Evolution Of Radon Research Paper
CHAPTER 1 – GENERAL INTRODUCTION
1.1 Origin of Radon and Exposure
Radon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas, occurring naturally as the decay product of uranium. Radon is a gas produced by the radioactive decay of the element radium. Radioactive decay is a natural, spontaneous process in which an atom of one element decays or breaks down to form another element by losing atomic particles (protons, neutrons, or electrons). When solid radium decays to form radon gas, it loses two protons and two neutrons. These two protons and two neutrons are called an alpha particle, which is a type of radiation. The elements that produce radiation are called radioactive. …show more content…
Radon itself is radioactive because it also decays, losing an alpha particle and forming the element polonium.
Radon is formed as part of the normal radioactive decay chain of uranium. Uranium has been around since the earth was formed and its most common isotope has a very long half-life (4.5 billion years). It is one of the densest substances that remains a gas under normal conditions and is considered to be a health hazard due to its radioactivity. Radon is not produced as a commercial product. Radon is a naturally occurring radioactive gas and comes from the natural breakdown (radioactive decay) of uranium. It is usually found in igneous rock and soil, but in some cases, well water may also be a source of radon.
Radon is also fairly soluble in water and organic solvents.
Although reaction with other compounds is comparatively rare, it is not completely inert and forms stable molecules with highly electronegative materials. Radon is considered a noble gas that occurs in several isotopic forms. Only two are found in significant concentrations in the human environment: radon-222, and radon-220. Radon-222 is a member of the radioactive decay chain of uranium-238. Radon-220 is formed in the decay chain of thorium-232. It is radon-222 that most readily occurs in the environment. Atmospheric releases of radon-222 results in the formation of decay products that are radioisotopes of heavy metals (polonium, lead, bismuth) and rapidly attach to other airborne materials such as dust and other materials facilitating inhalation. The amount of radon in the soil depends on complex soil chemistry, that varies from one house to the next. Radon levels in the soil range from a few hundred to several thousands of pCi/L. The amount of radon that escapes from the soil to enter the house depends on the weather, soil porosity, soil moisture, and the suction within the …show more content…
house.
Radon is a cancer-causing radioactive gas. You cannot see, smell or taste radon, but it may be a problem in your home. The Surgeon General has warned that radon is the second leading cause of lung cancer in the United States today. If you smoke and your home has high radon levels, you're at high risk for developing lung cancer. Some scientific studies of radon exposure indicate that children may be more sensitive to radon. This may be due to their higher respiration rate and their rapidly dividing cells, which may be more vulnerable to radiation damage.
1.2 EXPOSURE OF RADON
Radon is responsible for the majority of the public exposure to ionizing radiation. It is often the single largest contributor to an individual's background radiation dose, and is the most variable from location to location.
The primary routes of potential human exposure to radon are inhalation and ingestion. Radon in the ground, groundwater, or building materials enters working and living spaces and disintegrates into its decay products. Although high concentrations of radon in groundwater may contribute to radon exposure through ingestion, the inhalation of radon released from water is usually more important.
In comparison with levels in outdoor air, humans in confined air spaces, particularly in underground work areas such as mines and buildings, are exposed to elevated concentrations of radon and its decay products.
Exhalation of radon from ordinary rock and soils and from radon-rich water can cause significant radon concentrations in tunnels, power stations, caves, public baths, and spas. The average radon concentrations in houses are generally much lower than the average radon concentrations in underground ore mines.
Workers are exposed to radon in several occupations. In countries for which data were available, concentrations of radon decay products in underground mines are now typically less than 1000 Bq/m3 EEC Rn (approx. 28 pCi/l). Underground uranium miners are exposed to the highest levels of radon and its decay products. Other underground workers and certain mineral processing workers may also be exposed to significant levels. Radon gas from natural sources can also accumulate in buildings, especially in confined areas such as attics, and
basements.
Epidemiological evidence shows a clear link between breathing high concentrations of radon and incidence of lung cancer. Thus, radon is considered a significant contaminant that affects indoor air quality worldwide. According to the United States Environmental Protection Agency, radon is the second most frequent cause of lung cancer, after cigarette smoking, causing 21,000 lung cancer deaths per year in the United States.
Scientists believe radon exposure is the second leading cause of lung cancer. When radon decays, it shoots off alpha particles. These are small, heavy, electrically charged, sub-atomic particles consisting of two protons and two neutrons. If an alpha particle strikes the chromosomes in a lung cell, it could alter the way that cell reproduces. Our bodies immune system should recognize and destroy these mutant cells before they can multiply over the next 10 to 20 years into a recognizable cancerous growth. Some peoples immune system is better than others. Because of these inherent differences, radon doesn't affect everyone the same. If you smoke and your home has high radon levels, your risk of lung cancer is especially high.
1.3 – Radon in Soil
The radon concentration in soil air greatly influences the radon migration into a building and almost all types of soil contain some radon. All rocks contain some uranium, between 1 and 3 parts per million (ppm) of uranium. In another word, the uranium content of a soil will be about the same as the uranium content of the rock from which the soil was derived.
Underground well water can transport the radon from the soil into the house, when taking a shower, doing laundry, or washing dishes. The EPA says it takes about 10,000 pCi/L of radon in water to contribute 1.0 pCi/L of radon in air throughout the house. The ratio of radon in water to radon in bathroom air while showering can be much higher, typically from 100 to 1; to about 300 to 1. The average Colorado well tests about 3,000 pCi/L with one well testing more than 3,000,000 pCi/L.
1.4 – How Radon Enters Houses
Radon is a radioactive gas. It comes from the natural decay of uranium that is found in nearly all soils. It moves up through the ground to the air above and into your home through cracks and other holes in the foundation. Your home traps radon inside, where it can build up.
Radon can gets in the thouse through :
1. Cracks in solid floors
2. Construction joints
3. Cracks in walls
4. Gaps in suspended floors
5. Gaps around service pipes
6. Cavities inside walls
7. The water supply
Since Radon is orginating from uranium decay, we could also say that the higher the uranium level is in an area, the greater the chances are that houses in the area have high levels of indoor radon. But some houses in areas with lots of uranium in the soil have low levels of indoor radon, and other houses on uranium-poor soils have high levels of indoor radon. This is because other factors also effects the movement of radon to the atmosphere such as the location of radium atom in the mineral grain, the direction of the recoil of the radon atom, the ease and efficiency with which radon moves in the pore space or fracture and the amount of water present in the pore space
The location of the radium atom in the mineral grain (how close it is to the surface of the grain) and the direction of the recoil of the radon atom (whether it is toward the surface or the interior of the grain) determine whether or not the newly formed radon atom enters the pore space between mineral grains. If a radium atom is deep within a big grain, then regardless of the direction of recoil, it will not free the radon from the grain, and the radon atom will remain embedded in the mineral. Even when a radium atom is near the surface of a grain, the recoil will send the radon atom deeper into the mineral if the direction of recoil is toward the grain's core. However, the recoil of some radon atoms near the surface of a grain is directed toward the grain's surface. When this happens, the newly formed radon leaves the mineral and enters the pore space between the grains or the fractures in the rocks.
Because radon is a gas, it has much greater mobility than uranium and radium, which are fixed in the solid matter in rocks and soils. Radon can more easily leave the rocks and soils by escaping into fractures and openings in rocks and into the pore spaces between grains of soil.
The method and speed of radon's movement through soils is controlled by the amount of water present in the pore space (the soil moisture content), the percentage of pore space in the soil (the porosity), and the "interconnectedness" of the pore spaces that determines the soil's ability to transmit water and air (called soil permeability).
Radon moves more rapidily through permeable soils, such as coarse sand and gravel, than through impermeable soils, such as clays. Fractures in any soil or rock allow radon to move more quickly.
According to EPA statistics, about one-third of all homes have radon gas levels above the recommended limit of 4 Picocuries per liter, usually from soil and Radon gas leads to more than 20,000 lung cancer deaths each year.
1.4 – Methods of Measurement of Radon
There are a few methods to measure level of Radon :
a) Picocurie
A curie is a type of unit that measures an amount of radioactivity. A picocurie measures down to one trillionth of a measurement in curie.
b) Air Sampling
Air samples can be taken within your home to measure the amount of radon in the air by using Radon kits
Radon tests should be conducted away from drafts, high heat, and high humidity in a regularly used room on the lowest level in the home that is used as living space, or in radon-testing lingo: test the lowest habitable space. So if your home has a full-height ceiling basement that is presently un-finished but that could be made into living space, it's reasonable to perform the test there.
Short-term radon tests last for 2 to 90 days, and long-term tests run for up to a year. Place the radon test canister 2-3 feet above the floor on a chair, box, or table, in a house that has been closed for at least 24 hours before starting the test and that will be kept closed for the duration of the test period.
Place the radon test canister close to the center of the room, not by a window, door, or masonry such as a brick fireplace that can cause abnormal readings (some bricks contain and emit radon).
Do not place the radon test kit in a dead-air space, and do not place the canister where the building's HVAC system will blow on or across it.
Because radon levels vary daily and seasonally, longer test periods are better indicators of the average level.
c) Alpha Dosimetry
An alpha dosimetry measures the amount of radon within your home. The amount of radioactive decay that's taking place in conjunction with the amount of radon atoms found is measured. Within the dosimetry is a small piece of plastic---as radon particles enter the dosimetry, the particles will hit the plastic, causing the plastic to etch across the dosimetry. The more intense the markings, the higher the measurement of radon.
d) Activated Charcoal
Activated charcoal devices can be placed within your home through a radon investigator. As the activated charcoal is exposed to the air within your home, the charcoal will suck in the radon. After a few days, your investigator will send the charcoal devices to a laboratory. The lab can measure the amount of radon found within the charcoal.
e) Radon Detector
A radon investigator can place electret-ion chamber radon detectors within your home. Within this type of detector is a chamber that collects ions if radiation is present. If radon is measured within your home, the detector will reduce its voltage. These type of devices can be used over a course of a few days to up to 12 months to help identify radon levels.
Radon detectors are inexpensive and easy to use. There are various types, but they fall into two general categories: short-term detectors that measure radon levels over a period of a few hours or days and long-term detectors that measure levels for three to 12 months. Some detectors can be used for both short- and long-term monitoring.
Common short-term detectors include charcoal liquid scintillation detectors and activated charcoal adsorption detectors. These types use charcoal to soak up radon gas that is present in the atmosphere. The radon gas content is analyzed. Long-term radon detectors have the advantage of giving a more accurate picture of the amount of radon present. They types include the alpha track device, which uses a section of sensitive plastic. When the alpha radiation particles given off by radon gas hit the plastic, they produce microscopic tracks on the surface. These tracks can be analyzed by researchers to deduce the amount of radon gas that is present.
1.1 Origin of Radon and Exposure
Radon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas, occurring naturally as the decay product of uranium. Radon is a gas produced by the radioactive decay of the element radium. Radioactive decay is a natural, spontaneous process in which an atom of one element decays or breaks down to form another element by losing atomic particles (protons, neutrons, or electrons). When solid radium decays to form radon gas, it loses two protons and two neutrons. These two protons and two neutrons are called an alpha particle, which is a type of radiation. The elements that produce radiation are called radioactive. …show more content…
Radon itself is radioactive because it also decays, losing an alpha particle and forming the element polonium.
Radon is formed as part of the normal radioactive decay chain of uranium. Uranium has been around since the earth was formed and its most common isotope has a very long half-life (4.5 billion years). It is one of the densest substances that remains a gas under normal conditions and is considered to be a health hazard due to its radioactivity. Radon is not produced as a commercial product. Radon is a naturally occurring radioactive gas and comes from the natural breakdown (radioactive decay) of uranium. It is usually found in igneous rock and soil, but in some cases, well water may also be a source of radon.
Radon is also fairly soluble in water and organic solvents.
Although reaction with other compounds is comparatively rare, it is not completely inert and forms stable molecules with highly electronegative materials. Radon is considered a noble gas that occurs in several isotopic forms. Only two are found in significant concentrations in the human environment: radon-222, and radon-220. Radon-222 is a member of the radioactive decay chain of uranium-238. Radon-220 is formed in the decay chain of thorium-232. It is radon-222 that most readily occurs in the environment. Atmospheric releases of radon-222 results in the formation of decay products that are radioisotopes of heavy metals (polonium, lead, bismuth) and rapidly attach to other airborne materials such as dust and other materials facilitating inhalation. The amount of radon in the soil depends on complex soil chemistry, that varies from one house to the next. Radon levels in the soil range from a few hundred to several thousands of pCi/L. The amount of radon that escapes from the soil to enter the house depends on the weather, soil porosity, soil moisture, and the suction within the …show more content…
house.
Radon is a cancer-causing radioactive gas. You cannot see, smell or taste radon, but it may be a problem in your home. The Surgeon General has warned that radon is the second leading cause of lung cancer in the United States today. If you smoke and your home has high radon levels, you're at high risk for developing lung cancer. Some scientific studies of radon exposure indicate that children may be more sensitive to radon. This may be due to their higher respiration rate and their rapidly dividing cells, which may be more vulnerable to radiation damage.
1.2 EXPOSURE OF RADON
Radon is responsible for the majority of the public exposure to ionizing radiation. It is often the single largest contributor to an individual's background radiation dose, and is the most variable from location to location.
The primary routes of potential human exposure to radon are inhalation and ingestion. Radon in the ground, groundwater, or building materials enters working and living spaces and disintegrates into its decay products. Although high concentrations of radon in groundwater may contribute to radon exposure through ingestion, the inhalation of radon released from water is usually more important.
In comparison with levels in outdoor air, humans in confined air spaces, particularly in underground work areas such as mines and buildings, are exposed to elevated concentrations of radon and its decay products.
Exhalation of radon from ordinary rock and soils and from radon-rich water can cause significant radon concentrations in tunnels, power stations, caves, public baths, and spas. The average radon concentrations in houses are generally much lower than the average radon concentrations in underground ore mines.
Workers are exposed to radon in several occupations. In countries for which data were available, concentrations of radon decay products in underground mines are now typically less than 1000 Bq/m3 EEC Rn (approx. 28 pCi/l). Underground uranium miners are exposed to the highest levels of radon and its decay products. Other underground workers and certain mineral processing workers may also be exposed to significant levels. Radon gas from natural sources can also accumulate in buildings, especially in confined areas such as attics, and
basements.
Epidemiological evidence shows a clear link between breathing high concentrations of radon and incidence of lung cancer. Thus, radon is considered a significant contaminant that affects indoor air quality worldwide. According to the United States Environmental Protection Agency, radon is the second most frequent cause of lung cancer, after cigarette smoking, causing 21,000 lung cancer deaths per year in the United States.
Scientists believe radon exposure is the second leading cause of lung cancer. When radon decays, it shoots off alpha particles. These are small, heavy, electrically charged, sub-atomic particles consisting of two protons and two neutrons. If an alpha particle strikes the chromosomes in a lung cell, it could alter the way that cell reproduces. Our bodies immune system should recognize and destroy these mutant cells before they can multiply over the next 10 to 20 years into a recognizable cancerous growth. Some peoples immune system is better than others. Because of these inherent differences, radon doesn't affect everyone the same. If you smoke and your home has high radon levels, your risk of lung cancer is especially high.
1.3 – Radon in Soil
The radon concentration in soil air greatly influences the radon migration into a building and almost all types of soil contain some radon. All rocks contain some uranium, between 1 and 3 parts per million (ppm) of uranium. In another word, the uranium content of a soil will be about the same as the uranium content of the rock from which the soil was derived.
Underground well water can transport the radon from the soil into the house, when taking a shower, doing laundry, or washing dishes. The EPA says it takes about 10,000 pCi/L of radon in water to contribute 1.0 pCi/L of radon in air throughout the house. The ratio of radon in water to radon in bathroom air while showering can be much higher, typically from 100 to 1; to about 300 to 1. The average Colorado well tests about 3,000 pCi/L with one well testing more than 3,000,000 pCi/L.
1.4 – How Radon Enters Houses
Radon is a radioactive gas. It comes from the natural decay of uranium that is found in nearly all soils. It moves up through the ground to the air above and into your home through cracks and other holes in the foundation. Your home traps radon inside, where it can build up.
Radon can gets in the thouse through :
1. Cracks in solid floors
2. Construction joints
3. Cracks in walls
4. Gaps in suspended floors
5. Gaps around service pipes
6. Cavities inside walls
7. The water supply
Since Radon is orginating from uranium decay, we could also say that the higher the uranium level is in an area, the greater the chances are that houses in the area have high levels of indoor radon. But some houses in areas with lots of uranium in the soil have low levels of indoor radon, and other houses on uranium-poor soils have high levels of indoor radon. This is because other factors also effects the movement of radon to the atmosphere such as the location of radium atom in the mineral grain, the direction of the recoil of the radon atom, the ease and efficiency with which radon moves in the pore space or fracture and the amount of water present in the pore space
The location of the radium atom in the mineral grain (how close it is to the surface of the grain) and the direction of the recoil of the radon atom (whether it is toward the surface or the interior of the grain) determine whether or not the newly formed radon atom enters the pore space between mineral grains. If a radium atom is deep within a big grain, then regardless of the direction of recoil, it will not free the radon from the grain, and the radon atom will remain embedded in the mineral. Even when a radium atom is near the surface of a grain, the recoil will send the radon atom deeper into the mineral if the direction of recoil is toward the grain's core. However, the recoil of some radon atoms near the surface of a grain is directed toward the grain's surface. When this happens, the newly formed radon leaves the mineral and enters the pore space between the grains or the fractures in the rocks.
Because radon is a gas, it has much greater mobility than uranium and radium, which are fixed in the solid matter in rocks and soils. Radon can more easily leave the rocks and soils by escaping into fractures and openings in rocks and into the pore spaces between grains of soil.
The method and speed of radon's movement through soils is controlled by the amount of water present in the pore space (the soil moisture content), the percentage of pore space in the soil (the porosity), and the "interconnectedness" of the pore spaces that determines the soil's ability to transmit water and air (called soil permeability).
Radon moves more rapidily through permeable soils, such as coarse sand and gravel, than through impermeable soils, such as clays. Fractures in any soil or rock allow radon to move more quickly.
According to EPA statistics, about one-third of all homes have radon gas levels above the recommended limit of 4 Picocuries per liter, usually from soil and Radon gas leads to more than 20,000 lung cancer deaths each year.
1.4 – Methods of Measurement of Radon
There are a few methods to measure level of Radon :
a) Picocurie
A curie is a type of unit that measures an amount of radioactivity. A picocurie measures down to one trillionth of a measurement in curie.
b) Air Sampling
Air samples can be taken within your home to measure the amount of radon in the air by using Radon kits
Radon tests should be conducted away from drafts, high heat, and high humidity in a regularly used room on the lowest level in the home that is used as living space, or in radon-testing lingo: test the lowest habitable space. So if your home has a full-height ceiling basement that is presently un-finished but that could be made into living space, it's reasonable to perform the test there.
Short-term radon tests last for 2 to 90 days, and long-term tests run for up to a year. Place the radon test canister 2-3 feet above the floor on a chair, box, or table, in a house that has been closed for at least 24 hours before starting the test and that will be kept closed for the duration of the test period.
Place the radon test canister close to the center of the room, not by a window, door, or masonry such as a brick fireplace that can cause abnormal readings (some bricks contain and emit radon).
Do not place the radon test kit in a dead-air space, and do not place the canister where the building's HVAC system will blow on or across it.
Because radon levels vary daily and seasonally, longer test periods are better indicators of the average level.
c) Alpha Dosimetry
An alpha dosimetry measures the amount of radon within your home. The amount of radioactive decay that's taking place in conjunction with the amount of radon atoms found is measured. Within the dosimetry is a small piece of plastic---as radon particles enter the dosimetry, the particles will hit the plastic, causing the plastic to etch across the dosimetry. The more intense the markings, the higher the measurement of radon.
d) Activated Charcoal
Activated charcoal devices can be placed within your home through a radon investigator. As the activated charcoal is exposed to the air within your home, the charcoal will suck in the radon. After a few days, your investigator will send the charcoal devices to a laboratory. The lab can measure the amount of radon found within the charcoal.
e) Radon Detector
A radon investigator can place electret-ion chamber radon detectors within your home. Within this type of detector is a chamber that collects ions if radiation is present. If radon is measured within your home, the detector will reduce its voltage. These type of devices can be used over a course of a few days to up to 12 months to help identify radon levels.
Radon detectors are inexpensive and easy to use. There are various types, but they fall into two general categories: short-term detectors that measure radon levels over a period of a few hours or days and long-term detectors that measure levels for three to 12 months. Some detectors can be used for both short- and long-term monitoring.
Common short-term detectors include charcoal liquid scintillation detectors and activated charcoal adsorption detectors. These types use charcoal to soak up radon gas that is present in the atmosphere. The radon gas content is analyzed. Long-term radon detectors have the advantage of giving a more accurate picture of the amount of radon present. They types include the alpha track device, which uses a section of sensitive plastic. When the alpha radiation particles given off by radon gas hit the plastic, they produce microscopic tracks on the surface. These tracks can be analyzed by researchers to deduce the amount of radon gas that is present.