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Recognized effects of higher acute radiation doses are described in more detail in the article on radiation poisoning. Although the International System of Units (SI) defines the sievert (Sv) as the unit of radiation dose equivalent, chronic radiation levels and standards are still often given in units of millirems (mrem), where 1 mrem equals 1/1,000 of a rem and 1 rem equals 0.01 Sv. Light radiation sickness begins at about 50–100 rad (0.5–1 gray (Gy), 0.5–1 Sv, 50–100 rem, 50,000–100,000 mrem).
The following table includes some dosages for comparison purposes, using millisieverts (mSv) (one thousandth of a sievert). The concept of radiation hormesis is relevant to this table – radiation hormesis is a hypothesis stating that the effects of a given acute dose may differ from the effects of an equal fractionated dose. Thus 100 mSv is considered twice in the table below – once as received over a 5-year period, and once as an acute dose, received over a short period of time, with differing predicted effects. The table describes doses and their official limits, rather than effects.
| Dosage Level | Description |
|---|---|
| 250 mGy | Lowest dose to cause clinically observable blood changes |
| 260 mGy | Peak natural background dose after one year in Ramsar, Iran [1] |
| 2 Gy | Local dose for onset of erythema in humans |
| 48.5 Gy (4.85 krad) | Roughly calculated from the estimated 4,500 + 350 rad dose for fatality of Russian experimenter on June 17, 1997, at Sarov. [2] |
| 100 Gy (10 krad) | Estimated fatality at the United Nuclear Fuels Recovery Plant on July 24, 1964. [2] |
| 2 kGy | One second of the estimated dose applied to the inner wall in ITER [3] |
| 10 kGy (1 Mrad) | Typical tolerance of radiation-hardened microchips |
| 10 MGy (1 Grad) | The maximum radiation dosage of the most hardened electronics. [4] |
| Level (mSv) | Level in standard form (mSv) | Duration | Hourly equivalent (μSv/hour) | Description |
|---|---|---|---|---|
| 0.001 | 1×10−3 | Hourly | 1 | Cosmic ray dose rate on commercial flights varies from 1 to 10 μSv/hour, depending on altitude, position and solar sunspot phase. [5] |
| 0.01 | 1×10−2 | Daily | 0.4 | Natural background radiation, including radon [6] |
| 0.06 | 6×10−2 | Acute | - | Chest X-ray (AP+Lat) [7] |
| 0.07 | 7×10−2 | Acute | - | Transatlantic airplane flight. |
| 0.09 | 9×10−2 | Acute | - | Dental X-ray (Panoramic) [7] |
| 0.1 | 1×10−1 | Annual | 0.011 | Average USA dose from consumer products [8] |
| 0.15 | 1.5×10−1 | Annual | 0.017 | USA EPA cleanup standard [ citation needed ] |
| 0.25 | 2.5×10−1 | Annual | 0.028 | USA NRC cleanup standard for individual sites/sources [ citation needed ] |
| 0.27 | 2.7×10−1 | Annual | 0.031 | Yearly dose from natural cosmic radiation at sea level (0.5 in Denver due to altitude) [8] |
| 0.28 | 2.8×10−1 | Annual | 0.032 | USA yearly dose from natural terrestrial radiation (0.16-0.63 depending on soil composition) [8] |
| 0.46 | 4.6×10−1 | Acute | - | Estimated largest off-site dose possible from March 28, 1979 Three Mile Island accident [ citation needed ] |
| 0.48 | 4.8×10−1 | Day | 20 | USA NRC public area exposure limit[ citation needed ] |
| 0.66 | 6.6×10−1 | Annual | 0.075 | Average USA dose from human-made sources [6] |
| 0.7 | 7×10−1 | Acute | - | Mammogram [7] |
| 1 | 1×100 | Annual | 0.11 | Limit of dose from man-made sources to a member of the public who is not a radiation worker in the US and Canada [6] [9] |
| 1.1 | 1.1×100 | Annual | 0.13 | Average USA radiation worker occupational dose in 1980 [6] |
| 1.2 | 1.2×100 | Acute | - | Abdominal X-ray [7] |
| 2 | 2×100 | Annual | 0.23 | USA average medical and natural background Human internal radiation due to radon, varies with radon levels [8] |
| 2 | 2×100 | Acute | - | Head CT [7] |
| 3 | 3×100 | Annual | 0.34 | USA average dose from all natural sources [6] |
| 3.66 | 3.66×100 | Annual | 0.42 | USA average from all sources, including medical diagnostic radiation doses[ citation needed ] |
| 4 | 4×100 | Duration of the pregnancy | 0.6 | Canada CNSC maximum occupational dose to a pregnant woman who is a designated Nuclear Energy Worker. [9] |
| 5 | 5×100 | Annual | 0.57 | USA NRC occupational limit for minors (10% of adult limit) USA NRC limit for visitors [10] |
| 5 | 5×100 | Pregnancy | 0.77 | USA NRC occupational limit for pregnant women[ citation needed ] |
| 6.4 | 6.4×100 | Annual | 0.73 | High Background Radiation Area (HBRA) of Yangjiang, China [11] |
| 7.6 | 7.6×100 | Annual | 0.87 | Fountainhead Rock Place, Santa Fe, NM natural[ citation needed ] |
| 8 | 8×100 | Acute | - | Chest CT [7] |
| 10 | 1×101 | Acute | - | Lower dose level for public calculated from the 1 to 5 rem range for which USA EPA guidelines mandate emergency action when resulting from a nuclear accident [6] Abdominal CT [7] |
| 14 | 1.4×101 | Acute | - | 18F FDG PET scan, [12] Whole Body |
| 50 | 5×101 | Annual | 5.7 | USA NRC/ Canada CNSC occupational limit for designated Nuclear Energy Workers [9] (10 CFR 20) |
| 100 | 1×102 | 5 years | 2.3 | Canada CNSC occupational limit over a 5-year dosimetry period for designated Nuclear Energy Workers [9] |
| 100 | 1×102 | Acute | - | USA EPA acute dose level estimated to increase cancer risk 0.8% [6] |
| 120 | 1.2×102 | 30 years | 0.46 | Exposure, long duration, Ural Mountains, lower limit, lower cancer mortality rate [13] |
| 150 | 1.5×102 | Annual | 17 | USA NRC occupational eye lens exposure limit [ citation needed ][ clarification needed ] |
| 170 | 1.7×102 | Acute | Average dose for 187,000 Chernobyl recovery operation workers in 1986 [14] [15] | |
| 175 | 1.75×102 | Annual | 20 | Guarapari, Brazil natural radiation sources[ citation needed ] |
| 250 | 2.5×102 | 2 hours | 125,000 | (125 mSv/hour) Whole body dose exclusion zone criteria for US nuclear reactor siting [16] (converted from 25 rem) |
| 250 | 2.5×102 | Acute | - | USA EPA voluntary maximum dose for emergency non-life-saving work [6] |
| 400-900 | 4–9×102 | Annual | 46-103 | Unshielded in interplanetary space. [17] |
| 500 | 5×102 | Annual | 57 | USA NRC occupational whole skin, limb skin, or single organ exposure limit |
| 500 | 5×102 | Acute | - | Canada CNSC occupational limit for designated Nuclear Energy Workers carrying out urgent and necessary work during an emergency. [9] Low-level radiation sickness due to short-term exposure [18] |
| 750 | 7.5×102 | Acute | - | USA EPA voluntary maximum dose for emergency life-saving work [6] |
| 1,000 | 10×102 | Hourly | 1,000,000 | Level reported during Fukushima I nuclear accidents, in immediate vicinity of reactor [19] |
| 3,000 | 3×103 | Acute | - | Thyroid dose (due to iodine absorption) exclusion zone criteria for US nuclear reactor siting [16] (converted from 300 rem) |
| 4,800 | 4.8×103 | Acute | - | LD50 (actually LD50/60) in humans from radiation poisoning with medical treatment estimated from 480 to 540 rem. [20] |
| 5,000 | 5×103 | Acute | - | Calculated from the estimated 510 rem dose fatally received by Harry Daghlian on August 21, 1945, at Los Alamos and lower estimate for fatality of Russian specialist on April 5, 1968, at Chelyabinsk-70. [2] |
| 5,000 | 5×103 | 5,000 - 10,000 mSv. Most commercial electronics can survive this radiation level. [21] | ||
| 16,000 | 1.6×104 | Acute | Highest estimated dose to Chernobyl emergency worker diagnosed with acute radiation syndrome [15] | |
| 20,000 | 2×104 | Acute | 2,114,536 | Interplanetary exposure to solar particle event (SPE) of October 1989. [22] [23] |
| 21,000 | 2.1×104 | Acute | - | Calculated from the estimated 2,100 rem dose fatally received by Louis Slotin on May 21, 1946, at Los Alamos and lower estimate for fatality of Russian specialist on April 5, 1968 Chelyabinsk-70. [2] |
| 48,500 | 4.85×104 | Acute | - | Roughly calculated from the estimated 4,500 + 350 rad dose for fatality of Russian experimenter on June 17, 1997, at Sarov. [2] |
| 60,000 | 6×104 | Acute | - | Roughly calculated from the estimated 6,000 rem doses for several Russian fatalities from 1958 onwards, such as on May 26, 1971, at the Kurchatov Institute. Lower estimate for fatality of Cecil Kelley at Los Alamos on December 30, 1958. [2] |
| 100,000 | 1×105 | Acute | - | Roughly calculated from the estimated 10,000 rad dose for fatality at the United Nuclear Fuels Recovery Plant on July 24, 1964. [2] |
| 30,000,000 | 3×107 | 3,600,000 | Radiation tolerated by Thermococcus gammatolerans , a microbe extremely resistant to radiation. [24] | |
| 70,000,000,000 | 7×1010 | Hourly | 70,000,000,000,000 | Estimated dose rate for the inner wall in ITER (2 kGy/s with an approximate weighting factor of 10) [3] |
Background radiation is a measure of the level of ionizing radiation present in the environment at a particular location which is not due to deliberate introduction of radiation sources.
Acute radiation syndrome (ARS), also known as radiation sickness or radiation poisoning, is a collection of health effects that are caused by being exposed to high amounts of ionizing radiation in a short period of time. Symptoms can start within an hour of exposure, and can last for several months. Early symptoms are usually nausea, vomiting and loss of appetite. In the following hours or weeks, initial symptoms may appear to improve, before the development of additional symptoms, after which either recovery or death follow.
The sievert is a unit in the International System of Units (SI) intended to represent the stochastic health risk of ionizing radiation, which is defined as the probability of causing radiation-induced cancer and genetic damage. The sievert is important in dosimetry and radiation protection. It is named after Rolf Maximilian Sievert, a Swedish medical physicist renowned for work on radiation dose measurement and research into the biological effects of radiation.
Ionizing radiation, including nuclear radiation, consists of subatomic particles or electromagnetic waves that have sufficient energy to ionize atoms or molecules by detaching electrons from them. Some particles can travel up to 99% of the speed of light, and the electromagnetic waves are on the high-energy portion of the electromagnetic spectrum.
Radiation dosimetry in the fields of health physics and radiation protection is the measurement, calculation and assessment of the ionizing radiation dose absorbed by an object, usually the human body. This applies both internally, due to ingested or inhaled radioactive substances, or externally due to irradiation by sources of radiation.
Hormesis is a two-phased dose-response relationship to an environmental agent whereby low-dose amounts have a beneficial effect and high-dose amounts are either inhibitory to function or toxic. Within the hormetic zone, the biological response to low-dose amounts of some stressors is generally favorable. An example is the breathing of oxygen, which is required in low amounts via respiration in living animals, but can be toxic in high amounts, even in a managed clinical setting.
Health physics, also referred to as the science of radiation protection, is the profession devoted to protecting people and their environment from potential radiation hazards, while making it possible to enjoy the beneficial uses of radiation. Health physicists normally require a four-year bachelor’s degree and qualifying experience that demonstrates a professional knowledge of the theory and application of radiation protection principles and closely related sciences. Health physicists principally work at facilities where radionuclides or other sources of ionizing radiation are used or produced; these include research, industry, education, medical facilities, nuclear power, military, environmental protection, enforcement of government regulations, and decontamination and decommissioning—the combination of education and experience for health physicists depends on the specific field in which the health physicist is engaged.
The roentgen equivalent man (rem) is a CGS unit of equivalent dose, effective dose, and committed dose, which are dose measures used to estimate potential health effects of low levels of ionizing radiation on the human body.
The linear no-threshold model (LNT) is a dose-response model used in radiation protection to estimate stochastic health effects such as radiation-induced cancer, genetic mutations and teratogenic effects on the human body due to exposure to ionizing radiation. The model assumes a linear relationship between dose and health effects, even for very low doses where biological effects are more difficult to observe. The LNT model implies that all exposure to ionizing radiation is harmful, regardless of how low the dose is, and that the effect is cumulative over lifetime.
Radiation hormesis is the hypothesis that low doses of ionizing radiation are beneficial, stimulating the activation of repair mechanisms that protect against disease, that are not activated in absence of ionizing radiation. The reserve repair mechanisms are hypothesized to be sufficiently effective when stimulated as to not only cancel the detrimental effects of ionizing radiation but also inhibit disease not related to radiation exposure. It has been a mainstream concept since at least 2009.
Rolf Maximilian Sievert was a Swedish medical physicist whose major contribution was in the study of the biological effects of ionizing radiation.
Background radiation equivalent time (BRET) or background equivalent radiation time (BERT) is a unit of measurement of ionizing radiation dosage amounting to one day worth of average human exposure to background radiation.
Chernobyl liquidators were the civil and military personnel who were called upon to deal with the consequences of the 1986 Chernobyl nuclear disaster in the Soviet Union on the site of the event. The liquidators are widely credited with limiting both the immediate and long-term damage from the disaster.
The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) was set up by resolution of the United Nations General Assembly in 1955. Twenty-one states are designated to provide scientists to serve as members of the committee which holds formal meetings (sessions) annually and submits a report to the General Assembly. The organisation has no power to set radiation standards nor to make recommendations in regard to nuclear testing. It was established solely to "define precisely the present exposure of the population of the world to ionizing radiation". A small secretariat, located in Vienna and functionally linked to the United Nations Environment Programme (UNEP), organizes the annual sessions and manages the preparation of documents for the committee's scrutiny.
Radiobiology is a field of clinical and basic medical sciences that involves the study of the effects of ionizing radiation on living things, in particular health effects of radiation. Ionizing radiation is generally harmful and potentially lethal to living things but can have health benefits in radiation therapy for the treatment of cancer and thyrotoxicosis. Its most common impact is the induction of cancer with a latent period of years or decades after exposure. High doses can cause visually dramatic radiation burns, and/or rapid fatality through acute radiation syndrome. Controlled doses are used for medical imaging and radiotherapy.
Health threats from cosmic rays are the dangers posed by cosmic rays to astronauts on interplanetary missions or any missions that venture through the Van-Allen Belts or outside the Earth's magnetosphere. They are one of the greatest barriers standing in the way of plans for interplanetary travel by crewed spacecraft, but space radiation health risks also occur for missions in low Earth orbit such as the International Space Station (ISS).
Astronauts are exposed to approximately 72 millisieverts (mSv) while on six-month-duration missions to the International Space Station (ISS). Longer 3-year missions to Mars, however, have the potential to expose astronauts to radiation in excess of 1,000 mSv. Without the protection provided by Earth's magnetic field, the rate of exposure is dramatically increased. The risk of cancer caused by ionizing radiation is well documented at radiation doses beginning at 100 mSv and above.
Exposure to ionizing radiation is known to increase the future incidence of cancer, particularly leukemia. The mechanism by which this occurs is well understood, but quantitative models predicting the level of risk remain controversial. The most widely accepted model posits that the incidence of cancers due to ionizing radiation increases linearly with effective radiation dose at a rate of 5.5% per sievert; if correct, natural background radiation is the most hazardous source of radiation to general public health, followed by medical imaging as a close second. Additionally, the vast majority of non-invasive cancers are non-melanoma skin cancers caused by ultraviolet radiation. Non-ionizing radio frequency radiation from mobile phones, electric power transmission, and other similar sources have been investigated as a possible carcinogen by the WHO's International Agency for Research on Cancer, but to date, no evidence of this has been observed.
The Radiation Assessment Detector (RAD) is an instrument mounted on the Mars Science Laboratory'sCuriosity rover. It was the first of ten instruments to be turned on during the mission.
Radiation exposure is a measure of the ionization of air due to ionizing radiation from photons. It is defined as the electric charge freed by such radiation in a specified volume of air divided by the mass of that air. As of 2007, "medical radiation exposure" was defined by the International Commission on Radiological Protection as exposure incurred by people as part of their own medical or dental diagnosis or treatment; by persons, other than those occupationally exposed, knowingly, while voluntarily helping in the support and comfort of patients; and by volunteers in a programme of biomedical research involving their exposure. Common medical tests and treatments involving radiation include X-rays, CT scans, mammography, lung ventilation and perfusion scans, bone scans, cardiac perfusion scan, angiography, radiation therapy, and more. Each type of test carries its own amount of radiation exposure. There are two general categories of adverse health effects caused by radiation exposure: deterministic effects and stochastic effects. Deterministic effects are due to the killing/malfunction of cells following high doses; and stochastic effects involve either cancer development in exposed individuals caused by mutation of somatic cells, or heritable disease in their offspring from mutation of reproductive (germ) cells.
high as 260 mGy/year
Orvieto town, Italy
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