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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 • • • • 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 • • • • Silica Asbestos Fiberglass Coal Dust Silica • • • • 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