Control & Prevention
This section provides information on controlling ionizing radiation hazards and preventing dose.
This section does not address the range of non-radiological safety and health hazards for workers in occupational settings with ionizing radiation hazards. For example, these non-radiological safety and health hazards may include electrical hazards from associated electrical equipment and extension cords, shift work and long work hours, worker ingress (entry) into and egress (exit) from shielded enclosures (e.g., at fixed industrial radiography facilities), and laser hazards if lasers are incorporated into radiation-emitting equipment (e.g., lasers are sometimes used to align an external beam with the target).
Radiation Protection Program
Developing and implementing a radiation protection program is a best practice for protecting workers from ionizing radiation. A radiation protection program is usually managed by a qualified expert (e.g., health physicist), who is often called a radiation safety officer (RSO).
Another best practice is designating a radiation safety committee, which includes the RSO, a management representative, and workers who work with radiation-producing equipment, radiation sources, or radioactive materials (or who are otherwise at risk of exposure on the job).
A radiation protection program should include, at a minimum:
Federal and state regulatory agencies require some types of radiation-producing equipment or radiation sources to be registered or licensed by manufacturers and/or users.
Registration or licensing requirements apply to many specific radiation sources and occupational settings (e.g., medicine, manufacturing and construction). Equipment registration or licensing helps ensure that radiation sources emitting ionizing radiation do not pose radiation hazards for workers (and the public).
Some radiation sources, such as most X-ray equipment and some accelerators, must be registered with a state agency (e.g., state radiation control agency, state health department) or local agency (e.g., health department) and different registration requirements may apply, depending on the agency. Registrants may be required to perform equipment tests or allow state or local inspectors to perform equipment tests. In some states, equipment registration requirements may include regular inspections, shielding, or signage.
- Qualified staff (e.g., RSO, health physicist) to provide oversight and responsibility for radiation protection policies and procedures.
- ALARA stands for As Low As Reasonably Achievable (ALARA). It is a guiding principle in radiation protection used to eliminate radiation doses that have no direct benefit.
- A dosimetry program in which personal exposure monitoring is conducted, as required by federal or state regulations, for external dose and, as needed, for internal dose.
- Surveys and area monitoring to document radiation levels, contamination with radioactive materials, and potential worker exposures.
- Radiological controls, including entry and exit controls, receiving, inventory control, storage, and disposal.
- Worker training on radiation protection, including health effects associated with ionizing radiation dose, and radiation protection procedures and controls to minimize dose and prevent contamination.
- Emergency procedures to identify and respond to radiological emergency situations. (OSHA's Radiation Emergency Preparedness and Response page also provides information about this topic.)
- Recordkeeping and reporting programs to maintain all records and provide dosimetry reports and notifications, as required by federal or state regulations.
- Internal audit procedures to annually audit all aspects of the radiation protection program.
NRC (U.S. Nuclear Regulatory Commission) regulations for radiation protection programs (10 CFR 20.1101) or state regulations for such programs apply to some specific radiation sources and occupational settings.
OSHA's Ionizing Radiation standards apply where they are not pre-empted, and, in those cases, require certain elements of a radiation protection program.
A key concept underlying radiation protection programs is keeping each worker's occupational radiation dose As Low As Reasonably Achievable (ALARA). An ALARA program usually involves maintaining radiation doses to workers as far below the federal and state regulatory occupational dose limits as is reasonably achievable taking into consideration the state of technology, economics, and social factors.
ALARA in the workplace minimizes radiation doses and releases of radioactive materials using all reasonable methods available. ALARA procedures are typically developed for working with specific radiation sources, for example, diagnostic radiography (e.g., medical X-rays), fluoroscopy in medicine, or industrial radiography.
Time, Distance, and Shielding
When it comes to ionizing radiation, remember time, distance, and shielding:
- Minimize time spent in areas with elevated radiation levels. Minimizing the exposure time reduces a worker's dose from the radiation source.
- Maximize distance from source(s) of radiation. A worker's radiation dose decreases as the worker's distance from the source increases. For gamma rays and X-rays, the radiation intensity is inversely proportional to the square of the distance from the source (i.e., the inverse square law). This means increasing the distance by a factor of 2 decreases the dose rate by a factor of 4.
- Use shielding for radiation sources (i.e., placing an appropriate shield between source(s) of radiation and workers). Inserting the proper shielding (e.g., lead, concrete, or special plastic shields depending on the type of radiation) between a worker and a radiation source will greatly reduce or eliminate the dose received by the worker.
Time, Distance, and Shielding for Radiation Protection
Employers should use engineering controls to maintain occupational radiation doses (and doses to the public) ALARA is applied after determining that radiation dose will not exceed applicable regulatory dose limits. To the greatest extent possible, administrative controls should not be used as substitutes for engineering controls. Engineering controls, in some cases, may be incorporated into facility design.
Some examples of engineering controls are discussed below, including shielding and interlock systems. In addition, radioactive material containment is sometimes incorporated into shielding, such as in gamma cameras used for nuclear medicine or industrial radiography devices containing a radioactive source.
The need for shielding depends on the type and activity of the radiation source. Uses in adjacent areas, including the areas above and below the room or facility, should also be considered.
For shielding of rooms containing medical X-ray equipment or rooms with other medical X-ray imaging devices, the National Council on Radiation Protection and Measurements (NCRP) recommends that the shielding design goal be 500 mrad (5 mGy) in a year to any person in controlled (restricted) areas. For uncontrolled (unrestricted) areas, NCRP recommends that the shielding design goal be a maximum of 100 mrad (1 mGy) to any person in a year (~0.02 mGy per week).1
Shielding design requires a qualified expert (e.g., health physicist). Before using any new or remodeled rooms or facilities or any new or relocated X-ray equipment, a qualified expert should conduct an area survey and evaluate shielding to verify radiation protection behind shielding materials. Before performing any room modifications or if any changes occur to a facility that may change radiation exposure levels (e.g., new equipment, increased workload, altered use of adjacent spaces), a qualified expert should review the shielding design.
In general, the floors, walls, ceilings, and doors should be built with materials that provide shielding for the desired radiation protection. Lead shielding may be installed, if appropriate, including leaded glass, sheet lead (e.g., built into walls), pre-fabricated lead-lined drywall or lead-lined plywood, pre-fabricated lead-lined doors and door frames, lead plates, and lead bricks. Sometimes it may be sufficient to construct a wall of a suitable thickness of normal building materials (e.g., dense concrete). The shielding design may include a control booth or load/lead-equivalent drapes provided for protection of workers operating equipment or devices that emit ionizing radiation.
More information on shielding criteria is provided in the following NCRP reports:
- Report No. 151: Structural Shielding Design and Evaluation for Megavoltage X- and Gamma-Ray Radiotherapy Facilities.
- Report No. 148: Radiation Protection in Veterinary Medicine.
- Report No. 147: Structural Shielding Design for Medical X-ray Imaging Facilities.
- Report No. 145: Radiation Protection in Dentistry.
- Report No. 144: Radiation Protection for Particle Accelerator Facilities.
- Report No. 133: Radiation Protection for Procedures Performed Outside the Radiology Department.
Portable or temporary shielding materials (e.g., thick steel, lead, or high-density concrete blocks) can sometimes be fabricated in the area of the inspection when conducting portable industrial radiography (e.g., using industrial radiography cameras to inspect pipe welding or concrete slabs). Where such portable or temporary shielding is not practical or adequate to protect workers (and the public), employers should ensure that operating procedures maximize distance from the portable industrial radiography equipment while it is operating.
When working with high-energy beta particles, avoid shielding with high atomic number (Z>13) materials as this can result in production of X-rays (Bremsstrahlung radiation), which are more penetrating than the original beta radiation. Beta particles should be shielded using an appropriate thickness of low atomic number (Z<14) materials such as aluminum or plastics (e.g., Plexiglas®).
A radiation safety interlock system is a device that automatically shuts off or reduces the radiation emission rate from radiation-producing equipment (gamma or X-ray equipment or accelerator). The purpose of a radiation safety interlock system is to prevent worker exposure and injury from high radiation levels. Typically, interlock systems are required by state or federal (e.g., NRC, FDA (U.S. Food and Drug Administration)) regulations for equipment registration/licensing and performance/safety standards.
In most applications, interlock systems to stop X-ray or particle beam production can be activated by the opening of a worker access point (e.g., door) into a controlled (restricted) area. Interlock safety systems may also include door pressure sensors or motion detectors.
For applications involving high-energy radiation sources, a system with interlock keys can control access or prevent entry into a radiation treatment room or during accelerator operations. Because removal of interlock keys will stop X-ray or particle beam production, such interlock systems rely on constant monitoring of all interlock keys and appropriate worker training for controlled access to high radiation areas.
In addition to worker safety, patient safety is a concern for interlock systems for medical X-ray equipment or accelerators. NCRP recommends that interlock systems that stop X-ray or particle beam production should not be placed on doors to any diagnostic or interventional X-ray room to prevent inadvertent patient injury or the need to repeat exposures to patients.1 As an alternative, appropriate access control measures could be implemented at such facilities for both worker and patient radiation safety.
When used, interlock systems should be inspected regularly by a qualified expert.
Administrative controls generally supplement engineering controls. Examples of administrative controls include signage, warning systems, and written operating procedures to prevent, reduce, or eliminate radiation exposure. Operating procedures typically include both normal operating procedures and emergency procedures (i.e., those for spills, leaks, and emergency evacuation).
OSHA's Ionizing Radiation standards specify certain types of administrative controls in worksites where they apply.
The bullets below provide more details about specific posting provisions for rooms in workplaces covered by the Ionizing Radiation standard for general industry (29 CFR 1910.1096)—including on vessels and on shore in shipyard employment, marine terminals, and longshoring. Employers may also be required to comply with provisions of other OSHA standards, including the Ionizing Radiation standards for construction (29 CFR 1926.53), which incorporates by reference the same types of controls described in the general industry standard, and shipyard employment (29 CFR 1915.57), which applies the NRC's Standards for Protection Against Radiation (10 CFR part 20) to activities involving the use of and exposure to sources of ionizing radiation on conventionally and nuclear-powered vessels.
- Each radiation area must be conspicuously posted with a sign or signs with the radiation caution symbol and the words: Caution Radiation Area (29 CFR 1910.1096(e)(2)). This sign is used to indicate areas where radiation exists at such levels that a major portion of the body could receive a dose in excess of 5 mrem per hour, or in any 5 consecutive days a dose in excess of 100 mrem.
- Each high radiation area must be conspicuously posted with a sign or signs with the radiation caution symbol and the words: Caution High Radiation Area (29 CFR 1910.1096(e)(3)). This sign is used to indicate areas where radiation exists at such levels that a major portion of the body could receive a dose in excess of 100 mrem per hour.
- Each airborne radioactivity area must be conspicuously posted with a sign or signs with the radiation caution symbol and the words: Caution Airborne Radioactivity Area (29 CFR 1910.1096(e)(4)).
- A sign with the wording Caution Radioactive Material (29 CFR 1910.1096(e)(5)) is required in each area or room in which radioactive material is used or stored, and which contains any radioactive material (other than natural uranium or thorium) in any amount exceeding 10 times the quantity of such material specified in appendix C to 10 CFR 20 (1971 version). For natural uranium or thorium, the sign is required when the amount present exceeds 100 times the quantity of such material specified in 10 CFR 20 (29 CFR 1910.1096(e)(5)(ii)).
Warning systems can be integrated into the design of radiation-producing equipment or devices and can also be used with radioactive materials. Such warning systems will set off an audible (easy to hear) alarm (e.g., to warn workers that a radiation hazard exists) or a visible (lighted) warning signal whenever ionizing radiation is being emitted.
As an example, industrial radiography equipment located in a fixed facility or room (e.g., industrial radiography room for conducting materials testing for quality control at a manufacturing facility) may include visible warning signals with colored or flashing lights or audible alarms with a distinct sound, which are located inside and outside the shielded enclosure for conducting industrial radiography. In this example, the visible alarm would activate when the radiation source is exposed or when X-rays or gamma rays are generated during industrial radiography operations. The audible alarm would sound if the door is opened to the shielded enclosure for the industrial radiography equipment. Other facilities, such as gamma irradiation facilities, also use warning systems. Warning systems should be checked regularly for proper function.
Warning systems should be checked regularly for proper function.
Personal Protective Equipment
Personal Protective Equipment (PPE) is used to prevent workers from becoming contaminated with radioactive material. It can be used to prevent skin contamination with particulate radiation (alpha and beta particles) and prevent inhalation of radioactive materials.
PPE will not protect workers from direct, external radiation exposure (e.g., standing in an X-ray field), unless the PPE contains shielding material. For example, a leaded apron will reduce X-ray doses to covered areas.
Consult a qualified expert (e.g., a health physicist) when choosing PPE and developing a PPE policy for a workplace. Consistent with the hierarchy of controls, PPE should only be used when appropriate engineering controls or administrative controls are infeasible.
Alpha particles have very low penetrating power, travel only a few centimeters in air, and will not penetrate the dead outer layer of skin. Shielding is generally not required for alpha particles because external exposure to alpha particles delivers no radiation dose. Where particulates contaminated with alpha particles are present, engineering controls (e.g. glove boxes) or respiratory protection may be required to prevent an internal exposure and dose. More information about respirators is provided below. When working with liquid sources that contain alpha particles, additional PPE, such as gloves, a lab coat, and safety glasses, may be required to prevent contamination or contact with the eyes.
High-energy beta particles can travel several meters in air and can penetrate several millimeters into the skin. For high-energy beta particles, first select adequate shielding with an appropriate thickness of low atomic number (Z<14) materials, such as specialized plastics (e.g., Plexiglas®) or aluminum. Using safety goggles as PPE can help protect workers' eyes against beta particles as well as provide splash protection for the eyes (preventing potential internal exposure). Gloves and a lab coat may be used to prevent skin contamination.
X-ray and Gamma Radiation
Gamma rays and X-rays can travel kilometers in air and can penetrate deep into the human body or pass through it entirely. Proper shielding should be in place to prevent or reduce radiation dose rates. Some PPE for worker protection from gamma and X-rays incorporates lead or other dense, high atomic number (high Z) materials. As described under the ALARA section, it is also important to consider the inverse square law for gamma and X-rays when choosing appropriate PPE.
Examples of commonly used PPE for radiation protection from X-rays and gamma rays include:
- Lead aprons or vests. Wearing lead aprons can reduce a worker's radiation dose. Customized lead (or lead equivalent) aprons are available for a wide range of occupational settings and job tasks. A lead apron is only effective when it is worn properly and provides adequate protection necessary from the radiation source. Employers should ensure that visual and tactile inspections of lead aprons are performed regularly for signs of damage (e.g., wear and tear, holes, or cracks) or prior misuse (e.g., sagging or deformed lead arising from a lead apron being folded or otherwise stored improperly). Potential defects in lead aprons can also be inspected radiographically. Workers in high-dose fluoroscopy settings may be asked to wear two dosimeters for additional monitoring. Oftentimes one dosimeter is worn on the outside of the lead apron at the collar (unshielded) and one on the inside at the waist (shielded). Some states allow dose weighting for diagnostic and interventional radiology procedures (see your State regulations and Webster 1989).
- Lead thyroid collar. A lead thyroid collar offers additional radiation protection for the thyroid (a gland located in front of the neck) that is particularly sensitive to radiation.
- Lead gloves. Lead-lined gloves offer some protection for workers from radiation exposure to the hands and should be used for some X-ray equipment if hands must be placed in the direct X-ray field. During fluoroscopy, however, wearing lead gloves when the worker's hand is in the primary beam (sometimes unavoidable for clinical reasons) can cause the equipment to automatically increase radiation production rate that will increase dose to the worker's hands, to the patient, and other workers in the room.
- Safety goggles. Leaded eye wear (lead glasses or radiation glasses) or opaque safety goggles can protect a worker's eyes from radiation exposure.
Although respirators are typically the last choice for controlling internal exposure to airborne radionuclides, reducing internal radiation dose, employers should ensure that workers use properly selected respirators and wear those respirators when required. Respirators should only be used by workers qualified to wear them. See 29 CFR 1910.134 for requirements for using respiratory protection.
Radiation Measurement and Sampling
OSHA's Ionizing Radiation standards often require employers to monitor radiation exposure, including by measuring radiation levels in the work environment and tracking the radiation doses that workers receive. Several types of area monitoring, personal dosimetry, and sample analysis equipment and techniques may be involved in effective radiation measurement efforts. This section discusses
Radiation survey instruments can be used to evaluate exposure rates, dose rates, and the quantities (activity) of radioactive materials and contamination. The survey instrument must be appropriate for the type and energy of the radiation being measured. A qualified expert should provide oversight for selecting appropriate area survey instruments, using survey instruments properly when conducting area surveys or monitoring, interpreting survey results, and ensuring accurate calibration and maintenance. Under OSHA's Ionizing Radiation standards, employer responsibilities typically include surveying radiation hazards to comply with the standard (29 CFR 1910.1096(d)(1), 29 CFR 1926.53). This is true for most operations in general industry, construction, shipyards, marine terminals, and longshoring.
|Handheld Survey Meters|
|Handheld survey meters are the most widely used and recognizable instruments for measuring ionizing radiation. These meters are typically used to measure radiation exposure rate, dose rate, or evaluate levels of radiological contamination. These types of instruments include ionization detectors, Geiger-Muller (GM) detectors, proportional detectors, or scintillation detectors. Each type of instrument has unique characteristics, and a radiation professional should be consulted to select a handheld survey instrument best suited to the application.|
|Radioisotope Identification Devices|
|Radioisotope Identification Devices (RIID) are hand held radiation instruments designed to identify the radioactive isotopes in a radiation source. A RIID is often a small handheld device designed to be easy to operate. These instruments use a scintillation detector in order to evaluate gamma energies emitted by a radioactive source and comparing the measured gamma spectrum to libraries of characteristic gamma spectra.|
|Personal Radiation Detectors|
|Personal Radiation Detectors (PRD) are small electronic devices designed to alert the wearer to the presence of radiation. These devices are often used to monitor for illicit radioactive materials. A type of PRD, a Spectroscopic Personal Radiation Detectors (SPRD), can also measure the gamma spectrum of the radiation source, which can be used to identify the radioisotopes present.|
OSHA’s Ionizing Radiation standard requires employers to conduct dose monitoring when a worker who enters a restricted area receives or is likely to receive a dose in any calendar quarter in excess of 25% of the applicable occupational limit (or 5% for workers under age 18) and for each worker who enters a high radiation area (1910.1096(d)(2) and 1910.1096(d)(3), 29 CFR 1926.53). See the Standards page for information about OSHA’s Ionizing Radiation Standard. An employer’s radiation protection program may require more stringent personal exposure monitoring for workers who enter restricted or high radiation areas, or use equipment or conduct job tasks that produce high levels of radiation (e.g., fluoroscopically-guided heart (cardiac) catheterizations, other fluoroscopically-guided procedures, radiography, industrial radiography).
Radiation dosimeters are devise used to measure the amount of external radiation dose received by an individual. Dosimeters are typically assigned to an individual to record only their radiation dose. Badge type dosimeters include thermoluminescent dosimeters (TLD), optically stimulated luminescent dosimeters (OSL), and film badges. These types of dosimeters are typically worn for a specified period, most commonly monthly or quarterly, and are then sent to a commercial laboratory for processing.
Electronic person dosimeters (EPD) can also be used to monitor an individual’s radiation dose. These devices can provide a continuous readout of the wearer’s radiation dose, dose rate, and can be set to alarm at user defined dose thresholds and dose rates.
Pocket ion chambers (PIC) can also be used to provide a real time measurement of the wearer’s cumulative radiation dose. A PIC can be read by the wearer by looking through an eyepiece at the end of the device and viewing the deflection of the quartz fiber inside. Use of these devices is now very limited having largely been replaced with the use of EPDs.
Radiological Sampling and Analysis
Sampling and analytical methods and equipment allow radiation safety professionals to identify areas with radioactivity, including where radioactive materials have contaminated environmental surfaces and other objects as well as environments that have radioactive materials in the air. Radiation safety professionals also use such methods and equipment to quantify how much radiation is present in order to determine how best to protect workers. This section discusses several sampling methods.
Radiological contamination sampling is used to evaluate the presence of unwanted radioactive materials, also known as contamination, deposited in an uncontrolled manner on or in objects and on surfaces. Radiological contamination is often referred to as fixed or removable. Fixed contamination is radioactive materials that are not easily removed from the object or surface. Removable contamination is radioactive material that is easily removed from the object or surface. Adding the amount of fixed and removable contamination provides the amount of total contamination.
The amount of total contamination can be measured using survey instrument equipped with an appropriate detector, such as a GM detector or a scintillation detector. Removable contamination is measured by wiping a known surface area, often 100 cm2, then measuring the amount of radioactive material on the wipe sampler using an appropriate instrument such as scaler / counter equipped with a proportional or scintillation detector. The Department of Energy provides guidance for surface contamination values in 10 CFR 835 Appendix D. Contamination sampling, analysis, and interpretation of results should be conducted under the direction of a radiation safety professional.
|Radiological air sampling is used to determine the amount of radioactive materials suspended in the air. This sampling is often conducted to evaluate the need for engineering, administrative, or respiratory protection by comparing results to appropriate airborne exposure limits. Air sampling and analysis should always be conducted under the direction of a radiation safety professional.|
|Personal and Area Sampling|
Personal and area air sampling are conducted by using a pump to pull a known volume of air through sampling collection media, such as a filter cassette. Personal air sampling collects air from the breathing zone of a worker, while an area sample collects general room air. Once sampling is completed the sample media is evaluated using appropriate detection equipment for the radionuclides being evaluated. Some types of analysis equipment are scaler/counters, proportional counters, scintillation counters, liquid scintillation counters, gamma spectroscopy, and alpha spectroscopy.
|Continuous Air Monitors|
|Continuous air monitors (CAM) can be used to evaluate the presence of airborne radioactive material. These devices can be used to alert personnel to an increased level of radioactive material in the air that may require some action, such as evacuation. These devices use a pump to draw air through a particulate filter or gas chamber that is continuously monitored with a radiation detector. These devices can often be set to trigger an alarm at a user specified level of measured airborne radioactivity.|
Measurements of the concentration of radon in air can be conducted using several different methods. Diffusive samplers can be deployed for several days to months to measure the average airborne radon concentration over the sampling period. Commercially available radon test kits are an example of a diffusive type sampler. OSHA Method ID-208 is a diffusing sampling method that describes the use of a short-term (2-7 day) electret-passive environmental radon monitor (E-PERM).
Direct reading portable airborne radiation monitors can be used to provide a nearly instantaneous measurement of airborne radon concentration. These monitors typically draw air into the instrument and rely on devices such as a scintillation detector or a pulsed ion chamber to measure alpha particles emitted by the radon gas or radon decay products. Most of these devices are capable of performing sequential short-term measurements (minutes) and logging the data over a relatively long period (weeks). These instruments allow radiation professionals to determine how radon levels vary within a space and vary over time.
Sample Analysis Equipment
Radioactive samples can be evaluated using a variety of equipment types depending on the type of sample (e.g. air, water, soil, surface wipe) and the types of radiations emitted by the sample. The following are examples of some of the types of equipment used to evaluate radioactive samples.
|Scaler / Counters|
|These devices are often portable and are used to measure the amount of alpha or beta radiations on a radiological sample. A sample, such as an air sample or surface wipe, is placed near the internal radiation detector and the radiations are counted for a user specified time. The device registers the total number of radiations counted over the measurement time. Scaler / counters are sometimes equipped with scintillation detectors, G-M detectors, proportional detectors, or passivated implanted planar silicon (PIPS) detectors.|
|Liquid Scintillation Counters|
|A liquid scintillation counter is piece of equipment that is not portable and is usually used in a laboratory. This instrument can be used for all types of radiations, but it is most often used for measuring beta particles. In liquid scintillation counting, the sample is place in a transparent glass vialed that is then filled with a scintillation fluid. Radiations from the sample that interact within the fluid cause the fluid to emit photons of light. The intensity of the light is proportional to the energy of the radiation. This allows for the determination of what the radioactive material is (radioisotope identification) and how much radioactive material is present (radioactivity).|
|Gamma spectroscopy is a method used to identify the radioisotopes present in a radiological sample and quantify the amount of radioactivity in that sample. While these devices can be handheld like the RIID, the most sensitive and accurate instruments are not portable and are used in the laboratory. Common detectors used for gamma spectroscopy are semiconductor-based detectors such as germanium, cadmium telluride, and cadmium zinc telluride detectors, and scintillation detectors such as sodium iodide (NAI) detectors.|
|Alpha spectroscopy is a method used to identify and quantify alpha emitting radioisotopes. Radioactive samples are chemically digested and the solution is placed onto a thin metal disk. The amount of radioactivity on the disk is measured using a radiation detector, most often a PIPS detector. These instruments are not portable and are typically only used in a laboratory.|
Whole Body Counting
A whole body counter is a detector, or series of detectors, used to measure the amount of radioactivity in the human body. These instruments rely on the measurement of gamma and x-rays emitted from the radioactive material deposited in the body. Gamma spectroscopy systems are usually used in whole body counting systems. Counting is often used in occupational settings to conduct measurements of radiological workers at the beginning of employment, periodically during employment, after known or suspected intakes, and at the termination of employment in order to determine occupational radiation doses.
Bioassay sampling is sometime used in occupational settings to determine the uptake of radioactive material for radiological workers. Samples are typically collect at the beginning of employment, periodically during employment, after known or suspected intakes, and at the termination of employment in order to determine occupational radiation doses. Bioassay samples most commonly include urine, feces, and blood.
One of the most important functions of a radiation protection program is training radiation workers on safe work practices. Employers should provide workers with information and training to ensure that those who are potentially exposed to ionizing radiation hazards understand how to safely use all radiation-producing equipment or radiation sources in the workplace.
Providing workers with information and training is closely tied to awareness of regulations because federal and state regulations often include performance and safety standards for specific radiation-producing equipment or radiation sources. Employers should ensure that workers understand mandatory performance and safety standards that help protect workers from exposure to ionizing radiation.
Some state agencies may regulate the operation of electronically-produced radiation equipment through recommendations and requirements for personnel qualifications (e.g., licensing or certification), quality assurance and quality control programs, and facility accreditation. Those mandatory personnel qualifications are another important part of protecting workers from exposure to ionizing radiation.
For more information, read the American National Standards Institute (ANSI)/Health Physics Society (HPS) N13.36, Ionizing Radiation Safety Training for Workers.
Hazard-Specific Control Resources
In addition to the general methods of control described above, there are several resources included on the Additional Resources page that provide information on controlling specific radiation hazards, including medical sources (i.e., diagnostic X-rays and fluoroscopically-guided interventional procedures), dental and veterinary X-rays, particle accelerators, industrial radiography, security screening, and radon.
1 U.S. Environmental Protection Agency (EPA). (2014). Publication No. EPA-402-R-10003, Federal Guidance Report #14, Radiation Protection Guidance for Diagnostic and Interventional X-Ray Procedures. Washington, DC: EPA; National Council on Radiation Protection and Measurements (NCRP). (2004). Report No. 147: Structural shielding design for medical x-ray imaging facilities. Bethesda, MD: NCRP.