zone.

http://www.asahi.com/national/update...111160523.html 630 Bq/kg was found in unpolished rice (300 Bq/kg in polished rice) from Fukushima city's Oonami district (former Oguni village).

http://mainichi.jp/select/wadai/news...40049000c.html The Oonami district has produced 142 tons of rice. 67 tons are stored by each farmer. 57.6 tons have been shipped to Japan Agricultural Cooperatives. 15 tons have been shipped to relatives or friends. 2 tons have been sold to shops in Fukushima city and Date city. The people who have this rice at home or who received it are advised, at this step, not to eat it. The prefecture administration plans to perform radiation tests with the rice from each farm in the Oonami district.

http://www.yomiuri.co.jp/national/ne...OYT1T00353.htm Rice samples from the 4 farms from Oonami district which had shipped rice to shops in Fukushima city and Date city have been tested. The results are 11 Bq/kg, 22 Bq/kg and no cesium detected in the two other farms. The 70 bags (2 tons) were stored in the shops and had not been sold to customers.

http://sankei.jp.msn.com/affairs/new...2040029-n1.htm The Oonami district rice problem was found as a result of a self-decided testing at the local level. 136 Bq/kg before harvest and from 28 to 33 Bq/kg after harvest is what had been found for the Oonami district rice until then. The prefecture administration is studying a plan to reinforce controls by controlling each farm in all areas where cesium was detected after harvest.

http://www.nikkei.com/news/category/...2E2E2E2;at=ALL 550 Bq/kg was found in dried Kikurage mushrooms from Aizuwakamatsu. Shipment is banned. 16 kg (783 bags) have already been shipped to 12 shops and must be recalled.

http://www.yomiuri.co.jp/e-japan/fuk...OYT8T00042.htm Radiation control equipment is going to be installed for the general population to use after harvesting vegetables in gardens, taking water from wells, or picking mushrooms in forests. First of all, one equipment will be installed in each of 14 cities or towns in Fukushima prefecture.

http://online.wsj.com/video/voluntee...D57249BA5.html Cleaning efforts in Koriyama.

Azby

An interesting and even-handed journalistic canvassing of opinion on post-Fukushima health risks in Japan:

Future cancers from Fukushima plant may be hidden
By MALCOLM RITTER, Associated Press
http://www.google.com/hostednews/ap/...12dda569488e08


It's refreshingly free of spin. Not a lot of it will be news to people who have been following the debate closely, but I think it will be very good in helping people get up to speed on the main issues.

NUCENG

One problam may be separating suicides related to the tsunami, loss of employment, loss of family members and mental health issues other than the Fukushima accident. How many triggers are too many when sometimes one is enough?

You have provided documented numbers, Thank You. I suspect Luca and I might interpret those numbers differently. It is unlikely that unless suicide notes were left by all 323 people we may not be able to tie this to a specific cause. Two years of data doesn't even give us a standard deviation for evaluation of numeric uncertainty.

NUCENG

Thank you for posting this article, Azby. It is an excellent example of an article requiring careful reading and evaluation. It describes a potential that the health effects of the Fukushima accidents may not be detectable. For most people, that is a valuable point, much preferred to the hysterical rhetoric of some other stories.

By providing some level of balance, I agree this article is a worthwhile read. However, look at the comments by Ed Lyman of UCS. UCS always makes the point that they do not oppose nuclear power (Yeah, right!) Here is the quote from the article:

"The idea that Fukushima-related cancers may go undetected gives no comfort to Edwin Lyman, a physicist and senior scientist with the Union of Concerned Scientists, a group that advocates for nuclear safety. He said that even if cancers don't turn up in population studies, that "doesn't mean the cancers aren't there, and it doesn't mean it doesn't matter."

"I think that a prediction of thousands of cancer deaths as a result of the radiation from Fukushima is not out of line," Lyman said. But he stressed that authorities can do a lot to limit the toll by reducing future exposure to the radiation. That could mean expensive decontamination projects, large areas of condemned land and people never returning home, he said. "There's some difficult choices ahead." "

I hope you recognize that he is spinning like a top. What he is saying is that he believes that "thousands" will die as a direct result of radiation. He admits that it may not show up in population studies, but this lack of evidence proves his hypothesis is true because he tells us it is true. The anithesis cannot be true because it also lacks evidence and he tells us it is false. I must have been absent the day they taught that form in Logic class.

In the article you hear the fear and questions from Japanese citizens that comes from this irresponsible grandstanding. If it turns out that the population studies don't find an increase in cancer deaths. if the impact is not measureable, it means exactly that the stress of worrying about it is probably as big a risk.

Go ahead and remediate the contaminated area. Monitor the health of those exposed. Limit future exposures. If cancer numbers change the Ed Lymans out there will claim to be right. If the numbers don't change they will claim to be right. Or maybe , just maybe, it DOES "mean it doesn't matter."

The article didn't claim "We are all going to die!" even though we will, eventually. That is, indeed, refreshing.

joewein

While any increase in suicides is bad, a lower increase in Fukushima vs. Japan as a whole would at least appear relatively positive. It might indicate fewer people suffering from depression there than one might expect.

On the other hand, about 0.1% of the population of the prefecture perished or disappeared on 3/11 and probably a much larger percentage will have left the prefecture altogether, for example to find work elsewhere or to raise their children in a place with fewer contamination problems.

Without up to date data on who is still around and who isn't it's hard to interpret these numbers.