Nick Connor

As was written, all people also have some radioactive isotopes inside their bodies from birth. These isotopes are especially potassium-40, carbon-14 and isotopes from the uranium and thorium series. The variation in radiation dose from one person to another is not as great as the variation in dose from cosmic and terrestrial sources. The average annual radiation dose to a person from internal radioactive materials other than radon is about 0.3 mSv/year of which:

• 0.2 mSv/year comes from potassium-40,
• 0.12 mSv/year comes from the uranium and thorium series,
• 12 μSv/year comes from carbon-14.

UNSCEAR have, based on a large number of investigations, presented values about the annual intake by humans of the different isotopes. We can mention the following:

• Ra-226 (22 Bq/year),
• Pb-210 (30 Bq/year),
• Po-210 (58 Bq/year) and
• Ra-228 (15 Bq/year).

Note that, the dominant component of natural background exposure, which comes from the short-lived decay products of radon, is not involved here. This issue is so important, that it was treated separately in the previous section (Terrestrial Radiation).

As a result, the UNSCEAR 2000 report estimates an annual effective dose of 0.12 mSv, which comes from internal exposure by isotopes of the uranium and thorium series. The main contributor to this dose is Po-210. Note that, polonium-210, the decay product of lead-210, emits a 5.3 MeV alpha particle, which provides most of equivalent dose. The radiation weighting factor for alpha radiation is equal to 20. An absorbed dose of 1 mGy by alpha particles will lead to an equivalent dose of 20 mSv.

Internal Radiation – Is it dangerous?

We must emphasize, eating bananas, working as airline flight crew or living in locations with, increases your annual dose rate. But it does not mean, that it must be dangerous. In each case, intensity of radiation also matters. It is very similar as for heat from a fire (less energetic radiation). If you are too close, the intensity of heat radiation is high and you can get burned. If you are at the right distance, you can withstand there without any problems and moreover it is comfortable. If you are too far from heat source, the insufficiency of heat can also hurt you. This analogy, in a certain sense, can be applied to radiation also from radiation sources.

See also: Internal Source of Radiation

See also:

Internal Sources

We must emphasize, eating bananas, working as airline flight crew or living in locations with, increases your annual dose rate. But it does not mean, that it must be dangerous. In each case, intensity of radiation also matters. It is very similar as for heat from a fire (less energetic radiation). If you are too close, the intensity of heat radiation is high and you can get burned. If you are at the right distance, you can withstand there without any problems and moreover it is comfortable. If you are too far from heat source, the insufficiency of heat can also hurt you. This analogy, in a certain sense, can be applied to radiation also from radiation sources.

In case of internal radiation, we are talking usually about so called “low doses”. Low dose here means additional small doses comparable to the normal background radiation (10 µSv = average daily dose received from natural background). The doses are very very low and therefore the probability of cancer induction could be almost negligible. Secondly, and this is crucial, the truth about low-dose radiation health effects still needs to be found. It is not exactly known, whether these low doses of radiation are detrimental or beneficial (and where is the threshold). Government and regulatory bodies assume a LNT model instead of a threshold or hormesis not because it is the more scientifically convincing, but because it is the more conservative estimate. Problem of this model is that it neglects a number of defence biological processes that may be crucial at low doses. The research during the last two decades is very interesting and show that small doses of radiation given at a low dose rate stimulate the defense mechanisms. Therefore the LNT model is not universally accepted with some proposing an adaptive dose–response relationship where low doses are protective and high doses are detrimental. Many studies have contradicted the LNT model and many of these have shown adaptive response to low dose radiation resulting in reduced mutations and cancers. This phenomenon is known as radiation hormesis.

See also:

Internal Sources

Traces of K-40 are found in all potassium, and it is the most common radioisotope in the human body. K-40 is a radioactive isotope of potassium which has a very long half-life of 1.251×10⁹ years and undergoes both types of beta decay. From this point of view, also a human body can be considered as a source of antimatter.

• About 89.28% of the time (10.72% is by electron capture), it decays to calcium-40 with emission of a beta particle (β−, an electron) with a maximum energy of 1.33 MeV and an antineutrino, which is an antiparticle to the neutrino.
• Very rarely (0.001% of the time) it will decay to Ar-40 by emitting a positron (β+) and a neutrino.

We must emphasize, eating bananas, working as airline flight crew or living in locations with, increases your annual dose rate. But it does not mean, that it must be dangerous. In each case, intensity of radiation also matters. It is very similar as for heat from a fire (less energetic radiation). If you are too close, the intensity of heat radiation is high and you can get burned. If you are at the right distance, you can withstand there without any problems and moreover it is comfortable. If you are too far from heat source, the insufficiency of heat can also hurt you. This analogy, in a certain sense, can be applied to radiation also from radiation sources.

In case of internal radiation, we are talking usually about so called “low doses”. Low dose here means additional small doses comparable to the normal background radiation (10 µSv = average daily dose received from natural background). The doses are very very low and therefore the probability of cancer induction could be almost negligible. Secondly, and this is crucial, the truth about low-dose radiation health effects still needs to be found. It is not exactly known, whether these low doses of radiation are detrimental or beneficial (and where is the threshold). Government and regulatory bodies assume a LNT model instead of a threshold or hormesis not because it is the more scientifically convincing, but because it is the more conservative estimate. Problem of this model is that it neglects a number of defence biological processes that may be crucial at low doses. The research during the last two decades is very interesting and show that small doses of radiation given at a low dose rate stimulate the defense mechanisms. Therefore the LNT model is not universally accepted with some proposing an adaptive dose–response relationship where low doses are protective and high doses are detrimental. Many studies have contradicted the LNT model and many of these have shown adaptive response to low dose radiation resulting in reduced mutations and cancers. This phenomenon is known as radiation hormesis.

See also:

Internal Sources

Banana equivalent dose, BED, is an informal dose quantity of ionizing radiation exposure. Banana equivalent dose is intended as a general educational example to compare a dose of radioactivity to the dose one is exposed to by eating one average-sized banana. One BED is often correlated to 10^-7 Sievert (0.1 µSv).

Bananas contain significantly high potassium concentrations, which is vital for the functioning of all living cells. The transfer of potassium ions through nerve cell membranes is necessary for normal nerve transmission. But natural potassium also contains a radioactive isotope potassium-40 (0.012%). Potassium-40 is a radioactive isotope of potassium which has a very long half-life of 1.251×10⁹ years and undergoes both types of beta decay.

• About 89.28% of the time (10.72% is by electron capture), it decays to calcium-40 with emission of a beta particle (β−, an electron) with a maximum energy of 1.33 MeV and an antineutrino, which is an antiparticle to the neutrino.
• Very rarely (0.001% of the time) it will decay to Ar-40 by emitting a positron (β+) and a neutrino.

One BED is often correlated to 10^-7 Sievert (0.1 µSv). The radiation exposure from consuming a banana is approximately 1% of the average daily exposure to radiation, which is 100 banana equivalent doses (BED). A chest CT scan delivers 58,000 BED (5.8 mSv). A lethal dose, the dose that kills a human with a 50% risk within 30 days (LD50/30) of radiation, is approximately 50,000,000 BED (5000 mSv). However, in practice, this dose is not cumulative, as the principal radioactive component is excreted to maintain metabolic equilibrium. Moreover, there is also a problem with the collective dose.

The BED is only meant to inform the public about the existence of very low levels of natural radioactivity within a natural food and is not a formally adopted dose measurement.

Radiation from Bananas – Is it dangerous?

We must emphasize, eating bananas, working as airline flight crew or living in locations with, increases your annual dose rate. But it does not mean, that it must be dangerous. In each case, intensity of radiation also matters. It is very similar as for heat from a fire (less energetic radiation). If you are too close, the intensity of heat radiation is high and you can get burned. If you are at the right distance, you can withstand there without any problems and moreover it is comfortable. If you are too far from heat source, the insufficiency of heat can also hurt you. This analogy, in a certain sense, can be applied to radiation also from radiation sources.

In case of internal radiation, we are talking usually about so called “low doses”. Low dose here means additional small doses comparable to the normal background radiation (10 µSv = average daily dose received from natural background). The doses are very very low and therefore the probability of cancer induction could be almost negligible. Secondly, and this is crucial, the truth about low-dose radiation health effects still needs to be found. It is not exactly known, whether these low doses of radiation are detrimental or beneficial (and where is the threshold). Government and regulatory bodies assume a LNT model instead of a threshold or hormesis not because it is the more scientifically convincing, but because it is the more conservative estimate. Problem of this model is that it neglects a number of defence biological processes that may be crucial at low doses. The research during the last two decades is very interesting and show that small doses of radiation given at a low dose rate stimulate the defense mechanisms. Therefore the LNT model is not universally accepted with some proposing an adaptive dose–response relationship where low doses are protective and high doses are detrimental. Many studies have contradicted the LNT model and many of these have shown adaptive response to low dose radiation resulting in reduced mutations and cancers. This phenomenon is known as radiation hormesis.

See also:

Internal Sources

Traces of K-40 are found in all potassium, and it is the most common radioisotope in the human body. K-40 is a radioactive isotope of potassium which has a very long half-life of 1.251×10⁹ years and undergoes both types of beta decay. From this point of view, also a human body can be considered as a source of antimatter.

• About 89.28% of the time (10.72% is by electron capture), it decays to calcium-40 with emission of a beta particle (β−, an electron) with a maximum energy of 1.33 MeV and an antineutrino, which is an antiparticle to the neutrino.
• Very rarely (0.001% of the time) it will decay to Ar-40 by emitting a positron (β+) and a neutrino.

The potassium concentration in the human body is strictly based on the homeostatic principle. Potassium is more or less distributed in the body (especially in soft tissues) following intake in foods. A 70-kg man contains about 126 g of potassium (0.18%), most of that is located in muscles. The daily consumption of potassium is approximately 2.5 gram. Hence the concentration of potassium-40 is nearly stable in all persons at a level of about 55 Bq/kg (3850 Bq in total), which corresponds to the annual effective dose of 0.2 mSv.

See also:

Internal Sources

Potassium is a naturally-occurring chemical element with atomic number 19 which means there are 19 protons and 19 electrons in the atomic structure. The chemical symbol for potassium is K (from Neo-Latin kalium).

Natural potassium consists primarily of isotope K-39 (93.26%), therefore the atomic mass of potassium element is close to the atomic mass of K-39 isotope (39.098 u).  Natural potassium also consists of two other isotopes: K-41 (6.73%) and K-40 (0.012%). Potassium-40 is an unstable (radioactive) naturally-occurring isotope of potassium. It has a very long half-life of 1.251×10⁹ years. Therefore, this isotope belong to primordial nuclides, because its half-life is comparable to the age of the Earth.

Traces of K-40 are found in all potassium, and it is the most common radioisotope in the human body. K-40 is a radioactive isotope of potassium which has a very long half-life of 1.251×10⁹ years and undergoes both types of beta decay. From this point of view, also a human body can be considered as a source of antimatter.

• About 89.28% of the time (10.72% is by electron capture), it decays to calcium-40 with emission of a beta particle (β−, an electron) with a maximum energy of 1.33 MeV and an antineutrino, which is an antiparticle to the neutrino.
• Very rarely (0.001% of the time) it will decay to Ar-40 by emitting a positron (β+) and a neutrino.

Potassium-40 inside Body – Radiation Dose

The potassium concentration in the human body is strictly based on the homeostatic principle. Potassium is more or less distributed in the body (especially in soft tissues) following intake in foods. A 70-kg man contains about 126 g of potassium (0.18%), most of that is located in muscles. The daily consumption of potassium is approximately 2.5 gram. Hence the concentration of potassium-40 is nearly stable in all persons at a level of about 55 Bq/kg (3850 Bq in total), which corresponds to the annual effective dose of 0.2 mSv.

Banana Equivalent Dose – BED

Banana equivalent dose, BED, is an informal dose quantity of ionizing radiation exposure. Banana equivalent dose is intended as a general educational example to compare a dose of radioactivity to the dose one is exposed to by eating one average-sized banana. One BED is often correlated to 10^-7 Sievert (0.1 µSv).

Bananas contain significantly high potassium concentrations, which is vital for the functioning of all living cells. The transfer of potassium ions through nerve cell membranes is necessary for normal nerve transmission. But natural potassium also contains a radioactive isotope potassium-40 (0.012%). Potassium-40 is a radioactive isotope of potassium which has a very long half-life of 1.251×10⁹ years and undergoes both types of beta decay.

One BED is often correlated to 10^-7 Sievert (0.1 µSv). The radiation exposure from consuming a banana is approximately 1% of the average daily exposure to radiation, which is 100 banana equivalent doses (BED). A chest CT scan delivers 58,000 BED (5.8 mSv). A lethal dose, the dose that kills a human with a 50% risk within 30 days (LD50/30) of radiation, is approximately 50,000,000 BED (5000 mSv). However, in practice, this dose is not cumulative, as the principal radioactive component is excreted to maintain metabolic equilibrium. Moreover, there is also a problem with the collective dose.

The BED is only meant to inform the public about the existence of very low levels of natural radioactivity within a natural food and is not a formally adopted dose measurement.

Internal Radiation – Is it dangerous?

We must emphasize, eating bananas, working as airline flight crew or living in locations with, increases your annual dose rate. But it does not mean, that it must be dangerous. In each case, intensity of radiation also matters. It is very similar as for heat from a fire (less energetic radiation). If you are too close, the intensity of heat radiation is high and you can get burned. If you are at the right distance, you can withstand there without any problems and moreover it is comfortable. If you are too far from heat source, the insufficiency of heat can also hurt you. This analogy, in a certain sense, can be applied to radiation also from radiation sources.

In case of internal radiation, we are talking usually about so called “low doses”. Low dose here means additional small doses comparable to the normal background radiation (10 µSv = average daily dose received from natural background). The doses are very very low and therefore the probability of cancer induction could be almost negligible. Secondly, and this is crucial, the truth about low-dose radiation health effects still needs to be found. It is not exactly known, whether these low doses of radiation are detrimental or beneficial (and where is the threshold). Government and regulatory bodies assume a LNT model instead of a threshold or hormesis not because it is the more scientifically convincing, but because it is the more conservative estimate. Problem of this model is that it neglects a number of defence biological processes that may be crucial at low doses. The research during the last two decades is very interesting and show that small doses of radiation given at a low dose rate stimulate the defense mechanisms. Therefore the LNT model is not universally accepted with some proposing an adaptive dose–response relationship where low doses are protective and high doses are detrimental. Many studies have contradicted the LNT model and many of these have shown adaptive response to low dose radiation resulting in reduced mutations and cancers. This phenomenon is known as radiation hormesis.

See also:

Internal Sources

Radon is a colorless, odorless, tasteless noble gas, occurring naturally as the decay product of radium. All isotopes of radon are radioactive, but the two radon isotopes radon-222 and radon-220 are very important from radiation protection point of view.

Isotopes of Radon

• 

  Radon-222. The radon-222 isotope is a natural decay product of the most stable uranium isotope (uranium-238), thus it is a member of uranium series. The half-life of radon-222 is 3.8 days and it decays via alpha decay to polonium-218.

• Radon-220. The radon-220 isotope, commonly referred to as thoron,  is a natural decay product of the most stable thorium isotope (thorium-232), thus it is a member of thorium series. The half-life of radon-220 is 55 seconds and it decays via alpha decay to polonium-216.

It is important to note that radon is a noble gas, whereas all its decay products are metals. The main mechanism for the entry of radon into the atmosphere is diffusion through the soil. As a gas, radon diffuses through rocks and the soil. When radon disintegrates, the daughter metallic isotopes are ions that will be attached to other molecules like water and to aerosol particles in the air. Therefore all discussions of radon concentrations in the environment refer to radon-222. While the average rate of production of radon-220 (thoron) is about the same as that of radon-222, the amount of radon-220 in the environment is much less than that of radon-222 because of significantly shorter half-life (it has less time to diffuse) of radon-222 (55 seconds, versus 3.8 days respectively). Simply radon-220 has lower chance to escape from bedrock.

Radon-222

Radon-222 is a gas produced by the decay of radium-226. Both are a part of the natural uranium series. Since uranium is found in soil throughout the world in varying concentrations, also dose from gaseous radon is varying throughout the world. Radon-222 is the most important and most stable isotope of radon. It has a half-life of only 3.8 days, making radon one of the rarest elements since it decays away so quickly. An important source of natural radiation is radon gas, which seeps continuously from bedrock but can, because of its high density, accumulate in poorly ventilated houses. The fact radon is gas plays a crucial role in spreading of all its daughter nuclei. Simply radon is a transport medium from bedrock to atmosphere (or inside buildings) for its short-lived decay products (Pb-210 and Po-210), that posses much more health risks.

See also:

Radon

Radon is a colorless, odorless, tasteless noble gas, occurring naturally as the decay product of radium. All isotopes of radon are radioactive, but the two radon isotopes radon-222 and radon-220 are very important from radiation protection point of view.

• 

  Radon-222. The radon-222 isotope is a natural decay product of the most stable uranium isotope (uranium-238), thus it is a member of uranium series. The half-life of radon-222 is 3.8 days and it decays via alpha decay to polonium-218.

• Radon-220. The radon-220 isotope, commonly referred to as thoron,  is a natural decay product of the most stable thorium isotope (thorium-232), thus it is a member of thorium series. The half-life of radon-220 is 55 seconds and it decays via alpha decay to polonium-216.

It is important to note that radon is a noble gas, whereas all its decay products are metals. The main mechanism for the entry of radon into the atmosphere is diffusion through the soil. As a gas, radon diffuses through rocks and the soil. When radon disintegrates, the daughter metallic isotopes are ions that will be attached to other molecules like water and to aerosol particles in the air. Therefore all discussions of radon concentrations in the environment refer to radon-222. While the average rate of production of radon-220 (thoron) is about the same as that of radon-222, the amount of radon-220 in the environment is much less than that of radon-222 because of significantly shorter half-life (it has less time to diffuse) of radon-222 (55 seconds, versus 3.8 days respectively). Simply radon-220 has lower chance to escape from bedrock.

Alpha Decay

Alpha decay (or α-decay and also alpha radioactivity) represents the disintegration of a parent nucleus to a daughter through the emission of the nucleus of a helium atom. Alpha decay is a quantum tunneling process. In order to be emitted, the alpha particle must penetrate a potential barrier. This is similar to cluster decay, in which an atomic nucleus emits a small “cluster” of neutrons and protons (e.g. ¹²C). This transition can be characterized as:

As can be seen from the figure, alpha particle is emitted in alpha decay. Alpha particles are energetic nuclei of helium. Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus. Alpha particles are relatively large and carry a double positive charge. They are not very penetrating and a piece of paper can stop them. They travel only a few centimeters but deposit all their energies along their short paths.

Radon-222

Radon-222 is a gas produced by the decay of radium-226. Both are a part of the natural uranium series. Since uranium is found in soil throughout the world in varying concentrations, also dose from gaseous radon is varying throughout the world. Radon-222 is the most important and most stable isotope of radon. It has a half-life of only 3.8 days, making radon one of the rarest elements since it decays away so quickly. An important source of natural radiation is radon gas, which seeps continuously from bedrock but can, because of its high density, accumulate in poorly ventilated houses. The fact radon is gas plays a crucial role in spreading of all its daughter nuclei. Simply radon is a transport medium from bedrock to atmosphere (or inside buildings) for its short-lived decay products (Pb-210 and Po-210), that posses much more health risks.

See also:

Radon

Mitigation of radon in the air is accomplished through ventilation, either collected below a concrete floor slab or a membrane on the ground, or by increasing the air changes per hour in the building. A radon resisting membranes are usually produced from low density polyethylene (LDPE) and are extended across the whole of the building, including the floor and walls. Another way for mitigation of radon is a treatment system using aeration or activated charcoal to remove radon from domestic water supplies.

Problems with radon are in houses, where it can accumulate especially, due to its high density, in low areas such as basements and crawl spaces. Radon can also occur in ground water – for example, in some spring waters and hot springs. Several possibilities exist for the release of radon into houses. The fact radon is a noble gas plays a crucial role in spreading of all its daughter nuclei. Simply radon is a transport medium from bedrock to atmosphere (or inside buildings) for its short-lived decay products (Pb-210 and Po-210), that posses much more health risks. The main sources are the rock or soil on which the house is built, as well as the water supply. The main mechanism for the entry of radon into buildings is diffusion through the soil. As a gas, radon diffuses through rocks and the soil. The radon gas can penetrate into the house through cracks (due to a chimney effect) in the floor and walls of the basement. Heating of the air creates a suction of air from the lower part of the house, towards the higher part of the house. Without any radon membrane,  this actually means that air from the ground beneath the house is sucked into the house through numerous floor cracks and openings.

Furthermore, the building materials (e.g., some granites) is also a source for radon. Another source for radon is the water supply. Water from wells, in particular in regions with radium rich granite, may contain high radon concentrations. This is material with higher uranium/radium concentrations from which radon is continuously generated. Such materials, e.g., slag, fly ash, etc., could be used in some locations. For building materials that are used for the construction of houses, the critical limits for the specific radium concentrations must be determined.

The greatest risk of radon exposure arises in buildings that are airtight, insufficiently ventilated, and have foundation leaks that allow air from the soil into basements and dwelling rooms. The inside radon level vary considerable with weather, time of the year and even time of the day – and of course with the airing system. For example, sleeping with an open window can reduce the radon content considerable.

See also: Radon – Health Effects

See also:

Radon

It must be emphasized, the concentrations of radon-222 and radon-220 in the soil and in the building materials vary over many orders of magnitude from place to place and show significant time variation at any given site. Locations with higher radon background are well mapped in each country. In the open air, it ranges from 1 to 100 Bq/m3, even less (0.1 Bq/m3) above the ocean. In caves or aerated mines, or ill-aerated houses, its concentration climbs to 20–2,000 Bq/m3. In the outdoor atmosphere, there is also some advection caused by wind and changes in barometric pressure.

Problems with radon are in houses, where it can accumulate especially, due to its high density, in low areas such as basements and crawl spaces. Radon can also occur in ground water – for example, in some spring waters and hot springs. Several possibilities exist for the release of radon into houses. The fact radon is a noble gas plays a crucial role in spreading of all its daughter nuclei. Simply radon is a transport medium from bedrock to atmosphere (or inside buildings) for its short-lived decay products (Pb-210 and Po-210), that posses much more health risks. The main sources are the rock or soil on which the house is built, as well as the water supply. The main mechanism for the entry of radon into buildings is diffusion through the soil. As a gas, radon diffuses through rocks and the soil. The radon gas can penetrate into the house through cracks (due to a chimney effect) in the floor and walls of the basement. Heating of the air creates a suction of air from the lower part of the house, towards the higher part of the house. Without any radon membrane,  this actually means that air from the ground beneath the house is sucked into the house through numerous floor cracks and openings.

Furthermore, the building materials (e.g., some granites) is also a source for radon. Another source for radon is the water supply. Water from wells, in particular in regions with radium rich granite, may contain high radon concentrations. This is material with higher uranium/radium concentrations from which radon is continuously generated. Such materials, e.g., slag, fly ash, etc., could be used in some locations. For building materials that are used for the construction of houses, the critical limits for the specific radium concentrations must be determined.

The greatest risk of radon exposure arises in buildings that are airtight, insufficiently ventilated, and have foundation leaks that allow air from the soil into basements and dwelling rooms. The inside radon level vary considerable with weather, time of the year and even time of the day – and of course with the airing system. For example, sleeping with an open window can reduce the radon content considerable.

Most countries have adopted a radon concentration of 200–400 Bq/m³ for indoor air as an Action or Reference Level. If testing shows levels less than 4 picocuries radon per liter of air (150 Bq/m³), then no action is necessary. Very high radon concentrations (>1000 Bq/m³) have been found in houses built on soils with a high uranium content and/or high permeability of the ground.

Mitigation of radon in the air is accomplished through ventilation, either collected below a concrete floor slab or a membrane on the ground, or by increasing the air changes per hour in the building. A radon resisting membranes are usually produced from low density polyethylene (LDPE) and are extended across the whole of the building, including the floor and walls. Another way for mitigation of radon is a treatment system using aeration or activated charcoal to remove radon from domestic water supplies.

See also: Radon – Health Effects

See also:

Radon