Page 278 - Industrial Ventilation Design Guidebook

5.3 TOXICITY AND RISKS INDUCED BY OCCUPATIONAL EXPOSURE TO CHEMICAL COMPOUNDS 239

Respiration: Physiological process of taking in oxygen and expelling oxida-
tive waste products (carbon dioxide, water).
Respiratory air conditioning: Heat and water vapor exchange occurring in
proximal airways that warms and humidifies inspired air to approximate
alveolar conditions.
Respiratory bronchioles:
Respiratory exchange ration: Ratio of carbon dioxide production to oxygen
uptake, a measure of aerobic metabolism.
Reverse flow: Portion of a flow moving in a direction opposite that of the
bulk of the flow.
Secretory cells: Cells producing substances (e.g., mucus) with physiochemi-
cal properties differing from cellular components.
Smooth muscle: Involuntary muscle tissue found in viscera and blood vessel
walls.
Soft palate: Movable fold along the posterior superior portion of the oral
cavity dividing the nasopharynx and oropharynx.
Squamous epithelium: Flattened, interlocking, toughened epithelial cells.
Submicrometric particle: Airborne particle with a diameter less than one
micrometer.
Submucosa: Layer of tissue beneath the airway epithelium.
Surfactant: Monomolecular layer of material secreted by Type II alveolar
cells that lowers alveolar surface tension and stabilizes alveolar volume.
Temperature gradient: Difference in temperature measured between two points.
Thermoregulation: Physiological process attempting to maintain body core
temperature at approximately 37 °C.
Tidal volume (V T ): Volume of air inspired or expired with each breath.
Total lung capacity (TLC): Total volume of air that can be contained within
the respiratory tract during maximal inspiration.
Toxin: Poisonous material.
Tracheobronchial tree: Series of bifurcating tubes originating at the trachea
that conduct air to and from the respiratory airways.
Transepithelial: Passing across a layer of epithelial cells.
Upper airway: The portion of the human conducting airways proximal to
and including the larynx.
Ureolysis: Physiological process that breaks down urea and releases ammonia.
Vasculature: Blood supply consisting of arteries, capillaries, and veins.
Vital capacity (VC): Greatest possible inspired volume.
Wetted perimeter: Perimeter of conduit in contact with moving fluid.
Work of breathing: Metabolic cost of breathing.

5.3 TOXICITY AND RISKS INDUCED BY OCCUPATIONAL
EXPOSURE TO CHEMICAL COMPOUNDS

5.3.1 Introduction and Background
5.3.1. i Health Hazards Due to Occupational Exposure
Workers exposed to chemicals often experience discomfort and adverse
health effects which may progress to occupational diseases. Even though
working conditions have improved markedly during recent decades, in general