(Created 12/02)
UNL Environmental Health and Safety · (402) 472-4925 · http://ehs.unl.edu
conducting airway between the nasopharyngeal region and alveoli. These passage ways are lined
with ciliated epithelium coated by mucous, which serves as an escalator to move particles from
deep in the lungs back up to the oral cavity so they can be swallowed. These ciliated cells can be
temporarily paralyzed by smoking or using cough suppressants. (3) Pulmonary acinus--is the
basic functional unit in the lung and the primary location of gas exchange. It consists of small
bronchioles which connect to the alveoli. The alveoli, of which there are 100
million in humans,
contact the pulmonary capillaries.
Inhaled particles settle in the respiratory tract according to their diameters:
• 5-30 micron particles are deposited in the nasopharyngeal region.
• 1-5 micron particles are deposited in the tracheobronchial region.
• Less than 1 micron particles are deposited in the alveolar region by diffusion and
Brownian motion.
In general, most particles 5-10 microns in diameter are removed. However, certain small
inorganic particles, settle into smaller regions of the lung and kill the cells which attempt to
remove them. The result is fibrous lesions of the lung.
Many chemicals used or produced in industry can produce acute or chronic diseases of the
respiratory tract when they are inhaled
(Table 5). The toxicants can
be classified according to
how they affect the respiratory tract.
•
Asphyxiants: gases that deprive the body tissues of oxygen
•
Simple asphyxiants are physiologically inert gases that at high concentrations displace
air leading to suffocation. Examples: nitrogen, helium, methane, neon, argon.
•
Chemical asphyxiants are gases that prevent the tissues from getting enough oxygen.
Examples: carbon monoxide and cyanide. Carbon monoxide binds to hemoglobin 200
times more readily than oxygen. Cyanide prevents the transfer of oxygen from blood to
tissues by inhibiting the necessary transfer enzymes.
•
Irritants: chemicals that irritate the air passages. Constriction of the airways occurs and
may lead to edema (liquid in the lungs) and infection. Examples: hydrogen fluoride,
chlorine, hydrogen chloride, and ammonia.
•
Necrosis producers: Chemicals that result in cell death and edema. Examples: ozone and
nitrogen dioxide.
•
Fibrosis producers: Chemicals that produce fibrotic tissue which, if massive, blocks
airways and decreases lung capacity. Examples: silicates, asbestos, and beryllium.
•
Allergens: Chemicals that induce an allergic
response characterized by
bronchoconstriction and pulmonary disease. Examples: isocyanates and sulfur dioxide.
•
Carcinogens: Chemicals that are associated with lung cancer. Examples: cigarette
smoke, coke oven emissions, asbestos, and arsenic.
Not only can various chemicals affect the respiratory tract, but the tract is also a route for
chemicals to reach other organs. Solvents, such as benzene and tetrachloroethane, anesthetic
gases, and many other chemical compounds can be absorbed through
the respiratory tract and
cause systemic effects.
(Created 12/02)
UNL Environmental Health and Safety · (402) 472-4925 · http://ehs.unl.edu
