Radiation is energy that comes from a source and travels through space and may be able to penetrate various materials. Light, radio, and microwaves are types of radiation that are called nonionizing. The kind of radiation discussed in this document is called ionizing radiation because it can produce charged particles (ions) in matter.
Ionizing radiation is produced by unstable atoms. Unstable atoms differ from stable atoms because unstable atoms have an excess of energy or mass or both. Radiation can also be produced by high-voltage devices (e.g., x-ray machines).
Atoms with unstable nuclei are said to be radioactive. In order to reach stability, these atoms give off, or emit, the excess energy or mass. These emissions are called radiation. The kinds of radiation are electromagnetic (like light) and particulate (i.e., mass given off with the energy of motion). Gamma radiation and x rays are examples of electromagnetic radiation. Gamma radiation originates in the nucleus while x rays come from the electronic part of the atom. Beta and alpha radiation are examples of particulate radiation.
Interestingly, there is a "background" of natural radiation everywhere in our environment. It comes from space (i.e., cosmic rays) and from naturally occurring radioactive materials contained in the earth and in living things.
Radiation Exposure from Various Sources
Source Exposure
External Background Radiation
60 mrem/yr, U.S. Average
Natural K-40 and Other Radioactivity in Body
40 mrem/yr
Air Travel Round Trip (NY-LA)
5 mrem
Chest X-Ray Effective Dose
10 mrem per film
Radon in the Home
200 mrem/yr (variable)
Man-Made (medical x rays, etc.)
60 mrem/yr (average)
Thursday, April 22, 2010
How many different types of Radiation are there?
The radiation one typically encounters is one of four types: alpha radiation, beta radiation, gamma radiation, and x radiation. Neutron radiation is also encountered in nuclear power plants and high-altitude flight and emitted from some industrial radioactive sources.
Alpha Radiation
Alpha radiation is a heavy, very short-range particle and is actually an ejected helium nucleus. Some characteristics of alpha radiation are:
o Most alpha radiation is not able to penetrate human skin.
o Alpha-emitting materials can be harmful to humans if the materials are inhaled, swallowed, or absorbed through open wounds.
o A variety of instruments has been designed to measure alpha radiation. Special training in the use of these instruments is essential for making accurate measurements.
o A thin-window Geiger-Mueller (GM) probe can detect the presence of alpha radiation.
o Instruments cannot detect alpha radiation through even a thin layer of water, dust, paper, or other material, because alpha radiation is not penetrating.
o Alpha radiation travels only a short distance (a few inches) in air, but is not an external hazard.
o Alpha radiation is not able to penetrate clothing.
Examples of some alpha emitters: radium, radon, uranium, thorium.
Beta Radiation
Beta radiation is a light, short-range particle and is actually an ejected electron. Some characteristics of beta radiation are:
o Beta radiation may travel several feet in air and is moderately penetrating.
o Beta radiation can penetrate human skin to the "germinal layer," where new skin cells are produced. If high levels of beta-emitting contaminants are allowed to remain on the skin for a prolonged period of time, they may cause skin injury.
o Beta-emitting contaminants may be harmful if deposited internally.
o Most beta emitters can be detected with a survey instrument and a thin-window GM probe (e.g., "pancake" type). Some beta emitters, however, produce very low-energy, poorly penetrating radiation that may be difficult or impossible to detect. Examples of these difficult-to-detect beta emitters are hydrogen-3 (tritium), carbon-14, and sulfur-35.
o Clothing provides some protection against beta radiation.
Examples of some pure beta emitters: strontium-90, carbon-14, tritium, and sulfur-35.
Gamma and X Radiation
Gamma radiation and x rays are highly penetrating electromagnetic radiation. Some characteristics of these radiations are:
o Gamma radiation or x rays are able to travel many feet in air and many inches in human tissue. They readily penetrate most materials and are sometimes called "penetrating" radiation.
o X rays are like gamma rays. X rays, too, are penetrating radiation. Sealed radioactive sources and machines that emit gamma radiation and x rays respectively constitute mainly an external hazard to humans.
o Gamma radiation and x rays are electromagnetic radiation like visible light, radiowaves, and ultraviolet light. These electromagnetic radiations differ only in the amount of energy they have. Gamma rays and x rays are the most energetic of these.
o Dense materials are needed for shielding from gamma radiation. Clothing provides little shielding from penetrating radiation, but will prevent contamination of the skin by gamma-emitting radioactive materials.
o Gamma radiation is easily detected by survey meters with a sodium iodide detector probe.
o Gamma radiation and/or characteristic x rays frequently accompany the emission of alpha and beta radiation during radioactive decay.
Examples of some gamma emitters: iodine-131, cesium-137, cobalt-60, radium-226, and technetium-99m.
Alpha Radiation
Alpha radiation is a heavy, very short-range particle and is actually an ejected helium nucleus. Some characteristics of alpha radiation are:
o Most alpha radiation is not able to penetrate human skin.
o Alpha-emitting materials can be harmful to humans if the materials are inhaled, swallowed, or absorbed through open wounds.
o A variety of instruments has been designed to measure alpha radiation. Special training in the use of these instruments is essential for making accurate measurements.
o A thin-window Geiger-Mueller (GM) probe can detect the presence of alpha radiation.
o Instruments cannot detect alpha radiation through even a thin layer of water, dust, paper, or other material, because alpha radiation is not penetrating.
o Alpha radiation travels only a short distance (a few inches) in air, but is not an external hazard.
o Alpha radiation is not able to penetrate clothing.
Examples of some alpha emitters: radium, radon, uranium, thorium.
Beta Radiation
Beta radiation is a light, short-range particle and is actually an ejected electron. Some characteristics of beta radiation are:
o Beta radiation may travel several feet in air and is moderately penetrating.
o Beta radiation can penetrate human skin to the "germinal layer," where new skin cells are produced. If high levels of beta-emitting contaminants are allowed to remain on the skin for a prolonged period of time, they may cause skin injury.
o Beta-emitting contaminants may be harmful if deposited internally.
o Most beta emitters can be detected with a survey instrument and a thin-window GM probe (e.g., "pancake" type). Some beta emitters, however, produce very low-energy, poorly penetrating radiation that may be difficult or impossible to detect. Examples of these difficult-to-detect beta emitters are hydrogen-3 (tritium), carbon-14, and sulfur-35.
o Clothing provides some protection against beta radiation.
Examples of some pure beta emitters: strontium-90, carbon-14, tritium, and sulfur-35.
Gamma and X Radiation
Gamma radiation and x rays are highly penetrating electromagnetic radiation. Some characteristics of these radiations are:
o Gamma radiation or x rays are able to travel many feet in air and many inches in human tissue. They readily penetrate most materials and are sometimes called "penetrating" radiation.
o X rays are like gamma rays. X rays, too, are penetrating radiation. Sealed radioactive sources and machines that emit gamma radiation and x rays respectively constitute mainly an external hazard to humans.
o Gamma radiation and x rays are electromagnetic radiation like visible light, radiowaves, and ultraviolet light. These electromagnetic radiations differ only in the amount of energy they have. Gamma rays and x rays are the most energetic of these.
o Dense materials are needed for shielding from gamma radiation. Clothing provides little shielding from penetrating radiation, but will prevent contamination of the skin by gamma-emitting radioactive materials.
o Gamma radiation is easily detected by survey meters with a sodium iodide detector probe.
o Gamma radiation and/or characteristic x rays frequently accompany the emission of alpha and beta radiation during radioactive decay.
Examples of some gamma emitters: iodine-131, cesium-137, cobalt-60, radium-226, and technetium-99m.
Lead Garments
Have you ever had any of the following questions concerning Lead garments?
How long does a lead apron need to be? Does it need to cover the femurs? Does it need to be a wrap-around if I routinely have my back to the fluoroscopy table?
With regard to types of leaded aprons, I strongly recommend a wrap-around or coat-type apron to reduce exposures to the bone marrow in the vertebrae and critical organs in the trunk when your back is toward the fluoroscopy unit. A very good option is a combination vest and skirt apron, which wraps around the body and distributes the weight across the shoulders and hips. Nearly all the critical organs can be shielded by a lead apron that has a length to about mid-femur. The bone marrow not shielded by a standard leaded apron is in the skull, cervical vertebrae, and long bones of the arms and lower long bones of the legs.
Why is Lead Shielding Important?
The cancer risks from low-level, low-dose-rate radiation exposure are based on the doses to various radiosensitive critical organs. The major critical organs include the gonads, breast, active bone marrow, lungs, thyroid, bone surfaces, and, to a lesser degree, various other organs in the trunk of the body. Except for various regions of active bone marrow and the brain, these body parts have a small associated risk from radiation exposure,
If the chances of damage to reproductive organs from x-rays are so small, why do patients have to wear protective aprons?
Leaded aprons are used for diagnostic x-ray procedures to protect those portions of the body that are not involved in the image. The risk to the patient from diagnostic doses is very small and may even be zero. However, the apron is used in an application of the ALARA concept: the dose should be kept As Low As Reasonably Achievable. The apron is inexpensive and carries no discomfort or risk. Although it may be unnecessary for many very low-dose procedures such as chest or dental x rays, it is a prudent practice.
How long does a lead apron need to be? Does it need to cover the femurs? Does it need to be a wrap-around if I routinely have my back to the fluoroscopy table?
With regard to types of leaded aprons, I strongly recommend a wrap-around or coat-type apron to reduce exposures to the bone marrow in the vertebrae and critical organs in the trunk when your back is toward the fluoroscopy unit. A very good option is a combination vest and skirt apron, which wraps around the body and distributes the weight across the shoulders and hips. Nearly all the critical organs can be shielded by a lead apron that has a length to about mid-femur. The bone marrow not shielded by a standard leaded apron is in the skull, cervical vertebrae, and long bones of the arms and lower long bones of the legs.
Why is Lead Shielding Important?
The cancer risks from low-level, low-dose-rate radiation exposure are based on the doses to various radiosensitive critical organs. The major critical organs include the gonads, breast, active bone marrow, lungs, thyroid, bone surfaces, and, to a lesser degree, various other organs in the trunk of the body. Except for various regions of active bone marrow and the brain, these body parts have a small associated risk from radiation exposure,
If the chances of damage to reproductive organs from x-rays are so small, why do patients have to wear protective aprons?
Leaded aprons are used for diagnostic x-ray procedures to protect those portions of the body that are not involved in the image. The risk to the patient from diagnostic doses is very small and may even be zero. However, the apron is used in an application of the ALARA concept: the dose should be kept As Low As Reasonably Achievable. The apron is inexpensive and carries no discomfort or risk. Although it may be unnecessary for many very low-dose procedures such as chest or dental x rays, it is a prudent practice.
Is Anything We Use in Everyday Life Radioactive?
Everything we encounter in our daily lives contains some radioactive material, some naturally occurring and some man-made: the air we breathe, the water we drink, the food we eat, the ground we walk upon, and the consumer products we purchase and use. Although they might be familiar with the use of radiation to diagnose disease and treat cancer, many people, when they hear the terms "radioactive" and "radiation," tend to think of mushroom clouds and the monster mutants that inhabit the world of science fiction movies and comic books. Careful analyses can identify and quantify the radioactive material in just about anything. This document describes a few of the more commonly encountered and familiar consumer products that can contain sufficient radioactive material for it to be distinguished from background with a simple handheld radiation survey meter.
Smoke Detectors
Most residential smoke detectors contain a low-activity americium-241 source. Alpha particles emitted by the americium ionize the air, making the air conductive. Any smoke particles that enter the unit reduce the current and set off an alarm. Despite the fact that these devices save lives, the question "are smoke detectors safe?" is still asked by those with an inordinate fear of radiation. The answer, of course, is "yes, they are safe." Instructions for proper installation, handling, and disposal of smoke detectors are found on the package.
Watches and Clock
Modern watches and clocks sometimes use a small quantity of hydrogen-3 (tritium) or promethium-147 as a source of light. Older (for example, pre-1970) watches and clocks used radium-226 as a source of light. If these older timepieces are opened and the dial or hands handled, some of the radium could be picked up and possibly ingested. As such, caution should be exercised when handling these items
Ceramics
Ceramic materials (for example, tiles, pottery) often contain elevated levels of naturally occurring uranium, thorium, and/or potassium. In many cases, the activity is concentrated in the glaze. Unless there is a large quantity of the material, readings above background are unlikely. Nevertheless, some older (for example, pre-1960) tiles and pottery, especially those with an orange-red glaze (for example, Fiesta® ware) can be quite radioactive.
Glass
Glassware, especially antique glassware with a yellow or greenish color, can contain easily detectable quantities of uranium. Such uranium-containing glass is often referred to as canary or vaseline glass. In part, collectors like uranium glass for the attractive glow that is produced when the glass is exposed to a black light. Even ordinary glass can contain high-enough levels of potassium-40 or thorium-232 to be detectable with a survey instrument. Older camera lenses (1950s-1970s) often employed coatings of thorium-232 to alter the index of refraction.
Fertilizer
Commercial fertilizers are designed to provide varying levels of potassium, phosphorous, and nitrogen. Such fertilizers can be measurably radioactive for two reasons: potassium is naturally radioactive, and the phosphorous can be derived from phosphate ore that contains elevated levels of uranium.
Food
Food contains a variety of different types and amounts of naturally occurring radioactive materials. Although the relatively small quantities of food in the home contain too little radioactivity for the latter to be readily detectable, bulk shipments of food have been known to set off the alarms of radiation monitors at border crossings. One exception would be low-sodium salt substitutes that often contain enough potassium-40 to double the background count rate of a radiation detector.
Gas Lantern Mantles
While it is less common than it once was, some brands of gas lantern mantles incorporate thorium-232. In fact it is the heating of the thorium by the burning gas that is responsible for the emission of light. Such mantles are sufficiently radioactive that they are often used as a check source for radiation detectors.
Antique Radioactive Curative Claims
In the past, primarily 1920 through 1950, a wide range of radioactive products were sold as cure-alls, for example, radium-containing pills, pads, solutions, and devices designed to add radon to drinking water. The states generally have regulatory authority over these devices. In some cases, a state might even require that these devices be registered or licensed. Most such devices are relatively harmless but occasionally one can be encountered that contains potentially hazardous levels of radium. If there is any question about the safety of such devices, the public is strongly encouraged to contact the state radiation-control program for advice.
Information taken from a Health Physics Society Fact Sheet, "Consumer Products Containing Radioactive Materials," published in November 2002.
Additional Information
• National Council on Radiation Protection and Measurements, "Radiation Exposure of the US Population from Consumer Products and Miscellaneous Sources," NCRP Report No. 95, Bethesda, MD, 1987.
• US Nuclear Regulatory Commission, "Systematic Radiological Assessment of Exemptions for Source and Byproduct Materials, NUREG-1717, Washington, DC, 2001.
Smoke Detectors
Most residential smoke detectors contain a low-activity americium-241 source. Alpha particles emitted by the americium ionize the air, making the air conductive. Any smoke particles that enter the unit reduce the current and set off an alarm. Despite the fact that these devices save lives, the question "are smoke detectors safe?" is still asked by those with an inordinate fear of radiation. The answer, of course, is "yes, they are safe." Instructions for proper installation, handling, and disposal of smoke detectors are found on the package.
Watches and Clock
Modern watches and clocks sometimes use a small quantity of hydrogen-3 (tritium) or promethium-147 as a source of light. Older (for example, pre-1970) watches and clocks used radium-226 as a source of light. If these older timepieces are opened and the dial or hands handled, some of the radium could be picked up and possibly ingested. As such, caution should be exercised when handling these items
Ceramics
Ceramic materials (for example, tiles, pottery) often contain elevated levels of naturally occurring uranium, thorium, and/or potassium. In many cases, the activity is concentrated in the glaze. Unless there is a large quantity of the material, readings above background are unlikely. Nevertheless, some older (for example, pre-1960) tiles and pottery, especially those with an orange-red glaze (for example, Fiesta® ware) can be quite radioactive.
Glass
Glassware, especially antique glassware with a yellow or greenish color, can contain easily detectable quantities of uranium. Such uranium-containing glass is often referred to as canary or vaseline glass. In part, collectors like uranium glass for the attractive glow that is produced when the glass is exposed to a black light. Even ordinary glass can contain high-enough levels of potassium-40 or thorium-232 to be detectable with a survey instrument. Older camera lenses (1950s-1970s) often employed coatings of thorium-232 to alter the index of refraction.
Fertilizer
Commercial fertilizers are designed to provide varying levels of potassium, phosphorous, and nitrogen. Such fertilizers can be measurably radioactive for two reasons: potassium is naturally radioactive, and the phosphorous can be derived from phosphate ore that contains elevated levels of uranium.
Food
Food contains a variety of different types and amounts of naturally occurring radioactive materials. Although the relatively small quantities of food in the home contain too little radioactivity for the latter to be readily detectable, bulk shipments of food have been known to set off the alarms of radiation monitors at border crossings. One exception would be low-sodium salt substitutes that often contain enough potassium-40 to double the background count rate of a radiation detector.
Gas Lantern Mantles
While it is less common than it once was, some brands of gas lantern mantles incorporate thorium-232. In fact it is the heating of the thorium by the burning gas that is responsible for the emission of light. Such mantles are sufficiently radioactive that they are often used as a check source for radiation detectors.
Antique Radioactive Curative Claims
In the past, primarily 1920 through 1950, a wide range of radioactive products were sold as cure-alls, for example, radium-containing pills, pads, solutions, and devices designed to add radon to drinking water. The states generally have regulatory authority over these devices. In some cases, a state might even require that these devices be registered or licensed. Most such devices are relatively harmless but occasionally one can be encountered that contains potentially hazardous levels of radium. If there is any question about the safety of such devices, the public is strongly encouraged to contact the state radiation-control program for advice.
Information taken from a Health Physics Society Fact Sheet, "Consumer Products Containing Radioactive Materials," published in November 2002.
Additional Information
• National Council on Radiation Protection and Measurements, "Radiation Exposure of the US Population from Consumer Products and Miscellaneous Sources," NCRP Report No. 95, Bethesda, MD, 1987.
• US Nuclear Regulatory Commission, "Systematic Radiological Assessment of Exemptions for Source and Byproduct Materials, NUREG-1717, Washington, DC, 2001.
Sun tanning and Tanning Booths
A tanning booth uses ultraviolet (UV) light bulbs that emit UV radiation that causes the skin to tan. This result is similar to the sun’s effect on the skin.
An increased risk to cancer comes to those who use tanning beds, which is based on studies on individuals that have had skin cancer. It is now a well known fact that an increase in UV radiation also causes an increase in risk of skin cancer. This is why Dermatologists and Physicians recommend the general public to limit their exposure to natural sunlight as well as tanning booths.
The US Food and Drug Administration do recommend that tanning booths should be avoided. This doesn’t mean that everyone who uses a tanning booth will have an adverse health effect, just as people who go out in the sunlight unprotected from the UV will not all suffer harmful effects. We all need to be aware that some harmful effects like skin cancer take many years to appear.
Many health studies have been done on large groups of people and the experts have found that there is a significant increase in the risk of harmful health effects from UV light. The risk of harmful effects is not 100% even if you are exposed to UV every day, and the risk cannot be reduced to zero even if you completely eliminate UV exposure. But what you can do is minimize your risk by taking reasonable measures such as avoiding unnecessary or excessive exposure.
Ultraviolet radiation does not penetrate to any significant depth in the body, which is why the majority of cancer resulting from UV rays is majorly skin cancer. You should know that if these skin cancers aren’t caught in enough time they will carry throughout the rest of the body.
The eye also absorbs ultraviolet light wavelengths. If there is a significant exposure to the cornea, it can eventually cause a corneal burn that is quite painful but does repair itself over time. If the lens is exposed to ultraviolet light in a significant amount or chronically, cataracts can form.
I would recommend using sun block, but even with its aid you can still develop cancer. Sunblock will help lessen your exposure to UV rays, but is not totally effective in preventing skin cancer. One of the primary reasons is that it wears off and needs to be reapplied. If sunscreen is not applied often enough, it may give a false sense of security leading to even more time in the sun. A rough guide of when you should renew your Sunblock is roughly every 10 minutes.
When looking for a good Sunblock you should buy the more opaque the sunscreens. Not all sunscreens are equally effective. Some sunscreens are manufactured to block short-wave ultraviolet (UVB) radiation, which damages the skin's surface and causes redness and burning. Yet it is the longer-wave ultraviolet (UVA) radiation that penetrates deeper into the skin. Unfortunately, UVA radiation is less likely to cause noticeable sunburn symptoms, even though it severely damages the elastic fibers and collagen and is significant in producing malignant melanoma. The best sunscreens block both UVB and UVA rays. Both avobenzone and benzophenone are good UVA blockers. For maximum benefits, sunscreen must be applied evenly to cool, dry skin 30 minutes before sun exposure. Waterproof and water-resistant sunscreens are best since effectiveness is not reduced by perspiration.
Will general clothing worn outdoors stop ultraviolet radiation?
While outdoors one needs to know that different fabrics have different protection levels, the tighter the weave the greater the protection level. In addition, dark colors of the same material tend to absorb/block more ultraviolet (UV) radiation than light colors. Many fabrics tend to have a lower protection factor when wet. UV absorbers can be added to materials by clothing manufactures to enhance UV protection and those are sold specifically as UV-blocking clothing (and they are generally more expensive).
An increased risk to cancer comes to those who use tanning beds, which is based on studies on individuals that have had skin cancer. It is now a well known fact that an increase in UV radiation also causes an increase in risk of skin cancer. This is why Dermatologists and Physicians recommend the general public to limit their exposure to natural sunlight as well as tanning booths.
The US Food and Drug Administration do recommend that tanning booths should be avoided. This doesn’t mean that everyone who uses a tanning booth will have an adverse health effect, just as people who go out in the sunlight unprotected from the UV will not all suffer harmful effects. We all need to be aware that some harmful effects like skin cancer take many years to appear.
Many health studies have been done on large groups of people and the experts have found that there is a significant increase in the risk of harmful health effects from UV light. The risk of harmful effects is not 100% even if you are exposed to UV every day, and the risk cannot be reduced to zero even if you completely eliminate UV exposure. But what you can do is minimize your risk by taking reasonable measures such as avoiding unnecessary or excessive exposure.
Ultraviolet radiation does not penetrate to any significant depth in the body, which is why the majority of cancer resulting from UV rays is majorly skin cancer. You should know that if these skin cancers aren’t caught in enough time they will carry throughout the rest of the body.
The eye also absorbs ultraviolet light wavelengths. If there is a significant exposure to the cornea, it can eventually cause a corneal burn that is quite painful but does repair itself over time. If the lens is exposed to ultraviolet light in a significant amount or chronically, cataracts can form.
I would recommend using sun block, but even with its aid you can still develop cancer. Sunblock will help lessen your exposure to UV rays, but is not totally effective in preventing skin cancer. One of the primary reasons is that it wears off and needs to be reapplied. If sunscreen is not applied often enough, it may give a false sense of security leading to even more time in the sun. A rough guide of when you should renew your Sunblock is roughly every 10 minutes.
When looking for a good Sunblock you should buy the more opaque the sunscreens. Not all sunscreens are equally effective. Some sunscreens are manufactured to block short-wave ultraviolet (UVB) radiation, which damages the skin's surface and causes redness and burning. Yet it is the longer-wave ultraviolet (UVA) radiation that penetrates deeper into the skin. Unfortunately, UVA radiation is less likely to cause noticeable sunburn symptoms, even though it severely damages the elastic fibers and collagen and is significant in producing malignant melanoma. The best sunscreens block both UVB and UVA rays. Both avobenzone and benzophenone are good UVA blockers. For maximum benefits, sunscreen must be applied evenly to cool, dry skin 30 minutes before sun exposure. Waterproof and water-resistant sunscreens are best since effectiveness is not reduced by perspiration.
Will general clothing worn outdoors stop ultraviolet radiation?
While outdoors one needs to know that different fabrics have different protection levels, the tighter the weave the greater the protection level. In addition, dark colors of the same material tend to absorb/block more ultraviolet (UV) radiation than light colors. Many fabrics tend to have a lower protection factor when wet. UV absorbers can be added to materials by clothing manufactures to enhance UV protection and those are sold specifically as UV-blocking clothing (and they are generally more expensive).
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