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Health physics, also referred to as the science of
radiation protection 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". Expos ...
, is the profession devoted to protecting people and their environment from potential
radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes: * ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...
hazards, while making it possible to enjoy the beneficial uses of radiation. Health physicists normally require a four-year bachelor’s degree and qualifying experience that demonstrates a professional knowledge of the theory and application of radiation protection principles and closely related sciences
Health physicists
principally work at facilities where
radionuclide A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transfer ...
s or other sources of
ionizing radiation Ionizing radiation (or ionising 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 ...
(such as
X-ray generator An X-ray generator is a device that produces X-rays. Together with an X-ray detector, it is commonly used in a variety of applications including medicine, X-ray fluorescence, electronic assembly inspection, and measurement of material thickness ...
s) are used or produced; these include research, industry, education, medical facilities, nuclear power, military, environmental protection, enforcement of government regulations, and decontamination and decommissioning—the combination of education and experience for health physicists depends on the specific field in which the health physicist is engaged.


Sub Specialties

There are many sub-specialties in the field of health physics, including *
Ionising radiation Ionizing radiation (or ionising 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 ...
instrumentation and measurement *
Internal dosimetry Internal dosimetry is the science and art of internal ionising radiation dose assessment due to radionuclides incorporated inside the human body. Radionuclides deposited within a body will irradiate tissues and organs and give rise to committed do ...
and external
dosimetry Radiation dosimetry in the fields of health physics and radiation protection is the measurement, calculation and assessment of the ionizing radiation dose absorbed by an object, usually the human body. This applies both internally, due to ingested o ...
*
Radioactive waste Radioactive waste is a type of hazardous waste that contains radioactive material. Radioactive waste is a result of many activities, including nuclear medicine, nuclear research, nuclear power generation, rare-earth mining, and nuclear weapons r ...
management *
Radioactive contamination Radioactive contamination, also called radiological pollution, is the deposition of, or presence of radioactive substances on surfaces or within solids, liquids, or gases (including the human body), where their presence is unintended or undesirab ...
, decontamination and decommissioning * Radiological
engineering Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad rang ...
(shielding, holdup, etc.) * Environmental assessment, radiation monitoring and radon evaluation * Operational
radiation protection 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". Expos ...
/health physics * Particle accelerator physics * Radiological emergency response/planning - (e.g.,
Nuclear Emergency Support Team The Nuclear Emergency Support Team (NEST), formerly known as the Nuclear Emergency Search Team, is a team of scientists, technicians, and engineers operating under the United States Department of Energy's National Nuclear Security Administration ...
) * Industrial uses of radioactive material * Medical health physics * Public information and communication involving radioactive materials * Biological effects/radiation biology * Radiation standards * Radiation risk analysis * Nuclear power * Radioactive materials and homeland security *
Radiation protection 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". Expos ...
* Nanotechnology


Operational health physics

The subfield of operational health physics, also called applied health physics in older sources, focuses on field work and the practical application of health physics knowledge to real-world situations, rather than basic research.


Medical physics

The field of Health Physics is related to the field of
medical physics Medical physics deals with the application of the concepts and methods of physics to the prevention, diagnosis and treatment of human diseases with a specific goal of improving human health and well-being. Since 2008, medical physics has been incl ...
and they are similar to each other in that practitioners rely on much of the same fundamental science (i.e., radiation physics, biology, etc.) in both fields. Health physicists, however, focus on the evaluation and protection of human health from radiation, whereas medical health physicists and medical physicists support the use of radiation and other physics-based technologies by medical practitioners for the diagnosis and treatment of disease.


Radiation protection instruments

Practical ionising radiation measurement is essential for health physics. It enables the evaluation of protection measures, and the assessment of the radiation dose likely, or actually received by individuals. The provision of such instruments is normally controlled by law. In the UK it is the Ionising Radiation Regulations 1999. The measuring instruments for radiation protection are both "installed" (in a fixed position) and portable (hand-held or transportable).


Installed instruments

Installed instruments are fixed in positions which are known to be important in assessing the general radiation hazard in an area. Examples are installed "area" radiation monitors, Gamma interlock monitors, personnel exit monitors, and airborne contamination monitors. The area monitor will measure the ambient radiation, usually X-Ray, Gamma or neutrons; these are radiations which can have significant radiation levels over a range in excess of tens of metres from their source, and thereby cover a wide area. Interlock monitors are used in applications to prevent inadvertent exposure of workers to an excess dose by preventing personnel access to an area when a high radiation level is present. Airborne contamination monitors measure the concentration of radioactive particles in the atmosphere to guard against radioactive particles being deposited in the lungs of personnel. Personnel exit monitors are used to monitor workers who are exiting a "contamination controlled" or potentially contaminated area. These can be in the form of hand monitors, clothing frisk probes, or whole body monitors. These monitor the surface of the workers body and clothing to check if any
radioactive contamination Radioactive contamination, also called radiological pollution, is the deposition of, or presence of radioactive substances on surfaces or within solids, liquids, or gases (including the human body), where their presence is unintended or undesirab ...
has been deposited. These generally measure alpha or beta or gamma, or combinations of these. The UK National Physical Laboratory has published a good practice guide through its Ionising Radiation Metrology Forum concerning the provision of such equipment and the methodology of calculating the alarm levels to be used.


Portable instruments

Portable instruments are hand-held or transportable. The hand-held instrument is generally used as a
survey meter Survey meters in radiation protection are hand-held ionising radiation measurement instruments used to check such as personnel, equipment and the environment for radioactive contamination and ambient radiation. The hand-held survey meter is proba ...
to check an object or person in detail, or assess an area where no installed instrumentation exists. They can also be used for personnel exit monitoring or personnel contamination checks in the field. These generally measure alpha, beta or gamma, or combinations of these. Transportable instruments are generally instruments that would have been permanently installed, but are temporarily placed in an area to provide continuous monitoring where it is likely there will be a hazard. Such instruments are often installed on trolleys to allow easy deployment, and are associated with temporary operational situations.


Instrument types

A number of commonly used detection instruments are listed below. *
ionization chamber The ionization chamber is the simplest type of gas-filled radiation detector, and is widely used for the detection and measurement of certain types of ionizing radiation, including X-rays, gamma rays, and beta particles. Conventionally, the term ...
s *
proportional counter The proportional counter is a type of gaseous ionization detector device used to measure particles of ionizing radiation. The key feature is its ability to measure the energy of incident radiation, by producing a detector output pulse that is ''prop ...
s *
Geiger counter A Geiger counter (also known as a Geiger–Müller counter) is an electronic instrument used for detecting and measuring ionizing radiation. It is widely used in applications such as radiation dosimetry, radiological protection, experimental ph ...
s *
Semiconductor detector A semiconductor detector in ionizing radiation detection physics is a device that uses a semiconductor (usually silicon or germanium) to measure the effect of incident charged particles or photons. Semiconductor detectors find broad applicati ...
s * Scintillation detectors The links should be followed for a fuller description of each.


Guidance on use

In the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...
the HSE has issued a user guidance note on selecting the correct radiation measurement instrument for the application concerne

. This covers all ionising radiation instrument technologies, and is a useful comparative guide.


Radiation dosimeters

Dosimeter A radiation dosimeter is a device that measures dose uptake of external ionizing radiation. It is worn by the person being monitored when used as a personal dosimeter, and is a record of the radiation dose received. Modern electronic personal dos ...
s are devices worn by the user which measure the
radiation dose Ionizing radiation (or ionising 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 ...
that the user is receiving. Common types of wearable dosimeters for ionizing radiation include: *
Quartz fiber dosimeter A quartz fiber dosimeter, sometimes called a self indicating pocket dosimeter (SIPD) or self reading pocket dosimeter (SRPD) or quartz fibre electrometer (QFE), is a type of radiation dosimeter, a pen-like device that measures the cumulativ ...
*
Film badge dosimeter A film badge dosimeter or film badge is a personal dosimeter used for monitoring cumulative radiation dose due to ionizing radiation. The badge consists of two parts: photographic film and a holder. The film emulsion is black and white photograp ...
*
Thermoluminescent dosimeter A thermoluminescent dosimeter, or TLD, is a type of radiation dosimeter, consisting of a piece of a thermoluminescent crystalline material inside a radiolucent package. When a thermoluminescent crystal is exposed to ionizing radiation, it abso ...
* Solid state (
MOSFET The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which d ...
or silicon diode) dosimeter


Units of measure


Absorbed dose

The fundamental units do not take into account the amount of damage done to matter (especially living tissue) by ionizing radiation. This is more closely related to the amount of
energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat a ...
deposited rather than the charge. This is called the
absorbed dose Absorbed dose is a dose quantity which is the measure of the energy deposited in matter by ionizing radiation per unit mass. Absorbed dose is used in the calculation of dose uptake in living tissue in both radiation protection (reduction of harmf ...
. *The
gray Grey (more common in British English) or gray (more common in American English) is an intermediate color between black and white. It is a neutral or achromatic color, meaning literally that it is "without color", because it can be composed o ...
(Gy), with units J/kg, is the SI unit of absorbed dose, which represents the amount of radiation required to deposit 1
joule The joule ( , ; symbol: J) is the unit of energy in the International System of Units (SI). It is equal to the amount of work done when a force of 1 newton displaces a mass through a distance of 1 metre in the direction of the force applied ...
of energy in 1 kilogram of any kind of matter. *The
rad RAD or Rad may refer to: People * Robert Anthony Rad Dougall (born 1951), South African former racing driver * Rad Hourani, Canadian fashion designer and artist * Nickname of Leonardus Rad Kortenhorst (1886–1963), Dutch politician * Radley R ...
(radiation absorbed dose), is the corresponding traditional unit, which is 0.01 J deposited per kg. 100 rad = 1 Gy.


Equivalent dose

Equal doses of different types or energies of radiation cause different amounts of damage to living tissue. For example, 1 Gy of
alpha radiation Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or 'decays' into a different atomic nucleus, with a mass number that is reduced by four and an atom ...
causes about 20 times as much damage as 1 Gy of
X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10  picometers to 10  nanometers, corresponding to frequencies in the range 30&nb ...
s. Therefore, the
equivalent dose Equivalent dose is a dose quantity '' H '' representing the stochastic health effects of low levels of ionizing radiation on the human body which represents the probability of radiation-induced cancer and genetic damage. It is derived from the ...
was defined to give an approximate measure of the biological effect of radiation. It is calculated by multiplying the absorbed dose by a weighting factor WR, which is different for each type of radiation (see table at Relative biological effectiveness#Standardization). This weighting factor is also called the Q (quality factor), or RBE (
relative biological effectiveness In radiobiology, the relative biological effectiveness (often abbreviated as RBE) is the ratio of biological effectiveness of one type of ionizing radiation relative to another, given the same absorbed dose, amount of absorbed energy. The RBE i ...
of the radiation). *The
sievert The sievert (symbol: SvNot be confused with the sverdrup or the svedberg, two non-SI units that sometimes use the same symbol.) is a unit in the International System of Units (SI) intended to represent the stochastic health risk of ionizing radi ...
(Sv) is the SI unit of equivalent dose. Although it has the same units as the gray, J/kg, it measures something different. For a given type and dose of radiation(s) applied to a certain body part(s) of a certain organism, it measures the magnitude of an X-rays or
gamma radiation A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically s ...
dose applied to the whole body of the organism, such that the probabilities of the two scenarios to induce cancer is the same according to current statistics. *The rem (Roentgen equivalent man) is the traditional unit of equivalent dose. 1 sievert = 100 rem. Because the rem is a relatively large unit, typical equivalent dose is measured in millirem (mrem), 10−3 rem, or in microsievert (μSv), 10−6 Sv. 1 mrem = 10 μSv. *A unit sometimes used for low-level doses of radiation is the BRET ( Background Radiation Equivalent Time). This is the number of days of an average person's
background radiation Background radiation is a measure of the level of ionizing radiation present in the environment at a particular location which is not due to deliberate introduction of radiation sources. Background radiation originates from a variety of sources ...
exposure the dose is equivalent to. This unit is not standardized, and depends on the value used for the average background radiation dose. Using the 2000
UNSCEAR The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) was set up by resolution of the United Nations General Assembly in 1955. 21 states are designated to provide scientists to serve as members of the committee which ...
value (below), one BRET unit is equal to about 6.6 μSv. For comparison, the average 'background' dose of natural radiation received by a person per day, based on 2000 UNSCEAR estimate, makes BRET 6.6 μSv (660 μrem). However local exposures vary, with the yearly average in the US being around 3.6 mSv (360 mrem), and in a small area in India as high as 30 mSv (3 rem). The lethal full-body dose of radiation for a human is around 4–5 Sv (400–500 rem).


History

In 1898, The Röntgen Society (Currently the
British Institute of Radiology The British Institute of Radiology (BIR) is a radiology society and charity based in London, United Kingdom. It is the oldest institute of its kind in the world, forming on 2 April 1897. History The society can be traced back to two separate i ...
) established a committee on X-ray injuries, thus initiating the discipline of radiation protection.


The term "health physics"

According to Paul Frame:
"The term Health Physics is believed to have originated in the
Metallurgical Laboratory The Metallurgical Laboratory (or Met Lab) was a scientific laboratory at the University of Chicago that was established in February 1942 to study and use the newly discovered chemical element plutonium. It researched plutonium's chemistry and m ...
at the
University of Chicago The University of Chicago (UChicago, Chicago, U of C, or UChi) is a private research university in Chicago, Illinois. Its main campus is located in Chicago's Hyde Park neighborhood. The University of Chicago is consistently ranked among the b ...
in 1942, but the exact origin is unknown. The term was possibly coined by Robert Stone or
Arthur Compton Arthur Holly Compton (September 10, 1892 – March 15, 1962) was an American physicist who won the Nobel Prize in Physics in 1927 for his 1923 discovery of the Compton effect, which demonstrated the particle nature of electromagnetic radia ...
, since Stone was the head of the Health Division and Arthur Compton was the head of the Metallurgical Laboratory. The first task of the Health Physics Section was to design shielding for reactor CP-1 that
Enrico Fermi Enrico Fermi (; 29 September 1901 – 28 November 1954) was an Italian (later naturalized American) physicist and the creator of the world's first nuclear reactor, the Chicago Pile-1. He has been called the "architect of the nuclear age" and ...
was constructing, so the original HPs were mostly
physicists A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate caus ...
trying to solve health-related problems. The explanation given by Robert Stone was that '...the term Health Physics has been used on the Plutonium Project to define that field in which physical methods are used to determine the existence of hazards to the health of personnel.' A variation was given by Raymond Finkle, a Health Division employee during this time frame. 'The coinage at first merely denoted the physics section of the Health Division... the name also served security: '
radiation protection 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". Expos ...
' might arouse unwelcome interest; 'health physics' conveyed nothing.'"


Radiation-related quantities

The following table shows radiation quantities in SI and non-SI units. Although the United States Nuclear Regulatory Commission permits the use of the units
curie In computing, a CURIE (or ''Compact URI'') defines a generic, abbreviated syntax for expressing Uniform Resource Identifiers (URIs). It is an abbreviated URI expressed in a compact syntax, and may be found in both XML and non-XML grammars. A CURIE ...
, rad, and rem alongside SI units, the
European Union The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been des ...
European units of measurement directives As of 2009, the European Union had issued two units of measurement directives: In 1971 it issued Directive 71/354/EEC which required EU member states to standardise on the International System of Units (SI) rather than use a variety of CGS ...
required that their use for "public health ... purposes" be phased out by 31 December 1985.


See also

*
Health Physics Society The Health Physics Society (HPS) is a nonprofit scientific professional organization whose mission is excellence in the science and practice of radiation safety. It is based in the United States and the specific purposes of the society's activiti ...
* Certified Health Physicist *
Radiological Protection of Patients Patients are exposed to ionizing radiation when they undergo diagnostic examinations using x-rays or radiopharmaceuticals. Radiation emitted by radioisotopes or radiation generators is utilized in therapy for cancer or benign lesions and also in i ...
*
Radiation protection 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". Expos ...
*
Society for Radiological Protection The Society for Radiological Protection is the leading UK professional body promoting learning and skills in the field of Radiological Protection. The Society was formed in 1963, and received its Royal Charter in 2007. It has the overall objective ...
The principal UK body concerned with promoting the science and practice of radiation protection. It is the UK national affiliated body to IRPA * IRPA The International Radiation Protection Association. The International body concerned with promoting the science and practice of radiation protection.


References


External links

*Th
Health Physics Society
a scientific and professional organization whose members specialize in occupational and environmental radiation safety.

- "The confusing world of radiation dosimetry" - M.A. Boyd, 2009, U.S. Environmental Protection Agency. An account of chronological differences between USA and ICRP dosimetry systems.
Q&A: Health effects of radiation exposure
''BBC News'', 21 July 2011. {{Occupational safety and health Nuclear safety and security Medical physics Radiation health effects Health physicists