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- 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
- Condenstation of materials from the gaseous state
- size: 1 micron to 0.01 microns or less
- Example: metal fumes
Incomplete combustion of materials containing carbon such as coal or oil
Condensation from gaseous to liquid state. Occurs in spraying operations/ splashing
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.
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)
What are the 4 methods of disposition of particle in the lung?
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.
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
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
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
List the aerodynamic diameter where 50% is inhalable, thoracic and respirable.
- Inhalable is 100 micrometer
- Thoracic is 10 micrometer
- Respirable is 4 micrometer
How has ACGIH considered aerodynamic diameter?
There are different TLV for inhalable fraction, thoracic fraction and respirable fraction
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
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.
What does it mean mechanical actions moving particulate?
- particulate clouds moved by fan, dust dispersion by fan action
- air movement generated by grinding wheel
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
What is induction?
- Air escapes through cracks in chute dispersing the dust
- Material falling down chutes induces the air to follow down with material.
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
What is Silicon?
Silicon is the element.
What is Silica?
- Silica is silicon dioxide (SiO2)The oxide that is found in the highest % in the earths crust
What is Silicones?
Silicones are silicon + carbon, and usually oxygen as well
What is Silicates?
Silicates are silicon-oxygen tetrahedron (SiO4), bound with sodium, potassium, calcium, magnesium, iron and aluminum
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
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.
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
What is Silicosis?
- Fibrosis (Scarring) of the lungs
- Forms in patches, so can still be some functional tissue and lungs still compliant
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.
What is another name for acute silicosis? What is a complication with this type of silicosis.
- Silicotic Alveolar Proteinosis [ rare]
- often complicated by tuberculosis
What other diseases are associated with accelerated silicosis?
Associated with autoimmune disease such as scleroderma (hardening of skin)....can occur even after exposure stops
What are other toxicities of silica?
glomerulonephritis, liver, spleen, immune disorders (scleroderma, rheumatoid arthritis, progressive systemic sclerosis)
What is the cancer rating of Quartz and Cristobalite?
Group 1 by IARC
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