Ionizing radiation

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Ionizing_radiation 

Ionizing radiation (ionising radiation) consists of subatomic particles or electromagnetic waves that have sufficient energy to ionize atoms or molecules by detaching electrons from them. The particles generally travel at a speed that is greater than 1% of that of light, and the electromagnetic waves are on the high-energy portion of the electromagnetic spectrum.

Gamma rays, X-rays and the higher ultraviolet part of the electromagnetic spectrum are ionizing radiation, whereas the lower energy ultraviolet, visible light, nearly all types of laser light, infrared, microwaves, and radio waves are non-ionizing radiation. The boundary between ionizing and non-ionizing radiation in the ultraviolet area is not sharply defined, since different molecules and atoms ionize at different energies, but is between 10 electronvolts (eV) and 33 eV.

Typical ionizing subatomic particles due to radioactive decay include alpha particles, beta particles and neutrons and almost all are energetic enough to be ionizing. Secondary cosmic particles produced after cosmic rays interact with Earth's atmosphere include muons, mesons, and positrons. Cosmic rays may also produce radioisotopes on Earth (for example, carbon-14), which in turn decays and emits ionizing radiation. Cosmic rays and the decay of radioactive isotopes are the primary sources of natural ionizing radiation on Earth contributing to background radiation. Ionizing radiation is also generated artificially by such as X-ray tubes, particle accelerators, and nuclear fission.

Ionizing radiation is not detectable by human senses, so instruments such as Geiger counters must be used to detect and measure it. However, very high intensities can produce visible light such as in Cherenkov radiation. Ionizing radiation is used in a wide variety of fields such as medicine, nuclear power, research, and industrial manufacturing, but presents a health hazard if proper measures against excessive exposure are not taken. Exposure to ionizing radiation causes cell damage to living tissue and in high acute doses will result in radiation burns and radiation sickness, and lower level doses over a protracted time can cause cancer. The International Commission on Radiological Protection (ICRP) issues guidance on ionizing radiation protection, and the effects of dose uptake on human health.

Directly ionizing radiation

Alpha (α) radiation consists of a fast-moving helium-4 (⁴
He
) nucleus and is stopped by a sheet of paper. Beta (β) radiation, consisting of electrons, is halted by an aluminium plate. Gamma (γ) radiation, consisting of energetic photons, is eventually absorbed as it penetrates a dense material. Neutron (n) radiation consists of free neutrons that are blocked by light elements, like hydrogen, which slow and/or capture them. Not shown: galactic cosmic rays that consist of energetic charged nuclei such as protons, helium nuclei, and high-charged nuclei called HZE ions.

 

Cloud chambers are used to visualise ionizing radiation. This image show the tracks of particles, which ionise saturated air and leave a trail of water vapour.

Ionizing radiation may be grouped as directly or indirectly ionizing.

Any charged particle with mass can ionize atoms directly by fundamental interaction through the Coulomb force if it carries sufficient kinetic energy. Such particles include atomic nuclei, electrons, muons, charged pions, protons, and energetic charged nuclei stripped of their electrons. When moving at relativistic speeds (near the speed of light, c) these particles have enough kinetic energy to be ionizing, but there is considerable speed variation. For example, a typical alpha particle moves at about 5% of c, but an electron with 33 eV (just enough to ionize) moves at about 1% of c.

Two of the first types of directly ionizing radiation to be discovered are alpha particles which are helium nuclei ejected from the nucleus of an atom during radioactive decay, and energetic electrons, which are called beta particles.

Natural cosmic rays are made up primarily of relativistic protons but also include heavier atomic nuclei like helium ions and HZE ions. In the atmosphere such particles are often stopped by air molecules, and this produces short-lived charged pions, which soon decay to muons, a primary type of cosmic ray radiation that reaches the surface of the earth. Pions can also be produced in large amounts in particle accelerators.

Alpha particles

Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus. Alpha particle emissions are generally produced in the process of alpha decay.

Alpha particles are a strongly ionizing form of radiation, but when emitted by radioactive decay they have low penetration power and can be absorbed by a few centimeters of air, or by the top layer of human skin. More powerful alpha particles from ternary fission are three times as energetic, and penetrate proportionately farther in air. The helium nuclei that form 10–12% of cosmic rays, are also usually of much higher energy than those produced by radioactive decay and pose shielding problems in space. However, this type of radiation is significantly absorbed by the Earth's atmosphere, which is a radiation shield equivalent to about 10 meters of water.

Alpha particles are named after the first letter in the Greek alphabet, α. The symbol for the alpha particle is α or α²⁺. Because they are identical to helium nuclei, they are also sometimes written as He²⁺
or ⁴
₂He²⁺
indicating a Helium ion with a +2 charge (missing its two electrons). If the ion gains electrons from its environment, the alpha particle can be written as a normal (electrically neutral) helium atom ⁴
₂He.

Beta particles

Beta particles are high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei, such as potassium-40. The production of beta particles is termed beta decay. They are designated by the Greek letter beta (β). There are two forms of beta decay, β⁻ and β⁺, which respectively give rise to the electron and the positron. Beta particles are less penetrating than gamma radiation, but more penetrating than alpha particles.

High-energy beta particles may produce X-rays known as bremsstrahlung ("braking radiation") or secondary electrons (delta ray) as they pass through matter. Both of these can cause an indirect ionization effect. Bremsstrahlung is of concern when shielding beta emitters, as the interaction of beta particles with the shielding material produces Bremsstrahlung. This effect is greater with material of high atomic numbers, so material with low atomic numbers is used for beta source shielding.

Positrons and other types of antimatter

The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. When a low-energy positron collides with a low-energy electron, annihilation occurs, resulting in their conversion into the energy of two or more gamma ray photons (see electron–positron annihilation). As positrons are positively charged particles they can directly ionize an atom through Coulomb interactions.

Positrons can be generated by positron emission nuclear decay (through weak interactions), or by pair production from a sufficiently energetic photon. Positrons are common artificial sources of ionizing radiation used in medical positron emission tomography (PET) scans.

Charged nuclei

Charged nuclei are characteristic of galactic cosmic rays and solar particle events and except for alpha particles (charged helium nuclei) have no natural sources on the earth. In space, however, very high energy protons, helium nuclei, and HZE ions can be initially stopped by relatively thin layers of shielding, clothes, or skin. However, the resulting interaction will generate secondary radiation and cause cascading biological effects. If just one atom of tissue is displaced by an energetic proton, for example, the collision will cause further interactions in the body. This is called "linear energy transfer" (LET), which utilizes elastic scattering.

LET can be visualized as a billiard ball hitting another in the manner of the conservation of momentum, sending both away with the energy of the first ball divided between the two unequally. When a charged nucleus strikes a relatively slow-moving nucleus of an object in space, LET occurs and neutrons, alpha particles, low-energy protons, and other nuclei will be released by the collisions and contribute to the total absorbed dose of tissue.

Indirectly ionizing radiation

Indirectly ionizing radiation is electrically neutral and does not interact strongly with matter, therefore the bulk of the ionization effects are due to secondary ionization.

Photon radiation

Different types of electromagnetic radiation

 

The total absorption coefficient of lead (atomic number 82) for gamma rays, plotted versus gamma energy, and contributions by the three effects. The photoelectric effect dominates at low energy, but above 5 MeV, pair production starts to dominate.

Even though photons are electrically neutral, they can ionize atoms indirectly through the photoelectric effect and the Compton effect. Either of those interactions will cause the ejection of an electron from an atom at relativistic speeds, turning that electron into a beta particle (secondary beta particle) that will ionize other atoms. Since most of the ionized atoms are due to the secondary beta particles, photons are indirectly ionizing radiation.

Photon radiation is called gamma rays if produced by a nuclear reaction, subatomic particle decay, or radioactive decay within the nucleus. It is otherwise called x-rays if produced outside the nucleus. The generic term photon is used to describe both.

X-rays normally have a lower energy than gamma rays, and an older convention was to define the boundary as a wavelength of 10⁻¹¹ m or a photon energy of 100 keV. That threshold was driven by historic limitations of older X-ray tubes and low awareness of isomeric transitions. Modern technologies and discoveries have shown an overlap between X-ray and gamma energies. In many fields they are functionally identical, differing for terrestrial studies only in origin of the radiation. In astronomy, however, where radiation origin often cannot be reliably determined, the old energy division has been preserved, with X-rays defined as being between about 120 eV and 120 keV, and gamma rays as being of any energy above 100 to 120 keV, regardless of source. Most astronomical "gamma-ray astronomy" are known not to originate in nuclear radioactive processes but, rather, result from processes like those that produce astronomical X-rays, except driven by much more energetic electrons.

Photoelectric absorption is the dominant mechanism in organic materials for photon energies below 100 keV, typical of classical X-ray tube originated X-rays. At energies beyond 100 keV, photons ionize matter increasingly through the Compton effect, and then indirectly through pair production at energies beyond 5 MeV. The accompanying interaction diagram shows two Compton scatterings happening sequentially. In every scattering event, the gamma ray transfers energy to an electron, and it continues on its path in a different direction and with reduced energy.

Definition boundary for lower-energy photons

The lowest ionization energy of any element is 3.89 eV, for caesium. However, US Federal Communications Commission material defines ionizing radiation as that with a photon energy greater than 10 eV (equivalent to a far ultraviolet wavelength of 124 nanometers). Roughly, this corresponds to both the first ionization energy of oxygen, and the ionization energy of hydrogen, both about 14 eV. In some Environmental Protection Agency references, the ionization of a typical water molecule at an energy of 33 eV is referenced as the appropriate biological threshold for ionizing radiation: this value represents the so-called W-value, the colloquial name for the ICRU's mean energy expended in a gas per ion pair formed, which combines ionization energy plus the energy lost to other processes such as excitation. At 38 nanometers wavelength for electromagnetic radiation, 33 eV is close to the energy at the conventional 10 nm wavelength transition between extreme ultraviolet and X-ray radiation, which occurs at about 125 eV. Thus, X-ray radiation is always ionizing, but only extreme-ultraviolet radiation can be considered ionizing under all definitions.

Radiation interaction: gamma rays are represented by wavy lines, charged particles and neutrons by straight lines. The small circles show where ionization occurs.

Neutrons

Neutrons have a neutral electrical charge often misunderstood as zero electrical charge and thus often do not directly cause ionization in a single step or interaction with matter. However, fast neutrons will interact with the protons in hydrogen via LET, and this mechanism scatters the nuclei of the materials in the target area, causing direct ionization of the hydrogen atoms. When neutrons strike the hydrogen nuclei, proton radiation (fast protons) results. These protons are themselves ionizing because they are of high energy, are charged, and interact with the electrons in matter.

Neutrons that strike other nuclei besides hydrogen will transfer less energy to the other particle if LET does occur. But, for many nuclei struck by neutrons, inelastic scattering occurs. Whether elastic or inelastic scatter occurs is dependent on the speed of the neutron, whether fast or thermal or somewhere in between. It is also dependent on the nuclei it strikes and its neutron cross section.

In inelastic scattering, neutrons are readily absorbed in a type of nuclear reaction called neutron capture and attributes to the neutron activation of the nucleus. Neutron interactions with most types of matter in this manner usually produce radioactive nuclei. The abundant oxygen-16 nucleus, for example, undergoes neutron activation, rapidly decays by a proton emission forming nitrogen-16, which decays to oxygen-16. The short-lived nitrogen-16 decay emits a powerful beta ray. This process can be written as:

¹⁶O (n,p) ¹⁶N (fast neutron capture possible with >11 MeV neutron)

¹⁶N → ¹⁶O + β⁻ (Decay t_1/2 = 7.13 s)

This high-energy β⁻ further interacts rapidly with other nuclei, emitting high-energy γ via Bremsstrahlung

While not a favorable reaction, the ¹⁶O (n,p) ¹⁶N reaction is a major source of X-rays emitted from the cooling water of a pressurized water reactor and contributes enormously to the radiation generated by a water-cooled nuclear reactor while operating.

For the best shielding of neutrons, hydrocarbons that have an abundance of hydrogen are used.

In fissile materials, secondary neutrons may produce nuclear chain reactions, causing a larger amount of ionization from the daughter products of fission.

Outside the nucleus, free neutrons are unstable and have a mean lifetime of 14 minutes, 42 seconds. Free neutrons decay by emission of an electron and an electron antineutrino to become a proton, a process known as beta decay:

In the adjacent diagram, a neutron collides with a proton of the target material, and then becomes a fast recoil proton that ionizes in turn. At the end of its path, the neutron is captured by a nucleus in an (n,γ)-reaction that leads to the emission of a neutron capture photon. Such photons always have enough energy to qualify as ionizing radiation.

Physical effects

Ionized air glows blue around a beam of particulate ionizing radiation from a cyclotron

Nuclear effects

Neutron radiation, alpha radiation, and extremely energetic gamma (> ~20 MeV) can cause nuclear transmutation and induced radioactivity. The relevant mechanisms are neutron activation, alpha absorption, and photodisintegration. A large enough number of transmutations can change macroscopic properties and cause targets to become radioactive themselves, even after the original source is removed.

Chemical effects

Ionization of molecules can lead to radiolysis (breaking chemical bonds), and formation of highly reactive free radicals. These free radicals may then react chemically with neighbouring materials even after the original radiation has stopped. (e.g., ozone cracking of polymers by ozone formed by ionization of air). Ionizing radiation can also accelerate existing chemical reactions such as polymerization and corrosion, by contributing to the activation energy required for the reaction. Optical materials deteriorate under the effect of ionizing radiation.

High-intensity ionizing radiation in air can produce a visible ionized air glow of telltale bluish-purple color. The glow can be observed, e.g., during criticality accidents, around mushroom clouds shortly after a nuclear explosion, or the inside of a damaged nuclear reactor like during the Chernobyl disaster.

Monatomic fluids, e.g. molten sodium, have no chemical bonds to break and no crystal lattice to disturb, so they are immune to the chemical effects of ionizing radiation. Simple diatomic compounds with very negative enthalpy of formation, such as hydrogen fluoride will reform rapidly and spontaneously after ionization.

Electrical effects

Ionization of materials temporarily increases their conductivity, potentially permitting damaging current levels. This is a particular hazard in semiconductor microelectronics employed in electronic equipment, with subsequent currents introducing operation errors or even permanently damaging the devices. Devices intended for high radiation environments such as the nuclear industry and extra-atmospheric (space) applications may be made radiation hard to resist such effects through design, material selection, and fabrication methods.

Proton radiation found in space can also cause single-event upsets in digital circuits. The electrical effects of ionizing radiation are exploited in gas-filled radiation detectors, e.g. the Geiger-Muller counter or the ion chamber.

Health effects

Most adverse health effects of exposure to ionizing radiation may be grouped in two general categories:

• deterministic effects (harmful tissue reactions) due in large part to killing or malfunction of cells following high doses from radiation burns.
• stochastic effects, i.e., cancer and heritable effects involving either cancer development in exposed individuals owing to mutation of somatic cells or heritable disease in their offspring owing to mutation of reproductive (germ) cells.

The most common impact is stochastic induction of cancer with a latent period of years or decades after exposure. For example, ionizing radiation is one cause of chronic myelogenous leukemia, although most people with CML have not been exposed to radiation. The mechanism by which this occurs is well understood, but quantitative models predicting the level of risk remain controversial.

The most widely accepted model the Linear no-threshold model (LNT) holds that the incidence of cancers due to ionizing radiation increases linearly with effective radiation dose at a rate of 5.5% per sievert. If this is correct, then natural background radiation is the most hazardous source of radiation to general public health, followed by medical imaging as a close second. Other stochastic effects of ionizing radiation are teratogenesis, cognitive decline, and heart disease.

Although DNA is always susceptible to damage by ionizing radiation, the DNA molecule may also be damaged by radiation with enough energy to excite certain molecular bonds to form pyrimidine dimers. This energy may be less than ionizing, but near to it. A good example is ultraviolet spectrum energy which begins at about 3.1 eV (400 nm) at close to the same energy level which can cause sunburn to unprotected skin, as a result of photoreactions in collagen and (in the UV-B range) also damage in DNA (for example, pyrimidine dimers). Thus, the mid and lower ultraviolet electromagnetic spectrum is damaging to biological tissues as a result of electronic excitation in molecules which falls short of ionization, but produces similar non-thermal effects. To some extent, visible light and also ultraviolet A (UVA) which is closest to visible energies, have been proven to result in formation of reactive oxygen species in skin, which cause indirect damage since these are electronically excited molecules which can inflict reactive damage, although they do not cause sunburn (erythema). Like ionization-damage, all these effects in skin are beyond those produced by simple thermal effects.

Measurement of radiation

The table below shows radiation and dose quantities in SI and non-SI units.

Relationship between radioactivity and detected ionizing radiation. Key factors are; strength of the radioactive source, transmission effects and instrument sensitivity

 

Methods of radiation measurement

Quantity	Detector	CGS units	SI units	Other units
Disintegration rate		curie	becquerel
Particle flux	Geiger counter, proportional counter, scintillator	counts/cm2 · second	counts/metre2 · second	counts per minute, particles per cm2 per second
Energy fluence	thermoluminescent dosimeter, film badge dosimeter	MeV/cm2	joule/metre2
Beam energy	proportional counter	electronvolt	joule
Linear energy transfer	derived quantity	MeV/cm	Joule/metre	keV/μm
Kerma	ionization chamber, semiconductor detector, quartz fiber dosimeter, Kearny fallout meter	esu/cm3	gray	roentgen
Absorbed dose	calorimeter	rad	gray	rep
Equivalent dose	derived quantity	rem	sievert
Effective dose	derived quantity	rem	sievert	BRET
Committed dose	derived quantity	rem	sievert	banana equivalent dose

Uses of radiation

Ionizing radiation has many industrial, military, and medical uses. Its usefulness must be balanced with its hazards, a compromise that has shifted over time. For example, at one time, assistants in shoe shops used X-rays to check a child's shoe size, but this practice was halted when the risks of ionizing radiation were better understood.

Neutron radiation is essential to the working of nuclear reactors and nuclear weapons. The penetrating power of x-ray, gamma, beta, and positron radiation is used for medical imaging, nondestructive testing, and a variety of industrial gauges. Radioactive tracers are used in medical and industrial applications, as well as biological and radiation chemistry. Alpha radiation is used in static eliminators and smoke detectors. The sterilizing effects of ionizing radiation are useful for cleaning medical instruments, food irradiation, and the sterile insect technique. Measurements of carbon-14, can be used to date the remains of long-dead organisms (such as wood that is thousands of years old).

Sources of radiation

Ionizing radiation is generated through nuclear reactions, nuclear decay, by very high temperature, or via acceleration of charged particles in electromagnetic fields. Natural sources include the sun, lightning and supernova explosions. Artificial sources include nuclear reactors, particle accelerators, and x-ray tubes.

The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) itemized types of human exposures.

Type of radiation exposures

Public exposure
Natural Sources	Normal occurrences	Cosmic radiation
		Terrestrial radiation
	Enhanced sources	Metal mining and smelting
		Phosphate industry
		Coal mining and power production from coal
		Oil and gas drilling
		Rare earth and titanium dioxide industries
		Zirconium and ceramics industries
		Application of radium and thorium
		Other exposure situations
Man-made sources	Peaceful purposes	Nuclear power production
		Transport of nuclear and radioactive material
		Application other than nuclear power
	Military purposes	Nuclear tests
		Residues in the environment. Nuclear fallout
Historical situations
Exposure from accidents
Occupational radiation exposure
Natural Sources		Cosmic ray exposures of aircrew and space crew
		Exposures in extractive and processing industries
		Gas and oil extraction industries
		Radon exposure in workplaces other than mines
Man-made sources	Peaceful purposes	Nuclear power industries
		Medical uses of radiation
		Industrial uses of radiation
		Miscellaneous uses
	Military purposes	Other exposed workers
Source UNSCEAR 2008 Annex B retrieved 2011-7-4

The International Commission on Radiological Protection manages the International System of Radiological Protection, which sets recommended limits for dose uptake.

Background radiation

Background radiation comes from both natural and man-made sources.

The global average exposure of humans to ionizing radiation is about 3 mSv (0.3 rem) per year, 80% of which comes from nature. The remaining 20% results from exposure to man-made radiation sources, primarily from medical imaging. Average man-made exposure is much higher in developed countries, mostly due to CT scans and nuclear medicine.

Natural background radiation comes from five primary sources: cosmic radiation, solar radiation, external terrestrial sources, radiation in the human body, and radon.

The background rate for natural radiation varies considerably with location, being as low as 1.5 mSv/a (1.5 mSv per year) in some areas and over 100 mSv/a in others. The highest level of purely natural radiation recorded on the Earth's surface is 90 µGy/h (0.8 Gy/a) on a Brazilian black beach composed of monazite. The highest background radiation in an inhabited area is found in Ramsar, primarily due to naturally radioactive limestone used as a building material. Some 2000 of the most exposed residents receive an average radiation dose of 10 mGy per year, (1 rad/yr) ten times more than the ICRP recommended limit for exposure to the public from artificial sources. Record levels were found in a house where the effective radiation dose due to external radiation was 135 mSv/a, (13.5 rem/yr) and the committed dose from radon was 640 mSv/a (64.0 rem/yr). This unique case is over 200 times higher than the world average background radiation. Despite the high levels of background radiation that the residents of Ramsar receive there is no compelling evidence that they experience a greater health risk. The ICRP recommendations are conservative limits and may represent an over representation of the actual health risk. Generally radiation safety organization recommend the most conservative limits assuming it is best to err on the side of caution. This level of caution is appropriate but should not be used to create fear about background radiation danger. Radiation danger from background radiation may be a serious threat but is more likely a small overall risk compared to all other factors in the environment.

Cosmic radiation

The Earth, and all living things on it, are constantly bombarded by radiation from outside our solar system. This cosmic radiation consists of relativistic particles: positively charged nuclei (ions) from 1 amu protons (about 85% of it) to 26 amu iron nuclei and even beyond. (The high-atomic number particles are called HZE ions.) The energy of this radiation can far exceed that which humans can create, even in the largest particle accelerators (see ultra-high-energy cosmic ray). This radiation interacts in the atmosphere to create secondary radiation that rains down, including x-rays, muons, protons, antiprotons, alpha particles, pions, electrons, positrons, and neutrons.

The dose from cosmic radiation is largely from muons, neutrons, and electrons, with a dose rate that varies in different parts of the world and based largely on the geomagnetic field, altitude, and solar cycle. The cosmic-radiation dose rate on airplanes is so high that, according to the United Nations UNSCEAR 2000 Report (see links at bottom), airline flight crew workers receive more dose on average than any other worker, including those in nuclear power plants. Airline crews receive more cosmic rays if they routinely work flight routes that take them close to the North or South pole at high altitudes, where this type of radiation is maximal.

Cosmic rays also include high-energy gamma rays, which are far beyond the energies produced by solar or human sources.

External terrestrial sources

Most materials on Earth contain some radioactive atoms, even if in small quantities. Most of the dose received from these sources is from gamma-ray emitters in building materials, or rocks and soil when outside. The major radionuclides of concern for terrestrial radiation are isotopes of potassium, uranium, and thorium. Each of these sources has been decreasing in activity since the formation of the Earth.

Internal radiation sources

All earthly materials that are the building blocks of life contain a radioactive component. As humans, plants, and animals consume food, air, and water, an inventory of radioisotopes builds up within the organism. Some radionuclides, like potassium-40, emit a high-energy gamma ray that can be measured by sensitive electronic radiation measurement systems. These internal radiation sources contribute to an individual's total radiation dose from natural background radiation.

Radon

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.

Radon-222 is a gas produced by the α-decay of radium-226. Both are a part of the natural uranium decay chain. Uranium is found in soil throughout the world in varying concentrations. Radon is the largest cause of lung cancer among non-smokers and the second-leading cause overall.

Radiation exposure

Various doses of radiation in sieverts, ranging from trivial to lethal.

There are three standard ways to limit exposure:

1. Time: For people exposed to radiation in addition to natural background radiation, limiting or minimizing the exposure time will reduce the dose from the radiation source.
2. Distance: Radiation intensity decreases sharply with distance, according to an inverse-square law (in an absolute vacuum).
3. Shielding: Air or skin can be sufficient to substantially attenuate alpha and beta radiation. Barriers of lead, concrete, or water are often used to give effective protection from more penetrating particles such as gamma rays and neutrons. Some radioactive materials are stored or handled underwater or by remote control in rooms constructed of thick concrete or lined with lead. There are special plastic shields that stop beta particles, and air will stop most alpha particles. The effectiveness of a material in shielding radiation is determined by its half-value thicknesses, the thickness of material that reduces the radiation by half. This value is a function of the material itself and of the type and energy of ionizing radiation. Some generally accepted thicknesses of attenuating material are 5 mm of aluminum for most beta particles, and 3 inches of lead for gamma radiation.

These can all be applied to natural and man-made sources. For man-made sources the use of Containment is a major tool in reducing dose uptake and is effectively a combination of shielding and isolation from the open environment. Radioactive materials are confined in the smallest possible space and kept out of the environment such as in a hot cell (for radiation) or glove box (for contamination). Radioactive isotopes for medical use, for example, are dispensed in closed handling facilities, usually gloveboxes, while nuclear reactors operate within closed systems with multiple barriers that keep the radioactive materials contained. Work rooms, hot cells and gloveboxes have slightly reduced air pressures to prevent escape of airborne material to the open environment.

In nuclear conflicts or civil nuclear releases civil defense measures can help reduce exposure of populations by reducing ingestion of isotopes and occupational exposure. One is the issue of potassium iodide (KI) tablets, which blocks the uptake of radioactive iodine (one of the major radioisotope products of nuclear fission) into the human thyroid gland.

Occupational exposure

Occupationally exposed individuals are controlled within the regulatory framework of the country they work in, and in accordance with any local nuclear licence constraints. These are usually based on the recommendations of the International Commission on Radiological Protection. The ICRP recommends limiting artificial irradiation. For occupational exposure, the limit is 50 mSv in a single year with a maximum of 100 mSv in a consecutive five-year period.

The radiation exposure of these individuals is carefully monitored with the use of dosimeters and other radiological protection instruments which will measure radioactive particulate concentrations, area gamma dose readings and radioactive contamination. A legal record of dose is kept.

Examples of activities where occupational exposure is a concern include:

• Airline crew (the most exposed population)
• Industrial radiography
• Medical radiology and nuclear medicine
• Uranium mining
• Nuclear power plant and nuclear fuel reprocessing plant workers
• Research laboratories (government, university and private)

Some human-made radiation sources affect the body through direct radiation, known as effective dose (radiation) while others take the form of radioactive contamination and irradiate the body from within. The latter is known as committed dose.

Public exposure

Medical procedures, such as diagnostic X-rays, nuclear medicine, and radiation therapy are by far the most significant source of human-made radiation exposure to the general public. Some of the major radionuclides used are I-131, Tc-99m, Co-60, Ir-192, and Cs-137. The public also is exposed to radiation from consumer products, such as tobacco (polonium-210), combustible fuels (gas, coal, etc.), televisions, luminous watches and dials (tritium), airport X-ray systems, smoke detectors (americium), electron tubes, and gas lantern mantles (thorium).

Of lesser magnitude, members of the public are exposed to radiation from the nuclear fuel cycle, which includes the entire sequence from processing uranium to the disposal of the spent fuel. The effects of such exposure have not been reliably measured due to the extremely low doses involved. Opponents use a cancer per dose model to assert that such activities cause several hundred cases of cancer per year, an application of the widely accepted Linear no-threshold model (LNT).

The International Commission on Radiological Protection recommends limiting artificial irradiation to the public to an average of 1 mSv (0.001 Sv) of effective dose per year, not including medical and occupational exposures.

In a nuclear war, gamma rays from both the initial weapon explosion and fallout would be the sources of radiation exposure.

Spaceflight

Massive particles are a concern for astronauts outside the earth's magnetic field who would receive solar particles from solar proton events (SPE) and galactic cosmic rays from cosmic sources. These high-energy charged nuclei are blocked by Earth's magnetic field but pose a major health concern for astronauts traveling to the moon and to any distant location beyond the earth orbit. Highly charged HZE ions in particular are known to be extremely damaging, although protons make up the vast majority of galactic cosmic rays. Evidence indicates past SPE radiation levels that would have been lethal for unprotected astronauts.

Air travel

Air travel exposes people on aircraft to increased radiation from space as compared to sea level, including cosmic rays and from solar flare events. Software programs such as Epcard, CARI, SIEVERT, PCAIRE are attempts to simulate exposure by aircrews and passengers. An example of a measured dose (not simulated dose) is 6 μSv per hour from London Heathrow to Tokyo Narita on a high-latitude polar route. However, dosages can vary, such as during periods of high solar activity. The United States FAA requires airlines to provide flight crew with information about cosmic radiation, and an International Commission on Radiological Protection recommendation for the general public is no more than 1 mSv per year. In addition, many airlines do not allow pregnant flightcrew members, to comply with a European Directive. The FAA has a recommended limit of 1 mSv total for a pregnancy, and no more than 0.5 mSv per month. Information originally based on Fundamentals of Aerospace Medicine published in 2008.

Radiation hazard warning signs

Hazardous levels of ionizing radiation are signified by the trefoil sign on a yellow background. These are usually posted at the boundary of a radiation controlled area or in any place where radiation levels are significantly above background due to human intervention.

The red ionizing radiation warning symbol (ISO 21482) was launched in 2007, and is intended for IAEA Category 1, 2 and 3 sources defined as dangerous sources capable of death or serious injury, including food irradiators, teletherapy machines for cancer treatment and industrial radiography units. The symbol is to be placed on the device housing the source, as a warning not to dismantle the device or to get any closer. It will not be visible under normal use, only if someone attempts to disassemble the device. The symbol will not.

Electromagnetic radiation and health

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Electromagnetic_radiation_and_health 

Electromagnetic radiation can be classified into two types: ionizing radiation and non-ionizing radiation, based on the capability of a single photon with more than 10 eV energy to ionize atoms or break chemical bonds. Extreme ultraviolet and higher frequencies, such as X-rays or gamma rays are ionizing, and these pose their own special hazards: see radiation poisoning.

The most common health hazard of radiation is sunburn, which causes between approximately 100,000 and 1 million new skin cancers annually in the United States.

Claims of harm from low levels of non-ionizing radiation (sometimes described as "electrosmog") are unsupported by science.

Hazards

Dielectric heating from electromagnetic fields can create a biological hazard. For example, touching or standing around an antenna while a high-power transmitter is in operation can cause burns (the mechanism is the same as that used in a microwave oven).

The heating effect varies with the power and the frequency of the electromagnetic energy, as well as the inverse square of distance to the source. The eyes and testes are particularly susceptible to radio frequency heating due to the paucity of blood flow in these areas that could otherwise dissipate the heat buildup.

Radio frequency (RF) energy at power density levels of 1–10 mW/cm² or higher can cause measurable heating of tissues. Typical RF energy levels encountered by the general public are well below the level needed to cause significant heating, but certain workplace environments near high power RF sources may exceed safe exposure limits. A measure of the heating effect is the specific absorption rate or SAR, which has units of watts per kilogram (W/kg). The IEEE and many national governments have established safety limits for exposure to various frequencies of electromagnetic energy based on SAR, mainly based on ICNIRP Guidelines, which guard against thermal damage.

Low-level exposure

The World Health Organization began a research effort in 1996 to study the health effects from the ever-increasing exposure of people to a diverse range of EMR sources. After 30 years of extensive study, science has yet to establish a health risk from exposure to low-level fields.

Epidemiological studies look for statistical correlations between EM exposure in the field and specific health effects. As of 2019, much of the current work is focused on the study of EM fields in relation to cancer. There are publications which support the existence of complex biological and neurological effects of weaker non-thermal electromagnetic fields (see Bioelectromagnetics), including weak ELF electromagnetic fields and modulated RF and microwave fields.

Effects by frequency

Warning sign next to a transmitter with high field strengths

While the most acute exposures to harmful levels of electromagnetic radiation are immediately realized as burns, the health effects due to chronic or occupational exposure may not manifest effects for months or years.

Extremely-low frequency

Electric and magnetic fields occur where electricity is generated or distributed in power lines, cables, or electrical appliances. Human responses depend on the field strength, ambient environmental conditions, and individual sensitivity. 7% of volunteers exposed to power-frequency electric fields of high-power, extremely-low-frequency RF with electric field levels in the low kV/m range reported painful currents that flowed to ground through a body contact surface such as the feet, or arced to ground where the body was well insulated.

The International Agency for Research on Cancer (IARC) finds "inadequate evidence" for human carcinogenicity.

Shortwave

Shortwave (1.6 to 30 MHz) diathermy can be used as a therapeutic technique for its analgesic effect and deep muscle relaxation, but has largely been replaced by ultrasound. Temperatures in muscles can increase by 4–6 °C, and subcutaneous fat by 15 °C. The FCC has restricted the frequencies allowed for medical treatment, and most machines in the US use 27.12 MHz. Shortwave diathermy can be applied in either continuous or pulsed mode. The latter came to prominence because the continuous mode produced too much heating too rapidly, making patients uncomfortable. The technique only heats tissues that are good electrical conductors, such as blood vessels and muscle. Adipose tissue (fat) receives little heating by induction fields because an electrical current is not actually going through the tissues.

Studies have been performed on the use of shortwave radiation for cancer therapy and promoting wound healing, with some success. However, at a sufficiently high energy level, shortwave energy can be harmful to human health, potentially causing damage to biological tissues. The FCC limits for maximum permissible workplace exposure to shortwave radio frequency energy in the range of 3–30 MHz has a plane-wave equivalent power density of (900/f²) mW/cm² where f is the frequency in MHz, and 100 mW/cm² from 0.3 to 3.0 MHz. For uncontrolled exposure to the general public, the limit is 180/f² between 1.34 and 30 MHz.

Radio frequency field

The designation of mobile phone signals as "possibly carcinogenic to humans" by the World Health Organization (WHO) (e.g. its IARC, see below) has often been misinterpreted as indicating that some measure of risk has been observed – however the designation indicates only that the possibility could not be conclusively ruled out using the available data.

In 2011, International Agency for Research on Cancer (IARC) classified mobile phone radiation as Group 2B "possibly carcinogenic" (rather than Group 2A "probably carcinogenic" nor the "is carcinogenic" Group 1). That means that there "could be some risk" of carcinogenicity, so additional research into the long-term, heavy use of mobile phones needs to be conducted. The WHO concluded in 2014 that "A large number of studies have been performed over the last two decades to assess whether mobile phones pose a potential health risk. To date, no adverse health effects have been established as being caused by mobile phone use."

Since 1962, the microwave auditory effect or tinnitus has been shown from radio frequency exposure at levels below significant heating. Studies during the 1960s in Europe and Russia claimed to show effects on humans, especially the nervous system, from low energy RF radiation; the studies were disputed at the time.

In 2019 reporters from the Chicago Tribune tested the level of radiation from smartphones and found it to exceed safe levels. The federal communications commission begun to check the findings.

Radio frequency radiation is found to have more thermal related effects. A person's body temperature can be raised which could result in death if exposed to high dosage of RF radiation.  Focused RF radiation can also cause burns on the skin or cataracts to form in the eyes. Overall, some health effects are observed at a high levels of RF radiation, but the effects aren't clear at low levels of exposure.

Millimeter waves

In 2009, the US TSA introduced full-body scanners as a primary screening modality in airport security, first as backscatter x-ray scanners, which the European Union banned in 2011 due to health and safety concerns, followed by Millimeter wave scanners . Likewise WiGig for personal area networks have opened the 60 GHz and above microwave band to SAR exposure regulations. Previously, microwave applications in these bands were for point-to-point satellite communication with minimal human exposure.

Infrared

Infrared wavelengths longer than 750 nm can produce changes in the lens of the eye. Glassblower's cataract is an example of a heat injury that damages the anterior lens capsule among unprotected glass and iron workers. Cataract-like changes can occur in workers who observe glowing masses of glass or iron without protective eyewear for prolonged periods over many years.

Exposing skin to infrared radiation near visible light (IR-A) leads to increased production of free radicals. Short-term exposure can be beneficial (activating protective responses), while prolonged exposure can lead to photoaging.

Another important factor is the distance between the worker and the source of radiation. In the case of arc welding, infrared radiation decreases rapidly as a function of distance, so that farther than three feet away from where welding takes place, it does not pose an ocular hazard anymore but, ultraviolet radiation still does. This is why welders wear tinted glasses and surrounding workers only have to wear clear ones that filter UV.

Visible light

Photic retinopathy is damage to the macular area of the eye's retina that results from prolonged exposure to sunlight, particularly with dilated pupils. This can happen, for example, while observing a solar eclipse without suitable eye protection. The Sun's radiation creates a photochemical reaction that can result in visual dazzling and a scotoma. The initial lesions and edema will disappear after several weeks, but may leave behind a permanent reduction in visual acuity.

Moderate and high-power lasers are potentially hazardous because they can burn the retina of the eye, or even the skin. To control the risk of injury, various specifications – for example ANSI Z136 in the US, EN 60825-1/A2 in Europe, and IEC 60825 internationally – define "classes" of lasers depending on their power and wavelength. Regulations prescribe required safety measures, such as labeling lasers with specific warnings, and wearing laser safety goggles during operation.

As with its infrared and ultraviolet radiation dangers, welding creates an intense brightness in the visible light spectrum, which may cause temporary flash blindness. Some sources state that there is no minimum safe distance for exposure to these radiation emissions without adequate eye protection.

Ultraviolet

Sunlight includes sufficient ultraviolet power to cause sunburn within hours of exposure, and the burn severity increases with the duration of exposure. This effect is a response of the skin called erythema, which is caused by a sufficient strong dose of UV-B. The Sun's UV output is divided into UV-A and UV-B: solar UV-A flux is 100 times that of UV-B, but the erythema response is 1,000 times higher for UV-B.^{[citation needed]} This exposure can increase at higher altitudes and when reflected by snow, ice, or sand. The UV-B flux is 2–4 times greater during the middle 4–6 hours of the day, and is not significantly absorbed by cloud cover or up to a meter of water.

Ultraviolet light, specifically UV-B, has been shown to cause cataracts and there is some evidence that sunglasses worn at an early age can slow its development in later life. Most UV light from the sun is filtered out by the atmosphere and consequently airline pilots often have high rates of cataracts because of the increased levels of UV radiation in the upper atmosphere. It is hypothesized that depletion of the ozone layer and a consequent increase in levels of UV light on the ground may increase future rates of cataracts. Note that the lens filters UV light, so if it is removed via surgery, one may be able to see UV light.

Prolonged exposure to ultraviolet radiation from the sun can lead to melanoma and other skin malignancies. Clear evidence establishes ultraviolet radiation, especially the non-ionizing medium wave UVB, as the cause of most non-melanoma skin cancers, which are the most common forms of cancer in the world. UV rays can also cause wrinkles, liver spots, moles, and freckles. In addition to sunlight, other sources include tanning beds, and bright desk lights. Damage is cumulative over one's lifetime, so that permanent effects may not be evident for some time after exposure.

Ultraviolet radiation of wavelengths shorter than 300 nm (actinic rays) can damage the corneal epithelium. This is most commonly the result of exposure to the sun at high altitude, and in areas where shorter wavelengths are readily reflected from bright surfaces, such as snow, water, and sand. UV generated by a welding arc can similarly cause damage to the cornea, known as "arc eye" or welding flash burn, a form of photokeratitis.

Fluorescent light bulbs and tubes internally produce ultraviolet light. Normally this is converted to visible light by the phosphor film inside a protective coating. When the film is cracked by mishandling or faulty manufacturing then UV may escape at levels that could cause sunburn or even skin cancer.

Regulation

In the United States, nonionizing radiation is regulated in the Radiation Control for Health and Safety Act of 1968 and the Occupational Safety and Health Act of 1970.

Animal magnetism

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Animal_magnetism 

Electromagnetism
Electricity Magnetism History Textbooks

Animal magnetism, also known as mesmerism, was the name given by German doctor Franz Mesmer in the 18th century to what he believed to be an invisible natural force (Lebensmagnetismus) possessed by all living things, including humans, animals, and vegetables. He believed that the force could have physical effects, including healing, and he tried persistently but without success to achieve scientific recognition of his ideas.

The vitalist theory attracted numerous followers in Europe and the United States and was popular into the 19th century. Practitioners were often known as magnetizers rather than mesmerists. It was an important specialty in medicine for about 75 years from its beginnings in 1779, and continued to have some influence for another 50 years. Hundreds of books were written on the subject between 1766 and 1925, but it is almost entirely forgotten today. Mesmerism is still practised as a form of alternative medicine in some countries, but magnetic practices are not recognized as part of medical science.

Etymology and definitions

"Magnetizer"

The terms "magnetizer" and "mesmerizer" have been applied to people who study and practice animal magnetism. These terms have been distinguished from "mesmerist" and "magnetist", which are regarded as denoting those who study animal magnetism without being practitioners; and from "hypnotist", someone who practises hypnosis.

The etymology of the word magnetizer comes from the French "magnétiseur" ("practicing the methods of mesmerism"), which in turn is derived from the French verb magnétiser. The term refers to an individual who has the power to manipulate the "magnetic fluid" with effects upon other people present that were regarded as analogous to magnetic effects. This sense of the term is found, for example, in the expression of Antoine Joseph Gorsas: "The magnetizer is the imam of vital energy".

"Mesmerism"

A tendency emerged amongst British magnetizers to call their clinical techniques "mesmerism"; they wanted to distance themselves from the theoretical orientation of animal magnetism that was based on the concept of "magnetic fluid". At the time, some magnetizers attempted to channel what they thought was a magnetic "fluid", and sometimes they attempted this with a "laying on of hands". Reported effects included various feelings: intense heat, trembling, trances, and seizures.

Many practitioners took a scientific approach, such as Joseph Philippe François Deleuze (1753–1835), a French physician, anatomist, gynecologist, and physicist. One of his pupils was Théodore Léger (1799–1853), who wrote that the label "mesmerism" was "most improper". (Léger moved to Texas around 1836).

Noting that, by 1846, the term "galvanism" had been replaced by "electricity", Léger wrote that year:

Mesmerism, of all the names proposed [to replace the term animal magnetism], is decidedly the most improper; for, in the first place, no true science has ever been designated by the name of a man, whatever be the claims he could urge in his favor; and secondly, what are the claims of Mesmer for such an honor? He is not the inventor of the practical part of the science, since we can trace the practice of it through the most remote ages; and in that respect, the part which he introduced has been completely abandoned. He proposed for it a theory which is now [viz., 1846] exploded, and which, on account of his errors, has been fatal to our progress. He never spoke of the phenomena which have rehabilitated our cause among scientific men; and since nothing remains to be attributed to Mesmer, either in the practice and theory, or the discoveries that constitute our science, why should it be called mesmerism?

Royal Commission

In 1784 two French Royal Commissions appointed by Louis XVI studied Mesmer's magnetic fluid theory to try to establish it by scientific evidence. The commission of the Academy of Sciences included Majault, Benjamin Franklin, Jean Sylvain Bailly, Jean-Baptiste Le Roy, Sallin, Jean Darcet, de Borey, Joseph-Ignace Guillotin, Antoine Lavoisier. The Commission of the Royal Society of Medicine was composed of Poissonnier, Caille, Mauduyt de la Varenne, Andry, and Antoine Laurent de Jussieu.

Whilst the commission agreed that the cures claimed by Mesmer were indeed cures, it also concluded there was no evidence of the existence of his "magnetic fluid", and that its effects derived from either the imaginations of its subjects or charlatanry.

Royal Academy investigation

A generation later another investigating committee, appointed by a majority vote in 1826 in The Royal Academy of Medicine in Paris, studied the effects and clinical potentials of the mesmeric procedure - without trying to establish the physical nature of any magnetic fluidum. The report says:

what we have seen in the course of our experiments bears no sort of resemblance to what the Report of 1784 relates with regard to the magnetizers of that period. We neither admit nor reject the existence of the fluid, because we have not verified the fact ; we do not speak of the baquet ... nor of the assemblage of a great number of people together, who were magnetized in the presence of a crowd of witnesses; because all our experiments were made in the most complete stillness ... and always upon a single person at a time. We do not speak of ... the crisis.

Among the conclusions were:

Magnetism has taken effect upon persons of different sexes and ages.
... In general, magnetism does not act upon persons in a sound state of health.
... Neither does it act upon all sick persons.
... we may conclude with certainty that this state exists, when it gives rise to the development of new faculties, which have been designated by the names of clairvoyance; intuition; internal prevision; or when it produces great changes in the physical economy, such as insensibility; a sudden and considerable increase of strength; and when these effects cannot be referred to any other cause.
... We can not only act upon the magnetized person, but even place him in a complete state of somnambulism, and bring him out of it without his knowledge, out of his sight, at a certain distance, and with doors intervening.
... The greater number of the somnambulists whom we have seen, were completely insensible ... we might pinch their skin, so as to leave a mark, prick them with pins under the nails, &c. without producing any pain, without even their perceiving it. Finally, we saw one who was insensible to one of the most painful operations in surgery, and who did not manifest the slightest emotion in her countenance, her pulse, or her respiration.
... Magnetism is as intense, and as speedily felt, at a distance of six feet as of six inches; and the phenomena developed are the same in both cases.
...Magnetism ought to be allowed a place within the circle of medical sciences...

Mesmerism and hypnotism

Baquet. Interior view: Drawing room scene with many people sitting and standing around a large table; a man on a crutch has an iron band wrapped around his ankle; others in the group are holding bands similarly; to the left, a man has magnetised a woman. (1780)

 

Advertisement poster of 1857:
Instant sleep. Miscellaneous effects of paralysis, partial and complete catalepsy, partial or complete attraction. Phreno-magnetic effects (...) Musical ectasy (...) Insensitivity to physical pain and instant awakening (...) transfusion of magnetic power to others

Faria and "oriental hypnosis"

Abbé Faria was one of the disciples of Franz Anton Mesmer who continued with Mesmer's work following the conclusions of the Royal Commission. In the early 19th century, Abbé Faria is said to have introduced oriental hypnosis to Paris and to have conducted experiments to prove that "no special force was necessary for the production of the mesmeric phenomena such as the trance, but that the determining cause lay within the subject himself"—in other words, that it worked purely by the power of suggestion.

Braid and "hypnotism"

Hypnotism, a designation coined by the Scottish surgeon, James Braid, originates in Braid's response to an 1841 exhibition of "animal magnetism", by Charles Lafontaine, in Manchester. Writing in 1851, Braid was adamant that, in the absence of the sorts of "higher phenomena" reportedly produced by the mesmerists,

and in contra-distinction to the Transcendental [i.e., metaphysical] Mesmerism of the Mesmerists … [allegedly] induced through the transmission of an occult influence from [the body of the operator to that of the subject,] Hypnotism, [by which] I mean a peculiar condition of the nervous system, into which it can be thrown by artificial contrivance … [a theoretical position that is entirely] consistent with generally admitted principles in physiological and psychological science [would] therefore [be most aptly] designated Rational Mesmerism.

"Mesmerism" and "hypnotism"

While there is a great range of theories and practices collectively denoted mesmerism, research has clearly identified that there are substantial and significant differences between "mesmerism" and "hypnotism" however they may be defined.

Vital fluid and animal magnetism

A 1791 London publication explains Mesmer's theory of the vital fluid :

Modern philosophy has admitted a plenum or universal principle of fluid matter, which occupies all space; and that as all bodies moving in the world, abound with pores, this fluid matter introduces itself through the interstices and returns backwards and forwards, flowing through one body by the currents which issue therefrom to another, as in a magnet, which produces that phenomenon which we call Animal Magnetism. This fluid consists of fire, air and spirit, and like all other fluids tends to an equilibrium, therefore it is easy to conceive how the efforts which the bodies make towards each other produce animal electricity, which in fact is no more than the effect produced between two bodies, one of which has more motion than the other; a phenomenon serving to prove that the body which has most motion communicates it to the other, until the medium of motion becomes an equilibrium between the two bodies, and then this equality of motion produces animal electricity.

According to an anonymous writer of a series of letters published by editor John Pearson in 1790, animal magnetism can cause a wide range of effects ranging from vomiting to what is termed the "crisis". The purpose of the treatment (inducing the "crisis") was to shock the body into convulsion in order to remove obstructions in the humoral system that were causing sicknesses. Furthermore, this anonymous supporter of the animal magnetism theory purported that the "crisis" created two effects: first, a state in which the "[individual who is] completely reduced under Magnetic influence, although he should seem to be possessed of his senses, yet he ceases to be an accountable creature", and a second "remarkable" state, which would be "conferred upon the [magnetized] subject … [namely] that of perfect and unobstructed vision … in other words, all opacity is removed, and every object becomes luminous and transparent". A patient under crisis was believed to be able to see through the body and find the cause of illness, either in themselves or in other patients.

The Marquis of Puységur's miraculous healing of a young man named Victor in 1784 was attributed to, and used as evidence in support of, this "crisis" treatment. The Marquis was allegedly able to hypnotize Victor and, while hypnotized, Victor was said to have been able to speak articulately and diagnose his own sickness.

Jacob Melo discusses in his books some mechanisms by which the perceived effects of animal magnetism have been claimed to operate.

Social skepticism in the Romantic Era

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A caricature of Mesmer filmed by George Mèliés, 1905

The study of animal magnetism spurred the creation of the Societies of Harmony in France, where members paid to join and learn the practice of magnetism. Doctor John Bell was a member of the Philosophical Harmonic Society of Paris, and was certified by the society to lecture and teach on animal magnetism in England. The existence of the societies transformed animal magnetism into a secretive art, where its practitioners and lecturers did not reveal the techniques of the practice based on the society members that have paid for instruction, veiling the idea that it was unfair to reveal the practice to others for free. Although the heightened secrecy of the practice contributed to the skepticism about it, many supporters and practitioners of animal magnetism touted the ease and possibility for everyone to acquire the skills to perform its techniques.

Popularization of animal magnetism was denounced and ridiculed by newspaper journals and theatre during the Romantic Era. Many deemed animal magnetism to be nothing more than a theatrical falsity or quackery. In a 1790 publication, an editor presented a series of letters written by an avid supporter of animal magnetism and included his own thoughts in an appendix stating: "No fanatics ever divulged notions more wild and extravagant; no impudent empiric ever retailed promises more preposterous, or histories of cures more devoid of reality, than the tribe of magnetisers".

The novelist and playwright Elizabeth Inchbald wrote the farce Animal Magnetism in the late 1780s. The plot revolved around multiple love triangles and the absurdity of animal magnetism. The following passage mocks the medical prowess of those qualified only as mesmerists:

Doctor: They have refused to grant me a diploma—forbid me to practice as a physician, and all because I don't know a parcel of insignificant words; but exercise my profession according to the rules of reason and nature; Is it not natural to die, then if a dozen or two of my patients have died under my hands, is not that natural? …

Although the doctor's obsession with the use of animal magnetism, not merely to cure but to force his ward to fall in love with him, made for a humorous storyline, Inchbald’s light-hearted play commented on what society perceived as threats posed by the practice.

De Mainanduc brought animal magnetism to England in 1787 and promulgated it into the social arena. In 1785, he had published proposals to the ladies of Britain to establish a "hygean society" or society of health, by which they would pay to join and enjoy his treatments. As both popularity and skepticism increased, many became convinced that animal magnetism could lead to sexual exploitation of women. Not only did the practice involve close personal contact via the waving of hands over the body, but people were concerned that the animal magnetists could hypnotize women and direct them at will.

Having removed all misconceptions, foretelling of the future, explicit or implicit invocation of the devil, the use of animal magnetism is indeed merely an act of making use of physical media that are otherwise licit and hence it is not morally forbidden, provided it does not tend toward an illicit end or toward anything depraved. (The Sacred Congregation of the Holy Office: 28 July 1847.)

Political influence

The French revolution catalyzed existing internal political friction in Britain in the 1790s; a few political radicals used animal magnetism as more than just a moral threat but also a political threat. Among many lectures warning society against government oppression, Samuel Taylor Coleridge wrote:

William Pitt, the great political Animal Magnetist, ... has most foully worked on the diseased fancy of Englishmen ... thrown the nation into a feverish slumber, and is now bringing it to a crisis which may convulse mortality!

Major politicians and people in power were accused by radicals of practising animal magnetism on the general population.

In his article "Under the Influence: Mesmerism in England", Roy Porter notes that James Tilly Matthews suggested that the French were infiltrating England via animal magnetism. Matthews believed that "magnetic spies" would invade England and bring it under subjection by transmitting waves of animal magnetism to subdue the government and people. Such an invasion from foreign influences was perceived as a radical threat.

Mesmerism and spiritual healing practices

According to Yeates, mesmerism has been used in many parts of the world as an intervention to treat profound illness in humans, as well as in the treatment of disease in domestic, farm, circus, and zoo animals.

During the Romantic period, mesmerism produced enthusiasm and inspired horror in the spiritual and religious context. Though discredited as a medical practice by many, mesmerism created a venue for spiritual healing. Some animal magnetists advertised their practices by stressing the "spiritual rather than physical benefits to be gained from animal magnetism" and were able to gather a good clientele from among the spiritually inspired population.

Some researchers, including Johann Peter Lange and Allan Kardec, suggested that Jesus was the greatest of all magnetizers, and that the source of his miracles was animal magnetism. Other writers, such as John Campbell Colquhoun and Mary Baker Eddy, denounced the comparison. Mary Baker Eddy went so far as to claim animal magnetism "lead to moral and to physical death."

Today, some scholars believe mesmerism to share a concept of life force or energy with such Asian practices as reiki and qigong. However, the practical and theoretical positions of such practices are on whole substantially different from those of mesmerism.

Contemporary development

Sporadic research into animal magnetism was conducted in the 20th century, and the results published; for example, Bernard Grad wrote a number of papers related to his observations of "a single, reputed healer, [Hungarian] Oskar Estebany" on the subject.