Food irradiation (sometimes American English: radurization; British English: radurisation) is the process of exposing food and food packaging to ionizing radiation, such as from gamma rays, x-rays, or electron beams. [1] [2] [3] Food irradiation improves food safety and extends product shelf life (preservation) by effectively destroying organisms responsible for spoilage and foodborne illness, inhibits sprouting or ripening, and is a means of controlling insects and invasive pests. [1] [3]
In the United States, consumer perception of foods treated with irradiation is more negative than those processed by other means. [4] The U.S. Food and Drug Administration (FDA), the World Health Organization (WHO), the Centers for Disease Control and Prevention (CDC), and U.S. Department of Agriculture (USDA) have performed studies that confirm irradiation to be safe. [1] [5] [6] [7] [8] In order for a food to be irradiated in the U.S., the FDA will still require that the specific food be thoroughly tested for irradiation safety. [9]
Food irradiation is permitted in over 60 countries, and about 500,000 metric tons of food are processed annually worldwide. [10] The regulations for how food is to be irradiated, as well as the foods allowed to be irradiated, vary greatly from country to country. In Austria, Germany, and many other countries of the European Union only dried herbs, spices, and seasonings can be processed with irradiation and only at a specific dose, while in Brazil all foods are allowed at any dose. [11] [12] [13] [14] [15]
Irradiation is used to reduce or eliminate pests and the risk of food-borne illnesses as well as prevent or slow spoilage and plant maturation or sprouting. Depending on the dose, some or all of the organisms, microorganisms, bacteria, and viruses present are destroyed, slowed, or rendered incapable of reproduction. When targeting bacteria, most foods are irradiated to significantly reduce the number of active microbes, not to sterilize all microbes in the product. Irradiation cannot return spoiled or over-ripe food to a fresh state. If this food was processed by irradiation, further spoilage would cease and ripening would slow, yet the irradiation would not destroy the toxins or repair the texture, color, or taste of the food. [16]
Irradiation slows the speed at which enzymes change the food. By reducing or removing spoilage organisms and slowing ripening and sprouting (e.g. potato, onion, and garlic) irradiation is used to reduce the amount of food that goes bad between harvest and final use. [16] Shelf-stable products are created by irradiating foods in sealed packages, as irradiation reduces chance of spoilage, the packaging prevents re-contamination of the final product. [2] Foods that can tolerate the higher doses of radiation required to do so can be sterilized. This is useful for people at high risk of infection in hospitals as well as situations where proper food storage is not feasible, such as rations for astronauts. [17]
Pests such as insects have been transported to new habitats through the trade in fresh produce and significantly affected agricultural production and the environment once they established themselves. To reduce this threat and enable trade across quarantine boundaries, food is irradiated using a technique called phytosanitary irradiation. [18] Phytosanitary irradiation sterilizes the pests preventing breeding by treating the produce with low doses of irradiation (less than 1000 Gy). [19] [20] The higher doses required to destroy pests are not used due to either affecting the look or taste, or cannot be tolerated by fresh produce. [21]
The target material is exposed to a radiation source that is separated from the target material. The radiation source supplies energetic particles or waves. As these waves/particles enter the target material they collide with other particles. The higher the likelihood of these collisions over a distance are, the lower the penetration depth of the irradiation process is as the energy is more quickly depleted.
Around the sites of these collisions chemical bonds are broken, creating short lived radicals (e.g. the hydroxyl radical, the hydrogen atom and solvated electrons). These radicals cause further chemical changes by bonding with and or stripping particles from nearby molecules. When collisions occur in cells, cell division is often suppressed, halting or slowing the processes that cause the food to mature.
When the process damages DNA or RNA, effective reproduction becomes unlikely halting the population growth of viruses and organisms. [2] The distribution of the dose of radiation varies from the food surface and the interior as it is absorbed as it moves through food and depends on the energy and density of the food and the type of radiation used. [22]
Irradiation leaves a product with qualities (sensory and chemical) that are more similar to unprocessed food than any preservation method that can achieve a similar degree of preservation. [23]
Irradiated food does not become radioactive; only power levels that are incapable of causing significant induced radioactivity are used for food irradiation. In the United States this limit is deemed to be 4 mega electron volts for electron beams and x-ray sources – cobalt-60 or caesium-137 sources are never energetic enough to be of concern. Particles below this energy can never be strong enough to modify the nucleus of the targeted atom in the food, regardless of how many particles hit the target material, and so radioactivity can not be induced. [23]
The radiation absorbed dose is the amount energy absorbed per unit weight of the target material. Dose is used because, when the same substance is given the same dose, similar changes are observed in the target material(Gy or J/kg). Dosimeters are used to measure dose, and are small components that, when exposed to ionizing radiation, change measurable physical attributes to a degree that can be correlated to the dose received. Measuring dose (dosimetry) involves exposing one or more dosimeters along with the target material. [24] [25]
For purposes of legislation doses are divided into low (up to 1 kGy), medium (1 kGy to 10 kGy), and high-dose applications (above 10 kGy). [26] High-dose applications are above those currently permitted in the US for commercial food items by the FDA and other regulators around the world, [27] though these doses are approved for non commercial applications, such as sterilizing frozen meat for NASA astronauts (doses of 44 kGy) [28] and food for hospital patients.
The ratio of the maximum dose permitted at the outer edge (Dmax) to the minimum limit to achieve processing conditions (Dmin) determines the uniformity of dose distribution. This ratio determines how uniform the irradiation process is. [22]
Application | Dose (kGy) | |
Low dose (up to 1 kGy) | Inhibit sprouting (potatoes, onions, yams, garlic) | 0.06 - 0.2 |
Delay in ripening (strawberries, potatoes) | 0.5 - 1.0 | |
Prevent insect infestation (grains, cereals, coffee beans, spices, dried nuts, dried fruits, dried fish, mangoes, papayas) | 0.15 - 1.0 | |
Parasite control and inactivation (tape worm, trichina) | 0.3 - 1.0 | |
Medium dose (1 kGy to 10 kGy) | Extend shelf-life of raw and fresh fish, seafood, fresh produce | 1.0 - 5.5 |
Extend shelf-life of refrigerated and frozen meat products | 4.5 - 7.0 | |
Reduce risk of pathogenic and spoilage microbes (meat, seafood, spices, and poultry) | 1.0 - 7.0 | |
Increased juice yield, reduction in cooking time of dried vegetables | 3.0 - 7.0 | |
High dose (above 10 kGy) | Enzymes (dehydrated) | 10.0 |
Sterilization of spices, dry vegetable seasonings | 30.0 max | |
Sterilization of packaging material | 10.0 - 25.0 | |
Sterilization of foods (NASA and hospitals) | 44.0 |
As ionising radiation passes through food, it creates a trail of chemical transformations due to radiolysis effects. Irradiation does not make foods radioactive, change food chemistry, compromise nutrient contents, or change the taste, texture, or appearance of food. [1] [30]
Assessed rigorously over several decades, irradiation in commercial amounts to treat food has no negative impact on the sensory qualities and nutrient content of foods. [1] [3]
Watercress (Nasturtium officinale) is a rapidly growing aquatic or semi aquatic perennial plant. Because chemical agents do not provide efficient microbial reductions, watercress has been tested with gamma irradiation treatment in order to improve both safety and the shelf life of the product. [31] It is traditionally used on horticultural products to prevent sprouting and post-packaging contamination, delay post-harvest ripening, maturation and senescence. [32]
Some who advocate against food irradiation argue the long-term health effects and safety of irradiated food cannot be scientifically proven, however there have been hundreds of animal feeding studies of irradiated food performed since 1950 [5] Endpoints include subchronic and chronic changes in metabolism, histopathology, function of most organs, reproductive effects, growth, teratogenicity, and mutagenicity. [5] [33] [6] [8]
Up to the point where the food is processed by irradiation, the food is processed in the same way as all other food.[ citation needed ]
For some forms of treatment, packaging is used to ensure the food stuffs never come in contact with radioactive substances [34] and prevent re-contamination of the final product. [2] Food processors and manufacturers today struggle with using affordable, efficient packaging materials for irradiation-based processing. The implementation of irradiation on prepackaged foods has been found to impact foods by inducing specific chemical alterations to the food packaging material that migrates into the food. Cross-linking in various plastics can lead to physical and chemical modifications that can increase the overall molecular weight. On the other hand, chain scission is fragmentation of polymer chains that leads to a molecular mass reduction. [1]
To treat the food, it is exposed to a radioactive source for a set period of time to achieve a desired dose. Radiation may be emitted by a radioactive substance, or by X-ray and electron beam accelerators. Special precautions are taken to ensure the food stuffs never come in contact with the radioactive substances and that the personnel and the environment are protected from radiation exposure. [34] Irradiation treatments are typically classified by dose (high, medium, and low), but are sometimes classified by the effects of the treatment [35] (radappertisation, radicidation and radurisation). Food irradiation is sometimes referred to as "cold pasteurisation" [36] or "electronic pasteurisation" [37] because ionising the food does not heat it to high temperatures during the process, and the effect is similar to pasteurisation. The term "cold pasteurisation" is controversial because the term may be used to disguise the fact the food has been irradiated and pasteurisation and irradiation are fundamentally different processes.[ citation needed ]
Gamma irradiation is produced from the radioisotopes cobalt-60 and caesium-137, which are produced by neutron irradiation of cobalt-59 (the only stable isotope of cobalt) and as a nuclear fission product, respectively. [26] Cobalt-60 is the most common source of gamma rays for food irradiation in commercial scale facilities as it is water-insoluble and hence has little risk of environmental contamination by leakage into the water systems. [26] As for transportation of the radiation source, cobalt-60 is transported in special trucks that prevent release of radiation and meet standards mentioned in the Regulations for Safe Transport of Radioactive Materials of the International Atomic Energy Act. [38] The special trucks must meet high safety standards and pass extensive tests to be approved to ship radiation sources. Conversely, caesium-137 is water-soluble and poses a risk of environmental contamination. Insufficient quantities are available for large-scale commercial use as the vast majority of Caesium-137 produced in nuclear reactors is not extracted from spent nuclear fuel. An incident where water-soluble caesium-137 leaked into the source storage pool requiring NRC intervention [39] has led to near elimination of this radioisotope.
Gamma irradiation is widely used due to its high penetration depth and dose uniformity, allowing for large-scale applications with high throughput. [26] Additionally, gamma irradiation is significantly less expensive than using an X-ray source. In most designs, the radioisotope, contained in stainless steel pencils, is stored in a water-filled storage pool which absorbs the radiation energy when not in use. For treatment, the source is lifted out of the storage tank, and product contained in totes is passed around the pencils to achieve required processing. [26]
Treatment costs vary as a function of dose and facility usage. A pallet or tote is typically exposed for several minutes to hours depending on dose. Low-dose applications such as disinfestation of fruit range between US$0.01/lb and US$0.08/lb while higher-dose applications can cost as much as US$0.20/lb. [40]
Treatment of electron beams is created as a result of high energy electrons in an accelerator that generates electrons accelerated to 99% the speed of light. [26] This system uses electrical energy and can be powered on and off. The high power correlates with a higher throughput and lower unit cost, but electron beams have low dose uniformity and a penetration depth of centimeters. [26] Therefore, electron beam treatment works for products that have low thickness.[ citation needed ]
X-rays are produced by bombardment of dense target material with high-energy accelerated electrons (this process is known as bremsstrahlung-conversion), giving rise to a continuous energy spectrum. [26] Heavy metals, such as tantalum and tungsten, are used because of their high atomic numbers and high melting temperatures. Tantalum is usually preferred over tungsten for industrial, large-area, high-power targets because it is more workable than the latter and has a higher threshold energy for induced reactions. [41] Like electron beams, X-rays do not require the use of radioactive materials and can be turned off when not in use. X-rays have high penetration depths and high dose uniformity but they are a very expensive source of irradiation as only 8% of the incident energy is converted into X-rays. [26]
UV-C does not penetrate as deeply as other methods. As such, its direct antimicrobial effect is limited to the surface only. Its DNA damage effect produces cyclobutane-type pyrimidine dimers. Besides the direct effects, UV-C also induces resistance even against pathogens not yet inoculated. Some of this induced resistance is understood, being the result of temporary inactivation of self-degradation enzymes like polygalacturonase and increased expression of enzymes associated with cell wall repair. [42]
Irradiation is a capital-intensive technology requiring a substantial initial investment, ranging from $1 million to $5 million. In the case of large research or contract irradiation facilities, major capital costs include a radiation source, hardware (irradiator, totes and conveyors, control systems, and other auxiliary equipment), land (1 to 1.5 acres), radiation shield, and warehouse. Operating costs include salaries (for fixed and variable labor), utilities, maintenance, taxes/insurance, cobalt-60 replenishment, general utilities, and miscellaneous operating costs. [40] [43] Perishable food items, like fruits, vegetables and meats would still require to be handled in the cold chain, so all other supply chain costs remain the same. Food manufacturers have not embraced food irradiation because the market does not support the increased price of irradiated foods, and because of potential consumer backlash due to irradiated foods. [44]
The cost of food irradiation is influenced by dose requirements, the food's tolerance of radiation, handling conditions, i.e., packaging and stacking requirements, construction costs, financing arrangements, and other variables particular to the situation. [45]
Irradiation has been approved by many countries. For example, in the U.S. and Canada, food irradiation has existed for decades. [1] [3] Food irradiation is used commercially and volumes are in general increasing at a slow rate, even in the European Union where all member countries allow the irradiation of dried herbs spices and vegetable seasonings, but only a few allow other foods to be sold as irradiated. [46]
Although there are some consumers who choose not to purchase irradiated food, a sufficient market has existed for retailers to have continuously stocked irradiated products for years. [47] When labelled irradiated food is offered for retail sale, consumers buy and re-purchase it, indicating a market for irradiated foods, although there is a continuing need for consumer education. [47] [48]
Food scientists have concluded that any fresh or frozen food undergoing irradiation at specified doses is safe to consume, with some 60 countries using irradiation to maintain quality in their food supply. [1] [33] [6] [48] [49]
The following risks can be mentioned: [50]
The Codex Alimentarius represents the global standard for irradiation of food, in particular under the WTO-agreement. Regardless of treatment source, all processing facilities must adhere to safety standards set by the International Atomic Energy Agency (IAEA), Codex Code of Practice for the Radiation Processing of Food, Nuclear Regulatory Commission (NRC), and the International Organization for Standardization (ISO). [51] More specifically, ISO 14470 and ISO 9001 provide in-depth information regarding safety in irradiation facilities. [51]
All commercial irradiation facilities contain safety systems which are designed to prevent exposure of personnel to radiation. The radiation source is constantly shielded by water, concrete, or metal. Irradiation facilities are designed with overlapping layers of protection, interlocks, and safeguards to prevent accidental radiation exposure. [38] Meltdowns are unlikely to occur due to low heat production from sources used. [38]
The provisions of the Codex Alimentarius are that any "first generation" product must be labeled "irradiated" as any product derived directly from an irradiated raw material; for ingredients the provision is that even the last molecule of an irradiated ingredient must be listed with the ingredients even in cases where the unirradiated ingredient does not appear on the label. The RADURA-logo is optional; several countries use a graphical version that differs from the Codex-version. The suggested rules for labeling is published at CODEX-STAN – 1 (2005), [52] and includes the usage of the Radura symbol for all products that contain irradiated foods. The Radura symbol is not a designator of quality. The amount of pathogens remaining is based upon dose and the original content and the dose applied can vary on a product by product basis. [53]
The European Union follows the Codex's provision to label irradiated ingredients down to the last molecule of irradiated food. The European Union does not provide for the use of the Radura logo and relies exclusively on labeling by the appropriate phrases in the respective languages of the Member States. The European Union enforces its irradiation labeling laws by requiring its member countries to perform tests on a cross section of food items in the market-place and to report to the European Commission. The results are published annually on EUR-Lex. [54]
The US defines irradiated foods as foods in which the irradiation causes a material change in the food, or a material change in the consequences that may result from the use of the food. Therefore, food that is processed as an ingredient by a restaurant or food processor is exempt from the labeling requirement in the US. All irradiated foods must include a prominent Radura symbol followed in addition to the statement "treated with irradiation" or "treated by irradiation. [43] Bulk foods must be individually labeled with the symbol and statement or, alternatively, the Radura and statement should be located next to the sale container. [1]
Under section 409 of the Federal Food, Drug, and Cosmetic Act, irradiation of prepackaged foods requires premarket approval for not only the irradiation source for a specific food but also for the food packaging material. Approved packaging materials include various plastic films, yet does not cover a variety of polymers and adhesive based materials that have been found to meet specific standards. The lack of packaging material approval limits manufacturers production and expansion of irradiated prepackaged foods. [26]
Approved materials by FDA for Irradiation according to 21 CFR 179.45: [26]
Material | Paper (kraft) | Paper (glassine) | Paperboard | Cellophane (coated) | Polyolefin film | Polyestyrene film | Nylon-6 | Vegetable Parchment | Nylon 11 |
Irradiation (kGy) | .05 | 10 | 10 | 10 | 10 | 10 | 10 | 60 | 60 |
In 2003, the Codex Alimentarius removed any upper dose limit for food irradiation as well as clearances for specific foods, declaring that all are safe to irradiate. Countries such as Pakistan and Brazil have adopted the Codex without any reservation or restriction.
Standards that describe calibration and operation for radiation dosimetry, as well as procedures to relate the measured dose to the effects achieved and to report and document such results, are maintained by the American Society for Testing and Materials (ASTM international) and are also available as ISO/ASTM standards. [55]
All of the rules involved in processing food are applied to all foods before they are irradiated.
The U.S. Food and Drug Administration (FDA) is the agency responsible for regulation of radiation sources in the United States. [1] Irradiation, as defined by the FDA is a "food additive" as opposed to a food process and therefore falls under the food additive regulations. Each food approved for irradiation has specific guidelines in terms of minimum and maximum dosage as determined safe by the FDA. [1] [56] Packaging materials containing the food processed by irradiation must also undergo approval. The United States Department of Agriculture (USDA) amends these rules for use with meat, poultry, and fresh fruit. [57]
The United States Department of Agriculture (USDA) has approved the use of low-level irradiation as an alternative treatment to pesticides for fruits and vegetables that are considered hosts to a number of insect pests, including fruit flies and seed weevils. Under bilateral agreements that allows less-developed countries to earn income through food exports agreements are made to allow them to irradiate fruits and vegetables at low doses to kill insects, so that the food can avoid quarantine.
The U.S. Food and Drug Administration and the U.S. Department of Agriculture have approved irradiation of the following foods and purposes:
European law stipulates that all member countries must allow the sale of irradiated dried aromatic herbs, spices and vegetable seasonings. [62] However, these Directives allow Member States to maintain previous clearances food categories the EC's Scientific Committee on Food (SCF) had previously approved (the approval body is now the European Food Safety Authority). Presently, Belgium, Czech Republic, France, Italy, Netherlands, and Poland allow the sale of many different types of irradiated foods. [63] Before individual items in an approved class can be added to the approved list, studies into the toxicology of each of such food and for each of the proposed dose ranges are requested. It also states that irradiation shall not be used "as a substitute for hygiene or health practices or good manufacturing or agricultural practice". These Directives only control food irradiation for food retail and their conditions and controls are not applicable to the irradiation of food for patients requiring sterile diets. In 2021 the most common food items irradiated were frog legs at 65.1%, poultry 20.6% and dried aromatic herbs, spices and vegetables seasoning. [64]
Due to the European Single Market, any food, even if irradiated, must be allowed to be marketed in any other member state even if a general ban of food irradiation prevails, under the condition that the food has been irradiated legally in the state of origin.
Furthermore, imports into the EC are possible from third countries if the irradiation facility had been inspected and approved by the EC and the treatment is legal within the EC or some Member state. [65] [66]
In Australia, following cat deaths [67] after irradiated cat food consumption and producer's voluntary recall, [68] cat food irradiation was banned. [69]
Interlocks and safeguards are mandated to minimize this risk. There have been radiation-related accidents, deaths, and injury at such facilities, many of them caused by operators overriding the safety related interlocks. [70] [71] [72] In a radiation processing facility, radiation specific concerns are supervised by special authorities, while "Ordinary" occupational safety regulations are handled much like other businesses.
The safety of irradiation facilities is regulated by the United Nations International Atomic Energy Agency and monitored by the different national Nuclear Regulatory Commissions. The regulators enforce a safety culture that mandates that all incidents that occur are documented and thoroughly analyzed to determine the cause and improvement potential. Such incidents are studied by personnel at multiple facilities, and improvements are mandated to retrofit existing facilities and future design.
In the US the Nuclear Regulatory Commission (NRC) regulates the safety of the processing facility, and the United States Department of Transportation (DOT) regulates the safe transport of the radioactive sources.
The word "radurisation" is derived from radura, combining the initial letters of the word "radiation" with the stem of "durus", the Latin word for hard, lasting. [73]
A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess numbers of either neutrons or protons, giving it excess nuclear energy, and making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferred to one of its electrons to release it as a conversion electron; or used to create and emit a new particle (alpha particle or beta particle) from the nucleus. During those processes, the radionuclide is said to undergo radioactive decay. These emissions are considered ionizing radiation because they are energetic enough to liberate an electron from another atom. The radioactive decay can produce a stable nuclide or will sometimes produce a new unstable radionuclide which may undergo further decay. Radioactive decay is a random process at the level of single atoms: it is impossible to predict when one particular atom will decay. However, for a collection of atoms of a single nuclide the decay rate, and thus the half-life (t1/2) for that collection, can be calculated from their measured decay constants. The range of the half-lives of radioactive atoms has no known limits and spans a time range of over 55 orders of magnitude.
A beta particle, also called beta ray or beta radiation, is a high-energy, high-speed electron or positron emitted by the radioactive decay of an atomic nucleus, known as beta decay. There are two forms of beta decay, β− decay and β+ decay, which produce electrons and positrons, respectively.
Nuclear fallout is residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and the shock wave has passed. It commonly refers to the radioactive dust and ash created when a nuclear weapon explodes. The amount and spread of fallout is a product of the size of the weapon and the altitude at which it is detonated. Fallout may get entrained with the products of a pyrocumulus cloud and when combined with precipitation falls as black rain, which occurred within 30–40 minutes of the atomic bombings of Hiroshima and Nagasaki. This radioactive dust, usually consisting of fission products mixed with bystanding atoms that are neutron-activated by exposure, is a form of radioactive contamination.
Nuclear technology is technology that involves the nuclear reactions of atomic nuclei. Among the notable nuclear technologies are nuclear reactors, nuclear medicine and nuclear weapons. It is also used, among other things, in smoke detectors and gun sights.
Acute radiation syndrome (ARS), also known as radiation sickness or radiation poisoning, is a collection of health effects that are caused by being exposed to high amounts of ionizing radiation in a short period of time. Symptoms can start within an hour of exposure, and can last for several months. Early symptoms are usually nausea, vomiting and loss of appetite. In the following hours or weeks, initial symptoms may appear to improve, before the development of additional symptoms, after which either recovery or death follow.
Ionizing radiation, including nuclear radiation, consists of subatomic particles or electromagnetic waves that have sufficient energy to ionize atoms or molecules by detaching electrons from them. Some particles can travel up to 99% of the speed of light, and the electromagnetic waves are on the high-energy portion of the electromagnetic spectrum.
The gray is the unit of ionizing radiation dose in the International System of Units (SI), defined as the absorption of one joule of radiation energy per kilogram of matter.
Radiation protection, also known as radiological protection, is defined by the International Atomic Energy Agency (IAEA) as "The protection of people from harmful effects of exposure to ionizing radiation, and the means for achieving this". Exposure can be from a source of radiation external to the human body or due to internal irradiation caused by the ingestion of radioactive contamination.
Sterilization refers to any process that removes, kills, or deactivates all forms of life and other biological agents present in fluid or on a specific surface or object. Sterilization can be achieved through various means, including heat, chemicals, irradiation, high pressure, and filtration. Sterilization is distinct from disinfection, sanitization, and pasteurization, in that those methods reduce rather than eliminate all forms of life and biological agents present. After sterilization, fluid or an object is referred to as being sterile or aseptic.
Radioactive contamination, also called radiological pollution, is the deposition of, or presence of radioactive substances on surfaces or within solids, liquids, or gases, where their presence is unintended or undesirable.
In radiation physics, kerma is an acronym for "kinetic energy released per unit mass", defined as the sum of the initial kinetic energies of all the charged particles liberated by uncharged ionizing radiation in a sample of matter, divided by the mass of the sample. It is defined by the quotient .
Irradiation is the process by which an object is exposed to radiation. An irradiator is a device used to expose an object to radiation, notably gamma radiation, for a variety of purposes. Irradiators may be used for sterilizing medical and pharmaceutical supplies, preserving foodstuffs, alteration of gemstone colors, studying radiation effects, eradicating insects through sterile male release programs, or calibrating thermoluminescent dosimeters (TLDs).
The Radura symbol serves as an international indicator that a food item has undergone irradiation. Typically depicted in green, it features a plant design within a circular outline, with the circle's top section represented by dashes. The specific design elements, including colors, can differ across various countries.
Iodine-131 is an important radioisotope of iodine discovered by Glenn Seaborg and John Livingood in 1938 at the University of California, Berkeley. It has a radioactive decay half-life of about eight days. It is associated with nuclear energy, medical diagnostic and treatment procedures, and natural gas production. It also plays a major role as a radioactive isotope present in nuclear fission products, and was a significant contributor to the health hazards from open-air atomic bomb testing in the 1950s, and from the Chernobyl disaster, as well as being a large fraction of the contamination hazard in the first weeks in the Fukushima nuclear crisis. This is because 131I is a major fission product of uranium and plutonium, comprising nearly 3% of the total products of fission. See fission product yield for a comparison with other radioactive fission products. 131I is also a major fission product of uranium-233, produced from thorium.
Cobalt-60 (60Co) is a synthetic radioactive isotope of cobalt with a half-life of 5.2714 years. It is produced artificially in nuclear reactors. Deliberate industrial production depends on neutron activation of bulk samples of the monoisotopic and mononuclidic cobalt isotope 59
Co
. Measurable quantities are also produced as a by-product of typical nuclear power plant operation and may be detected externally when leaks occur. In the latter case the incidentally produced 60
Co
is largely the result of multiple stages of neutron activation of iron isotopes in the reactor's steel structures via the creation of its 59
Co
precursor. The simplest case of the latter would result from the activation of 58
Fe
. 60
Co
undergoes beta decay to the stable isotope nickel-60. The activated cobalt nucleus emits two gamma rays with energies of 1.17 and 1.33 MeV, hence the overall equation of the nuclear reaction is: 59
27Co
+ n → 60
27Co
→ 60
28Ni
+ e− + 2 γ
Electron-beam processing or electron irradiation (EBI) is a process that involves using electrons, usually of high energy, to treat an object for a variety of purposes. This may take place under elevated temperatures and nitrogen atmosphere. Possible uses for electron irradiation include sterilization, alteration of gemstone colors, and cross-linking of polymers.
A gamma ray, also known as gamma radiation (symbol
γ
), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically shorter than those of X-rays. With frequencies above 30 exahertz (3×1019 Hz) and wavelengths less than 10 picometers (1×10−11 m), gamma ray photons have the highest photon energy of any form of electromagnetic radiation. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by radium. In 1903, Ernest Rutherford named this radiation gamma rays based on their relatively strong penetration of matter; in 1900, he had already named two less penetrating types of decay radiation (discovered by Henri Becquerel) alpha rays and beta rays in ascending order of penetrating power.
The Philippine Nuclear Research Institute (PNRI) is a government agency under the Department of Science and Technology mandated to undertake research and development activities in the peaceful uses of nuclear energy, institute regulations on the said uses, and carry out the enforcement of said regulations to protect the health and safety of radiation workers and the general public.
Phytosanitary irradiation is a treatment that uses ionizing radiation on commodities, such as fruits and vegetables to inactivate pests, such as insects. This method is used for international food trade as a means to prevent spread of non-native organisms. It is used as an alternative to conventional techniques, which includes heat treatment, cold treatment, pesticide sprays, high pressure treatment, cleaning, waxing or chemical fumigation. It is often used on spices, grains, and non-food items. It inhibits the species reproduction cycle by destroying nuclear material primarily, whereas other methods are measured by species mortality. Each country has different effective approved dosages, although most follow guidelines established by the IPPC which has issued guidelines referred to as the International Standards for Phytosanitary Measures (ISPM). The most commonly used dose is 400 Gy based on USDA-APHIS guidelines.
{{cite journal}}
: CS1 maint: unfit URL (link)