Which Of The Following Would Be Considered Natural Background Radiation?
Adv Biomed Res. 2013; 2: 65.
A review on natural groundwork radiation
Daryoush Shahbazi-Gahrouei
Department of Medical Physics and Medical Engineering, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
Mehrdad Gholami
iDepartment of Medical Physics, School of Medicine, Lorestan Academy of Medical Sciences, Khorram Abad, Iran
Samaneh Setayandeh
iiSection of Physics, Isfahan University, Isfahan, Islamic republic of iran
Received 2012 Mar 17; Accepted 2012 Nov 20.
Abstract
The world is naturally radioactive and approximately 82% of human-absorbed radiation doses, which are out of control, arise from natural sources such equally cosmic, terrestrial, and exposure from inhalation or intake radiation sources. In recent years, several international studies have been carried out, which have reported different values regarding the upshot of background radiation on human health. Gamma radiation emitted from natural sources (background radiation) is largely due to primordial radionuclides, mainly 232Thursday and 238U serial, and their decay products, likewise as 40K, which exist at trace levels in the world'due south crust. Their concentrations in soil, sands, and rocks depend on the local geology of each region in the world. Naturally occurring radioactive materials generally contain terrestrial-origin radionuclides, left over since the creation of the earth. In add-on, the beingness of some springs and quarries increases the dose rate of groundwork radiation in some regions that are known equally high level background radiations regions. The type of building materials used in houses can too bear on the dose charge per unit of groundwork radiations. The present review article was carried out to consider all of the natural radiations, including cosmic, terrestrial, and food radiation.
Keywords: Background radiation, cosmic, human's wellness, terrestrial
INTRODUCTION
More than sixty radionuclides tin can be establish in the environment, which tin can be divided into iii general categories: Primordial (which formed before the earth creation), cosmogenic (which formed as a consequence of cosmic ray interactions), and homo produced (which formed due to homo deportment; they are minor amounts compared to natural). Radionuclides are plant naturally in air, soil, water, and food.
Natural radioactivity is common in the rocks and soil that constitute planet world, in water and oceans, and in building materials and homes. There is no identify on earth that has no natural radioactive decay.[1]
Some radioactive nuclides are detectable in soil. They belong to natural radionuclides such every bit the members of the uranium and thorium disuse series. More specifically, natural environment radioactivity and the associated external exposure due to gamma radiation depend on the geological and geographical conditions and appear at dissimilar levels in the soils of each region in the world.[2,3] The specific levels of terrestrial radiations are related to the geological composition of each lithologically separated area and to the content of the stone from which the soils originated in each area in the radioactive elements of thorium (232Th), uranium (238U), and potassium (40K).
All building materials comprise various amounts of radioactivity. For example, materials derived from rock and soil contains natural radionuclides of the uranium and thorium series and the radioactive isotope of potassium. Bogus radionuclides can also be present, such as cesium (137Cs), resulting from the fallout from weapons testing and the Chernobyl accident. All these tin can be sources of both internal and external radiation exposures. Internal exposure occurs through the inhalation of radon gas, and external exposure occurs through the emission of penetrating gamma rays.[4]
Considering that about 50% of natural exposure of people is from radon gas, it is the leading cause of cancer patients suffering from respiratory and gastrointestinal system issues, and the highest per centum of radon that enters the human being torso is from drinking h2o and breathing. Once radon in h2o supplies reaches consumers, information technology may result in human exposure via inhalation and straight digestion. Radon in h2o transfers into the air during the rains, flushing toilets, washing dishes, and washing clothes. The aerosols tend to deposit in the lungs, where they release radiation that has been shown to increase the likelihood of lung cancer. Radon can also reach other body tissues through ingestion, resulting in radiations exposure to the internal organs. Ingestion of radon is believed to increment the risk of stomach cancer.[5,6] Besides the effect of soils in population exposure by using them as building textile, they tin can affect the human body by taking the nutrient containing radionuclide, which enters the food chain from deeper soil layers and too tainting the ground h2o.
Owing to the inevitable effects of radiations and health hazard from these exposures, information technology is necessary to investigate all reported data in the terminal few years. Hence, this review article aims to consider all natural radiation, including catholic, terrestrial, and food radiation.
DISCUSSION
Cosmic rays
Catholic radiation originates from the sun, stars, collapsed stars (such as neutron stars), quasars, and in the hot galactic and intergalactic plasma. It has many components, such every bit X-rays, gamma rays, and particles, which may exist mesons, electrons, protons, neutrons, or hyperons. The initial energy of the individual particles constitutes a broad spectrum from a few electron volts (eV) to near 1,020 eV. Cosmic radiation loses energy as it penetrates the atmosphere. The protective shield of the temper and the globe's magnetic field prevent the soft energy radiation components from penetrating the temper. The hardest components, the mesons, boss at sea level. Above about 5 km from the sea level, the electrons are equal or boss the mesons, whereas above 25 km protons dominate. Catholic radiation produces X-rays and neutrons as it penetrates through the atmosphere. All researchers believe that the contents of natural radionuclides (uranium, potassium, and thorium) as well as the thin layer of temper in the college altitude regions (mountains) are reasons why they take high levels of human exposure.[4]
More often than not, the natural dose rates from cosmic rays depend strongly on the altitude and slightly on the latitude. The breadth result is due to the charged particle nature of the primary cosmic rays, and the effect of the Earth's magnetic field, which tends to direct ions away from the equator and toward the poles.[4]
In addition, the main particles often transform to new particles. Penetration of charged particles depends strongly on the magnetic field. The radiation they produce, including neutrons, depends on the magnetic field.[4,7,8,9,10]
During and after slowing downwards in the atmosphere, the neutrons may in plough produce radioactive isotopes, such as fourteenC and 3H. The thickness of the temper corresponds to near 10 m of water or about 4 m of concrete.[7] Nevertheless, at the sea level the cosmic radiation contributes on the average of 0.27 mSv/year to the human body. At the ground level, only a modest fraction of that is due to neutrons. Cosmic radiation dose increases with distance. At two.five km, it is about 0.55 mSv/year on the order of 60 times greater (17 mSv/twelvemonth).[4,7,11] At a slightly higher altitude of 15 km and 60° magnetic latitude, it levels off and reaches a maximum of thirty mSv/year.
Cosmic radiation increases with magnetic breadth, peculiarly at higher elevations. For example, at 12.5 km distance, the dose charge per unit from neutrons solitary increases from 8 mSv/year at a magnetic breadth of 25° to 19 mSv/year at a magnetic latitude of fifty°.[7] Figure i shows how the cosmic neutron dose rate at ocean level and at 12.five km altitude depends on the magnetic latitude.[7] The neutron dose charge per unit at sea level and magnetic latitude of 43° is seen to exist approximately 300 times smaller than that at 12.five km over ocean level. At a magnetic latitude of 50°, the cosmic neutron dose at a tiptop of 12.5 km over body of water level is about xx mSv/year, whereas at the ground level and at the same magnetic breadth, the cosmic ray neutron dose is most 19/300 = 0.063 mSv/year.[7]
The ordinate shows the neutron dose rate. The curve with the lower slope shows the cosmic neutron dose rate at sea level multiplied by 300 as a function of the magnetic latitude on the abscissa. The steeper curve shows the cosmic neutron dose rate at 12.5 km altitude as a function of the magnetic latitude
Terrestrial rays
Terrestrial radiations from natural radioactive elements in the ground, stones, trees, and walls of houses contribute on the average nearly 0.28 1000 Sv/year. The terrestrial sources vary significantly from place to identify. These are categorized into edifice materials and soils surface.
Radioactivity in buildings
Determining population's exposure to radiations from building materials is important, considering almost eighty% of human life is spent indoors.[12] All edifice materials generally constitute rock and soil; these two raw materials include natural radioactive isotopes such as 232Th and 238U decay series and twoscoreK.[13]
The activity concentration of natural radionuclides in construction materials has been estimated in diverse countries and areas of the world such as Commonwealth of australia,[14] Bangladesh,[15] Islamic republic of pakistan,[sixteen,17] Tanzania,[eighteen] Eastern Europe,[xix] Syrian arab republic,[twenty] Kuwait,[21] Prc,[22] Egypt,[23,24,25,26] and Cyprus.[27]
Because of the importance of this investigation, a survey has been carried out in Portland cement industry. The results showed that all the measured values were commensurable with the worldwide data reported in United Nations Scientific Committee of the Result of Atomic Radiation (UNSCEAR publications).[28] A written report carried out in Turkey, determining the natural radioactivity levels of granites used in constructions, have showed that the presence of a large amount orthoclase and radiogenic accompaniment minerals are the sources of high activity congregation levels in the country.[29]
A survey carried out in Islamic republic of iran on natural radioactive decay in buildings examined v popular structure materials, namely cement, gypsum, cement blocks, brick, and gravel.[12] The survey results showed that cement specimens had maximum values of the mean 226Ra and 232Th congregation, whereas the lowest value for average congregation of these ii radionuclides was found in gypsum specimens. The highest and lowest values of 40K mean concentration was found in brick and gypsum samples, respectively. The calculated radium equivalent activities were beneath the open-door level of 370 Bq/kg for all construction materials. The values of hazard indexes were found below the exhorted levels; therefore, buildings constructed from such materials are considered secure for its inhabitants. These survey results are in agreement with other results of other investigations in carried out in diverse parts of the earth.[12] The radioactivity content of some building materials in some countries is shown in Table ane.[12]
Tabular array 1
Radioactivity content of building materials in some countries
In the last few decades, several surveys have calculated the concentration of indoor radionuclides in countries such as Canada and India.[thirty,31]
A survey conducted in public elementary schools in Canada showed, on average, targeted schools occupants are exposed to radon concentrations of 56 Bq/mthree, which is by and large below the Federal guideline levels (i.due east., 200 Bq/thousand3).[31]
In the estimated 222Rn and 220Rn concentrations in dwellings of s-western Punjab, a state in India, results have showed that the values of 222Rn differed from 21 to 79 Bq/m3, with a geometric mean of 45 Bq/k3.[6] In another report carried out in India, 222Rn and 220Rn levels were calculated in 200 various kinds of dwellings at 10 diverse locations in and around Bangalore Metropolitan, Republic of india. Overall, not much significant radiological gamble for inhabitants was observed and the 222Rn levels were found to be well within the limits of the global boilerplate concentration of 40 Bq/miii. However, the observed 220Rn levels were found to be higher than the global average of 10 Bq/m3.[5]
Radioactive decay in soils surface
It is of import that the natural radioactive decay, which exists in the soils surface, must be investigated because to determine the population's exposure to radiation from edifice materials, such as soils.
The concentration of potassium usually ranges from i,000 to xxx,000 ppm. It is usually lower only more variable in the basaltic stone region (1,500-xx,000 ppm) than in acidic (loftier concentration of SiOii) rock regions. For case, in granite rock, the concentration is often almost 29,000 ppm.
Radium (226Ra) is the most important radionuclide in the 238U decay chain from the radiobiological viewpoint; therefore, the measurements of 226Ra concentration in building materials are considered as reference in all investigations. Natural radionuclides in building materials may cause both external exposure, caused by their direct gamma radiation, and internal exposure from radon gas.
The concentration of rubidium (which is chemically similar to potassium) is often almost 1% of that of potassium. Appropriately, the concentration of radioactivity of rubidium is often about threescore% of that of potassium. Rubidium (87Rb), similar to 14C and 3H, emits only soft β-rays and contributes to internal radiation simply not to the external radiation exposure.
Most of the terrestrial groundwork radiation is due to potassium and to elements of the uranium series (238U to 206Pb), thorium serial (232Th to 209Pb), and actinium series (235U to 207Pb). Each of these serial consists of many α, β, and γ emitters. The concentration of these radioactive isotopes in the soil and water varies profoundly. In certain areas, such as in the coastal areas of Kerala in Bharat, the boilerplate dose was found to exist 11 mSv/twelvemonth. In sure areas of southwestern French republic, in Guarapari in Brazil, and in Ramsar in Islamic republic of iran, the dose charge per unit may exist about 17 mSv/year, and in small-scale places inside these areas the dose charge per unit may be every bit high as 170-430 mSv/yr. These levels are acquired by the higher than usual natural groundwork levels of uranium and thorium isotopes in the soil.[iv]
Several studies take been carried out in countries such as Vietnam[32] and Turkey.[33] In Vietnam, the estimated outdoor and indoor almanac constructive doses to the population were found to be higher than the corresponding values in the rest of the world. The results showed that the radium equivalent activity and the external hazard alphabetize of the Vietnam soils surface are lower than the corresponding admissible limits of 370 Bq/kg and 1, respectively. Therefore, Vietnam soil, which is being used equally a building material, is secure for the human population. In another report, the natural gamma radioactivity levels of the Samsun urban center center soil specimens, in Turkey, were calculated. The calculated external gamble index showed the radiation hazard in Samsun to be trivial.
It is important to mention that soil, by being used every bit edifice cloth, can affect a population'southward exposure to radionuclides; they tin can also affect the human being body by taking food that contains radionuclides; these radionuclides enter the food concatenation from the deeper soil layers, besides tainting the ground water.
Because of this effect, several surveys take estimated the distribution of natural and synthetic radionuclides in soil profiles and in the surface layer of the soil.
In one survey, the activity-depth profiles of 137Cs were determined in soil specimens from 20 sites in and around the urban center of Istanbul, Turkey. It was found that the activity concentrations of fortyK, 232Th, and 226Ra were distributed uniformly with regard to soil depth and the depth distribution of 137Cs generally fitted a linear office.[34]
Radioactivity in foods
Food, water, and air normally contain trace amounts of blastoff emitters from the uranium, thorium, and actinium series. Some of the radon (222Rn, and to a lesser extent 220Rn and 219Rn) gas diffuses into the food supply. For example, the radon in the basis and in the water, and its many decay products, precipitate onto the field and onto the vegetation in the field. Because these radioactive elements perfuse into the food chain and touch on the human body, several investigations were carried out to determine the concentration of the major trace elements in food. Tabular array 2 shows examples of concentrations of major trace elements in actual food samples.
Tabular array ii
Typical concentration of some of the major trace elements in foods
A study has investigated the radiology of natural and mineral drinking waters in Slovenia. In this survey, miscellaneous genres of water were accumulated for iii unlike age groups of the population. It was observed in all cases that the calculated median committed effective dose from the investigated radionuclides was well below the recommended value of 100 μSv/year. Results have shown that children are the near exposed with the highest accented dose. It is important to mention that the contribution of each specific radionuclide to total doses varied among diverse h2o types and within each genre, also equally betwixt various age groups.[35]
In the human body, the concentration of activity of potassium (40K), carbon (fourteenC), tritium (3H), polonium (210Po), and 226Ra is 63, 66, 133, 0.0002, and 2.7 × 10−5 Bq/kg, respectively.
The concentration of natural radioactivity in nutrient is oftentimes in the range of 40-600 Becquerel per kilogram of nutrient. For case, the radioactivity from potassium lonely may be typically 50 Bq/kg in milk, 420 Bq/kg in milk powder, 165 Bq/kg in potatoes, and 125 Bq/kg in beef. Investigation on the radioactivity in foods are reported by Ramachandran and Mishra.[36] They establish the concentration of 40K radioactivity in dissimilar foods varies from 45.9 to 649.0 Bq/kg; that of 226Ra varies from 0.01 to ane.xvi Bq/kg; and that of 228Th varies from 0.02 to 1.26 Bq/kg. To derive the corresponding dose in mSv/yr, it is necessary to take into business relationship the energy and fraction deposited in the body, besides taking into business relationship not but the radioactive lifetime but also the biological lifetime of the isotopes in the homo body.
To analyze natural and induced radioactivity in food, it is necessary to consider the elemental limerick of food.[37,38] The natural radioactivity from the xlChiliad isotope, which is a constant fraction (0.0117%) of the potassium content in food, varies significantly with potassium concentration from food to food. Normally, the concentration of potassium is in the range of one,000-6,000 ppm. The concentration of potassium in a reference food was found to exist four,000 ppm. The average concentration in the human torso is about 2,000 ppm. Of the daily intake, about 90% is excreted in the urine and x% in the stool. The concentrations of many other trace elements besides bear witness not bad variations. Table 2 shows concentration of some of the major trace elements in foods.[37] As shown in Table 2, the concentration of sodium may vary from 150 to 8,200 ppm, that of magnesium from 110 to 390, and that of phosphorus from 150 to 2,110 ppm.
CONCLUSIONS
Humans are always exposed to a background radiation spread of radioactive nuclei in the air, soil, rock, water, and building materials. The amount of background radiations is different in terms of height, the corporeality of the nuclei present in the soil, and the geographical weather condition of dissimilar regions. Radioactivity is common in rocks, soil, beach sand, sediment and riverbed soil, in rivers and oceans, and even in building materials and homes. The concentration of radioactive isotopes in soil is an indicator of radioactive accumulation in the surround, which impacts humans, plants, and animals. They are typically long lived, with half-lives oft about hundreds of millions of years. Some other point is that the number of radionuclides such as uranium and thorium that exist in the region's soil can modify the dose rate of groundwork radiations.
Footnotes
Source of Support: Cipher
Conflict of Interest: None declared.
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Which Of The Following Would Be Considered Natural Background Radiation?,
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