Downwinders : 風下住民

Downwinders refers to the individuals and communities in the inter-mountain area between the Cascade and Rocky Mountain ranges primarily in Arizona, Nevada and Utah but also in Oregon, Washington, and Idaho who were exposed to radioactive contamination or nuclear fallout from atmospheric or underground nuclear weapons testing, and nuclear accidents.

More generally, the term can also include those communities and individuals who are exposed to ionizing radiation and other emissions due to the regular production and maintenance of coal ash, nuclear weapons, nuclear power, nuclear waste and geothermal energy. In regions near U.S. nuclear sites, downwinders may be exposed to releases of radioactive materials into the environment that contaminate their groundwater systems, food chains, and the air they breathe. Some downwinders may have suffered acute exposure due to their involvement in uranium mining and nuclear experimentation.

Several severe adverse health effects, such as an increased incidence of cancers, thyroid diseases, CNS neoplasms, and possibly female reproductive cancers that could lead to congenital malformations have been observed in “downwind” communities exposed to nuclear fallout and radioactive contamination. The impact of nuclear contamination on an individual is generally estimated as the result of the dose of radiation received and the duration of exposure, using the linear no-threshold model (LNT). Sex, age, race, culture, occupation, class, location, and simultaneous exposure to additional environmental toxins are also significant, but often overlooked, factors that contribute to the health effects on a particular “downwind” community.

Downwinders and nuclear testing

Between 1945 and 1980, the United States, the U.S.S.R, the United Kingdom, France and China exploded 504 nuclear devices in atmospheric tests at thirteen primary sites yielding the explosive equivalent of 440 megatons of TNT. Of these atmospheric tests, 330 were conducted by the United States. Accounting for all types of nuclear tests, official counts show that the United States has conducted 1,054 nuclear weapons tests to date, involving at least 1,151 nuclear devices, most of which occurred at Nevada Test Site and the Pacific Proving Grounds in the Marshall Islands, with ten other tests taking place at various locations in the United States, including Alaska, Colorado, Mississippi, and New Mexico. There have been an estimated 2,000 nuclear tests conducted worldwide; the number of nuclear tests conducted by the United States alone is currently more than the sum of nuclear testing done by all other known nuclear states (the USSR, Great Britain, France, China, India, Pakistan, and North Korea) combined.

These nuclear tests infused vast quantities of radioactive material into the world’s atmosphere, which was widely dispersed and then deposited as global fallout.

How downwinders are exposed to fallout

Above-ground nuclear explosions produce a characteristic mushroom cloud, which moves downwind as it reaches its stabilization height. Dispersion of the radioactive elements causes vertical and lateral cloud movement, spreading radioactive materials over adjacent regions. While the large particles settle nearby the site of the detonation, smaller particles and gases may be dispersed around the world. Additionally, some explosions injected radioactive material into the stratosphere, more than 10 kilometers above ground level, meaning it may float there for years before being subsequently deposited uniformly around the earth. Global fallout is the result, which exposes everything to an elevated level of man-made background radiation. While “downwinders” refers to those who live and work closest to the explosion site and are thus most acutely affected, there is a global effect of increased health risks due to ionizing radiation in the atmosphere.

Health effects of nuclear testing

The earliest concerns raised about the health effects of exposure to nuclear fallout had to do with fears of genetic alterations that may occur among the offspring of those most exposed. However, the observed inheritable effects of radiation exposure by groups with histories of acute risk are considered minimal compared with the significant increase in thyroid cancer, leukemia and certain solid tumors that have developed within a decade or more after exposure. As studies of biological samples (including bone, thyroid glands and other tissues) have been undertaken, it has become increasingly clear that specific radionuclides in fallout are implicated in fallout-related cancers and other late effects.

In 1980, People magazine reported that of some 220 cast and crew who filmed a 1956 film, The Conqueror, on location near St. George, Utah, ninety-one had come down with cancer, and 50 had died of cancer. Of these, forty-six had died of cancer by 1980. Among the cancer deaths were John Wayne, Pedro Armendáriz and Susan Hayward, the stars of the film. However, the lifetime odds of developing cancer for men in the U.S. population are 43 percent and the odds of dying of cancer are 23 percent (38 percent and 19 percent, respectively, for women). This places the cancer mortality rate for the 220 primary cast and crew quite near the expected average.

Current status of U.S. nuclear testing

After adopting the Comprehensive Nuclear Test Ban Treaty in 1996, the U.S. and several other nuclear states pledged to stop nuclear testing. However, as of early 2017, the United States has failed to ratify the treaty.

Specific test sites


Downwind exposure produced by Nevada Test Site. This map strongly suggests that there are some state-specific differences in reporting.

From 1951 – mid-1962, the Nevada Test Site (NTS) was a primary site used for both surface and above-ground nuclear testing, with 86 tests at or above ground level, and 14 other tests underground, all of which involved releases of significant amounts of radioactive material into the atmosphere.

In the 1950s, people who lived in the vicinity of the NTS were encouraged to sit outside and watch the mushroom clouds that were created by nuclear bomb explosions. Many were given radiation badges to wear on their clothes, which were later collected by the Atomic Energy Commission to gather data about radiation levels.

In a report by the National Cancer Institute, released in 1997, it was determined that the nearly ninety atmospheric tests at the Nevada Test Site (NTS) left high levels of radioactive iodine-131 (5.5 exabecquerels, Ebq) across a large area of the continental United States, especially in the years 1952, 1953, 1955, and 1957. The National Cancer Institute report estimates that doses received in these years are estimated to be large enough to produce 10,000 to 75,000 additional cases of thyroid cancer in the U.S. A 1999 review of the 1997 report considered that their estimates of collective doses were in “good agreement” and “should provide confidence that the NCI estimate is not grossly under or over the actual value.” A 2006 report, published by the Scientific Research Society, estimates that about 22,000 additional radiation-related cancers and 2,000 additional deaths from radiation-related leukemia are expected to occur in the United States because of external and internal radiation from both NTS and global fallout. A 2010 report evaluating data on thyroid cancer incidence from 1973 to 2004 also supports a relationship between exposure from fallout and increased thyroid cancer incidence.

The threat of downwind exposure to radioactivity remaining at the Nevada Test Site from nuclear weapons tests was still an issue as late as 2007. The Pentagon planned to test a 700-ton ammonium nitrate-and-fuel oil “bunker buster” weapon. The planned “Divine Strake” test would have raised a large mushroom cloud of contaminated dust that could have blown toward population centers such as Las Vegas, Boise, Salt Lake City, and St. George, Utah. This project was cancelled in February 2007, in large part due to political pressure inspired by the threat of downwind exposure to radioactivity.


While many downwinders were exposed to weapons testing, millions more have been affected by radioactive fallout due to U.S. sites engaged in the production of nuclear weapons and/or nuclear power. For example, Hanford is a former nuclear weapons production site located in south central Washington state, where the Washington state Department of Health collaborated with the citizen-led Hanford Health Information Network (HHIN) to publicize significant data about the health effects of Hanford’s operations. Established in 1943, Hanford released radioactive materials into the air, water and soil, releases which largely resulted from the site’s routine operation, though some were also due to accidents and intentional releases.

By February 1986, mounting citizen pressure forced the U.S. Department of Energy to release to the public 19,000 pages of previously unavailable historical documents about Hanford’s operations. These reports revealed there had been radioactive materials released into the air and Columbia River. The reactors used large amounts of water from the river for cooling, which caused materials in the river water to become radioactive as they passed through the reactor. The water and the radioactive materials it contained were released into the river after passing through the reactors, thus contaminating both groundwater systems and aquatic animals downstream as far west as the Washington and Oregon coasts.

The Hanford Thyroid Disease Study, an epidemiologic study of the relationship between estimated exposure doses to radioiodine and incidence of thyroid disease amongst Hanford‘s downwinders, led by the Fred Hutchinson Cancer Center, was inconclusive. A consolidated lawsuit brought by two thousand Hanford downwinders for personal injury against the contractors that ran Hanford has been in the court system for many years. The defense in the litigation is fully funded by taxpayer dollars due to Price Anderson indeminification agreements. The first six bellwether plaintiffs went to trial in 2005, to test the legal issues applying to the remaining plaintiffs in the suit. In October 2015, the Department of Energy resolved the final cases. The DOE paid more than $60 million in legal fees and $7 million in damages.

Plutonium was also separated and purified for use in nuclear weapons, which resulted in the release of radioactive material into the air. Radioactive fallout from the Hanford site traveled throughout Washington, Oregon, Idaho, Montana, and even into Canada. Radioiodine entered into the food chain via contaminated fields where cows and goats grazed; hazardous fallout was ingested by communities who consumed the radioactive food and drank the milk. Another source of contaminated food came from Columbia River fish; their impact was disproportionately felt by Native American communities who depended on the river for their customary diets. The estimate of those exposed to radioactive contamination due to living downwind of Hanford or ingesting food or water that flowed downstream is unknown.

Marshall Islands

While the term “downwinders” generally connotes nuclear fallout victims based in the continental U.S. near sites such as Hanford and NTS, the population of the Marshall Islands bore a large brunt of nuclear testing under the United States’ Pacific Proving Ground program. Now known officially as the Republic of the Marshall Islands, it was a United Nations Trust Territory administered by the United States from 1944–1979, years during which the United States tested 66 nuclear weapons in the Marshall Islands.

One of these many tests, the March 1, 1954, explosion of Castle Bravo, a U.S. thermonuclear device, was responsible for most of the radiation the Marshall Islanders were exposed to. The fallout-related doses of this single test are believed to be the highest recorded in the history of worldwide nuclear testing. Many of the Marshall Islands which were part of the Pacific Proving Grounds remain contaminated by nuclear fallout, and many of those downwinders who were living on the islands at the time of testing have suffered from a highly increased incidence of several types of cancers and birth defects.

Effects of radiation on female downwinders

The primary long-term health hazard associated with exposure to ionizing radiation as a result of nuclear fallout is an increased risk for cancers of the thyroid, other solid tumor cancers, and leukemia. The relationship between radiation exposure and subsequent cancer risk is considered “the best understood, and certainly the most highly quantified, dose-response relationship for any common environmental human carcinogen”, according to report by the National Cancer Institute. Overall, men in the United States develop cancer at a rate 22% higher than that of women. However, women develop cancer from radiation at a rate from 37.5% to 52% higher than that of men. In recent years, studies conducted by both the National Research Council and the EPA have confirmed that compared to men, women are at a significantly higher risk of radiation-induced cancers, such and that women’s sensitivity to radiation-induced cancers is much higher than was previously estimated. The increased radio-sensitivity of certain organs in women, such as the breast, ovaries, and thyroid is likely the cause of this difference.

In the EPA’s 1999 Federal Guidance Report #13(FGR 13), Cancer Risk Coefficients for Environmental Exposure to Radionuclides, the authors conclude that women have a 48 percent higher radionuclide-related cancer mortality risk than men. Further evidence of sex-based disparities in radiation-induced cancers was published in the 2006 report by the National Research Council’s Committee to Assess Health Risks from Exposure to Low Levels of Ionizing Radiation (known as the BEIR VII report), which found that women’s risk due to radiation exposure exceeded men’s by 37.5 percent. When one considers rates of cancer incidence separately from rates of cancer fatality, the sex disparities are even greater. The BEIR VII Committee concluded that, given the same level of radiation exposure, women are 52 percent more likely than men to develop cancer, while the EPA report puts the estimate of difference as high as 58 percent.

The differences in risk are even greater when considering organ-specific cancers, especially given that both reports identify breast, ovarian, lung, colon, and thyroid tissues as the most radiosensitive among women. For example, the FGR 13 has estimated that the ratio of thyroid cancer incidence for women as compared to men is 2.14, while the findings of BEIR VII suggest that women are even more vulnerable to radiation-induced thyroid cancer at a ratio of 4.76.

As increasing concerns are raised regarding the environmental risks related to breast, the BEIR VII report cited evidence that suggests that “radiation may interact synergistically with other risk factors for breast cancer”, raising the possibility that endocrine disrupting chemicals like PCBs and dioxins might combine to increase the risks associated with radiation beyond that which would be caused by either separately. A related concern is that radionuclides that may be passed through the breast milk, causing some women who are downwinders to be understandably reluctant to breastfeed their children. While reducing the radioactive intake of their infants is an important preventative measure, it denies women the opportunity to engage a preventative measure for their own health; i.e. breastfeeding has been widely documented as a practice that can reduce women’s risk of developing breast cancer. By refraining from breastfeeding, women downwinders’ risks of breast cancer incidence becomes even more elevated.

Pregnancy and birth outcomes

Evidence about radiation-related pregnancy and birth outcomes comes from studies of nuclear bomb and test site survivors and studies of those exposed to diagnostic and therapeutic radiation. Mounting research indicates that above certain levels of radiation a miscarriage will result. It is also clear that fetal malformations are a greater risk if a woman is exposed to high doses of nuclear-related radiation in early pregnancy, when organs are being formed.

If acute radiation exposure occurs in the first ten days following conception, when few cells have formed, it is likely that the embryo will fail to develop and spontaneous abortion will occur. Fetal malformations are most likely to occur if a pregnant woman receives a radiation dose >500 mSv between the 10th and 40th day of pregnancy, the period of organogenesis during which the organs are formed. After the 40th day, the effects of radiation exposure are likely to include low birth weight, delayed growth, and possible mental deficits rather than fetal malformations. Radiation doses above 4,000 mSv are likely to kill both the mother and the fetus.

It has been shown that radiation damage including genome instability and carcinogenesis may occur transgenerationally in both males and females. The effects of radiation on fetal formation are also particularly relevant as a women’s health issue to the extent that female fetuses’ ova are formed while the fetus is still in utero. Adverse effects on a mother carrying a female fetus may therefore be multigenerational and increase both the daughter’s and grandchildren’s risks for ovarian cancer, infertility, and other reproductive developmental problems.

Compensation for downwinders

Under the Radiation Exposure Compensation Act of 1990, a $100 million compensation package and would pay $50,000 per person to fallout victims, and up to $100,000 to uranium miners who were exposed to unsafe levels of radiation. Downwinders eligible for compensation include those living in specified counties of Nevada, Utah, and Arizona for at least two years between January 1951 and October 1958, or during July 1962-periods when the United States conducted above ground nuclear tests without warning, and who are able to show correlations between certain diseases and their personal exposure to nuclear radiation. Miners’ compensation covers workers employed in uranium mines in five states-Colorado, New Mexico, Arizona, Wyoming, and Utah-between January 1947 and December 1971. Uranium miners are eligible for $100,000, and onsite participants are eligible for $75,000.

Navajo-related obstacles

There are particular obstacles to receiving needed health care and compensation faced by many widows and widowers of Navajo uranium miners, who were affected by disproportionately high incidences of fatal lung cancer. One problem for Navajo widows and widowers seeking the federal benefits for which they are qualified is the requirement that they document their marriages, although many were married in the 1930s and 1940s in undocumented tribal ceremonies. Language and cultural barriers pose further obstacles to Navajo downwinders; since many elderly Navajos do not speak English, their children bear the responsibility to do the research and procure from a tribal law judge a validation certificate of their tribal marriage. Similarly, it is difficult to access the outdated medical and occupational documentation that the government required even though the government’s and uranium companies’ own records for Navajo miners are sparse and difficult to access. An updated version of the RECA bill which expands the territories affected by Downwinders is currently in committee.











1980年のピープル誌 は米国内で行われたいくつかの核実験の結果を米国市民に明らかにした。ピープル誌はユタ州のセント・ジョージ市に近い場所でロケが行われた1956年の映画『征服者』の約220人の出演者と撮影スタッフのうち、91人が癌で死亡した事を明らかにした。41%というのは前代未聞の罹病率である。そのうち、46人は1980年までに癌で死亡していた。犠牲者の中にはジョン・ウェインやスーザン・ヘイワードなど映画スター達も含まれていた。







1997年に発行されたアメリカ国立癌研究所,による報告書では、ネバダ核実験場での約90回の大気圏内核実験で、北米大陸の広大な範囲にわたって放射性ヨウ素131(5.5 エクサベクレル)の高いレベル、特に1952年、1953年、1955年、1957年に記録したことを突き止めた。アメリカ国立癌研究所の報告書は、これらの年に受けた被曝は米国で推定10,000から75,000件の甲状腺癌の発生を増加させるのに十分な量だったと推定している。Scientific Research Society が発行する別のレポートでは、ネバダ核実験場と地球規模の死の灰による内部・外部被曝で、約22,000件のがんと、2,000人の白血病による死者が出たと推定している。

ネバダ核実験場の風下における放射能被曝の脅威は2007の後半でも依然として問題となっていた。ペンタゴンは700トンのアンホ爆薬による 地中貫通爆弾 をテストする計画を立てた。その神の条板作戦(Divine Strake)が計画通り行われていれば、大きなキノコ雲が発生し汚染されたほこりをラスベガス・バレー 、ボイジ、ソルトレイクシティ、セントジョージ、ユタ州などの人口密集地に向かって吹きつけたであろう。この計画が2007年2月に中止されたのは、主に、風下を放射能に暴露させる恐れがあるという政治的な圧力のためだった。



1986年2月までに、高まる市民の圧力によりアメリカ合衆国エネルギー省は非公開としてきたハンフォードでの操業に関する19,000ページの歴史的資料を公開する事を余儀なくされた。これらの報告書は、膨大な量の放射性物質が環境に放出されてコロンビア川と190,000 km2以上の土地を汚染した事を明らかにしていた。特に、報告書はコロンビア川沿いの原子炉で生産されたプルトニウムによる風下住民の被曝を明らかにした。それらの原子炉は冷却のために大量の川の水を使用するため、川の水に含まれる物質が原子炉を循環する事により放射性を帯びる結果をもたらした。放射性物質を含む原子炉冷却水が河川に放出された事により、地下水系と、下流西側のワシントン州およびオレゴン州の海岸の水生動物との両方を汚染した。








アメリカ合衆国環境保護庁の1999年の連邦指針報告書 No. 13 (FGR-13) 「放射性核種への環境曝露のための癌のリスク係数」 (英: Cancer Risk Coefficients for Environmental Exposure to Radionuclides) では、女性は男性より48%も高い放射性核種に関連した癌の死亡リスクを有すると著者達は結論付けている。放射線誘発癌の性別に基づく差のさらなる証拠は、2006年の全米研究評議会によるBEIR VII報告書として知られている「低線量電離放射線被曝による健康リスク」 (Biological Effects of Ionizing Radiation-VII Health Risks from Exposure to Low Levels of Ionizing Radiation) に掲載され、放射線被ばくに起因するリスクは女性が男性を37.5%上回っている事が発見された。癌の死亡率とは別に癌の発症率を考えると男女による差はさらに大きくなる。同じレベルの放射線被ばくを受けた場合に女性が癌を発症する可能性は、アメリカ合衆国環境保護庁の報告書は男性よりも58%多いと推定する一方で、BEIR VII委員会は52%高くなると結論づけた。

男女のリスクの差は特定の臓器について比較するとさらに大きくなる。両方の報告書は共に乳癌、卵巣、肺、大腸、および甲状腺の組織が女性において放射線の影響を受けやすい事を示している。例えばFGR 13は女性の甲状腺癌の発生率の比は男性に対し2.14倍であると推定しているのに対し、BEIR VIIの調査結果は女性は放射線により誘発される甲状腺癌は4.76倍とさらに脆弱であることを示唆している。

乳房に対する環境によるリスクへの懸念が高まる中で、BEIR VII報告書が「放射線は乳癌に対し他のリスク因子と相乗的に作用する可能性がある」および PCBやダイオキシン類のような内分泌を乱す化学物質が放射線と組み合わされると、単独で作用する場合よりもリスクを増加させる可能性を高める事を示唆する調査報告から引用したことは興味深い。それに関連する懸念は、放射性核種は母乳を通過する可能性がある事で、風下住民の女性達の中には自分の子供に母乳を与える事に消極的になってしまうのも無理はない。乳児の放射性摂取量を減らすことは重要な予防策であるが、それにより女性達は自分の健康のための予防措置を取る事を不可能にしてしまう。たとえば母乳を与える事は乳癌発症のリスクを減らすことができるという報告が幾つか知られている。授乳を控えることによって風下住民の女性の乳癌発生リスクはさらに上昇する、