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RAD. Radiation absorbed dose. Under the common system it is the basic unit of absorbed dose of any type radiation equivalent to absorption of 100 ergs per gram of any material. However, under SI, the unit is the gray (Gy). The gray is the energy imparted by ionizing radiation to a mass of matter corresponding to one joule per kilogram or 100 RAD.
RADIATION. The emission and propagation of energy through space or a material medium in the form of electromagnetic waves (gamma or x-rays) or particles (alpha and beta). Electromagnetic radiation may be ionizing or nonionizing; all particulate radiation is ionizing.
RADIATION CONTROL. Engineering measures, including devices, used to prevent worker exposure to harmful levels of ionizing and nonionizing radiation.
RADIATION DOSIMETRY. Measurement of the amount of radiation delivered to or absorbed at a specific place. Personnel dosimetry is accomplished with such devices as the film badge, thermoluminescent dosimeter, or pocket ionization chamber. In this way continuous recording of cumulative radiation dose can be maintained.
RADIATION MONITORING. Measurement of the amount of radiation present in a given area. Radiation exposures can be limited by monitoring and limiting access and stay time in areas in which high levels of radiation are present.
RADIOACTIVE CONTAMINATION. The deposition or presence of radioactive material in a place where it is not desired and may be harmful. In regard to personnel: External Contamination - The presence of radio active material on the skin. Internal Contamination - The presence of radioactive material within the body due to ingestion, inhalation, or absorption.
RANDOM NOISE. A sound or electrical wave whose instantaneous amplitudes occur, as a function of time according to a normal (Gaussian) distribution curve. Random noise is an oscillation whose instantaneous magnitude is not specified for any given instant of time. The instantaneous magnitudes of a random noise are specified only by probability functions giving the fraction of the total time that the magnitude, or some sequence of the magnitudes, lies within a specific range.
RANDOM SAMPLING. A procedure in which each sampling unit in the population has an equal chance of being included in the sample.
RATE. An expression of the speed or frequency with which a certain event or circumstance occurs in relation to a certain period of time, a specific population, or some other fixed standard (e.g., mortality rate, pulse rate, etc.).
RAYNAUD'S PHENOMENON (DEAD HAND OR WHITE HAND SYNDROME). A vascular disorder of the extremities, usually the hand, frequently resulting from the use of vibrating tools, particularly pneumatic tools. Intermittent cyanosis or pallor of the part, coldness, numbness, and paresthesias are typical. Once the disorder develops it generally does not improve even with cessation of work with vibrating tools.
RECOMMENDED EXPOSURE LIMIT (REL). The NIOSH REL is the recommended maximum allowable airborne concentration of a substance which is not expected to harm workers. It may be expressed as a time-weighted average (TWA) concentration, short-term exposure limit, or a ceiling value.
RECOMPRESSION THERAPY. Treatment of decompression sickness or air embolism by returning the victim to a hyperbaric environment, usually in a recompression chamber. Standard tables for treatment of diving casualties are available, the most frequently used being those developed by the U.S. Navy.
REGRESSION COEFFICIENT. In popular terms, it is the amount of change that will on the average take place in one characteristic when the other characteristic changes by one unit. It is the coefficient of an independent variable in a regression equation.
RELATIVE RISK. In an epidemiological study, the rate of disease among those exposed to a given factor divided by the rate of disease among those not exposed to the given factor. (For a rare disease, the relative risk may be approximated by the odds ratio.)
RELIABILITY. (See REPRODUCIBILITY.)
REM- ROENTGEN EQUIVALENT MAN. Unit of dose of any type radiation which produces in humans an effect equivalent to exposure to one rad or roentgen of x- or gamma rays. In the SI system the equivalent unit is the Sievert (Sv) = 100 REM.
REPETITIVE STRAIN INJURY. (See CUMULATIVE TRAUMA DISORDER.)
REPLACEMENT AIR. The volume of outdoor air that is delivered to a building in a controlled manner to assist in control of contaminants and to replace air being exhausted.
REPRODUCIBILITY (RELIABILITY, PRECISION). The extent to which a measurement produces the same results when repeatedly applied to the same situation.
RESEARCH DESIGN. The procedures and methods, predetermined by an investigator, to be adhered to in conducting a research project.
RESPIRATOR. A protective device for the human respiratory system designed to protect the wearer from inhalation of harmful air contaminants. There are two types of respiratory protective devices: a) air purifiers, which remove the contaminants from the air by filtering or chemical absorption before inhalation, and b) air suppliers, which provide clean air from an outside source or breathing air from a tank.
RESPIRATORY DISEASES. Disease conditions due to toxic agents in the respiratory tract, e.g., pneumonitis, bronchitis, pharyngitis, rhinitis, or acute congestion due to chemicals, dusts, gases, fumes, or infectious agents.
RESPIRATORY IRRITANTS. Irritants affecting the respiratory tract, e.g., dusts, vapors, gases.
RESPIRATORY PROTECTIVE EQUIPMENT. Protective devices for the human respiratory system designed to protect workers from over-exposure by inhalation of air contaminants (air-purifying and air-supplied) and oxygen deficiency (air-supplied). (See RESPIRATOR.)
RESPIRATORY SYSTEM. A system of the body consisting of (in descending order)-the nose, mouth, nasal passages, nasal pharynx, pharynx, larynx, trachea, bronchi, bronchioles, air sacs (alveoli) of the lungs, and muscles of respiration.
REST PERIOD (COFFEE BREAK, BREAK TIME). Brief interruption in the workday during which the worker rests or takes refreshments without loss of pay.
RETROGRADE SHOCK AMNESIA. The loss or impairment of memory due to shock. It can result from shock due to head injuries, severe loss of blood, and other conditions.
RETROSPECTIVE STUDY. (See CASE-CONTROL STUDY.)
REVERBERATION. The persistence of echoing of previously generated sound caused by reflection of acoustic waves from the surfaces of enclosed spaces.
RIGHT-OF-WAY. The right of one vehicle or pedestrian to proceed in a lawful manner in preference to another vehicle or pedestrian approaching under such circumstances of direction, speed, and proximity as to give rise to danger of collision unless one grants precedence to the other.
RISCIDENT. Comes from one of the same root words as accident, and means risk due to fortuitous change.- The study of riscidents has been approached in two ways: (a) the analysis of accident records, identifying the maneuvers of the various vehicles or other agents involved, and (b) by recording near accidents.
RISCUTANT. Refers to the behavior of a person which tends to bring about involvement in riscident or critical situations.
RISK. A probability that an event will occur, e.g., that an individual will become ill, injured, or will die within a stated period of time.
RISK (INSURANCE). The chance of physical or personal loss; the amount of possible loss to the insuring company. Also used in place of insured or prospect. Hazard, danger, peril. A company protected by insurance. A subjective evaluation of relative failure potential.
RISK FACTOR. A characteristic or agent whose presence increases the probability of occurrence of a disease or injury.
ROENTGEN (R). The common unit of exposure to x- or gamma rays equivalent to the absorption of 83 ergs per gram of air. Under SI, it is equal to 0.000 258 coulombs per kilogram of air (c/kg).
ROUTES OF ENTRY. The pathway by which material may gain access to the body including inhalation, ingestion, and skin contact.
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