Cih Glossary

Front 1

abduction

Back 1

Movement of an extremity or other body part
away from the axis of the body.

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absolute gain

Back 2

A ratio of the actual transmitted power density
in the main beam to the power density transmitted
from an isotropic radiator.

Front 3

absolute pressure

Back 3

It is never less than zero. The absolute
pressure in a system can approach zero, but for the
pressure to be negative it would first have to pass
through zero which is like absolute temperature on a
thermodynamic scale. It is possible to approach but not
reach absolute zero pressure.

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absolute temperature

Back 4

Temperature as measured above
absolute zero. (Also known as “thermodynamic temperature.”)

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absolute zero

Back 5

The temperature at which all molecular
motion stops. Either -273.15°C (0 K) in the SI system of
units, or -459.67°F (0°R) in the English system. (See
also Kelvin temperature, Rankine temperature.)

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absorbed dose

Back 6

1. The mass or moles of exposing compound
that actually enters the bloodstream through any external
routes of exposure; the absolute bioavailability. 2.
Amount of a substance penetrating the exchange boundaries
of an organism after contact. Calculated from intake
and absorption efficiency and expressed as mg/kg/day.

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absorbing medium

Back 7

A collection medium that allows for the
penetration of airborne chemicals into the material
where the chemicals will either physically dissolve or
chemically react with the collection medium.

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absorption

Back 8

To take in a substance across the exchange
boundaries of an organism (skin, lungs, or gastrointestinal
tract) and ultimately into body fluids and tissues

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acceleration

Back 9

Any gradual speeding up of a process. The time
rate of change of velocity.

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acceleration due to gravity

Back 10

The rate of increase in velocity of a
body falling freely in a vacuum; value varies with latitude
and elevation. The International Standard at sea
level and 45 latitude is 9.80665 meters per second squared
(m/sec2) or 31.174 feet per second squared (ft/sec2).

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accelerometer

Back 11

An instrument that measures acceleration or
gravitational force capable of imparting acceleration.

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acceptable air quality

Back 12

Air in which there are no known contaminants
at harmful levels as determined by occupational
hygienists, and air with which 80%–90% of the
people do not express dissatisfaction based on comfort
criteria: temperature, relative humidity, nonhazardous
odors, and air movement (draftiness/stuffiness).

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acceptable risk

Back 13

Risk level deemed acceptable by an individual,
organization, or society as a whole.

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acceptance sampling

Back 14

The procedures by which decisions to
accept or reject a sampled lot or population are made
based on the results of a sample inspection. In air pollution
work, acceptance sampling could be used when
checking a sample of filters for certain measurable
characteristics such as pH, tensile strength, or collection
efficiency to determine acceptance or rejection of a
shipment of filters, or when checking the chemical content
of a sample of vials of standard solutions from a
lot of vials to be used in an interlaboratory test.

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acceptance testing

Back 15

A systematic procedure to test asreceived
materials before use to determine whether
they are contaminated.
Glossary

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acclimatization

Back 16

Adaptation of a species or population to a
changed environment over several generations. (Also
known as “acclimation.”)

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accuracy

Back 17

1. The degree of agreement of a measurement, X,
with an accepted reference or true value, T, usually
expressed as the difference between the two values, X
– T, or the difference as a percentage of the reference or
true value, 100(X – T)/T, and sometimes expressed as a
ratio, X/T. 2. Measure of the correctness of data, as
given by differences between the measured value and
the true or specified value. Ideal accuracy is zero difference
between measured and true value. 3.
Conformity of an indicated value to an accepted standard
value, or true value. Quantitatively, expressed as
an error or an uncertainty. The property is the joint
effect of method, observation, apparatus, and environment.
Accuracy is impaired by mistakes, by systematic
bias (e.g., abnormal ambient temperature), or by random
errors (imprecision). 4. The degree of freedom
from error (i.e., the degree of conformity to truth or to
a rule). Accuracy is contrasted with precision (e.g.,
four-place numbers are less precise than six-place
numbers; nevertheless, a properly computed four-place
number might be more accurate than an improperly
computed six-place number). (See also precision,
repeatability.)

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acfm

Back 18

actual cubic feet per minute

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acid

Back 19

A compound that reacts with an alkali to form a salt
and water. It turns litmus paper red and has pH values
of 0 to 6.

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acne

Back 20

A pleomorphic, inflammatory skin disease involving
sebaceous follicles of the face, back, and chest and
characterized by blackheads, whiteheads, papules,
pustules, and nodules.

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acoustic trauma

Back 21

The temporary or permanent hearing loss
due to a sudden intense acoustic event such as an
explosion.

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acoustical absorption

Back 22

Material added to a workspace environment
to reduce noise above 300 Hz.

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acrid

Back 23

Sharp, bitter, stinging, or irritating to the taste or smell

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action level

Back 24

1. In general, the level of a pollutant at which
specified actions or counter measures are to be taken.
2. A term used by OSHA in several chemical standards.
A level of exposure at which the employer must initiate
some actions such as medical monitoring and training.
The action level is generally set at 50% of the PEL.
3. This is the concentration or level of an agent at
which it is deemed that some specific action should be
taken. The action can range from more closely monitoring
the exposure atmosphere to making engineering
adjustments. In general practice the action level is usually
set at one-half of the ACGIH TLV®.

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action potential (AP)

Back 25

A transient change in electric potential
at the surface of a nerve or muscle cell occurring at the
moment of excitation

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activated carbon

Back 26

Activated carbon is commonly used in gas
adsorption. (Also known as “activated charcoal.”)

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active sampling

Back 27

The collection of airborne contaminants by
means of a forced movement of air by a sampling
pump through an appropriate collection device.

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activity-based costing

Back 28

A method of identifying and allocating
costs based on measurable activities. There are two
elements of ABC: activity analysis and cost object
analysis.

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actual cubic feet per minute (acfm)

Back 29

Actual cubic feet per
minute of gas flowing at existing temperatures and
pressure.

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acuity

Back 30

Pertains to the sensitivity of a bodily organ to perform
its function.

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acute

Back 31

Severe, often dangerous effect used to denote an exposure
to high concentrations of a contaminant for short
duration.

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acute effect

Back 32

An adverse effect (usually) arising from a short
exposure (minutes to hours) to a chemical.

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acute exposure

Back 33

Large dose/short time

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Acute Exposure Guideline Levels (AEGLs)

Back 34

Developed by
the EPA, these guidelines are developed based on an
assessment of the health risks in extensive peer-review
processes and are published regularly in the United
States Federal Register.

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acute intake

Back 35

Intake averaged over a period of less than two
weeks.

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acute mountain sickness (AMS)

Back 36

Refers to high altitude pulmonary
edema and/or high altitude cerebral edema.
Symptoms (severe breathlessness and/or chest pain)
can rapidly become life-threatening if not treated by an
immediate descent to a lower altitude. AMS is subdivided
into benign and malignant.

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acute toxicity

Back 37

The adverse effects resulting from a single
dose or single exposure to a substance. Ordinarily
refers to effects occurring within a short time following
administration. Terminology and units used for different
descriptive categories of toxicity vary. Examples of
toxicity classifications as defined by different organizations
are:
• LC50 inhalation (ppm): extremely toxic = <10; highly
toxic = 10–100; moderately toxic = 100–1000; slightly
toxic = 1000–10,000; practically nontoxic =
10,000–100,000; relatively harmless = >100,000. • LC50 inhalation (ppm): highly toxic = <200; toxic =
200–2000. [29 CFR 1910.1200, Appendix A — Health
Hazard Definitions.]
• LC50 inhalation (ppm): extremely toxic = <10; highly
toxic = 10–100; moderately toxic = 100–1000; slightly
toxic = 1000–5000; practically nontoxic = >5000.

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acute toxicity study

Back 38

Toxicity study durations of less than
five days exposure.

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adduct

Back 39

The product of a reaction between an endogenous
macromolecule and an exposing chemical or its
metabolite.

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adenoma

Back 40

A benign tumor with glandular structure or of a
glandular organ.