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137セシウムと魚との関連についての論文や記事
論文１：なまずを調理すると、セシウムが74.7％減少する。
Removal of 137Cs in Japanese catfish during preparation for consumption.
http://www.jstage.jst.go.jp/article/jrr/45/2/309/_pdf
J Radiat Res (Tokyo). 2004 Jun;45(2):309-17.
Malek MA, Nakahara M, Nakamura R.
Bangladesh Atomic Energy Commission, Dhaka. Z_mam@yahoo.com
Abstract
Japanese catfish contaminated by (137)Cs have been used to investigate how dressing and cooking methods affect the removal of radioactivity from the fish. During the dressing, 6.0% of the initial (137)Cs activity in live fish was removed by washing them, and a further 30.3% of this activity relative to the washed fish was removed by discarding the nonedible body parts (such as the skeleton, fins, visceral mass, liver, and kidney) and by washing the chopped edible remains. Fish curry was cooked with various spices, vegetable oil, and greens and other vegetables following a method commonly used in Southeast Asian and East Asian countries. The cooking process removed a further 61.6% of the (137)Cs activity relative to the activity in dressed fish. Taken together, this normal domestic fish dressing and culinary process removed 74.7% of the initial (137)Cs activity that had been present in the live fish. During the cooking, the radioactivity removed from the fish pieces was found to be distributed throughout the ingredients of the curry. The cooked pieces retained, on average, 38.5% of the radioactivity present in the raw dressed pieces. Among the ingredients, the gravy was found to contain an average of 34.8% of the activity of the dressed fish. The activity in greens and vegetables was found to vary from 4.0% (in cauliflower) to 7.2% (in potatoes). It may be concluded that normal home preparation and culinary processes removed much of the radioactivity from the fish.
論文２：セシウム暴露の実験環境での、なまずの体内取り込み、分布の研究
定常状態に達するまで、数日から5〜6ヶ月を要する。（現時点では魚のセシウム量は
変わっていないが、数ヶ月先のデータがどうなるかが問題である！定期的に沿岸魚を測定しているので、必ず情報公開をしてもらいたい）
Uptake, retention and organ/tissue distribution of 137Cs by Japanese catfish (Silurus asotus Linnaeus).
http://www.ncbi.nlm.nih.gov/pubmed/15312703
J Environ Radioact. 2004;77(2):191-204.
Malek MA, Nakahara M, Nakamura R.
Laboratory for Radioecology, National Institute of Radiological Sciences, 3609 Isozaki, Hitachinaka City, Ibaraki-ken 311-1202, Japan. z_mam@yahoo.com
Abstract
The work describes the uptake, retention/biological elimination and organ/tissue distribution of 137Cs by freshwater Japanese catfish (Silurus asotus Linnaeus) under laboratory conditions. The fish were divided into three groups based on their size and age and reared in 137Cs-spiked water. The concentration of 137Cs in the whole body of the live fish was measured at regular intervals up to 60 days. A significant accumulation of 137Cs was found, but a steady state condition was not achieved by the end of the experiment. The bioaccumulation factors at steady state and the required time to reach steady state were estimated to be 1.55 and 255 days, 1.76 and 180 days and 1.99 and 160 days for large, medium and small size fish, respectively. To determine the effective half-life of 137Cs, the fish were transferred and reared in the non-contaminated host water. The concentration of the remaining 137Cs in the whole body of the live fish was measured up to 66 days. The average effective half-life of 137Cs in the fish species was found to be approximately 142 days for fish of all sizes. The distribution of 137Cs in different organs/tissues of the fish was determined. Accumulation of 137Cs in muscle/flesh of the fish was found to be approximately 75% of whole body accumulation. The uptake rate and the retention capability of juvenile fish were found to be higher and therefore, these were more susceptible to 137Cs than adult and old fish, and could be an important source of 137Cs in the human food chain.
論文3：日本の沿岸魚でのセシウムの濃縮率は、約50倍である。
Concentration factors for 137Cs in Japanese coastal fish (1984-1990).
http://www.journalarchive.jst.go.jp/jnlpdf.php?cdjournal=jrr1960&cdvol=37&noissue=2&startpage=71&lang=en&from=jnlabstract
Tateda Y, Koyanagi T.
J Radiat Res (Tokyo). 1996 Jun;37(2):71-9.
Central Research Institute of Electric Power Industry, Abiko Research Laboratory, Chiba, Japan.
Abstract
Concentration factors (CFs; Bq kg-1 in wet fish muscle/Bq kg-1 in filtered seawater) for 137Cs were determined in Japanese coastal fish collected from 1984 to 1990. 137Cs/Cs (stable) atom ratios were also examined to clarify the distribution equilibrium of 137Cs between marine fish and seawater. The geometric mean of CF in Japanese coastal fish was 52 +/- 4 (standard error of the mean), with values ranging from 14 to 133. 137Cs/Cs atom ratios both in marine fish and seawater indicate that the distribution of 137Cs was in equilibrium between fish muscle and seawater. Therefore, CF values obtained in the present study can be regarded as equilibrated. Our results show that the CFs for 137Cs in Japanese coastal fish were within the range of Japanese guidelines, but were below the recommended IAEA value.
論文４：和文なので、わかりやすい。
海産生物と放射能――特に海産魚中の137Cs濃度に影響を与える要因について―― †
笠松不二男
(財)海洋生物環境研究所
http://www.journalarchive.jst.go.jp/jnlpdf.php?cdjournal=radioisotopes1952&cdvol=48&noissue=4&startpage=266&lang=ja&from=jnlabstractRT
関連記事１．Japan Times onlineのコメント：
Q&A
Long-life cesium top threat to seafood
http://search.japantimes.co.jp/cgi-bin/nn20110329f1.html
Tuesday, March 29, 2011
By JUN HONGO
Staff writer
The damaged Fukushima No. 1 nuclear power plant is contaminating seawater with heavy amounts of iodine-131 and other radioactive materials.
Here are questions and answers regarding the latest threat from the ongoing radiation leaks.
Where is the leak into the ocean coming from?
Tokyo Electric Power Co. said it hasn't tracked down how radioactive materials leaked into the sea. Tepco officials speculated Saturday that it was somehow flowing directly from the plant, because no radioactivity spikes were observed on site. There was also no rain that could have caused atmospheric concentrations of iodine and other radioactive substances to fall to the sea.
Are the leaks substantial?
The Nuclear and Industrial Safety Agency said Monday it detected radioactive iodine-131 about 30 meters from reactors No. 5 and 6, or about 1,150 times the government safety limit. This followed revelations Sunday that iodine-131 measured about 300 meters away from reactor No. 1 hit 1,850 times the limit, suggesting the leak is spreading.
How long will the leaks continue to effect the environment?
That depends on the half-life of the materials, which is the time it takes the radioactivity of a specific substance to decrease by half. Iodine-131's half-life is about eight days but the half-life of cesium-137 is about 30 years.
The massive iodine-131 leak will not only be diluted by the sea, but also by the time it takes to reach fish and other marine products, pundits say. This is because both materials are water-soluble.
But this all depends on how fast Tepco can determine the cause of the leak and stop the radioactive water from discharging. So far the utility appear to be clueless.
Is the level of the leaks safe?
NISA said people within 20 km of the nuclear plant have already evacuated, hence the seawater contamination does not pose any immediate threat to their health. Nuclear Safety Commission of Japan Chairman Haruki Madarame also said Saturday that radioactive particles "are diluted and spread out" in seawater, adding there is no harm in eating fish from the coast because the levels of contamination would be negligible.
So far the agencies' claims appear to be true.
According to a survey conducted 30 km off the Fukushima plant by the Education, Culture, Sports, Science and Technology Ministry, the level of iodine-131 has seen a substantial drop.
Where is the radioactive water likely to flow?
The Okhotsk current and Kuroshio current meet off the Pacific coast. Seawater off Fukushima Prefecture is pushed southbound by the Okhotsk current toward Chiba Prefecture. There it will meet the northward Kuroshio (Black) current, and the two will push whatever radioactive water they contain away from Honshu into the Pacific.
Which marine products are vulnerable?
A survey by Tokyo-based Marine Ecology Research Institute shows that cesium-137 tends to accumulate in larger fish near the top of the food chain.
While the radioactivity of iodine-131 will be halved every 8 days, that will not be the case for cesium-137 — which is raising concerns.
Have there been any signs of fish contamination similar to that of the vegetables around the area?
At this point, no. For example, Chiba Prefecture on Friday studied anchovies, mackerel, spear squid and flounder caught off its shores. None was found to have contamination over state standards.
Is the situation under control?
As of now it appears things are not out of hand, but circumstances may change considering the tons of water that have been sprayed on the reactors to cool them down, as well as the leaks that may be coming from the reactor cores, or the spent-fuel pools above them, and the dangerous radioactive materials involved.
"The radioactive particles will be diluted, and iodine-131 has a half-life of 8 days," Kanazawa University professor Seiya Nagao told The Japan Times, hinting it is not a major concern.
But the expert on environmental monitoring and radionuclides warned that cesium has a much longer half-life and often accumulates in fish meat. While iodine-131 concentrates in the thyroid gland and increases the risk of thyroid cancer, cesium-137, once ingested, is accumulated by muscle tissues in the human body.
Experts say this may increase the risk of cancer.
"Its hard to tell if everything is under control at this point."
関連記事2．How the Disaster in Japan Affects Seafood
http://news.yahoo.com/s/dailybeast/20110401/ts_dailybeast/13259_nuclearsushihowthedisasterinjapanaffectsseafood
Thu Mar 31, 11:39 pm ET
NEW YORK – America imports sushi and seaweed from the coastal reefs near Japan. Ian Yarett on how nuclear-tainted seawater is affecting these rolled delicacies, from New York to Tokyo.
Ever since the March 11 tsunami crippled Japan’s Fukushima Daiichi nuclear reactors, radioactive materials from the plant have been spreading by air, contaminating milk, vegetables, and tap water. With highly radioactive water now leaking from the reactors into the Pacific, and levels of radioactive iodine and cesium in the sea near the plant as much as 4,000 times higher than normal, the safety of seafood—and of sushi in particular—has risen on the list of concerns not only in Japan but around the world.
In the United States, upscale sushi restaurants—which are more likely than cheaper establishments to import authentic Japanese fish and nori seaweed—are suddenly looking less appetizing than they once did. Importers of Japanese seafood are cancelling orders left and right amid radiation concerns, and many sushi chefs are scrambling to incorporate more locally sourced fish into their creations.
There is little doubt, experts say, that fish and seaweed in the waters near Fukushima are absorbing radionuclides such as iodine-131 and cesium-137. Fish don’t pick up much iodine from the water, and any that they do take in decays into harmless molecules within a few weeks. But cesium may be more of a problem, says Scott Fowler, a marine radioecologist who worked for 30 years at the International Atomic Energy Agency and is now a consultant. Fish exposed to cesium concentrate it in their bodies by an average factor of 100—meaning that there would be 100 times more cesium in the animal’s tissue than in the surrounding water. And because cesium is so persistent in the environment, it accumulates up the food chain and can become even more concentrated in top predators like tuna. As such, fish from the area around Fukushima are no longer being exported. Sushi restaurateurs can easily find fish elsewhere.
Seaweed sucks up vast amounts of iodine from its environment and doesn’t discriminate between the radioactive and non-radioactive varieties.
Of greater concern is the nori seaweed that’s used to wrap sushi. Nori, a mineral-rich Porphyra algae, is a fallout magnet. The seaweed sucks up vast amounts of iodine from its environment and doesn’t discriminate between the radioactive and non-radioactive varieties, readily incorporating the radioactive form at 10,000 times its concentration in the surrounding water. The good news is that iodine-131 has a short half life, so it would decay long before any contaminated nori could make it to market. Unfortunately, nori also sucks up plutonium, concentrating it by a factor of 4,000, and cesium by a factor of 50—and those two elements are much more persistent and dangerous to humans. The world’s nori comes primarily from Japan, China, and Korea, so sushi chefs have fewer alternate suppliers than they do for fish. Tim Mousseau, a radioecologist at the University of South Carolina, says the currents and winds appear to be carrying the fallout away from nori farms in southern Japan, at least so far. China and Korea’s waters have not been affected yet.
But with exports from the affected areas banned, the key question is whether the radioactive fallout in the sea will spread widely enough and remain at a high enough concentration to impact fisheries or seaweed production in other regions of Japan or elsewhere. While there are a number of unknowns, such as how long the Fukushima plant will release radiation and where the currents and prevailing winds will take it, experts say the dilution potential of the Pacific Ocean is so vast it should make the risk negligible. “Luckily, the Pacific is a big ocean,” says David Brenner, a radiation expert at Columbia University. “The amount of dilution you get in the ocean is enormous, so the amount of radioactivity per liter of water is ultimately going to be extremely small and probably undetectable.” Barring a substantial worsening of the situation, such as a Chernobyl-style explosion and meltdown, agrees Fowler, the effects on sea life should be both local and limited.
What if radioactive fallout traveled by air and then rained down into the sea elsewhere in the world, creating hotspots of radioactivity and contaminating seafood or seaweed? Fowler says that’s not likely. “If you’re getting fallout on the grass in Washington, you’re probably getting fallout on the beach and water surface,” he says. But given the distance from Japan, levels wouldn’t be significantly higher than the low background concentration of cesium and other radioactive isotopes that remain in the environment—and in virtually all plants and animals on earth—from past nuclear testing and fallout from releases like at Chernobyl.
For the moment, scientists say that the risk of consuming radioactive seafood isn’t high enough to warrant alarm, and that health risks of chemical pollutants such as mercury or PCBs are probably much higher. “I very much doubt that this is going to have a long-term effect on the sushi industry,” Brenner says.
Ian Yarett reports on science, the environment, and health for Newsweek.
関連記事3：
「魚食べて心配ない」 原子力安全委、海水汚染巡り見解2011年3月26日22時22分
http://www.asahi.com/national/update/0326/TKY201103260409.html
福島第一原発事故の影響で、原発からの排水が基準の千倍を超すなど、周辺海域で放射能汚染が深刻化している。これに対し、原子力安全委員会＝班目（まだらめ）春樹委員長＝は２６日、「放射性物質は海では希釈、拡散される」として、人が魚を食べてもまず心配はない、との見方を示した。
東京電力による原発の放水口付近の調査では、２５日朝にヨウ素１３１が１立方センチあたり５０ベクレル、セシウム１３７が同７．２ベクレル検出された。原発の排水を規制する基準に照らすと、ヨウ素は１２５０倍、セシウムは７９倍にあたる。東電は、１日１回だった測定回数を２回に増やすことにした。
一方、文部科学省が２３日から原発の沖合約３０キロ地点で調べると、最大で１リットルあたりセシウムが２６ベクレル検出。飲用水の基準に比べると、７分の１以下だが、０９年度に調べた通常値の１万倍を超えていた。
海洋生物への影響について、原子力安全委員会は２６日、「排水口付近では濃度が高いが、魚介類に取り込まれるまでに潮流に流されて拡散、希釈される。さらにヨウ素は半減期が８日と短いため、人が食べるまでには相当低減していると考えられる」とした。
一方で、財団法人海洋生物環境研究所の御園生（みそのう）淳研究参与（環境放射能）によると、濃度が高いと魚類が取り込んだ放射性物質が体内で最大で海水の３０〜５０倍の濃度まで蓄積されることもあるという。半減期が３０年のセシウムは心配が残るという。「２〜４カ月で魚に影響が出ることもある。継続的な広域の調査が必要。消費者や漁業者の安心にもつながる」と指摘した。
関連情報：勝川俊雄 公式サイト：漁業に関連する情報を並べていきます
放射性セシウムの海洋汚染が人体に及ぼす影響を数理モデルで試算してみたhttp://katukawa.com/?p=4198
一部のみ引用（詳細は上記ブログをご参照ください）
5万Bq/kgの魚が、市場にでる可能性はまず無いと思うけれど、汚染された海域の魚を何も考えずに食べ続けるた場合の被曝量を試算してみた。一年半後にはほぼ頭打ちになり、だいたい20mSV程度の被曝になる。もちろん、汚染の濃度や期間が変われば、この数値は大きく変わってくるので、あくまで参考ですよ。「このパラメータやシナリオでは甘い」という人は、エクセル形式でダウンロードして、いろいろいじってみて下さい。
ちなみに、国の基準値の500Bq/kgの魚を、平均的な日本人の摂取量だけ食べつづけると、0.2mSV/yearの被曝になります。
コメント：
沿岸魚がセシウムに汚染されているかは、数ヶ月〜半年後にしか判定できない。また、仮に汚染された魚を長期摂取することによる、長期低線量の被爆の影響についてのデータがない。アメリカが広島に原爆を投下した後の放射線障害のデータを日本の医学者などを
まきこみ、詳細な論文を報告している。
http://www.asahi-net.or.jp/~vb7y-td/L0/200821.htm （原爆調査団、加藤周一、羊の歌）
今回の福島原発事故に関しても、放射線医学などの専門家は詳細なデータを解析できる機会であり、「直ちに健康に影響はない」という欺瞞的な言葉を払拭し、放射線の長期暴露による健康調査（疫学的な前向き研究も必要）を、関連学会や厚生労働省が組織的に行うように提言する。
この記事を読んだ人はこんな記事も読んでいます（表示まで20秒程度時間がかかります。）
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