Transcript 4a. Inhalation Expos..

Inhalation Exposures
Respiratory System
• Nasal Cavity
• Pharynx and Bronchial Tubes
• Alveoli
Sources: http://seniorhealth.about.com/library/conditions/blresp.htm, http://www.udel.edu/biology/Wags/histopage/illuspage/ire/ire.htm
Sources: http://seniorhealth.about.com/library/conditions/blresp.htm, http://www.udel.edu/biology/Wags/histopage/illuspage/ire/ire.htm
Sources: http://seniorhealth.about.com/library/conditions/blresp.htm, http://www.udel.edu/biology/Wags/histopage/illuspage/ire/ire.htm
Sources: http://seniorhealth.about.com/library/conditions/blresp.htm, http://www.udel.edu/biology/Wags/histopage/illuspage/ire/ire.htm
Sources: http://seniorhealth.about.com/library/conditions/blresp.htm, http://www.udel.edu/biology/Wags/histopage/illuspage/ire/ire.htm
Nasal Cavity
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Mucous-lined passageway
Larger particles trapped in mucous
Sneezing reflex acts to expel particles
By-passed by mouth breathing under
exertion, congestion, or habituation
Pharynx and Bronchial Tubes
• Continuously subdividing branches
• Increased cross-sectional area leads to
decreased velocity
• Particles settle as velocity decreases
• Mucous migrates toward nasal cavity
through motion of cilia
Alveoli
• Small sacs (200 m diameter) at ends of
bronchi
• Tissue effects gas exchange with blood, O2
for CO2
• Phagocytic cells escort particles out of
alveolus if they can (but tobacco smoke
inhibits this)
Atmospheric Contaminants
• Particles
• Gases or vapors
Specific Hazardous Particulates
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Silica
Asbestos
Fiberglass
Coal Dust
Silica
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SiO2
Silicosis from respirable particles (> 5 m)
Toxic to phagogcytic cells
Enzymes resulting from digestion of dead
cells leads to fibrosis (scarring of tissues)
• Some concerns about juvenile exposure to
“play sand” (especially fine sand sold for
childrens’ sandboxes)
Asbestos
• Fibrous minerals resistant to heat
• Asbestosis is a fibrosis resulting from
penetration of short (e.g. 1 m) fibers
becoming embedded in respiratory passages
• Irritation, edema, and scarring
• Some varieties carcinogenic, and exacerbate
effect of carcinogens in tobacco smoke
Fiberglass
• Glass “wool” - thin fibers of glass
• Used as insulation and fabrication material
• Acts as irritant to lung tissue (as well as to
epidermis)
Coal Dust
• “Black Lung” disease
• Dusts raised during mining operations settle
in lungs
• Fibrosis associated with other materials in
mine atmosphere (e.g. silica)
Other Dusts
• Dusts from cotton in textile manufacturing
(“brown lung” disease)
• Plastic dusts from circuit board manufacture
(hole drilling for pin insertion)
• Infectious dusts from poultry excrement
(avian emphysema)
Hazards of Gases
• Asphyxiants
• Irritants
Asphyxiants
• Reduce available oxygen supply
• Brain most susceptible to diminished
oxygen availability
• Two kinds:
– Dilution - oxygen intake reduced due to lower
concentration (in company of such gases as
nitrogen, methane, or CO2)
– Chemical inhibition (CO, hydrogen cyanide,
hydrogen sulfide)
Irritants
• Often acids or acid precursors
• Upper and Lower respiratory tract
categories
• Upper RT usually more immediate, and
therefore more likely worker would leave
area
• Lower RT often characterized by long time
delay - worker may not react in time
Vapors
• Many volatile compounds associated with
toxic endpoints
• Boiling point a major determining factor in
degree of exposure
• Odor or immediate irritation sometimes
serves as warning
• But many (such as phosgene) do not present
such warnings until very toxic levels have
been experienced
Occupational Asthma
• Allergic inflammation of the lungs
• Effects 3% of the population
• Wheezing, coughing, shortness of breath in
a worker may indicate an allergic response
to a material in the workplace atmosphere