Inhalation Exposures

Respiratory System Nasal Cavity Pharynx and Bronchial Tubes Alveoli

Sources:

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, O 2 for CO 2 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 SiO 2 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 CO 2 ) –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