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Depleted uranium: sources, exposure and health effects
-- Executive summary --

― 概要 ―

World Health Organization (WHO)


この文書は、世界保健機構(WHO)が2001年に発表した劣化ウランに関する調査報告 "Depleted Uranium: Sources, Exposure and Health Effects" 中の "Executive summary" を日本語訳したものである。
翻訳は に基づいている。関連する文書は にて入手できる。


【TriNary :: Transcript 劣化ウラン概要報告シリーズ】

This scientific review on depleted uranium is part of the World Health Organization's (WHO's) ongoing process of assessment of possible health effects of exposure to chemical, physical and biological agents. Concerns about possible health consequences to populations residing in conflict areas where depleted uranium munitions were used have raised many important environmental health questions that are addressed in this monograph.
Purpose and scope
The main purpose of the monograph is to examine health risks that could arise from exposure to depleted uranium. The monograph is intended to be a desk reference providing useful information and recommendations to WHO Member States so that they may deal appropriately with the issue of depleted uranium and human health.
Information is given on sources of depleted uranium exposure, the likely routes of acute and chronic intake, the potential health risks from both the radiological and chemical toxicity standpoints and future research needs. Several ways of uptake of compounds with widely different solubility characteristics are also considered.
Information about uranium is used extensively because it behaves in the body the same way as depleted uranium.
Uranium and depleted uranium
Uranium is a naturally occurring, ubiquitous, heavy metal found in various chemical forms in all soils, rocks, seas and oceans. It is also present in drinking water and food. On average, approximately 90 μg (micrograms) of uranium exist in the human body from normal intakes of water, food and air; approximately 66% is found in the skeleton, 16% in the liver, 8% in the kidneys and 10% in other tissues.
ウランは、すべての土壌、岩石、および海洋中のいたるところで、さまざまな化学的形態で見受けられる天然起源の重金属であり、飲料水や食品中にもまた存在している。水、食品、および空気の正常な摂取により、平均で約 90 μg (マイクログラム:百万分の一グラム)のウランが人体に存在している;約 60% が骨格組織に、16% が肝組織に、8%が腎組織に、そして10% が他の組織に存在する。
Natural uranium consists of a mixture of three radioactive isotopes which are identified by the mass numbers 238U(99.27% by mass), 235U(0.72%) and 234U(0.0054%). Uranium is used primarily in nuclear power plants; most reactors require uranium in which the 235U content is enriched from 0.72% to about 3%. The uranium remaining after removal of the enriched fraction is referred to as depleted uranium. Depleted uranium typically contains about 99.8% 238U, 0.2% 235U and 0.0006% 234U by mass.
天然ウランは、3種類の放射性同位体が混ざって構成されており、それはその質量数により、238U (質量比 99.27%)、235U (質量比 0.72%)、および 234U (質量比 0.0054%) と同定される。ウランは原子力発電所において主に使用されている;ほとんどの原子炉は 235U の含有量を 0.72% から約 3% にまで濃縮したウランを必要としている。劣化ウランとよばれているのは、この濃縮された一部を分別した後の残存ウランのことである。劣化ウランは通常、質量比にして約 99.8% の 238U、0.2% の 235U、および 0.0006% の 234U から構成されている。
For the same mass, depleted uranium has about 60% of the radioactivity of uranium.
同じ質量で比較すると、劣化ウランはウランの約 60% の放射能を持っている。
Depleted uranium may also result from the reprocessing of spent nuclear reactor fuel. Under these conditions another uranium isotope, 236U may be present together with very small amounts of the transuranic elements plutonium, americium and neptunium and the fission product technetium-99. The increase in the radiation dose from the trace amounts of these additional elements is less than 1%. This is insignificant with respect to both chemical and radiological toxicity.
劣化ウランはまた、使用済み核燃料の再処理によっても生じるだろう。これらの条件の下では、別のウラン同位体、236U が非常に少量の超ウラン元素類のプルトニウム、アメリシウム、ネプツニウム、および核分裂生成物テクネチウム-99を伴って存在するだろう。これら微量の付加的な元素による放射線量の増加は 1% 以下である。これは化学および放射能毒性の両方において、取るに足らない無意味な量である。
Uses of depleted uranium
Depleted uranium has a number of peaceful applications: counterweights or ballast in aircraft, radiation shields in medical equipment used for radiation therapy and containers for the transport of radioactive materials.
Due to its high density, which is about twice that of lead, and other physical properties, depleted uranium is used in munitions designed to penetrate armour plate. It also reinforces military vehicles, such as tanks.
Exposure and exposure pathways
Individuals can be exposed to depleted uranium in the same way they are routinely exposed to natural uranium, i.e. by inhalation, ingestion and dermal contact (including injury by embedded fragments).
Inhalation is the most likely route of intake during or following the use of depleted uranium munitions in conflict or when depleted uranium in the environment is re-suspended in the atmosphere by wind or other forms of disturbance. Accidental inhalation may also occur as a consequence of a fire in a depleted uranium storage facility, an aircraft crash or the decontamination of vehicles from within or near conflict areas.
吸引 は紛争地域において劣化ウラン弾が使用されている間や使用された後、或いはその環境の劣化ウランが風や他の擾乱作用によって大気中に再び浮遊した場合に、最もありそうな摂取経路である。また、劣化ウラン貯蔵施設での火災や航空機の墜落、紛争地域またはその周辺から来た車両の汚染除去作業のために、偶然の吸引が発生するかもしれない。
Ingestion could occur in large sections of the population if their drinking water or food became contaminated with depleted uranium. In addition, the ingestion of soil by children is also considered a potentially important pathway.
経口摂取 は、食品や飲料水が汚染されていた場合、住民の大部分に起こりうるだろう。加えて、子供たちが土を口に入れる可能性もまた、重要な経路として考えられる。
Dermal contact is considered a relatively unimportant type of exposure since little of the depleted uranium will pass across the skin into the blood. However, depleted uranium could enter the systemic circulation through open wounds or from embedded depleted uranium fragments.
皮膚接触 は、劣化ウランが皮膚を通して血液中に摂取されるということはまず考えられないため、比較的重要でないタイプの被曝であると言えるだろう。しかしながら、劣化ウランは裂傷を通して、或いは体内に残されたままの劣化ウランの破片から、体循環に侵入する可能性はある。
Body retention
Most (>95%) uranium entering the body is not absorbed, but is eliminated via the faeces. Of the uranium that is absorbed into the blood, approximately 67% will be filtered by the kidney and excreted in the urine in 24 hours.
体内に侵入する劣化ウランのほとんど(>95%)は吸収されずに糞便として除去される。血液中に吸収されるウランのおよそ 67% は腎臓によって濾過され、24 時間以内に尿として排泄される。
Typically between 0.2 and 2% of the uranium in food and water is absorbed by the gastrointestinal tract. Soluble uranium compounds are more readily absorbed than those which are insoluble.
食品および飲料水に含まれるウランののうち、消化器官によって吸収されるのは、通常 0.2 から 2% である。可溶性ウラン化合物は不溶性のものに比べて容易に吸収される。
Health effects
Potentially depleted uranium has both chemical and radiological toxicity with the two important target organs being the kidneys and the lungs. Health consequences are determined by the physical and chemical nature of the depleted uranium to which an individual is exposed, and to the level and duration of exposure.
Long-term studies of workers exposed to uranium have reported some impairment of kidney function depending on the level of exposure. However, there is also some evidence that this impairment may be transient and that kidney function returns to normal once the source of excessive uranium exposure has been removed.
Insoluble inhaled uranium particles, 1-10 μm in size, tend to be retained in the lung and may lead to irradiation damage of the lung and even lung cancer if a high enough radiation dose results over a prolonged period.
吸引された直径 1-10 μm の不溶性ウラン粒子は肺に蓄積されやすく、肺に放射性障害や、長期間にわたる十分に高い被曝量があった場合には、肺癌まで引き起こすかもしれない。
Direct contact of depleted uranium metal with the skin, even for several weeks, is unlikely to produce radiation-induced erythematic (superficial inflammation of the skin) or other short term effects. Follow-up studies of veterans with embedded fragments in the tissue have shown detectable levels of depleted uranium in the urine, but without apparent health consequences. The radiation dose to military personnel within an armoured vehicle is very unlikely to exceed the average annual external dose from natural background radiation from all sources.
Guidance on chemical toxicity and radiological dose
The monograph gives for the different types of exposure the tolerable intake, an estimate of the intake of a substance that can occur over a lifetime without appreciable health risk. These tolerable intakes are applicable to long term exposure. Single and short term exposures to higher levels may be tolerated without adverse effects but quantitative information is not available to assess how much the long term tolerable intake values may be temporarily exceeded without risk.
The general public's ingestion of soluble uranium compounds should not exceed the tolerable intake of 0.5 μg per kg of body weight per day. Insoluble uranium compounds are markedly less toxic to the kidneys, and a tolerable intake of 5 μg per kg of body weight per day is applicable.
一般公衆の可溶性ウラン化合物の摂取は一日につき体重 1 kg あたり 0.5 μg の耐容摂取量を超過すべきでない。不溶性ウラン化合物は腎臓に対する毒性が著しく少なく、耐容摂取量を一日につき体重 1 kg あたり 5 μg とするのが適当である。
Inhalation of soluble or insoluble depleted uranium compounds by the public should not exceed 1 μg/m3 in the respirable fraction. This limit is derived from renal toxicity for soluble uranium compounds, and from radiation exposure for insoluble uranium compounds. Excessive worker exposure to depleted uranium via ingestion is unlikely in workplaces where occupational health measures are in place.
公衆による可溶性または不溶性の劣化ウラン化合物の吸引は、吸入可能粒子において 1 μg/m3 を超過すべきでない。この限度は可溶性ウラン化合物による腎臓への毒性と不溶性ウラン化合物による放射線被曝量から演繹される。労働者の経口摂取による極端な劣化ウラン被曝は、労働衛生の手段がきちんと整っている仕事場では、まずありえない。
Occupational exposure to soluble and insoluble uranium compounds, as an 8-hour time weighted average should not exceed 0.05 mg/m3. This limit is also based both on chemical effects and radiation exposure.
可溶性および不溶性ウラン化合物による職業被曝は、その 8 時間の重量平均が 0.05 mg/m3 を超過すべきでない。この限度もまた化学的影響および放射線被曝量の両方に基づいている。
Radiation dose limits
Radiation dose limits are prescribed for exposures above natural background levels. For occupational exposure, the effective dose should not exceed 20 millisieverts (mSv) per year averaged over five consecutive years, or an effective dose of 50 mSv in any single year. The equivalent dose to the extremities (hands and feet) or the skin should not exceed 500 mSv in a year.
放射線被曝量限度とは、全被曝量から自然な背景放射被曝量を減算したものである。職業被曝では、実効線量[1]が連続 5 年以上の計算で年平均 20 ミリシーベルト(mSv)、単年計算で 50 mSv を超過すべきでない。四肢(手足)または皮膚への等価線量[2]は年 500 mSv を超過すべきでない。
For exposure of the general public the effective dose should not exceed 1 mSv in a year; in special circumstances, the effective dose can be limited to 5 mSv in a single year provided that the average dose over five consecutive years does not exceed 1 mSv per year. The equivalent dose to the skin should not exceed 50 mSv in a year.
一般公衆の被曝では、実効線量が年 1 mSv を超過すべきでない;特別な状況においては、連続 5 年以上の計算で年平均 1 mSv を超過しない場合に限り、単年計算で 5 mSv までの実効線量が許される。皮膚への等価線量は、年 50 mSv を超過すべきでない。
Assessment of intake and treatment
For the general population it is unlikely that the exposure to depleted uranium will significantly exceed the normal background uranium levels. When there is a good reason to believe that an exceptional exposure has taken place, the best way to verify this is to measure uranium in the urine.
The intake of depleted uranium can be determined from the amounts excreted daily in urine. Depleted uranium levels are determined using sensitive mass spectrometric techniques; in such circumstances it should be possible to assess doses at the mSv level.
劣化ウランの摂取量は、尿中に日々排泄される量から測定することができる。劣化ウランレベルは高分解能質量分光(マススペクトル)技術を利用して測定される;このようにすれば、その状況における被曝量を mSv レベルで評価することは可能である。
Faecal monitoring can give useful information on intake if samples are collected soon after exposure.
External radiation monitoring of the chest is of limited application because it requires the use of specialist facilities, and measurements need to be made soon after exposure for the purpose of dose assessment. Even under optimal conditions the minimum doses that can be assessed are in the tens of mSv.
胸郭の外部放射線観察は、専門設備が必要で、さらに線量を評価するためにはその検査が被曝直後になされる必要があるため、その適用は限られたものになるだろう。最適な条件下であっても、評価可能な最小線量は数十 mSv であろう。
There is no suitable treatment for highly exposed individuals that can be used to appreciably reduce the systemic content of depleted uranium when the time between exposure and treatment exceeds a few hours. Patients should be treated based on the symptoms observed.
Conclusions: Environment
Only military use of depleted uranium is likely to have any significant impact on environmental levels. Measurements of depleted uranium at sites where depleted uranium munitions were used indicate only localized (within a few tens of metres of the impact site) contamination at the ground surface. However, in some instances the levels of contamination in food and groundwater could rise after some years and should be monitored and appropriate measures taken where there is a reasonable possibility of significant quantities of depleted uranium entering the food chain. The WHO guidelines for drinking-water quality, 2 μg of uranium per litre, would apply to depleted uranium.
劣化ウランについては、軍による使用だけが、環境レベルに重要な影響を与えうると言っていいだろう。劣化ウラン弾が使用された場所での劣化ウランの測定は、地表面の局地的な(着弾地点の半径数十メートル以内の)汚染しか示さない。しかしながら、いくつかの例では、食品や地下水の汚染のレベルが数年後に上昇する可能性があり、無視できぬ量の劣化ウランが食物連鎖に侵入する可能性があると考えるに足る理由がある場所について、観察と適切な調査がなされるべきである。飲料水の水質については、WHO のウラン濃度に関するガイドラインを劣化ウランにも適用して、一リットルあたり 2 μg とすべきだろう。
Where possible clean-up operations in conflict impact zones should be undertaken where there are substantial numbers of radioactive particles remaining and depleted uranium contamination levels are deemed unacceptable by qualified experts. Areas with very high concentrations of depleted uranium may need to be cordoned off until they are cleaned up.
Since depleted uranium is a mildly radioactive metal, restrictions are needed on the disposal of depleted uranium. There is the possibility that depleted uranium scrap metal could be added to other scrap metals for use in refabricated products. Disposal should conform to appropriate recommendations for use of radioactive materials.
Conclusions: Exposed populations
Limitation on human intake of soluble depleted uranium compounds should be based on a tolerable intake value of 0.5 μg per kg of body weight per day, and that the intake of insoluble depleted uranium compounds should be based on both chemical effects and the radiation dose limits prescribed in the International Basic Safety Standards (BSS) on radiation protection. Exposure to depleted uranium should be controlled to the levels recommended for protection against radiological and chemical toxicity outlined in the monograph for both soluble and insoluble depleted uranium compounds.
人間の可溶性劣化ウラン化合物摂取許容量は、一日につき体重 1 kg あたり 0.5 μg とすべきである。不溶性劣化ウランの許容量は化学作用と放射線量の両方によって決まり、それは放射線防護に関する国際基本安全基準(BSS: Basic Safety Standards)に従うべきである。劣化ウランに対する被曝は、このモノグラフで略述した可溶性および不溶性の劣化ウラン化合物の放射性および化学的毒性に対する防護のために推奨されるレベルまで規制されるべきである。
General screening or monitoring for possible depleted uranium-related health effects in populations living in conflict areas where depleted uranium has been used is not necessary. Individuals who believe they have been exposed to excessive amounts of depleted uranium should consult their medical practitioner for examination, appropriate treatment of any symptoms and follow-up.
Young children could receive greater depleted uranium exposure when playing within a conflict zone because of hand-to-mouth activity that could result in high depleted uranium ingestion from contaminated soil. This type of exposure needs to be monitored and necessary preventative measures taken.
Conclusions: Research
Gaps in knowledge exist and further research is recommended in key areas that would allow better health risk assessments to be made. In particular, studies are needed to clarify our understanding of the extent, reversibility and possible existence of thresholds for kidney damage in people exposed to depleted uranium. Important information could come from studies of populations exposed to naturally elevated concentrations of uranium in drinking water.

WHO, Geneva 2001 (WHO/SDE/PHE/01.1)


[1] 実効線量 ->

[2] 等価線量 ->


インターネットで劣化ウランに関する情報を検索する場合、バイアスのかかってないものを探し当てるのは非常に困難です。イラクで日本の反劣化ウラン運動家(?)が武装勢力に監禁された際に、マスコミやネットで劣化ウランが盛んに取り沙汰されましたが、結局劣化ウランってどうなのよ? という僕の疑問は解消できませんでした。
主に翻訳した人間はどちらかと言うと右翼(?)に好意的です。できるだけ忠実に翻訳したつもりではありますが、微妙なニュアンスに訳者の肩入れが混入しているかもしれません。疑問な点は原典にあたることをお勧めします。 一部誤訳を山形浩生さんに指摘していただきました。感謝いたします。

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