Radiation injuries are caused by ionizing radiation emitted by sources such as the sun, x-ray and other diagnostic machines, tanning beds, and radioactive elements released in nuclear power plant accidents and detonation of nuclear weapons during war and as part of terrorist acts.
Anyone has the potential for being injured by radiation, whether it is naturally, such as from a severe sunburn, or artificially, such as from radiation leaked from a nuclear power plant or expelled through a nuclear weapon.
Ionizing radiation derives from unstable atoms that contain an excess amount of energy. In an attempt to stabilize, the atoms emit the excess energy creating radiation. Radiation can either be electromagnetic (in the form of a wave) or as particles.
The energy of electromagnetic radiation is a direct function of its frequency. The high-energy, high-frequency waves that can penetrate solids to various depths cause damage by separating molecules into electrically charged pieces, a process known as ionization. X rays are a type of electromagnetic radiation. Sub-atomic particles come from radioactive isotopes as they decay to stable elements. Electrons traveling at high velocity form beta radiate. Alpha particles are the nuclei of helium atoms—two protons and two neutrons—without the surrounding electrons. Alpha particles interact so strongly with matter that they cannot penetrate a piece of paper unless greatly accelerated in electric and magnetic fields. Both beta and alpha particles are typical of ionizing particulate radiation. Exposure to ionizing radiation can lead to chromosomal damage in deoxyribonucleic acid (DNA), although DNA is very good at repairing itself; both strands of the double helix must be broken to produce genetic damage.
Because radiation is energy, it can be measured. There are a number of units used to quantify radiation energy. Some refer to effects on air, others to effects on living tissue. The roentgen, named after German physicist Wilhelm Conrad Röentgen (1845–1923), sometimes spelled Roentgen, who discovered x rays in 1895, measures ionizing energy in air. A rad expresses the energy transferred to tissue. The rem measures tissue response. A roentgen generates about a rad of effect and produces about a rem of response. The gray and the sievert are international units equivalent to 100 rads and rems, respectively. A curie, named after French physicists Marie Curie (1867–1934) and Pierre Curie (1859–1906) who experimented with radiation, is a measure of actual radioactivity given off by a radioactive element, not a measure of its effect. The average annual human exposure to natural background radiation is roughly 3 milliSieverts (mSv). The gray, Becquerel, and sievert have increasingly replaced the curie, rad, rem and roentgen.
Any amount of ionizing radiation will produce some damage; however, radiation is everywhere, from the sun (cosmic rays) and from traces of radioactive elements in the air (radon) and the ground (uranium, radium, carbon-14, potassium-40 and many others). Earth's atmosphere protects humans and other living beings from most of the sun's radiation. However, living at 5,000 feet (1,500 m) altitude in Denver, Colorado, approximately doubles exposure to radiation. Further, a flight in a commercial airliner increases it by about 24 times more when lifting humans above 80% of the atmosphere, or at about 32,800 feet (10,000 m) in altitude. Because no amount of radiation is perfectly safe and because radiation is ever present, arbitrary limits have been established to provide some measure of safety for those humans exposed to unusual amounts. Less than 1% of them reach the current annual permissible maximum of 2,000 mrem (20 mSv).
Many international agencies, such as the International Agency for Research on Cancer (IARC), part of the World Health Organization (WHO), suggests that even extremely low doses of radiation can be potentially harmful. For the most part, such doses are generally safe for nuclear workers, but the potential for harm remains, as based on internationally recognized scientific studies. Specifically, the IARC conducted an international study of nearly half a million nuclear workers in 15 countries. Their exposure to low levels of radiation was found to be “statistically compatible with the current bases for radiation protection standards.”
UV radiation from the sun (naturally produced by the closest star to Earth) and tanning beds and lamps (artificially produced by humans) can cause skin damage, premature aging, and skin cancers. Malignant melanoma is the most dangerous of skin cancers. Thus, a definite link exists between type UVA exposure used in tanning beds and its occurrence. UVB type UV radiation is associated with sunburn, and while not as penetrating as UVA, it still damages the skin during high exposures. Skin damage accumulates over time, and effects do not often manifest until individuals reach middle age. Light-skinned people who most often burn rather than tan are at a greater risk of skin damage than darker-skinned individuals who rarely burn. The U.S. Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) discourage the use of tanning beds and sun lamps and encourage all people to use sunscreen with a sun protection factor (SPF) of 15 or greater. In 2009, the International Agency for Research on Cancer classified tanning beds as “carcinogenic to humans”, with carcinogenic meaning that they cause cancer. This classification by the IARC is its highest cancer risk category. In fact, IARC studies that prompted the cancer classification found that UVA, UVB, and UVC radiation all cause cancer in laboratory animals.
Ionizing radiation has many uses in medicine, both in diagnosis and in treatment. X rays, CT (computed tomography) scanners, and fluoroscopes use it to form images of the body's insides. Nuclear medicine uses radioactive isotopes to diagnose and to treat medical conditions. In the body, radioactive elements localize to specific tissues and give off tiny amounts of radiation. Detecting that radiation provides information on both anatomy and function. Between 1995 and 2010, skin injuries caused by too much exposure during medical procedures were documented. In 1995, the FDA issued a recommendation to physicians and medical institutions to record and monitor the dosage of radiation used during medical procedures on patients in order to minimize the amount of skin injuries. The FDA suggested doses of radiation not exceed 1 Grey (Gy). (A Grey is roughly equivalent to a sievert.)
As of 2001, the FDA was preparing further guidelines for fluoroscopy, the procedure most often associated with medical-related radiation skin injuries such as rashes and more serious burns and tissue death. Injuries occurred most often during angioplasty procedures using fluoroscopy. As of late 2010, the FDA was still in the process of issuing updated guidelines for radiation safety performance standards for diagnostic x-ray systems, such as flurorscopic x-ray systems. These updated standards were expected to parallel developments in technology and product usage, along with being more similar to international standards.
CT scans of children have also been problematic. Oftentimes the dosage of radiation used for an adult is not decreased for a child, leading to radiation over exposure. Children are more sensitive to radiation and a February 2001 study indicated 1,500 out of 1.6 million children under 15 years of age receiving CT scans annually were expected to develop cancer. Studies showed that decreasing the radiation by half for CT scans of children would effectively decrease the possibility of over exposure while still providing an effective diagnostic image. The benefits to receiving the medical treatment utilizing radiation is still greater than the risks involved; however, more stringent control over the amount of radiation used during the procedures was expected to go far in minimizing the risk of radiation injury to the patient.
Minimizing the risk of medical radiation exposure in children can be accomplished by doing the following:
Between 1945 and 1987, there were 285 nuclear reactor accidents, injuring more than 1,550 people and killing 64. The most striking example was the meltdown of the graphite core nuclear reactor at Chernobyl (in Ukraine, part of the former Soviet Union) in 1986, which spread a cloud of radioactive particles across the entire continent of Europe. Over the following decades, information about radiation effects continued to be gathered from that disaster, but 31 people were killed in the immediate accident, and at least 1,800 children were subsequently diagnosed with thyroid cancer. In a study published in May 2001 by the British Royal Society, children born to individuals involved in the cleanup of Chernobyl and born after the accident are six times more likely to have genetic mutations than children born before the accident.
After the terrorist attacks on the World Trade Center and the Pentagon on September 11, 2001, the possibility of terrorist-caused nuclear accidents became a concern. As of 2008, All 104 active nuclear power plants in the United States were on full alert, but they were still vulnerable to sabotage such as bombing or attack from the air. The Federal Aviation Administration (FAA) established a no-fly zone of 12 miles (19 km), at an altitude of below 18,000 feet (5,500 m), around nuclear power plants. There was also growing concern over the security of spent nuclear fuel: More than 40,000 tons of spent fuel is housed in buildings at closed plants around the country. Unlike the active nuclear reactors that are enclosed in concrete-reinforced buildings, the spent fuel is stored in nonreinforced buildings. Housed in cooling pools, the spent fuel could emit dangerous levels of radioactive material if exploded or used in makeshift weaponry. Radioactive medical and industrial waste could also be used to make so-called dirty bombs. After 1993, the Nuclear Regulatory Commission (NRC) reported 376 cases of stolen radioactive materials.
On March 15, 2011, the Japanese government imposed a 18-mile (30-km) no-fly zone around the Fukushima Daiichi Nuclear Power Plant after it was damaged from a 9.0-magnitude earthquake (commonly called the 2011 Tõhoku earthquake) that hit on March 11, 2011, off the coast of northeastern Japan. At least three nuclear reactors sustained damage from the tsunamis that followed this major earthquake. Explosions arose from a build-up of gas within their containment walls. On March 18, 2011, the International Atomic Energy Agency (IAEA) described the situation as extremely serious.
Radiation can damage every tissue in the body. The particular manifestation will depend upon the amount of radiation, the time over which it is absorbed, and the susceptibility of the tissue. The fastest growing tissues are the most vulnerable because radiation as much as triples its effects during the growth phase. Bone marrow cells that make blood are the fastest growing cells in the body. A fetus is equally sensitive. The germinal cells in the testes and ovaries are only slightly less sensitive. Both can be rendered useless with very small doses of radiation. More resistant are the lining cells of the body, the skin and intestines. Most resistant are the brain cells, because they grow the slowest.
Many signs and symptoms can occur after a person has been exposed to a large amount of radiation. Some of these signs and symptoms from radiation sickness (radiation poisoning) are:
The length of exposure makes a big difference in what happens afteward. Over time the accumulating damage, if not enough to kill cells outright, distorts their growth and causes scarring and/or cancers. In addition to leukemias and cancers of the thyroid, brain, bone, breast, skin, stomach, and lung, all may arise after radiation. Damage depends, too, on the ability of the tissue to repair itself. Some tissues and some types of damage produce much greater consequences than others.
There are three types of radiation injuries.
Immediately after sudden irradiation, the fate of those affected depends mostly on the total dose absorbed. This information comes mostly from survivors of the two atomic bombs the United States dropped over two cities in Japan in 1945.
A person who has been exposed to a high dose of radiation should seek out immediate assistance from medical personnel. When a known major incident has occurred, medical personnel will be at the site within a short period. In any case, medical personnel will take the necessary steps to measure the amount of radiation absorbed into the body of these victims. The amount of radiation absorbed into the human victims will dictate which treatments will be used and how likely the person will survive over the next few days, weeks, and months.
Critical information is acquired in order to provide the best diagnosis and, thus, treatment, for these victims. This vital information is:
It is clearly important to have some idea of the dose received as early as possible, so that attention can be directed to those victims in the 2–10 Sv range who might survive with treatment. Blood transfusions, protection from infection in damaged organs, and possibly the use of newer stimulants to blood formation can save many victims in this category.
Local radiation exposures usually damage the skin and require careful wound care, removal of dead tissue, and skin grafting if the area is large. Again infection control is imperative.
One of the best known, and perhaps even mainstream, treatments of radiation injury is the use of Aloe vera preparations on damaged areas of skin. It has demonstrated remarkable healing properties even for chronic ulcerations resulting from radiation exposure.
There is considerable interest in benevolent chemicals called free radical scavengers. How well they work is yet to be determined, but population studies strongly suggest that certain diets are better than others and that those better diets are full of free radical scavengers, otherwise known as antioxidants. The recommended ingredients are beta-carotene, vitamins E and C, and selenium, all available as commercial preparations. Beta-carotene is yellow-orange and is present in yellow and orange fruits and vegetables. Vitamin C can be found naturally in citrus fruits. Traditional Chinese medicine (TCM) and acupuncture, botanical medicine, and homeopathy all have contributions to make to recovery from the damage of radiation injuries. The level of recovery will depend on the exposure.
Injuries caused by radiation exposure can be avoided by not working or living around known sources of radiation. If such sites cannot be avoided, then workers should wear badges that consistently measure exposure levels. When being diagnosed or treated with radiation, individuals ought to make sure protective shields are used over the part of their body not be diagnosed or treated. In addition, they should discuss with their family doctor or other medical professionals whenever radiation devices are used to make sure they are essentially needed.
See also Background radiation ; Melanoma ; Radiation ; Radiation exposure .
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Jacqueline L. Longe