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Define dust.
- created through mechanical action of crushing or griding
- size is 1- >100 um with the >100 um settle out of air due to gravity
- have different shapes and densities
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Define Fumes.
- Condenstation of materials from the gaseous state
- size: 1 micron to 0.01 microns or less
- Example: metal fumes
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Define smoke.
Incomplete combustion of materials containing carbon such as coal or oil
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Define mists.
Condensation from gaseous to liquid state. Occurs in spraying operations/ splashing
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Give example to illustrate lung defense mechanisms.
Coal miner inhales 1000 g of dust in a lifetime, but post mortem we only find 40 g of dust.
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List and explain the three repritory defenses.
- Nasopharyngeal region: nose acts as a filter
- Trachealbronchiolar Region: Mucociliary escalator (can be paralyzed by chemicals such as smoking)
- Alveolar region: Macrophages (if overwhelmed, can lyse, releasing enzymes that destroy lung tissues)
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What are the 4 methods of disposition of particle in the lung?
- Interception
- Impaction
- sedimentation
- diffusion
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What is the most important form of deposition for asbestos? What factors determine location.
- Interception is the most important factor because it can travel close to the surface of the airway passage
- Diamter and length of fiber determine the lcation. 1 micrometre diameter and length of 200 micrometer deposit in the bronchial tree.
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What is impaction? what factors affecting it?
- When bend in the airway system, the particles tend to continue their original path and stick to the surface in the particles original path.
- impaction depends on air velocity and the particle mass
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What is sedimentation? What factors determine sedimentation?
- Occurs when force of gravity = forces of the air resistance which creates terminal velocity of the particle.
- Aerodynamic diameter, size or density
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What is "brownian motion"? Name the mechanism by which particles deposit in smaller airways.
- It is the random motion of particles similar to gas molecules when the particle is < 0.5 micrometers. Smaller the particle the more vigorous the movement
- These particles deposit in lung and diffusion is the most important mechanism for deposition in the small airways and alveoli
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List the aerodynamic diameter where 50% is inhalable, thoracic and respirable.
- Inhalable is 100 micrometer
- Thoracic is 10 micrometer
- Respirable is 4 micrometer
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How has ACGIH considered aerodynamic diameter?
There are different TLV for inhalable fraction, thoracic fraction and respirable fraction
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According to ACGIH where are the inhalable, thoracic and respirable particle the most hazardous?
- Respirable - deposited anywhere in the respiratory tract
- Thoracic - deposited anywhere within the lung airways and the alveoli
- Respirable - particles that are small enough to reach the alveoli and deposit in that region
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Whats the difference between momentum of large and small particles? How can they be controlled?
- Large particles fly from the source with kinetic energy
- Smaller particles have less kinetic engery but move with the air that contains them
- Can be controlled by local exhaust ventilation.
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What does it mean mechanical actions moving particulate?
- particulate clouds moved by fan, dust dispersion by fan action
- air movement generated by grinding wheel
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What is entrainment? How can it be controlled?
- Drafts (drafts due to windows and doors being open)
- Wakes caused by the movement of equipment ex: truck as moves
- it can be controlled by good house keeping
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What is induction?
- Air escapes through cracks in chute dispersing the dust
- Material falling down chutes induces the air to follow down with material.
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What is conduction?
- Motion in air from differences in density and action of gravity
- Moving up with heating of air; cooling at ceiling
- Trapped air may not be remmoved by exhaust ventilation
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What is Silicon?
Silicon is the element.
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What is Silica?
- Silica is silicon dioxide (SiO2)The oxide that is found in the highest % in the earths crust
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What is Silicones?
Silicones are silicon + carbon, and usually oxygen as well
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What is Silicates?
Silicates are silicon-oxygen tetrahedron (SiO4), bound with sodium, potassium, calcium, magnesium, iron and aluminum
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What forms do Silica come in and what is the most toxic form?
- Crystalline and amorphous forms (non-crystalline)
- crystalline are most toxic causing scarring
- amourphous form causes irritation
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What are the different forms of Crystalline? What are the most prominant forms of crystalline?
- The four forms are Cristobalite, Tridymite, other rare and Quartz (alpha and beta).
- Quartz is the most prominent form (alpha > beta); and cristobalite is the second most popular.
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Where is Quartz Silica found the most? Why is the term quartz used in some places for crystalline silica?
- Abundant in most rock: granites, sandstones, sands, and soils
- The term is used because quartz is so abundant
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What is Silicosis?
- Fibrosis (Scarring) of the lungs
- Forms in patches, so can still be some functional tissue and lungs still compliant
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What are the three types of silicosis and their definition?
- Chronic Silcosis: after 10 or more years of over exposure
- Accelerated Silicosis: result of higher exposures and develops over 5-10 years
- Acute silicosis: occurs when exposures highest and devleops within weeks to 5 years.
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What is another name for acute silicosis? What is a complication with this type of silicosis.
- Silicotic Alveolar Proteinosis [ rare]
- often complicated by tuberculosis
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What other diseases are associated with accelerated silicosis?
Associated with autoimmune disease such as scleroderma (hardening of skin)....can occur even after exposure stops
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What are other toxicities of silica?
glomerulonephritis, liver, spleen, immune disorders (scleroderma, rheumatoid arthritis, progressive systemic sclerosis)
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What is the cancer rating of Quartz and Cristobalite?
Group 1 by IARC
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