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Z94.13 - Occupational Health & Safety

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P VALUE. A statement of probability that the differences observed have occurred by chance under the null hypothesis.

PAID ABSENCE ALLOWANCE. Payment for lost working time available to workers for various types of leave not otherwise compensated for, e.g., excused personal leave.

PARTICULATE. A particle of solid or liquid matter.

PATCH TEST. A test in which a diluted sample of a material suspected of causing an allergic dermatitis is applied to the patient's skin (usually the back) with an adhesive patch and removed in 48 hours. If the patient is sensitive, a small area of dermatitis will appear at the point of contact of the material. 

PEDESTRIAN. Any person who at the time of an accident is not in a motor vehicle or non-motor vehicle. Persons on other vehicles such as coaster wagons, child's tricycle, roller skates, etc., are considered pedestrians. A person hitched onto a vehicle is considered a pedestrian unless entirely in or on the vehicle.

PERCEPTION. (1) Awareness of objects or other data through the medium of the senses. The meaning or interpretation given to stimuli received through the senses. (2) Insight or intuition relative to information introduced through sensory reception.


PERMANENT DISABILITY. A permanent impairment, includes any degree of impairment from an amputation of a part of finger or a permanent impairment of vision to seriously and permanently nonreversible, nonfatal injuries.


PERMANENT PARTIAL DISABILITY. Any injury other than death or permanent total disability which results in the loss, or complete loss of use, of any member or part of a member of the body, or any permanent impairment of functions of the body or part thereof, regardless of any pre-existing disability of the injured member or impaired body function. These cases are used in computing ANSI Standard Z16 injury rates whether or not time is lost.

PERMANENT TOTAL DISABILITY. Any injury other than death which permanently and totally incapacitates an employee from following any gainful occupation, or which results in the loss, or the complete loss of use, of any of the following in one accident: a) both eyes, b) one eye and one hand, or arm, or leg, or foot, c) any two of the following not on the same limb: hand, arm, foot, or leg. Definition can vary from state to state.

PERMISSIBLE EXPOSURE LIMIT (PEL). An occupational exposure limit established by OSHA's regulatory authority.  It may be expressed as a time-weighted average (TWA) concentration limit or as a maximum concentration exposure limit. Ceiling concentrations may also be specified.

PERSON-YEARS. A unit of measurement combining persons and time, used as denominator in mortality rates of cohort study.  In a cohort study, each subject contributes only as many years of observation to the population at risk as the subject is actually observed; if the subject leaves after one year, one person-year is contributed; if after ten, ten person-years. 

PERSONAL FACTOR (UNSAFE). The mental or bodily characteristic which permitted or occasioned an act which contributed to an accidental occurrence.

PERSONAL PROTECTIVE EQUIPMENT. Clothing or devices worn or used by the worker to protect against exposure to hazardous agents in the workplace. Respirators, gloves, and ear protectors are examples.

PESTICIDES. General term for that group of chemicals used to control or kill such pests as rats, insects, fungi, bacteria, weeds, etc., that prey on humans or agricultural products. Among these are insecticides, herbicides, fungicides, rodenticides, miticides, fumigants, and repellents. 

PHON. The unit of loudness level.

PHYSICAL FACTORS (UNSAFE). Environmental factors conducive to accident occurrence. Physical or environmental hazards.

PHYSIOLOGY. The science and study of the functions or actions of living organisms.

PINCH POINT. Any point at which it is possible to be caught between the moving parts of a machine or between moving and stationary parts of a machine or other structure or between the material and the moving parts of a machine.

PITCH (HEARING). That attribute of auditory sensation in terms of which sounds may be ordered on a scale extending from low to high. Pitch depends primarily upon the frequency of the sound stimulus, but it also depends upon the sound pressure and wave form of the stimulus.

PNEUMOCONIOSIS.  A condition characterized by permanent deposition of substantial amounts of particulate matter in the lungs, usually of occupational or environmental origin. The condition is also characterized by the tissue reaction to the presence of the particulate matter. 

PNEUMONITIS. An inflammation of the lung.

POINT OF OPERATION. The place of contact between the primary functional part of any machine or tool and the material or substances in the production, or process, in which the machine or tool is being used. Generally considered to be the point of greatest danger to the operator.

POINT OF PERCEPTION. The time and place at which the individual actually first perceived"that is, saw, heard,     smelled or felt"the hazard, that is, the unusual or unexpected movement or condition that could be taken as a sign of the accident about to occur.

POINT OF POSSIBLE PERCEPTION. The place and time at which the unusual or unexpected movement or condition could have been perceived by a normal person. This point always comes at or before the point of (actual) perception.

POTENTIAL HAZARD. A situation, thing, or event having latent characteristics conducive to an accident occurrence.

POTENTIAL YEARS OF LIFE LOST. A measure of the relative impact of various diseases and injuries on a defined population.  Potential years of life lost due to a particular cause is the sum of the years that these persons in a population would have lived had they experienced normal life expectancy. 

POWER LEVEL (NOISE). The power level, in decibels, is 10 times the logarithm to the base 10, of the ratio of a given power to a reference power. The reference power must be indicated.

PRECAUTIONS. Actions taken in advance to reduce the probability of an accident.

PREEMPLOYMENT EXAMINATION. A medical examination of a job applicant that is job related, consistent with business necessity, and treated in a confidential manner.  In the preoffer phase, the employer may not subject the applicant to a medical exam.  In the postoffer phase, the employer may require a medical exam to consider physical and psychological criteria that are relevant to the performance of the contemplated work activity.

PREPONDERANCE OF EVIDENCE. A greater weight of evidence (facts, information from all sources, past experience) to support one judgment or decision versus the opposite. A phrase frequently used to describe the basis upon which a decision is made, such as determining if an injury is occupational or non-occupational.

PRESBYCUSIS. The hearing loss due to age. It is believed to be the degeneration of the nerve cells due to the ordinary wear and tear of the aging process.

PREVALENCE RATE. The number of new and existing cases, per unit population, occurring during a stated period of time. 

PREVENTION (OF ACCIDENT). The science and the art representing control of worker performance, machine   performance and environment to eliminate failures or losses. Prevention connotes correction of conditions as well as elimination or isolation of hazards.

PROBABILITY SAMPLING. Sampling in which each sampling unit has a known non-zero probability of being included in the sample. 

PRODUCT LIABILITY. The liability a merchant or a manufacturer may incur as the result of some defect in the product sold or manufactured, or the liability a contractor might incur after job completion from improperly performed work. The latter part of product liability is called  completed operations.-

PROPERTY DAMAGE ACCIDENT (PD). An accident wherein damage to or destruction of any property is the immediate and direct result. It does not include accidents resulting in loss of human life or personal injury.

PROPORTIONATE MORTALITY RATIOS (PMR). A ratio of two proportionate mortality rates. In occupational study, the PMR is a tool for estimating cause-specific risks when the available data consist only of deaths without knowledge of the population characteristics. It can lead to erroneous conclusions if used to compare the mortality experience of populations with different distributions of causes of death.


PROTECTIVE CLOTHING. Clothing worn to protect the worker from exposure to or contact with harmful chemical agents or physical agents such as heat.

PROTECTIVE COATING. A thin layer of metal or organic material as paint applied to a surface primarily to protect it from oxidation, weathering, and corrosion.

PROTECTIVE EQUIPMENT (PERSONAL). Equipment to protect the worker from exposure to harmful substances. Such equipment includes safety glasses, face shields, leggings, hard hats, safety shoes, etc.

PROTECTIVE HAND CREAM. A cream designed to protect the hands and other parts of the skin from exposure to harmful substances.

PROXIMATE CAUSE. The cause which directly produces the effect without the intervention of any other cause. Cause nearest to the effect in time or space.

PRUDENT. Cautious, careful, attentive, discrete, circumspect, and sensible as applied to action or conduct.

PSYCHOGENIC DEAFNESS. That originating in or produced by the mental reaction of an individual to physical or social environment. It is sometimes called functional deafness or feigned deafness.

PSYCHOLOGICAL EVALUATION. Studies of the relationships between accidents and emotional, or intellectual functions as distinct from sensory and sensorimotor factors. Intelligence tests and personality tests are examples of these measurement techniques, as are time sampling, activity analysis, and the observation of critical incidents.

PSYCHOPHYSICAL MEASUREMENT. Measurements of reaction times and various kinds of sensorimotor and psychomotor coordinations. (Laboratory experiments dealing with vision under conditions of low illumination illustrate this latter group.)

PSYCHOPHYSICAL, CHARACTERISTICS. A combination of mental and physical qualities of humans, such as visual acuity, reaction time, hearing, depth perception, peripheral vision, manipulative dexterity, color vision, etc.

PSYCHOSOCIAL EVALUATION. The evaluation of socially conditioned behavior and reactions in relation to the social environment. The measurement of attitudes, studying the effect of supervisory practices, and the use of indices of the adequacy of social adjustment, illustrate methods used in this approach to accident investigation.

PSYCHOSOCIAL FACTORS. Social influences that are related to or affect psychological factors of human behavior.

PULMONARY HYPERINFLATION SYNDROME (BURST LUNG).  Pulmonary barotrauma of ascent. It occurs during decreases in pressure from overdistension and rupture of the lungs by expanding gases.  It is a result of breath-holding or air-trapping during ascent. The clinical presentations are pneumothorax, mediastinal or subcutaneous emphysema, and air embolism.

PURE TONE. A pure tone has a unique pitch and is characterized by a sinusoidal variation in sound pressure with time.  The frequency spectrum of a pure tone shows a single line at a discrete frequency. 

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