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MACHINE GUARDING. The installation of equipment or devices on machines to eliminate hazards created by operation of the machines.
MAGNAFLUX. A test in which particles of iron are applied to the surfaces of a magnetized specimen; the particle pattern indicates surface or near-surface flaws or irregularities.
MAINTENANCE, PREVENTATIVE. A system of scheduled overhaul and replacement of key parts to forestall breakdown.
MAINTENANCE, ROUTINE AND BREAKDOWN. The function of preserving facilities and equipment by making needed repairs.
MAJOR INJURY. An injury where there is loss of time to the injured person and a medical expense.
MAJOR MEDICAL EXPENSE BENEFIT (CATASTROPHE INSURANCE). Plan designed to insure workers against the costly medical expenses resulting from catastrophic or prolonged illness or injury. If the benefit supplements the benefit payable by a basic health insurance plan (hospital, medical, or surgical), it is called a supplementary- plan; otherwise, it is called a comprehensive- plan.
MAKEUP AIR. Clean, tempered outdoor air supplied to a workspace to create a comfortable environment.
MALFORMATION. A deformity. (See CONGENITAL ABNORMALITY.)
MALIGNANCY. The property of a neoplasm, marginal invasion, relentless growth, and distal spread with a lethal effect.
MALIGNANT NEOPLASM. (See CANCER.)
MALPRACTICE. Misconduct or lack of proper professional skill on the part of any professional, such as a doctor, dentist, attorney, or engineer.
MANIPULATIVE DEXTERITY. The degree of skill a person has in using his wrists and fingers for fine tasks.
MANUAL CONTROL SWITCH. An auxiliary device for manual operation of an automatic controller. Any control switch that is actuated by a person.
MANUAL DEXTERITY. The degree of use and facility a person has in using the hands. Includes gross arm-hand movements as well as fine wrist-finger skills.
MANUAL RATE. The compensation insurance premium in dollars per hundred dollars of payroll, for a specified classification of operation or risk as listed in an official manual for a given state or jurisdiction.
MARGIN OF SAFETY. A border, edge, or limit beyond which a particular behavior, condition, or situation becomes hazardous or unsafe.
MASK. A protective covering for the face or head, such as a wire screen, a metal shield, a respirator, or a gas mask.
MASKING (NOISE). The stimulation of one ear of a subject by controlled noise to prevent hearing with that ear the tone or signal given to the other ear. This procedure is used where there is at least 15 to 20 dB difference in the two ears.
MATCHING FREQUENCY (STRATIFIED MATCHING). In a case-control epidemiological study, an attempt to make cases and controls according to certain variables and sampling such that the proportion of controls in each subgroup is the same as the proportion of cases in each subgroup. In a cohort study, the population not exposed to the risk under study would be subdivided and sampled such that the proportion of nonexposed in each subgroup was the same as the proportion of exposed in each subgroup.
MATCHING. In an epidemiological case-control study, the selection of controls such that the control group has the same distribution of certain variables as the case group; in a cohort study, the selection of those not exposed to a given factor such that they have the same distribution of certain variables as those exposed to the given factor.
MATCHING INDIVIDUAL. In a case-control epidemiological study, an attempt to make cases and controls comparable by selecting for each case a control who matches the case with respect to specific criteria.
MAXIMUM PERMISSIBLE BODY BURDEN (MPBB). That amount of an internally deposited radioisotope which will result in a maximum permissible dose to the individual or a critical organ.
MAXIMUM PERMISSIBLE CONCENTRATION (MPC). That amount of radioactive material in air, water, or food which will result in accumulation of a maximum permissible body burden when assimilated at a standard rate for that medium.
MAXIMUM PERMISSIBLE DOSE (MPD). A dose established by competent authority as the highest allowable dose which is not expected to cause injury to a person during his lifetime. A wide safety margin below the dose at which detrimental effects are known to occur is normally provided in establishing MPD'S.
MAXIMUM VOLUNTARY VENTILATION (MVV). Volume of air which a subject can breathe with voluntary maximal effort for a given time.
MEASUREMENT. The assigning of numbers to observations in such a way that the numbers are amenable to analysis according to certain rules.
MECHANICAL HAZARDS. Unsafe conditions involving machinery, equipment, tools, etc.
MEDIAN LETHAL DOSE (LD-50). The acute dose of radiation required to kill 50% of the population within a specified time, usually 30 days.
MEDICAL BENEFITS. Plans which provide employees, and in most cases their dependents, with specified medical care (other than that connected with surgery) or a cash allowance toward the cost of doctors' visits. Generally part of a health insurance program.
MEDICAL MONITORING. (See BIOLOGICAL MONITORING.)
MEDICAL ONLY (MO). An injury requiring medical attention only, without loss of time from work. In insurance terminology it describes an injury where medical costs only are paid, even when some loss of work time has been incurred.
MEDICAL RADIATION. Radiation from diagnostic or therapeutic radiological procedures, e.g., x-rays, radioactive tracers, cobalt therapy.
MEDICAL SURVEILLANCE. Systematic collection, analysis, and interpretation of medical data. In the workplace, surveillance is necessary to establish that a disease condition exists and that the particular disease manifestation may result from exposure to a specific harmful agent.
MEMBRANE FILTER. A thin, pliable material of varying porosity designed to be placed in filter holder and have air contaminants drawn across it entrapping particles for gravimetric or instrumental/chemical analysis.
META-ANALYSIS. The process of using statistical methods to combine the results of different studies.
METAL FUME FEVER. An acute illness characterized by the sudden onset of chills and fever several hours after exposure to metal fumes. It is most common in brass foundries and in the smelting of zinc. The condition is thought to be due to inhalation of metal oxides. Zinc, copper, iron, and magnesium have been documented as causing the syndrome, but other metals may behave in a similar manner under certain circumstances.
METASTATIC TUMOR. A secondary malignant growth that originates from a primary tumor and is separated from the primary site.
MICROWAVE BIOEFFECTS. Alteration in biological systems resulting from exposure to microwave radiation. Two broad types of bioeffects are generally described: Thermal effects - Effects produced by the heating effect of absorbed microwave energy. These effects are fairly well documented and most are accompanied by a detectable rise in tissue temperature. Some effects in which a temperature rise is not detected by available instrumentation are termed microthermal. Nonthermal effects - Effects which are thought to bedue to a mechanism other than heating. Certain experimentally produced field effects fall in this category.
MICROWAVE CATARACTS. Posterior subcapsular lenticular opacities attributed to exposure to microwave radiation. Such opacities have been experimentally produced and several cases involving human exposures have been reported. The occurrence of microwave cataracts in occupationally exposed personnel in normal industrial circumstances has not been demonstrated.
MICROWAVE DOSIMETRY. Measurement of the amount of microwave energy to which a system has been exposed. The term microwave is usually used to cover radiations in the radio and radar frequencies (kilohertz through gigahertz). Absorbed doses cannot currently be measured and can only be roughly estimated from measurements of temperature increase. Time integrating instruments are also lacking so that exposures are usually expressed in terms of power flux density (watts per square centimeter) or field strength (volts per meter).
MICROWAVE HEARING EFFECT. The auditory sensation evoked in people exposed to low level pulsed microwave radiation. It is perceived as an audible buzz or click. It was long thought to demonstrate a direct, nonthermal effect but recent evidence indicates that it may be due to rapid transient thermal expansion of fluid.
MILEAGE DEATH RATE. The number of deaths from vehicle accidents per 100,000,000 miles of vehicle travel in the area for which the rate is computed.
MINOR INJURY. An injury where no lost time or major medical costs are involved.
MISTS. Suspended liquid droplets generated by condensation from the gaseous to the liquid state or by breaking up a liquid into a dispersed state, such as by splashing, foaming, or atomizing. Mist is formed when a finely divided liquid is suspended in the atmosphere.
MOLECULAR WEIGHT. Weight (mass) of a molecule based on the sum of the atomic weights of the atoms that make up the molecule.
MONITORING. Testing to determine if the parameters being measured are within acceptable limits. This includes environmental and medical (biological) monitoring in the workplace.
MONITORING (RADIATION). The periodic or continuous determination of the amount of ionizing radiation or radioactive contamination. Area monitoring is the routine monitoring of the level of radiation or of radioactive contamination of any particular area, building, room, or equipment. Personnel monitoring is the monitoring of any part of an individual, breath, or excretions, or any part of the clothing.
MORBIDITY. A diseased condition or state; the incidence or prevalence of a disease or of all diseases in a population.
MORBIDITY RATE. The number of cases of a specific diseased condition or state occurring per unit population over a stated period of time.
MORTALITY. Death; the incidence or prevalence of death in a population.
MORTALITY RATE. The number of deaths occurring per unit population over a stated period of time.
MOTOR VEHICLE COLLISION. Any accident involving a motor vehicle in motion that results in death, injury, or property damage. However, motion of the motor vehicle is not required in a collision between a railroad train or another motor vehicle.
MOTOR VEHICLE NONTRAFFIC ACCIDENT. Any motor vehicle accident which occurs entirely in any place other than a trafficway.
MUSCULOSKELETAL INJURY. Acute and chronic injury to muscles, tendons, ligaments, nerves, joints, bones, and supporting vasculature.
MUTAGEN. Any agent capable of producing genetic or somatic mutation. (See GENETIC MUTATION, SOMATIC MUTATION.)
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