Basic Calculations for Occupational Safety and Environmental Health Professionals - Mathematics and Statistics for the Environment - page 393

Silica (SIO 2 )—A major component of the Earth's crust and the cause of silicosis.
Specific gravity —The ratio of the density of a substance to water.
Threshold limit value (TLV) —The same concept as PEL, except that TLVs do not have the
force of governmental regulations behind them but are based on recommended limits estab-
lished and promoted by the American Conference of Governmental Industrial Hygienists.
Time-weighted average (TWA) —A mathematical average of exposure concentration over a
specific time: Exposure (ppm) × Time (hours) × 1/4 Time (hours).
Total quality management (TQM) —A way of managing a company that entails a total and
willing commitment of all personnel at all levels to quality.
Toxicit y —The relative property of a chemical agent with reference to a harmful effect on
some biologic mechanism and the condition under which this effect occurs. The quality of
being poisonous.
Toxicology —The study of poisons, which are substances that can cause harmful effects to
living things.
Unsafe condition —Any physical state that deviates from that which is acceptable, normal, or
correct in terms of past production or potential future production of personal injury and/
or damage to property; any physical state that results in a reduction in the degree of safety
normally present.
Upper explosive limit (UEL) —The maximum concentration of a flammable gas in air required
for ignition in the presence of an ignition source.
Vulnerability assessment —A very regulated, controlled, cooperative, and documented evalu-
ation of an organization's security posture from outside-in and inside-out, for the purpose
of defining or greatly enhancing security policy.
Workers' compensation —A system of insurance required by state law and financed by
employers that provides payments to employees and their families for occupational ill-
nesses, injuries, or fatalities incurred while at work and resulting in loss of wage income,
usually regardless of the employer's or employee's negligence.
Zero energy state —The state of equipment in which every power source that can produce
movement of a part of the equipment, or the release of energy, has been rendered inactive.
15.4 INDOOR AIR QUALITY
Unless we are confronted by an unusual odor or are for some reason having trouble breathing, most
of us rarely think about the air we inhale and exhale with such regularity. For us, “The air is the air”
( Star Trek ), and few of us realize the risks conveyed by the air we breathe and that we all face a vari-
ety of risks to our health as we go about out day-to-day lives (USEPA, 2003). Driving our cars, fly-
ing in planes, engaging in recreational activities, and being exposed to environmental pollutants all
pose varying degrees of risk. Some risks are simply unavoidable. Some we choose to accept because
to do otherwise would restrict our ability to lead our lives the way we want. And some are risks
we might decide to avoid if we had the opportunity to make informed choices. Indoor air pollution
is one risk that we can do something about. In the last several years, a growing body of scientific
evidence has indicated that the air within homes and other buildings can be more seriously polluted
than the outdoor air, in even the largest and most industrialized cities. Other research indicates that
people spend approximately 90% of their time indoors. Thus, for many people, the risks to health
may be greater from exposure to air pollution indoors than outdoors (USEPA, 2003). In addition,
people who may be exposed to indoor air pollutants for the longest periods of time are often those
most susceptible to the effects of indoor air pollution. Such groups include the young, the elderly,
and the chronically ill, especially those suffering from respiratory or cardiovascular disease. The
impact of energy conservation on inside environments may be substantial, particularly with respect
to decreases in ventilation rates (Hollowell et al., 1979a) and “tight” buildings constructed to mini-
mize infiltration of outdoor air (Hollowell et al., 1979b; Woods, 1980).