Health physics

Health physics is the applied physics of radiation protection for health and health care purposes. It is the science concerned with the recognition, evaluation, and control of health hazards to permit the safe use and application of ionizing radiation. Health physics professionals promote excellence in the science and practice of radiation protection and safety. Health physicists principally work at facilities where radionuclides or other sources of ionizing radiation (such as X-ray generators) are used or produced; these include hospitals, government laboratories, academic and research institutions, nuclear power plants, regulatory agencies, and manufacturing plants.


There are many sub-specialties in the field of health physics,[1] including

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.[2]

Medical physics

The field of Health Physics is related to the field of medical physics[3] 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.[4]

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 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.[5]

Portable instruments

Portable instruments are hand-held or transportable. The hand-held instrument is generally used as a survey meter 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.

The links should be followed for a fuller description of each.

Guidance on use

In the United Kingdom the HSE has issued a user guidance note on selecting the correct radiation measurement instrument for the application concerned [2]. This covers all ionising radiation instrument technologies, and is a useful comparative guide.

Radiation dosimeters

Dosimeters are devices worn by the user which measure the radiation dose that the user is receiving. Common types of wearable dosimeters for ionizing radiation include:

Units of measure

Dose quantities and units
External dose quantities used in radiation protection and dosimetry
SI Radiation dose units
Graphic showing relationship of SI radiation dose units

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 deposited rather than the charge. This is called the absorbed dose.

  • The gray (Gy), with units J/kg, is the SI unit of absorbed dose, which represents the amount of radiation required to deposit 1 joule of energy in 1 kilogram of any kind of matter.
  • The rad (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 causes about 20 times as much damage as 1 Gy of X-rays. Therefore, the equivalent dose 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 of the radiation).

  • The sievert (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 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 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 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),[6] and in a small area in India as high as 30 mSv (3 rem).[7][8] The lethal full-body dose of radiation for a human is around 4–5 Sv (400–500 rem).[9]


In 1898, The Röntgen Society (Currently the British Institute of Radiology) established a committee on X-ray injuries, thus initiating the discipline of radiation protection.[10]

The term "health physics"

According to Paul Frame:[11]

"The term Health Physics is believed to have originated in the Metallurgical Laboratory at the University of Chicago in 1942, but the exact origin is unknown. The term was possibly coined by Robert Stone or Arthur Compton, 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 was constructing, so the original HPs were mostly physicists 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' might arouse unwelcome interest; 'health physics' conveyed nothing.'"

Radiation-related quantities

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

Ionising radiation related quantities
Quantity Unit Symbol Derivation Year SI equivalence
Activity (A) curie Ci 3.7 × 1010 s−1 1953 3.7×1010 Bq
becquerel Bq s−1 1974 SI unit
rutherford Rd 106 s−1 1946 1,000,000 Bq
Exposure (X) röntgen R esu / 0.001293 g of air 1928 2.58 × 10−4 C/kg
Absorbed dose (D) erg erg⋅g−1 1950 1.0 × 10−4 Gy
rad rad 100 erg⋅g−1 1953 0.010 Gy
gray Gy J⋅kg−1 1974 SI unit
Dose equivalent (H) röntgen equivalent man rem 100 erg⋅g−1 1971 0.010 Sv
sievert Sv J⋅kg−1 × WR 1977 SI unit

Although the United States Nuclear Regulatory Commission permits the use of the units curie, rad, and rem alongside SI units,[12] the European Union European units of measurement directives required that their use for "public health ... purposes" be phased out by 31 December 1985.[13]

See also


  1. ^ Careers in Health Physics
  2. ^ Miller, Kenneth L. (July 2005). "Operational Health Physics". Health Physics. 88 (6): 638–652. doi:10.1097/01.hp.0000138021.37701.30 – via ResearchGate.
  3. ^
  4. ^ AAPM - The Medical Physicist
  5. ^ Operational Monitoring Good Practice Guide "The Selection of Alarm Levels for Personnel Exit Monitors" Dec 2009 - National Physical Laboratory, Teddington UK [1]
  6. ^ Radioactivity in Nature <>
  7. ^ "Background Radiation: Natural versus Man-Made" Washington Stet Department of Health
  8. ^ "Monazite sand does not cause excess cancer incidence ", The Hindu
  9. ^ "Lethal dose", NRC Glossary (August 2, 2010)
  10. ^ Mould R. A Century of X-rays and Radioactivity in Medicine. Bristol: IOP Publishing, 1993
  11. ^ Origin of "health physics" Archived 2007-09-27 at the Wayback Machine
  12. ^ 10 CFR 20.1004. US Nuclear Regulatory Commission. 2009.
  13. ^ The Council of the European Communities (1979-12-21). "Council Directive 80/181/EEC of 20 December 1979 on the approximation of the laws of the Member States relating to Unit of measurement and on the repeal of Directive 71/354/EEC". Retrieved 19 May 2012.

External links

  • The Health Physics Society, a scientific and professional organization whose members specialize in occupational and environmental radiation safety.
  • [3] - "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.
American Academy of Health Physics

The American Academy of Health Physics (AAHP) is a non-profit organization based in McLean, VA which serves to advance the profession of health physics through networking opportunities for members, certification of health physicists, and advisement to professionals to increase the application of health physics. The Academy has selective criteria for membership in the organization.

Australian Atomic Energy Commission

The Australian Atomic Energy Commission (AAEC) was a statutory body of the Australian government.

It was established in 1952, replacing the Atomic Energy Policy Committee. In 1981 parts of the Commission were split off to become part of CSIRO, the remainder continuing until 1987, when it was replaced by the Australian Nuclear Science and Technology Organisation (ANSTO). The Commission head office was in the heritage-listed house Cliffbrook in Coogee, Sydney, New South Wales, while its main facilities were at the Atomic Energy Research Establishment at Lucas Heights, to the south of Sydney, established in 1958.

Highlights of the Commission's history included:

Major roles in the establishment of the IAEA and the system of international safeguards.

The construction of the HIFAR and MOATA research reactors at Lucas Heights.

The selection of the preferred tender for the construction of the proposed Jervis Bay Nuclear Power Plant.

The Ranger Uranium Mine joint venture.Other significant facilities constructed by the Commission at Lucas Heights included a 3MeV Van de Graaff particle accelerator, installed in 1964 to provide proton beams and now upgraded to become ANTARES, a smaller 1.3MeV betatron, and radioisotope production and remote handling facilities associated with HIFAR reactor.

Significant research work included:


Neutron diffraction.

Sodium coolant systems.

Use of beryllium as a neutron moderator.

Movement of spheres in a closed-packed lattice.

Gas centrifuge development.

Health physics.

Environmental science.

Development of synroc.

Molecular laser isotope separation and support of laser development for atomic vapor laser isotope separation.

C. Maurice Patterson

C. Maurice Patterson also known as Pat or Maurice Patterson (24 December 1913 – 21 May 1989) a pioneer in the establishment of health physics as a profession and part of a select group of engineers and scientists that made this happen.

Certified Health Physicist

Certified Health Physicist is an official title granted by the American Board of Health Physics, the certification board for health physicists in the United States. A Certified Health Physicist is designated by the letters CHP or DABHP (Diplomate of the American Board of Health Physics) after his or her name.

A certification by the ABHP is not a license to practice and does not confer any legal qualification to practice health physics. However, the certification is well respected and indicates a high level of achievement by those who obtain it.

Certified Health Physicists are plenary or emeritus members of the American Academy of Health Physics (AAHP). In 2015, the AAHP web site listed over 1500 plenary and emeritus members.


A radiation dosimeter is a device that measures exposure to ionizing radiation. It is normally worn by the person being monitored as it is a personal dosimeter, and is a record of the radiation dose received. Older dosimeters, such as a film badge, require processing after use to reveal the cumulative dose received. Modern electronic personal dosimeters can give a continuous readout of cumulative dose and current dose rate, and can warn the person wearing it when a specified dose rate or a cumulative dose is exceeded.


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 or inhaled radioactive substances, or externally due to irradiation by sources of radiation.

Internal dosimetry assessment relies on a variety of monitoring, bio-assay or radiation imaging techniques, whilst external dosimetry is based on measurements with a dosimeter, or inferred from measurements made by other radiological protection instruments.

Dosimetry is used extensively for radiation protection and is routinely applied to monitor occupational radiation workers, where irradiation is expected, or where radiation is unexpected, such as in the aftermath of the Three Mile Island, Chernobyl or Fukushima radiological release incidents. The public dose take-up is measured and calculated from a variety of indicators such as ambient measurements of gamma radiation, radioactive particulate monitoring, and the measurement of levels of radioactive contamination.

Other significant areas are medical dosimetry, where the required treatment absorbed dose and any collateral absorbed dose is monitored, and in environmental dosimetry, such as radon monitoring in buildings.

Elda Emma Anderson

Elda Emma Anderson (October 5, 1899 – April 17, 1961) was an American physicist and health researcher. During World War II, she worked on the Manhattan Project at Princeton University and the Los Alamos Laboratory, where she prepared the first sample of pure uranium-235 at the laboratory. A graduate of the University of Wisconsin, she became professor of physics at Milwaukee-Downer College in 1929. After the war, she became interested in health physics. She worked in the Health Physics Division of the Oak Ridge National Laboratory, and established the professional certification agency known as the American Board of Health Physics.

Frederick P. Cowan

Frederick P. Cowan, Ph.D, was a health physicist and head of the Instrumentation and Health Physics Department at Brookhaven National Laboratory.

F. P. Cowan grew up in the Boston, Massachusetts area. He attended Bowdoin College, then went on to Harvard University to complete his Ph.D.. After Harvard, Cowan went on to Rensselaer Polytechnic Institute to teach.

During World War II Dr. Cowan worked in radar countermeasures. This was followed by a stint at the Chrysler Corporation and finally he ended up at Brookhaven National Laboratory to lead the Health Physics Division.

Health Physics (journal)

Health Physics is a monthly peer-reviewed medical journal published by Lippincott Williams & Wilkins. Its scope includes research into radiation safety and healthcare applications. It is the official journal of the Health Physics Society. It was established in 1958 and it is edited by Brant Ulsh.

Operational Radiation Safety is published as a quarterly supplement to Health Physics.

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 activities include encouraging research in radiation science, developing standards, and disseminating radiation safety information. Society members are involved in understanding, evaluating, and controlling potential risks from radiation relative to the benefits.

The Society was formed in 1955, with an organizational meeting in June, 1955 at Ohio State University Columbus, Ohio. As of 2013, the membership consists of approximately 5,500 scientists, physicians, engineers, and other professionals. The headquarters are in McLean, VA. The society is an affiliate of the American Institute of Physics.

Herbert Mermagen

Herbert Mermagen noted x-ray pioneer and medical physicist was born on 19 April 1907 and died at the age of 73 in Rochester, New York on January 1981.

IIT Physics Department

The Department at the Illinois Institute of Technology has over 30 faculty members. It offers undergraduate academic programs including B.S. in physics, applied physics, and physics education and graduate programs in physics and health physics. Many notable physicists have both taught and studied at IIT including Nobel Prize for Physics laureates Leon M. Lederman and Jack Steinberger.

James Newell Stannard

James Newell Stannard (2 January 1910 – 19 September 2005), radiobiologist, Pharmacologist and Physiologist at the National Institutes of Health.

John C. Taschner

John Carroll Taschner (born 1929/1930) was a radiation biophysicist. He was a member of the technical staff in the Environment, Safety and Health Division of Los Alamos National Laboratory where he was involved in radiological transportation accident exercise planning.

Prior to coming to Los Alamos, Taschner was Deputy Director of the US Navy's Radiological Controls Program Office in Washington, DC, and has held numerous key health physics management positions with the US Navy, where he retired as a GM-15, he served as a part of the team responding to the accident at Three Mile Island while a staff member with the Bureau of Radiological Health, and served as an Air Force Health Physicist, where he retired as a lieutenant colonel. Since the 1970s, Taschner has served on several radiation protection standards committees. Since 1992, Taschner has been the Vice Chairman of the American National Standards Institute's N43 Committee, which writes radiation safety standards for non-medical radiation producing equipment.

As of March 2007, Taschner resided in Albuquerque, New Mexico. On September 1, 2017, Taschner died at the age of 87.

Karl Z. Morgan

Karl Ziegler Morgan (September 27, 1907 – June 8, 1999), was an American physicist who was one of the founders of the field of radiation health physics. Late in life, after a long career in the Manhattan Project and at Oak Ridge National Laboratory, he became a critic of nuclear power and nuclear weapons production.

Born in Enochville, North Carolina, Karl Morgan attended Lenoir-Rhyne College (now University) as a freshman and sophomore and then transferred to the University of North Carolina, where he graduated with bachelor's and master's degrees in physics and mathematics. He continued graduate study in physics at Duke University, where he received a PhD degree in 1934 for research into cosmic radiation. He began an academic career as a faculty member at Lenoir Rhyne College, but in 1943 was recruited to work in the secret project to develop an atomic bomb.Initially at the University of Chicago Metallurgical Laboratory and later in Oak Ridge, Morgan joined a small group of physicists who were interested in the health effects of radiation.Morgan became director of health physics at Oak Ridge National Laboratory (ORNL), serving from the late 1940s until his retirement in 1972. In 1955 he became the first president of the Health Physics Society, and was editor of the journal Health Physics from 1955 to 1977. After his retirement from ORNL, he joined the faculty of Georgia Institute of Technology as professor of nuclear energy in the school of nuclear engineering, retiring from that position in 1982, when he became a consulting professor at Appalachian State University.After decades as a "pillar of the nuclear establishment", Morgan had a "change of heart" about nuclear weapons production and nuclear power. He began to offer court testimony which was friendly to people who said they had been harmed by nuclear weapons and the nuclear power industry. In October 1982, he testified in a lawsuit brought by nearly 1,200 people who accused the government of negligence in atomic weapons testing at the Nevada Test Site in the 1950s, which they said had caused leukemia and other cancers. Morgan, then 75 years old, testified that radiation protection measures in the tests were substandard.Morgan also testified on behalf of Navajo uranium miners and their survivors, saying government officials had known about mine radiation dangers but had not protected the miners. He also testified in the case of Karen Silkwood against Kerr-McGee.Morgan's autobiography, The Angry Genie: One Man's Walk Through the Nuclear Age was published in 1999 by the University of Oklahoma Press. He died in Oak Ridge, Tennessee, on June 8, 1999, apparently from a ruptured aortic aneurysm.PhD John Cameron, the developer of a more accurate dosimeter in the 1960s, was however a major critic of Morgan's error prone autobiography that was otherwise interesting for its historical detailing of the Manhattan Project's health physics evolution. Cameron goes chapter by chapter of Morgan's generally "flawed" anti-nuclear stance, writing a critique in the year 2000 on Morgan's exaggeration of the small risks from exposure.

Medical physics

Medical physics (also called biomedical physics, medical biophysics, applied physics in medicine, physics applications in medical science, radiological physics or hospital radio-physics) is, in general, the application of physics concepts, theories, and methods to medicine or healthcare. Medical physics departments may be found in hospitals or universities.

In the case of hospital work, the term medical physicist is the title of a specific healthcare profession, usually working within a hospital. Medical physicists are often found in the following healthcare specialties: diagnostic and interventional radiology (also known as medical imaging), nuclear medicine, radiation protection and radiation oncology.

University departments are of two types. The first type are mainly concerned with preparing students for a career as a hospital medical physicist and research focuses on improving the practice of the profession. A second type (increasingly called 'biomedical physics') has a much wider scope and may include research in any applications of physics to medicine from the study of biomolecular structure to microscopy and nanomedicine. For example, physicist Richard Feynman theorized about the future of nanomedicine. He wrote about the idea of a medical use for biological machines (see nanobiotechnology). Feynman and Albert Hibbs suggested that certain repair machines might one day be reduced in size to the point that it would be possible to (as Feynman put it) "swallow the doctor". The idea was discussed in Feynman's 1959 essay There's Plenty of Room at the Bottom.

Walter Dunhan Claus

Walter Dunham Claus (6 March 1903 – 12 May 1995) was a pioneer in the field of radiation biology, especially in helping to establish the field in medical physics curriculum.

Whole-body counting

In health physics, whole-body counting refers to the measurement of radioactivity within the human body. The technique is primarily applicable to radioactive material that emits gamma rays. Alpha particle decays can also be detected indirectly by their coincident gamma radiation. In certain circumstances, beta emitters can be measured, but with degraded sensitivity. The instrument used is normally referred to as a whole body counter.

This must not be confused with a "whole body monitor" which used for personnel exit monitoring, which is the term used in radiation protection for checking for external contamination of a whole body of a person leaving a radioactive contamination controlled area.

William Taylor Ham

William Taylor Ham was an American health physicist and founding member of the Health Physics Society.

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