Radiation poisoning

Radiation poisoning
Classification and external resources
Japanese woman suffering burns from thermal radiation after the United States dropped nuclear bombs on Japan in World War II.
ICD-10	T66.
ICD-9	990
MeSH	D011832

Radiation poisoning
Accidents · Experiments · Biological timeline
Conditions
Radiation dermatitis · Radiation recall reactions · Radiation acne · Radiation cancer · Radiation-induced lung injury
Treatments
Dose fractionation · Radioresistance · Radiation protection · Radiation dose reconstruction

Radiation poisoning, radiation sickness or a creeping dose, is a form of damage to organ tissue caused by excessive exposure to ionizing radiation. The term is generally used to refer to acute problems caused by a large dosage of radiation in a short period, though this also has occurred with long term exposure. The clinical name for radiation sickness is acute radiation syndrome (ARS) as described by the CDC.^[1][2][3] A chronic radiation syndrome does exist but is very uncommon; this has been observed among workers in early radium source production sites and in the early days of the Soviet nuclear program. A short exposure can result in acute radiation syndrome; chronic radiation syndrome requires a prolonged high level of exposure.

Radiation exposure can also increase the probability of developing some other diseases, mainly cancer, tumours, and genetic damage. These are referred to as the stochastic effects of radiation, and are not included in the term radiation sickness.

The use of radionuclides in science and industry is strictly regulated in most countries (in the U.S. by the Nuclear Regulatory Commission). In the event of an accidental or deliberate release of radioactive material, either evacuation or sheltering in place are the recommended measures.

Signs and symptoms

Radiation sickness is generally associated with acute (a single large) exposure.^[4][5] Nausea and vomiting are usually the main symptoms.^[5] The amount of time between exposure to radiation and the onset of the initial symptoms may be an indicator of how much radiation was absorbed,^[5] as symptoms appear sooner with higher doses of exposure.^[6] The symptoms of radiation sickness become more serious (and the chance of survival decreases) as the dosage of radiation increases. A few symptom-free days may pass between the appearance of the initial symptoms and the onset of symptoms of more severe illness associated with higher doses of radiation.^[5] Nausea and vomiting generally occur within 24–48 hours after exposure to mild (1–2 Gy) doses of radiation. Headache, fatigue, and weakness are also seen with mild exposure.^[5] Moderate (2–3.5 Gy of radiation) exposure is associated with nausea and vomiting beginning within 12–24 hours after exposure.^[5] In addition to the symptoms of mild exposure, fever, hair loss, infections, bloody vomit and stools, and poor wound healing are seen with moderate exposure.^[5] Nausea and vomiting occur in less than 1 hour after exposure to severe (3.5–5.5 Gy) doses of radiation, followed by diarrhea and high fever in addition to the symptoms of lower levels of exposure.^[5] Very severe (5.5–8 Gy of radiation) exposure is followed by the onset of nausea and vomiting in less than 30 minutes followed by the appearance of dizziness, disorientation, and low blood pressure in addition to the symptoms of lower levels of exposure.^[5] Severe exposure is fatal about 50% of the time.^[5]

Longer term exposure to radiation, at doses less than that which produces serious radiation sickness, can induce cancer as cell-cycle genes are mutated. If a cancer is radiation-induced, then the disease, the speed at which the condition advances, the prognosis, the degree of pain, and every other feature of the disease are not functions of the radiation dose to which the sufferer is exposed. In this case, function of dose is the probability chronic effects will develop.

Since tumors grow by abnormally rapid cell division, the ability of radiation to disturb cell division is also used to treat cancer (see radiotherapy), and low levels of ionizing radiation have been claimed to lower one's risk of cancer (see hormesis).

Cutaneous radiation syndrome

The concept of cutaneous radiation syndrome (CRS) was introduced in recent years to describe the complex pathological syndrome that results from acute radiation exposure to the skin.^[3]

Acute radiation syndrome (ARS) usually will be accompanied by some skin damage. It is also possible to receive a damaging dose to the skin without symptoms of ARS, especially with acute exposures to beta radiation or X-rays. Sometimes this occurs when radioactive materials contaminate skin or clothes.^[3]

When the basal cell layer of the skin is damaged by radiation, inflammation, erythema, and dry or moist desquamation can occur. Also, hair follicles may be damaged, causing hair loss. Within a few hours after irradiation, a transient and inconsistent erythema (associated with itching) can occur. Then, a latent phase may occur and last from a few days up to several weeks, when intense reddening, blistering, and ulceration of the irradiated site are visible. In most cases, healing occurs by regenerative means; however, very large skin doses can cause permanent hair loss, damaged sebaceous and sweat glands, atrophy, fibrosis, decreased or increased skin pigmentation, and ulceration or necrosis of the exposed tissue.^[3]

Exposure levels

Annual limit on intake (ALI) is the derived limit for the amount of radioactive material taken into the body of an adult worker by inhalation or ingestion in a year. ALI is the smaller value of intake of a given radionuclide in a year by the reference man that would result in a committed effective dose equivalent of 0.05 Sv (5 rems) or a committed dose equivalent of 0.5 Sv (50 rems) to any individual organ or tissue.^[7] The rad (radiation absorbed dose, symbol rad) is a largely obsolete unit of absorbed radiation dose, equal to 1 centigrays. To gauge biological effects the dose in rads is multiplied by a 'quality factor' which is dependent on the type of ionising radiation. The modified dose can now be measured in rems (roentgen equivalent mammal, or man)^[8]. The SI unit is sievert (Sv). 100 rem = 1 Sv. The table below expresses doses in Gray (Gy);

^[9]

Cause

External vs internal exposure

External

External exposure is exposure which occurs when the radioactive source (or other radiation source) is outside (and remains outside) the organism which is exposed. Below are a series of three examples of external exposure.

• A person who places a sealed radioactive source in his pocket
• A space traveller who is irradiated by cosmic rays
• A person who is treated for cancer by either teletherapy or brachytherapy. While in brachytherapy the source is inside the person it is still external exposure because the active part of the source never comes into direct contact with the biological tissues of the person.

A schematic diagram showing an animal being irradiated by an external source (in red) of radiation (shown in yellow).

One of the key points is that external exposure is often relatively easy to estimate, and the irradiated objects do not become radioactive (except for a case where the radiation is an intense neutron beam which causes activation of the object). It is possible for an object to be contaminated on the outer surfaces; assuming that no radioactivity enters the object it is still a case of external exposure and it is normally the case that decontamination is relatively easy.

A schematic diagram showing an animal being irradiated by radioactive contamination (shown in red) which is present on an external surface such as the skin, this emits radiation (shown in yellow) which can enter the animal's body

Internal

Internal exposure occurs when the radioactive material enters the organism, and the radioactive atoms become incorporated into the organism. Below are a series of examples of internal exposure.

• The exposure caused by ⁴⁰K present within a normal person.
• The exposure to the ingestion of a soluble radioactive substance, such as ⁸⁹Sr in cows' milk.
• A person who is being treated for cancer by means of an open source radiotherapy method where a radioisotope is used as a drug. A review of this topic was published in 1999.^[10] Because the radioactive material becomes intimately mixed with the affected object it is often difficult to decontaminate the object or person in a case where internal exposure is occurring. While some very insoluble materials such as fission products within a uranium dioxide matrix might never be able to truly become part of an organism, it is normal to consider such particles in the lungs as a form of internal contamination which results in internal exposure. The reasoning is that the particles have entered via an orifice and can not be removed with ease from what the lay person (non biologist) would regard as within the animal. It is important to note that in a strictly topological sense, the contents of the digestive tract and the air within the lungs are outside the body of a mammal (whereas, for instance, the abdominal cavity is topologically inside the mammalian body).

A schematic diagram showing an animal being irradiated by radioactive contamination (shown in red) which is present within its lung, this emits radiation (shown in yellow) which can enter the animal's body

Nuclear warfare and bomb tests

Nuclear warfare and bomb tests are more complex because a person can be irradiated by at least three processes. The first (the major cause of burns) is not caused by ionizing radiation.

• Thermal burns from infrared heat radiation
• Beta burns from shallow ionizing beta radiation (this would be from fallout particles; the largest particles in local fallout would be likely to have very high activities because they would be deposited so soon after detonation and it is likely that one such particle upon the skin would be able to cause a localised burn); however, these particles are very weakly penetrating and have a short range.
• Gamma burns from highly penetrating gamma radiation. This would likely cause deep gamma penetration within the body, which would result in uniform whole body irradiation rather than only a surface burn. In cases of whole body gamma irradiation (circa 10 Gy) caused by accidents involving medical product irradiators, some of the human subjects have developed injuries to their skin between the time of irradiation and death.

In the picture on the right, the normal clothing that the woman was wearing would have been unable to attenuate the gamma radiation and it is likely that any such effect was evenly applied to her entire body. Beta burns would be likely all over the body caused by contact with fallout, but thermal burns are often on one side of the body as heat radiation does not penetrate the human body. In addition, the pattern on her clothing has been burnt into the skin. This is because white fabric reflects more infrared light than dark fabric. As a result, the skin close to dark fabric is burned more than the skin covered by white clothing.

There is also the risk of internal radiation poisoning by ingestion of fallout particles.

Nuclear reactor accidents

The first known incident of a reactor meltdown occurred in Canada in the NRX Reactor. Radiation poisoning was a major concern after the Chernobyl reactor accident. Thirty-one people died as an immediate result.^[11]

Of the 100 million curies (4 exabecquerels) of radioactive material, the short lived radioactive isotopes such as ¹³¹I Chernobyl released were initially the most dangerous. Due to their short half-lives of 5 and 8 days they have now decayed, leaving the more long-lived ¹³⁷Cs (with a half-life of 30.07 years) and ⁹⁰Sr (with a half-life of 28.78 years) as main dangers.

Other accidents

Improper handling of radioactive and nuclear materials lead to radiation release and radiation poisoning. The most serious of these, caused by improper disposal of a medical device containing a radioactive source (teletherapy), occurred in Goiânia, Brazil in 1987.

Spaceflight

During human spaceflights, particularly flights beyond low Earth orbit, astronauts are exposed to both galactic cosmic radiation (GCR) and possibly solar particle event (SPE) radiation. Evidence indicates past SPE radiation levels which would have been lethal for unprotected astronauts.^[12] GCR levels which might lead to acute radiation poisoning are less well understood.^[13]

Ingestion and inhalation

When radioactive compounds enter the human body, the effects are different from those resulting from exposure to an external radiation source. Especially in the case of alpha radiation, which normally does not penetrate the skin, the exposure can be much more damaging after ingestion or inhalation. The radiation exposure is normally expressed as a committed effective dose equivalent (CEDE). Some poisoned beings exposed will not be radiated, but their offspring will be .

Deliberate poisoning

On November 23, 2006, Alexander Litvinenko died from suspected deliberate poisoning with polonium-210.^{[14][15][16][17][18]} His is the first case of confirmed death by such a cause, although it is also known that there have been other cases of attempted assassination such as in the cases of KGB defector Nikolay Khokhlov and journalist Yuri Shchekochikhin where radioactive thallium was used. In addition, an incident occurred in 1990 at Point Lepreau Nuclear Generating Station where several employees acquired small doses of radiation because of the contamination of water in the office watercooler with tritium-contaminated heavy water.^[19][20]

Prevention

See also: Radiation protection.

The best prevention for radiation sickness is to minimize the dose suffered by the human, or to reduce the dose rate.

Distance

Increasing distance from the radiation source reduces the dose according to the inverse-square law for a point source. Distance can be increased by means as simple as handling a source with forceps rather than fingers.

Time

The longer that humans are subjected to radiation the larger the dose will be. The advice in the nuclear war manual entitled "Nuclear War Survival Skills" published by Cresson Kearny in the U.S. was that if one needed to leave the shelter then this should be done as rapidly as possible to minimize exposure.

In chapter 12 he states that "Quickly putting or dumping wastes outside is not hazardous once fallout is no longer being deposited. For example, assume the shelter is in an area of heavy fallout and the dose rate outside is 400 R/hr enough to give a potentially fatal dose in about an hour to a person exposed in the open. If a person needs to be exposed for only 10 seconds to dump a bucket, in this 1/360th of an hour he will receive a dose of only about 1 R. Under war conditions, an additional 1-R dose is of little concern."

In peacetime, radiation workers are taught to work as quickly as possible when performing a task which exposes them to radiation. For instance, the recovery of a lost radiography source should be done as quickly as possible.

Reduction of incorporation into the human body

Potassium iodide (KI), administered orally immediately after exposure, may be used to protect the thyroid from ingested radioactive iodine in the event of an accident or terrorist attack at a nuclear power plant, or the detonation of a nuclear explosive. KI would not be effective against a dirty bomb unless the bomb happened to contain radioactive iodine, and even then it would only help to prevent thyroid cancer.

Fractionation of dose

This is a graph showing the effect of fractionation on the ability of gamma rays to cause cell death. The blue line is for cells which were not given any time to recover, while the red line is for cells which were allowed to stand for a time and recover.

Devair Alves Ferreira received a large dose during the Goiânia accident of 7.0 Gy. He lived, while his wife received a dose of 5.7 Gy and died. The most likely explanation is that his dose was fractionated into many smaller doses which were absorbed over a length of time, while his wife stayed in the house more and was subjected to continuous irradiation without a break, giving her body less time to repair some of the damage done by the radiation. In the same way, some of the people who worked in the basement of the wrecked Chernobyl plant received doses of 10 Gy, but in small fractions, so the acute effects were avoided.

It has been found in radiation biology experiments that if a group of cells are irradiated, then as the dose increases, the number of cells which survive decreases. It has also been found that if a population of cells is irradiated, then set aside for a length of time before being irradiated again, the radiation causes less cell death. The human body contains many types of cells and a human can be killed by the loss of a single type of cells in a vital organ. For many short term radiation deaths (3 days to 30 days), the loss of cells forming blood cells (bone marrow) and the cells in the digestive system (microvilli which form part of the wall of the intestines are constantly being regenerated in a healthy human) causes death.

In the graph below, dose/survival curves for a hypothetical group of cells have been drawn, with and without a rest time for the cells to recover. Other than the recovery time partway through the irradiation, the cells would have been treated identically.

Treatment

Treatment reversing the effects of irradiation is currently not possible. Anaesthetics and antiemetics are administered to counter the symptoms of exposure, as well as antibiotics for countering secondary infections caused by the resulting immune system deficiency.

There are also a number of substances used to mitigate the prolonged effects of radiation poisoning, by eliminating the remaining radioactive materials, post exposure.

Whole body vs. part of body exposure

In the case of a person who has had only part of their body irradiated then the treatment is easier, as the human body can tolerate very large exposures to the non-vital parts such as hands and feet, without having a global effect on the entire body. For instance, if the hands get a 100 Gy dose which results in the body receiving a dose (averaged over the entire body) of less than 1 Gy then the hands may be lost but radiation poisoning may not occur. The resulting injury would be described as localized radiation burn.

As described below, one of the primary dangers of whole-body exposure is immunodeficiency caused by the destruction of bone marrow and consequent shortage of white blood cells. It is treated by maintaining a sterile environment, bone marrow transplants (see hematopoietic stem cell transplantation), and blood transfusions.

Experimental treatments

Neumune, an androstenediol, was introduced as a radiation countermeasure by the US Armed Forces Radiobiology Research Institute, and was under joint development with Hollis-Eden Pharmaceuticals until March, 2007. Neumune is in Investigational New Drug (IND) status and Phase I trials have been performed.

Some work has been published in which Cordyceps sinensis, a Chinese Herbal Medicine has been used to protect the bone marrow and digestive systems of mice from whole body irradation.^[21]

Recent lab studies conducted with bisphosphonate compounds have shown promise of mitigating radiation exposure effects.^[22]

History

Although radiation was discovered in late 19th century, the dangers of radioactivity and of radiation were not immediately recognized. Acute effects of radiation were first observed in the use of X-rays when Nikola Tesla intentionally subjected his fingers to X-rays in 1896. He published his observations concerning the burns that developed, though he attributed them to ozone rather than to X-rays. His injuries healed later.

The genetic effects of radiation, including the effects on cancer risk, were recognized much later. In 1927 Hermann Joseph Muller published research showing genetic effects, and in 1946 was awarded the Nobel prize for his findings.

Before the biological effects of radiation were known, many physicians and corporations had begun marketing radioactive substances as patent medicine and radioactive quackery. Examples were radium enema treatments, and radium-containing waters to be drunk as tonics. Marie Curie spoke out against this sort of treatment, warning that the effects of radiation on the human body were not well understood. Curie later died of aplastic anemia caused by radiation poisoning. Eben Byers, a famous American socialite, died in 1932 after consuming large quantities of radium over several years; his death drew public attention to dangers of radiation. By the 1930s, after a number of cases of bone necrosis and death in enthusiasts, radium-containing medical products had nearly vanished from the market.

Nevertheless, dangers of radiation were not fully appreciated by scientists until later. In 1945 and 1946, two U.S. scientists died from acute radiation exposure in separate criticality accidents. In both cases, victims were working with large quantities of fissile materials without any shielding or protection.

Atomic bombings of Hiroshima and Nagasaki resulted in a large number of incidents of radiation poisoning, allowing for greater insight into its symptoms and dangers. Actress Midori Naka, who was present during the atomic bombing of Hiroshima, was the first incident of radiation poisoning to be extensively studied. Her death on August 1945 was the first death ever to be officially certified as a result of radiation poisoning (or "Atomic bomb disease").

In other animals

An episode of MythBusters exposed insects to the Cobalt-60 source at the Pacific Northwest National Laboratory facility. At 100 Gy, 70% of cockroaches were dead after 30 days, and 30% survived. At 1000 Gy, all of the cockroaches died instantly and 90% of flour beetles were dead after 30 days, with only 10% surviving.^[23]

See also

• Background radiation
• Hibakusha – Japanese atomic bomb survivors
• List of civilian nuclear accidents
• List of military nuclear accidents
• Radioactive quackery
• Risks and benefits of sun exposure

References

Further reading

• Michihiko Hachiya, Hiroshima Diary (Chapel Hill: University of North Carolina, 1955), ISBN 0-8078-4547-7.
• John Hersey, Hiroshima (New York: Vintage, 1946, 1985 new chapter), ISBN 0-679-72103-7.
• Ibuse Masuji, Black Rain (1969) ISBN 0-87011-364-X
• Ernest J. Sternglass, Secret Fallout: low-level radiation from Hiroshima to Three-Mile Island (1981) ISBN 0-07-061242-0 (online)
• Norman Solomon, Harvey Wasserman Killing Our Own: The Disaster of America's Experience with Atomic Radiation, 1945–1982, New York: Dell, 1982. ISBN 0-385-28537-X, ISBN 0-385-28536-1, ISBN 0-440-04567-3 (online)

External links

• Radiation accidents with multi-organ failure in the United States
• List of radiation accidents and other events causing radiation casualties
• The criticality accident in Sarov, International Atomic Energy Agency, 2001 — well documented account of the biological effects of a criticality accident
• The Center for Disease Control's fact sheet on Acute Radiation Syndrome
• Therac-25 computerized radiation therapy machine accidents
• 50-KT to 1-MT surface burst thermal burns and radiation doses

 This article incorporates public domain material from websites or documents of the Centers for Disease Control and Prevention.