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Highlights in Radiation Research—A Timeline

2007  2005  2000  1990  1980  1970  1960  1950  1940  1930  1920  1910  1900  1890 


  • NASA and the National Space Biomedical Research Institute (NSBRI) fund 17 new research projects, enabling NASA to better understand and reduce health risks from exposure to space radiation. Scientists at universities, research institutions and private companies in eight states will conduct the studies.


  • The Atomic Testing Museum opens in February 2005 in Las Vegas, Nevada. It is a collection of everything known about or produced by the testing of nuclear weapons on the Nevada Test Site.
  • The French Academy of Science publishes a report on the effects of low doses of ionizing radiation on the risk for carcinogenesis. It concludes that at low doses, risks from per unit of dose are less than at high doses. This report suggests that repair or protective effects at low doses argue against the Linear-No-Threshold Hypothesis.
  • The BEIR VII (Biological Effects of Ionizing Radiation) Committee of the National Academy of Science and National Research Council published their report, Health Risks from Exposure to Low-LET Ionizing Radiation. This report concludes that the risk from radiation increases as a linear function of dose. This supports the Linear-No-Threshold Hypothesis and indicated that it is possible to extrapolate risk from high doses to low doses.


  • RISCRAD, an 8-year radiation research program, is organized and funded by the European Commission to evaluate the risk from low-dose radiation.


  • The journal Health Physics publishes a summary of low-dose radiation effects derived with new biology and technology. These effects included adaptive response, bystander effects, genomic instability, genetic susceptibility, changes in gene expression and alterations in DNA damage and repair.
  • The NASA Space Radiation Laboratory at the DOE's Brookhaven National Laboratory is dedicated on October 14, 2003.


  • Workshop on Cancer Risk Assessment: Should new Science be Applied? The workshop concluded that the new data was interesting but not sufficiently well developed to impact current risk estimates or regulations.
  • DOE Low Dose Radiation Research Workshop held. Summaries of the projects reviewed and the papers presented can be found on this website under currently funded projects. There is an abstract for each of the funded investigators.


  • NATO medical chiefs meet in Brussels to discuss potential risks of depleted uranium munitions to human health and the environment.
  • NCRP publishes a report on Evaluation of the Linear-Nonthreshold Dose-Response Model for Ionizing Radiation and concluded that this model was adequate for regulatory purposes. They demonstrate that there are many sets of scientific data that do not support it but that currently it is the best model for risk assessment.
  • Joint DOE Low Dose Radiation Research Program/NASA Radiation Investigators' Workshop held in Arlington, Virginia. Summaries of the projects reviewed and papers presented at this workshop can be found on other pages of this website.
  • Dr. Edward Radford, who gave early warnings on the dangers of radiation exposure, dies on Oct. 12. Radford stated in 1979 that 0.5 percent of Americans would get cancer because of radiation from artificial sources. He argues that even low levels of radiation exposure create a cancer risk.
  • The American Nuclear Society published a position statement on the health effects of low-level radiation concurring with the Health Physics Statement that below 10 rem, risks of health effects are either too small to be observed or are non-existent.
  • Completion of the sequencing of the human genome is done ahead of schedule through cooperation between DOE, other government agencies, and private companies.


  • The European Union passes a regulation stating that all European airlines must begin teaching crew members about low-level radiation and monitoring their in-flight exposure.
  • DOE reports that the amount of plutonium and other radioactive elements released into the soil or buried in containers during the first four decades of nuclear weapons production is 10 times larger than it had estimated.
  • Energy Secretary Bill Richardson announces plans to compensate workers who became seriously ill from exposure to radiation.
  • The Ukrainian government announces it will close the Chernobyl nuclear power plant, site of the world's worst nuclear accident, by the end of the year 2000.


  • Website to serve as the primary information resource for the Low Dose Radiation Research Program developed.
  • The Low-Dose Radiation Research Program, which consists of 44 funded projects, holds its first workshop in Bethesda, Maryland. Summaries of this workshop and the funded projects as well as other information about DOE's low-dose radiation initiative can be found on other pages of this website.
  • The book The Angry Genie, One Man's Walk Through The Nuclear Age published about the life and times of Karl Z. Morgan, a physicist with the Manhattan Project and the Oak Ridge National Laboratory, where he was the Director of Health Physics from the late 1940s to 1972. This book chronicles the use, control, and disposal of atomic waste at a national laboratory.
  • Pulitzer-Prize-winning reporter Eileen Welson publishes the book entitled The Plutonium Files, which deals with the 50-year intrigue surrounding human experiments with plutonium and other radioactive compounds.
  • The U.S. Department of Agriculture approves the use of radiation on all beef, lamb, veal, pork, and goat products as a means of eliminating microorganisms from raw meat offered for sale to consumers.
  • The American Nuclear Society issues a position statement on the health effects of low-level radiation (ANS Document PPS-41).
  • An accident at a uranium processing plant in Tokaimura, Japan exposes 55 workers to radiation; one dies.


  • Thirty-five workers are contaminated with radiation after a fire and explosion at a reprocessing plant in Tokaimura, Japan.


  • Congress directs DOE to initiate a new program to support the research needed to establish science-based risk assessment standards and guidelines for exposures to low levels of low LET ionizing radiation. DOE creates the Low Dose-Radiation Research Program.
  • Pakistan explodes its first nuclear bomb.
  • Myron Pollycove presents a paper to the NCRP entitled Human Biology, Epidemiology, and Low-Dose Ionizing Radiation. His paper provides biological data that he uses to question the NCRP's confidence in the Linear No-Threshold (LNT) hypothesis. He notes that the NCRP's confidence is based on the biochemical concept that the passage of a single charged particle through a cell could cause DNA damage, possibly leading to cancer. He contends that the data he presents contradicts this view.
  • The International Nuclear Society Council, in their action plan for 1997-1998, issues a statement that recommends the assumption, for all purposes other than scientific research, that there is no significant biological effect from low doses of radiation.


  • Final report of the President's Advisory Committee on Human Radiation Experiments is published under the title, The Human Radiation Experiments.
  • National Council on Radiation Protection and Measurements publish the report, Use of Personal Monitors to Estimate Effective Dose Equivalent and Effective Dose to Workers for External Exposure to Low LET Radiation.


  • The Committee on Interagency Radiation Research and Policy Coordination issues four recommendations on radiation risk assessment: (1) assess exposure to U.S. population from all radiation sources, (2) base risk estimates on latest scientific data, (3) examine alternatives with current use of absorbed dose in risk assessment, and (4) review how controlling radiation exposures are best used in assessing risks resulting from exposures.


  • President Clinton creates an Advisory Committee on Human Radiation Experiments with the charge to detail experiments conducted by the U.S. government and institutions funded by the government, on humans using ionizing radiation.


  • The Health Physics Society makes principal recommendations about radiation safety standards for the public that "...the sum of effective dose(s) to individual members of the public from exposure to controllable sources with the exception of occupational exposure, accidental releases, and indoor radon, normally should be limited to 1 mSv (100 mrem) in any year. In special (infrequent ) circumstances, an effective dose up to 5 mSv (500 mrem in a year may be permitted." The Health Physics Society also supported "...the establishment of an acceptable dose of radiation of 1 millisieverts/year (100 milirems/year) above the annual natural radiation background. At this dose, risks of radiation-induced health effects are either nonexistent or are too small to be observed."


  • Proceedings published on an international conference held in Kyoto, Japan, that examined various perspectives on the biological effects of low-dose radiation in conjunction with biological defense mechanisms and their implications for human health and risk assessment, "Low Dose Irradiation and Biological Defense Mechanisms"; in Proceedings of the International Conference on Low Dose Irradiation and Defense Mechanisms.
  • Oddvar F. Nyraard, Warren K. Sinclair and John T. Lett edit a book entitled Advances In Radiation Biology, Volume 16: Effects of Low Dose and Low Dose Rate Radiation, which examines the biological effects (primarily cancer and mutation induction) of low-dose and low-dose-rate ionizing radiation and the significance of low-dose and low-dose-rate exposures to radiation safety and standards for radiation protection.
  • President George Bush announces the United States will no longer produce plutonium or enriched uranium for nuclear warheads.
  • Edward J. Calabrese edits a book entitled Biological Effects of Low Level Exposure to Chemicals and Radiation, based on a workshop held in May 1991 at the University of Massachusetts.
"Pierre said to Marie, 'Do you remember the day when you said to me, I should like radium to have a beautiful color?' The reality was more entrancing that this simple wish of long ago. Radium had something better than a beautiful color: it was spontaneously luminous."

From "Madame Curie - A Biography" by Eve Curie, p. 176.
Doubleday, Doran and Company, Garden City, New York. 1937.


  • A reassessment of genetic studies on atomic bomb survivors show a lower genetic sensitivity than previously thought.
  • BEIR V Report (Committee on the Biological Effects of Ionizing Radiation-Health Effects of Exposure to Low Levels of Ionizing Radiation) is published.
  • Jay M. Gould and Benjamin A. Goldman publish the first edition of a book entitled Deadly Deceit, Low-Level Radiation, High-Level Cover-up. The theme of the book focuses of the dangers of low levels of radiation to human populations, the need to limit exposures whenever possible and the need for government to share information on health effects and exposure information with the public.
  • Another book, entitled Cancer From Low-Dose Exposure: An Independent Analysis, authored by John W. Gofman, is published. This book reviews human and physical evidence showing that cancer can be caused by the lowest conceivable doses and dose rates of ionizing radiation. The author rebuts claims that very low doses or dose rates of radiation are safe.


  • News about nuclear accidents at the government-operated Savannah River nuclear weapons plant in South Carolina over a 20-year period is released.
  • First recognition that adult-type tumors increased in frequency among individuals exposed prenatally to radiation from atomic bombs.
  • Dr. J. Newell Stannard publishes an extensive review of research, "Radioactivity and Health: A History," to define the health effects of internally deposited radioactive materials. There are no major surprises from the internally deposited radioactive materials: "...qualitatively the effects of ionizing radiation from deposited radionuclides are comparable to those from external radiation."


  • A nuclear reactor located at a power plant in the Ukrainian city of Chernobyl experiences a meltdown releasing massive quantities of radioactive material.
  • DOE launches the Human Genome Initiative for the purpose of identifying the genes (>50,000) on every chromosome in the human body and determining their biochemical nature and function.
  • The collected writings of H.M. Parker, Health Physics Director at Hanford for many years, are published, Herbert M. Parker-Publications and Other Contributions to Radiological and Health Physics. This compendium is a valuable resource and provides firsthand insight into the development of scientific-based radiation protection standards, the planning of radiation biology research and the disposal of radioactive waste.
  • On September 11, irradiated mangoes were made available in a farmer's market in Miami, Florida, marking the first time irradiated food was offered for sale in the United States. Concurrently, the first citizen's protest of the sale of irradiated food occurs.


  • Conference on radiation hormesis held in Oakland, California, and concludes that low doses of radiation are beneficial. Proceedings of the conference are published later in 1987 in the Health Physics Journal.


  • M. Brucer publishes an article in the Health Physics Newsletter entitled "Radiation is Good for You." This article adds fuel to the radiation hormesis debate.
"In 1902, forty-five months after the day on which the Curies announced the probable existence of radium, Marie finally carried off the victory: she succeeded in preparing a decigram of pure radium, and made a first determination of the atomic weight of the new substance, which was 225.---Radium officially existed."

From "Madame Curie - A Biography" by Eve Curie, p. 175.
Doubleday, Doran and Company, Garden City, New York. 1937.


  • Congress passes the Nuclear Waste Act that allows for temporary storage of up to 1900 tons of spent fuel from nuclear plants to lessen the threat around these plants.


  • T. Luckey revives the issue of hormesis as it relates to radiation in a monograph published by the CRC Press.


  • Nuclear reactor at the power plant located at Three Mile Island, Pennsylvania, experiences a meltdown; radioactive emissions are spread over a multistate area. Doses off-site were less than normal background radiation.


  • Congress passes the DOE Organization Act of 1977 (Public Law 95-91) and changes the name of the Energy Research and Development Administration to the U.S. Department of Energy (DOE). The new Law authorizes the Department to assure incorporation of national environmental protection goals in the formulation and implementation of energy programs, to advance the goals of restoring, protecting, and enhancing environmental quality, and ensuring public health and safety, and to conduct a comprehensive program of research and development on the environmental effects of energy technology.


  • The Radiation Effects Research Foundation is created to replace the ABCC.


  • The radioactive core in a reactor at the Lubmin nuclear power plant located in East Germany nearly melted down due to the failure of safety systems during a fire.


  • A total of 202 nuclear reactors are on order with 40 already operational, producing 5% of the United States' electricity.
  • India explodes its first atomic bomb.
  • Congress passes the Energy Reorganization Act of 1974 (Public Law 93-438). This law provides for the Energy Research and Development Administration (ERDA), formerly the AEC, to engage in and support environmental, biomedical, physical, and safety research related to the development of energy resources and utilization technologies; the Nuclear U.S. Regulatory Commission is also established under Public Law 93-438.


  • The National Academy of Science's Biological Effects of Ionizing Radiation Committee I (BEIR I) report is published; this report recommends using a linear model for estimating radiation risks.
  • The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) issues UNSCEAR VI, a report that questions the validity of using a linear model for estimating radiation risks.


  • NCRP adopts 170 mrem/year exposure limit for the general public.


  • Alice Stewart and George Kneale publish a study on children in England and Wales showing an increased risk of cancer due to radiation received from obstetric x‑rays.


  • A fire in a Rocky Flats plutonium processing building causes $50 million damage and shuts the plant down for six months.
  • Arthur D. Bloom publishes paper "Cytogenetic Effects of Low-Dose Internal and External Radiations," which concludes that all exposure to high-energy ionizing radiation, even at low doses, produces chromosomal and genetic damage and that this damage may well be deleterious to the host.


  • President Johnson signs Public Law 90-602, which is called the "Radiation Control for Health and Safety Act."


  • Partial meltdown of one of four reactors at plant near Annan, Scotland, occurs; plutonium released to atmosphere.
  • Biosatellite II launched containing the same 13 experiments lost in Biosatellite I to assess the sensitivity of organisms to ionizing radiation changes under microgravity conditions.


  • Biosatellite I is launched containing 13 experiments using bacteria, fungi, frog eggs, beetle pupae, amoeba, fruit flies, and wheat seedlings. Experiments designed to assess weightlessness and radiation effects on living systems. All experiments are lost on reentry into the Earth's atmosphere due to the failure of a retrorocket to fire.


  • New cytogenetic techniques are introduced and applied to estimate the dose atomic bomb survivors received and to estimate mutation damage.
  • The Pacific Northwest National Laboratory at the Hanford Site in Washington State is named. Pacific Northwest National Laboratory's mission focuses on nuclear technology and the environmental and health effects of radiation.


  • An interagency agreement between the AEC and the National Aeronautical and Space Administration (NASA) are drawn up to explore the health effects of radiation encountered in space.
  • China explodes its first atomic bomb.
"...on December 26, 1898 the existence of a second new chemical element in pitchblende was announced. The communication stated, 'the radioactive substance contains a new element to which we propose to give the name of 'radium'." Doubleday.

From "Madame Curie - A Biography" by Eve Curie, p. 164.
Doran and Company, Garden City, New York. 1937.


  • Irradiation of the testicles of convict volunteers at the Oregon State Prison and the Washington State Penitentiary at Walla Walla begins; dose levels range from 7.5 to 600 rads.


  • France explodes its first atomic bomb.


  • President Eisenhower mandates publication of a monthly report with the title Radiological Health Data, containing information on monthly environmental radiation levels.


  • United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) declares that fallout from nuclear bombs is harmful to human health.
  • Linus Pauling and Andrei Sakarov separately proclaim that low-level fallout from atomic tests was contaminating the food supply and would harm the immune system of consumers.


  • Karl Z. Morgan in testimony before a Congressional subcommittee states that there is "no safe level of exposure" to radiation.
  • A fire in a graphite-cooled reactor located north of Liverpool, England spreads radiation over a 200‑square-mile area.
  • An explosion at a Soviet nuclear weapons plant located in the South Ural Mountain city of Kyshtym forced the evacuation of over 10,000 people from the area contaminated by the blast.


  • A National Academy of Sciences Committee issues a report asserting no safe threshold for radiation exposure. The report condemns the excessive use of x‑rays in medical and dental practices, exposures to pregnant women, and people being fitted for shoes. Former AEC official, John C. Bugher, declares at an American Public Health Association meeting that an atomic power program would present a much greater health threat than nuclear weapons, due to large quantities of radioactive chemicals emitted into the environment during power generation.
  • Debate begins among scientists and politicians about the hazards of radiation to human populations.
  • The United States explodes the first airborne hydrogen bomb over Bikini Atoll in the Pacific.
  • Herbert Friedman discovers evidence for extra solar x‑rays.
  • Dr. Alice Stewart reported on an increase in childhood cancer following in utero exposure to x‑rays.


  • Several state health officials in areas exposed to nuclear fallout from the Nevada bomb tests conducted during the 1951-1954 period begin speaking out on the possible adverse health effects of bomb fallout.
  • Health Physics Society (HPS) organized as an international professional scientific organization dedicated to promoting the practice of radiation safety. The HPS is active in all aspects of radiation protection, including information dissemination, standards development, education, preparation of position papers, and promotion of scientific meetings.
  • The National Academy of Sciences, with funding from the Rockerfeller Foundation establishes the Biological Effects of Atomic Radiations (BEAR) Committee, later renamed the Biological Effects of Ionizing Radiation (BEIR) Committee.


  • The Atomic Energy Act of 1954 (Public Law 83-703) is passed by Congress that further authorizes the AEC to conduct research on the biological effects of ionizing radiation.
  • American Nuclear Society (ANS) is formed as a not-for-profit international scientific and educational organization. The ANS promotes radiation research, radiation safety, and environmental radiation protection standards through position papers and meetings.
  • Alexander Hollaender edits and publishes a landmark three volume book series under the title of Radiation Biology. These volumes chronicle the progress and assess the knowledge accumulated over the first 50 years of radiation research. The biological effects of all radiation spanning the energy spectrum—from the highest available energies to the near infraredmdash;were included.


  • Radiation Research Society is formed to encourage the advancement of radiation research in all areas of the natural sciences.


  • The first breeder reactor, which produces plutonium at the same time it produces energy from uranium, is built by the AEC.
  • The first accident at a nuclear reactor occurs at Chalk River Canada, where a worker error causes the nuclear core to explode.
  • Edward Teller leads group that produces the first hydrogen bomb.
  • Great Britain explodes its first atomic bomb.


  • First atomic test occurs in Nevada; five bombs detonated on successive days. Radioactive fallout reaches the New England area in two days.
  • Rocky Flats Nuclear Weapons Facility constructed in Colorado.
  • Studies on the health of plutonium workers at Los Alamos begins.
"...the radioactivity was concentrated principally in two different chemical fractions of the pitchblende. For M. and Mm. Curie it indicated the existence of two new elements instead of one. By July 1898, they were able to announce the discovery of one of these substances with certainty. ---we propose to call this new element "polonium" from the name of the original country of one of us."

From "Madame Curie - A Biography" by Eve Curie, p. 161.
Doubleday, Doran and Company, Garden City, New York. 1937.


  • President Truman calls for atomic testing of nuclear weapons in the continental United States in addition to testing in the Pacific.
  • Studies of the effects of radium on beagle dogs begin at the University of Utah and the University of California at Davis.


  • USSR explodes its first atomic bomb.
  • The National Council on Radiation Protection and Measurement (NCRP) lowers basic "maximum permissible dose" for radiation workers to 0.3rem/week; limits for the general public set at 10% of the occupational dose.
  • Lawrence Livermore National Laboratory (LLNL) established as a result of the USSR's acquisition of the atomic bomb. Lawrence Livermore National Laboratory was charged with providing competition, diversified expertise, and sharing the task with other U.S. scientists of handling the large volume of work that future fast-breaking discoveries in radiation research would bring.


  • ABCC initiates genetic studies of Hiroshima and Nagasaki atomic bomb survivors.


  • Atomic Bomb Casualty Commission (ABCC) created to study the biological effects of radiation on Japanese atomic bomb survivors.
  • Brookhaven National Laboratory established in Suffolk County, Long Island, New York. Brookhaven is charged with providing powerful tools to those engaged in radiation research.
  • Ames Laboratory established in Iowa as a result of a project (Ames' Project) that developed an efficient process to produce high-purity uranium for atomic energy.
  • Effects of strontium and plutonium on fetal and infant dogs reported.
"...on April 12, 1898 Marie Sklodovska Curie announced the probable presence in pitchblende ores of a new element endowed with powerful radioactivity. This was the first stage of the discovery of radium. She now had to (find it and) be able to announce with certainty "It is there." "

From "Madame Curie - A Biography" by Eve Curie, p. 158.
Doubleday, Doran and Company, Garden City, New York. 1937.


  • Karl Morgan and Lyle Borst of the Oak Ridge National Laboratory develop a film badge to measure worker exposure to fast neutrons.
  • Alexander Hollaender forms the Biology Division of the Oak Ridge National Laboratory for the purpose of studying the biological effects of radiation.
  • A Biology Section is organized at the Hanford Plutonium Plant to study the biological effects of radiation.
  • Argonne National Laboratory is established as the nation's first national laboratory devoted to exploring the applications and effects of radiation. Argonne is now home to three research reactors including the Advanced Photon Source.
  • Helmuth Ulrich publishes paper showing leukemia rate among radiologists to be 8 times higher than in other medical doctors.
  • Bill and Liane Russell begin their extensive experiments with mice to study the genetic effects of radiation at the Oak Ridge National Laboratory's Biology Division.
  • H.J. Muller wins the Nobel Prize for showing that radiation can induce heritable mutations in fruit flies (Drosophila melanogaster).
  • Congress passes Public Law 79-585 (The U.S. Atomic Energy Act) creating the Atomic Energy Commission (AEC), charged with conducting a comprehensive program of research and development related to the utilization of fissionable and radioactive materials for medical, biological, and health purposes.
  • President Truman directs the National Academy of Sciences to initiate studies to determine the long-term effects of the atomic bomb on survivors.
  • Dr Louis Slotin dies in a criticality accident at Los Alamos.


  • Sandia National Laboratories are established as part of the effort to develop the atomic bomb. Sandia served as a facility in the design, testing, and assembly of the bomb.
  • First atomic bomb is exploded in the desert near Alamagordo, New Mexico.
  • Second atomic bomb named "Little Boy" is dropped on the Japanese city of Hiroshima.
  • Third atomic bomb named "Fat Man" is dropped on the Japanese city of Nagasaki.
  • The Joint Committee for the Investigation of the Effects of the Atomic Bomb in Japan formed.
  • S.T. Cantril and H.M. Parker write a landmark paper on tolerance dose.
  • Eighteen human subjects are injected intravenously with plutonium at Los Alamos to determine how it is distributed in the body and what adverse effects are induced.
  • Two criticality accidents occur at Los Alamos. In the second, one man is fatally exposed with a dose of ~510 rem.
  • Nuclear physicist and future Director of the Oak Ridge National Laboratory, Alvin M. Weinberg, tells the Senate's Special Committee on Atomic Energy that "Atomic power can cure as well as kill. It can fertilize and enrich a region as well as devastate it. It can widen man's horizons as well as force him back into the cave."


  • Film badges to measure worker exposure to radiation are first put to use at Clinton Laboratory (subsequently namedOak Ridge National Laboratory).
  • H.M. Parker establishes air limits for plutonium.


  • Construction begins on the Hanford (Washington) reactor, which will produce plutonium.
  • Studies exploring the toxicology of uranium begins at the University of Rochester.
  • C. Southam and J. Erlich introduce the term "hormesis" to describe the phenomena of fungal growth being stimulated by low concentrations of an oak bark extract and harmful effects, including lethality, induced at high concentrations (Phytopathology 33:517). Hormesis will become part of the lexicon of radiation research, because some researchers will claim that exposures to low levels of radiation produce beneficial effects.


  • A team of physicists, led by Enrico Fermi, creates the first controlled chain reaction in a pile of uranium and graphite.
  • The Manhattan Project is formed to secretly build the atomic bomb.
  • Los Alamos, New Mexico, is selected as the site for the atomic bomb laboratory.
  • H.M. Parker shows that a radiation dose of 4 Roentgens/day is hazardous to humans.
  • The world's first nuclear reactor is activated at Clinton Laboratory (later renamed the Oak Ridge National Laboratory) in Oak Ridge, Tennessee.


  • Glenn Seaborg discovers plutonium.
  • The U.S. Committee on X‑ray Protection recommends adoption of maximum body burden of 0.1 microCurie for radium.
  • L.S. Taylor recommends lowering the x‑ray exposure dose to 0.02 Roentgens/day.
"...the radiation that I could not explain comes from a new chemical element. The element is there and I've got to find it."

From "Madame Curie - A Biography" by Eve Curie, p. 157.
Doubleday, Doran and Company, Garden City, New York. 1937.


  • Maurice Goldhaker discovers that beryllium slows down fast neutrons and makes them likely to fission uranium.


  • Lise Meiter, who worked with Otto Hahn on splitting the uranium atom, leaves Austria as World War II is beginning and goes to Sweden. She publishes a paper on the work she did with Hahn, and this paper stimulates the drive to produce the atomic bomb.
  • Frederic and Irene Joliot-Curie show that the fission of the uranium atom can lead to a chain reaction.
  • Leo Szilard and Walter Zinn confirm that fission reactions can be self-sustaining because of chain reactions.
  • Sterilization of criminals by x‑rays legalized in Michigan.


  • Otto Hahn is the first to split the atom of uranium, opening up the possibility of a chain reaction.


  • The U.S. Committee on X‑ray Protection recommends reducing the permissible radiation dose to 0.1 Roentgen/day.
  • The Lawrence cyclotron located in Berkley, California proves itself capable of producing radioactive isotopes of biologically significant elements.
  • The "Martyrs Memorial" is erected in Hamburg, Germany containing the names of 169 physicians and technicians who died from radiation-induced diseases.


  • An Idaho court rules that x‑rays are only useful when interpreted by experts.


  • E. Chadwick discovers the neutron.


  • The first x‑ray exposure standard is recommended at 0.2 Roentgens/day.
  • Ernest Lawrence invents the cyclotron.
  • The Laboratory that would become known as the Rad Lab (and subsequently renamed the Lawrence Berkeley National Laboratory) is established at the University of California at Berkeley to house Ernest O. Lawerence's newly developed cyclotron.


  • Charles Lauritsen develops high-voltage x‑ray machine for radiation therapy.


  • Organs such as the kidney, ureter, and bladder are successfully x‑rayed.
  • Bone cancer is observed in workers painting radium dials.


  • The International X‑ray and Radium Protection Committee is formed that becomes the forerunner of the International Committee for Radiation Protection.
  • The Second International Conference of Radiology meets in Stockholm and establishes the curie and roentgen as units of radiation.


  • H.J. Muller shows that mutations can be induced in Drosophila melanogaster by low levels of x‑rays.


  • Geiger-Muller counter detects and measures intensity of radiation.


  • First International Conference of Radiology meets in London and sets up a commission to define units of radiation.


  • First radiation tolerance dose proposed by Arthur Mutscheller for use as a guide to limiting exposure of an individual to radiation.


  • The American Medical Association approves a Section Council on Radiology limiting the practice to experts.


  • Film badges first developed to measure exposures to radiation.
  • Amelia Maggia is first of the "Radium Dial Painters" to die from radiation poisoning.
"Radioactivity so fascinated Marie that she never tired of examining the most diverse forms of matter, always by the same method. Curiosity, the first virtue of a scientist, was developed in Marie to the highest degree."

From "Madame Curie - A Biography" by Eve Curie, p. 156.
Doubleday, Doran and Company, Garden City, New York. 1937.


  • First indication that radium and radium emanation might be the causative agent for cancer induction in miners.


  • First x‑ray protection committee is formed by the American Roentgen Ray Society.


  • British Roentgen Society proposes standards for radiation protection of workers.


  • Hans Geiger unveils his radiation detector.


  • Max von Laue demonstrates that x‑rays are a form of electromagnetic radiation that creates diffraction patterns with crystals.
  • Hundreds of young women working in plants in New York and Illinois are accidentally exposed to a luminous paint containing radium while painting dials for watches and clocks.
  • Victor Hess discovers that the ionization of air increases with altitude, indicating the existence of cosmic radiation


  • First reports linking x‑rays to leukemia and cancer in physicians is published.
  • Arthritis patient dies from Radium-226 injections.


  • X‑rays are used to diagnose disorders of the digestive tract.
  • Marie Curie's Treatise on Radioactivity is published.
  • Theodor Wulf measures radiation levels at the top and bottom of the Eiffel Tower and notes that radiation increases with height. He suggests that this be further confirmed by having balloonists measure radiation at different heights.


  • X‑rays are reported to induce mutations in toads by C.R. Bardeen.


  • Radiation unit based on ionization is first proposed.


  • Ernst Rutherford publishes the book Radioactivity.
  • William Rollins describes hazards of radiation in "Notes on the X-Light"
  • First human death from x‑rays is reported.


  • Antoine-Henri Becquerel and, Pierre and Marie Curie share the Nobel Prize for physics, Becquerel for his discovery of natural radioactivity, and the Curies for their study of radioactivity.
  • First observation notes that radioactivity can induce tissue and organ damage.
  • George Perthes discovers that x‑rays can inhibit the growth of tumors and proposes the use of x‑rays in the treatment of cancer.
"It must be an error in the experiment," the young woman thought; for doubt is the scientist's first response to and unexpected phenomenon. She started over again 10 times, 20 times. And she was forced to yield to the evidence. Where did this excessive and abnormal radiation come from? Only one explanation was possible: the minerals must contain, in small quantity, a much more powerful radioactive substance than uranium or thorium."

From "Madame Curie - A Biography" by Eve Curie, p. 157
Doubleday, Doran and Company, Garden City, New York. 1937.


  • Ernst Rutherford and Frederick Soddy publish a paper, The Cause and Nature of Radioactivity. The paper contains the atomic disintegration theory of radioactivity, stating that atomic nuclei split to form other elements.
  • W.H. Rollins demonstrates that x‑rays are harmful to the mammalian fetus in utero.


  • Wilhelm Konrad Roentgen wins the Nobel Prize in physics for his discovery of x‑rays.
  • X‑rays are shown to be lethal to mammals through experiments conducted by W.H. Rollins.


  • Paul Ulrich Villard is the first to observe that gamma radiation is more penetrating than x‑rays.


  • The American Physical Society (APS) is formed. During the 20th century, the APS will play a prominent role in promoting research in the new era of physics initiated by the discoveries of Roentgen, Becqueral, and the Curies.
  • First malpractice lawsuit is awarded for x‑ray burns.
  • Ernst Rutherford discovers that radioactivity from uranium has at least two different forms, which he calls alpha and beta rays.
  • Fritz Geisel, Antoine-Henri Becquerel, and Marie Curie prove that beta rays consist of high-speed electrons.


  • Marie and Pierre Curie discover that thorium gives off "uranium rays," which Marie renames "radioactivity."
  • Marie and Pierre Curie discover polonium and announce the existence of another new radioactive element they name radium.
  • Paul Ulrich Villard discovers gamma rays.


  • U.S. Army begins using x‑rays in hospitals during Spanish-American War.
"Marie felt and could soon affirm that the incomprehensible radiation was an atomic property. She questioned: Even though the phenomenon had only been observed with uranium, nothing proved that uranium was the only chemical element capable of emitting radiation. Why should not other bodies possess the same power? ... it must be sought for elsewhere."

From "Madame Curie - A Biography" by Eve Curie, p. 155,
Doubleday, Doran and Company, Garden City, New York. 1937.


  • Antoine-Henri Becquerel discovers rays produced by uranium, the first observation of natural radioactivity.
  • Concerns first raised about possible injuries from x‑ray exposures.
  • Elihu Thomson conducts experiments on x‑ray burns.
  • H.S. Ward publishes first textbook on radiation, Practical Radiography.
  • X‑ray pictures are first used as evidence in a court of law.


  • Wilhelm Konrad Roentgen discovers x‑rays.
  • Roentgen's paper on x‑rays is published by the Physico-Medical Society of Wrzburg, December 28.

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