Pub Health 4310 Health Hazards in Industry

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Pub Health 4310Health Hazards in Industry

• Dave Wallace
• Lecture 6
• Dusts and Pneumoconiosis

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DUSTS AND PNEUMOCONIOSES

• Objectives
• This class session is intended to provide an
  overview of the health hazards and
  characteristics of important particulates that
  may be encountered in the workplace.
• Students should be able to
• Identify a variety of particulate hazards
• Know about diseases of particulate exposure,
  including disease mechanisms
• State methods of controlling particulate exposure

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DUSTS AND PNEUMOCONIOSES

• Introduction
• Many toxic agents occur as particulates.
• Factors which affect the hazard
• Particle size
• Other physical characteristics.
• Many important diseases are caused by
  particulate exposure
• Great many workers have suffered
• Dust exposure continues to be a serious
  industrial hygiene concern.
• There are too many cases of silicosis and other
  pneumoconiosis.

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DUSTS AND PNEUMOCONIOSES

• Definitions
• Particulate matter Fine solid or liquid
  particles, such as dust, fog, mist, smoke or
  sprays.
• Aerosol Liquid droplets or solid particles
  dispersed in air.
• Dust Solid particles generated by mechanical
  action, (crushing, grinding, impact, etc.)
• Fume Solid airborne solid particles formed by
  condensation of vapor (i.e., welding fumes).

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DUSTS AND PNEUMOCONIOSES

• Definitions
• Mist Suspended liquid droplets generated by
  condensation or atomization. (Fogs are formed by
  condensation).
• Smoke An aerosol of fine particle matter
  originating from combustion. Smoke usually
  contains droplets and dry particles
• Fiber at least 31 aspect ratio
• Pneumoconiosis Dusty lung disease, the
  accumulation of dust in the lugs and the tissue
  reaction to its presence

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DUSTS AND PNEUMOCONIOSES

• Particle Physics
• Physical characteristics of dust particles affect
• How they settle out from the air
• How they are deposited in the lung
• How they adhere to other particles and surfaces
• Particle size in a population
• Particles may be essentially the same size
  (monodisperse), often artificially created
• Different sizes, (polydisperse)
• Particles usually are logarithmically distributed

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Logarithmic particle distribution in air

• From the 1973 original NIOSH white book, The
  Industrial Environment, its Evaluation and Control

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DUSTS AND PNEUMOCONIOSES

• Particle Physics (cont.)
• Probability-log graph shows the distribution of
  particle size, mass, and surface area.
• For this distribution
• Mean diameter 1.5 µm (micrometers)
• Mean surface area 4.2µm (micrometers)
• Mean mass 7.8 µm (micrometers)
• Toxicity may be affected by factors of mass,
  particle size, and surface area

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DUSTS AND PNEUMOCONIOSES

• Particle Physics (cont.)
• Physical characteristics of dust particles affect
  how they settle out from the air and how they are
  deposited
• For particles from about 1 to 50 microns
  diameter, the settling velocity is a function of
  the specific gravity, ? and diameter, d in µm
  (micrometers)

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DUSTS AND PNEUMOCONIOSES

• Particle Physics (cont.)
• Larger particles can settle out of the air by
  gravity
• Small particles have very low settling velocity
  but they are removed from the air by attractive
  forces
• Particles attach to other particles
• Agglomerates form, which rapidly settle
• Particles attach to surfaces
• Humidity increases attractive forces
• Moisture on particles increases mass and surface
  area

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DUSTS AND PNEUMOCONIOSES

• Particle Physics (cont.)
• Deposition in the body
• Larger particles are trapped in the mucous of the
  airways and moved out of the lung by the action
  of cilia, the mucociliary escalator
• gt10 µm particles are deposited in the upper
  respiratory tract (nose and throat)
• 5-10 µm particles are deposited in the airways of
  the lung
• lt5 µm particles are deposited in the respiratory
  bronchioles and alveoli
• Removed by macrophages (white blood cells)

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DUSTS AND PNEUMOCONIOSES

• Diseases
• Occupational asthma
• An immunological response
• Sensitized individuals suffer from constricted
  airways (wheezing) upon exposure to certain
  dusts.
• Particulates that may cause asthma include
• Grain and cereal dusts
• Wood dust, especially western red cedar and
  hardwoods
• Detergent enzymes
• Isocyanates (these may be vapors or mists)
• Solder fumes (colophony or rosin)

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DUSTS AND PNEUMOCONIOSES

• Diseases
• Occupational asthma (cont.)
• OELs for allergic responses are set to prevent
  initial sensitization.
• OELs will not protect workers who have become
  sensitized
• Once a person has become sensitized, they usually
  must seek another line of work.

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DUSTS AND PNEUMOCONIOSES

• Diseases (cont.)
• Byssinosis
• Caused by exposure to dust from cotton, flax and
  hemp.
• Characterized by airway constriction, but is not
  an immunological response.
• Affected individuals suffer from chest
  tightness, cough, and shortness of breath.
• Symptoms usually occur when workers return on
  Monday after a weekend away from exposure.

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DUSTS AND PNEUMOCONIOSES

• Diseases (cont.)
• Byssinosis (cont.)
• those who hackle in the flax and hemp to prepare
  it for being spun and wove, afford frequent
  instances of the unwholesomeness of their trade
  for there files out of this matter a foul
  mischievous powder, that entering the lung by the
  moth and throat, causes continual coughs and
  gradually makes way for an asthma . . . but at
  the long run if they find their affliction grows
  upon them they must look out for another trade
  for tis a sordid profit thats accompanied with
  the destruction of health.
• Bernardino Ramazzini, 1705

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DUSTS AND PNEUMOCONIOSES

• Diseases (cont.)
• Extrinsic Allergic Alveolitis (hypersensitivity
  pneumonitis, or HP)
• Allergic type response that affects the lung
  parenchyma rather than the airways.
• Sensitized individuals suffer from fevers, chills
  shortness of breath and cough
• Symptoms occur 4 - 8 hours after exposure.
• Names of various conditions reflect the cause
• Farmers lung, mushroom workers lung, malt
  workers lung, bird fanciers lung, coffee
  workers lung, etc.,

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DUSTS AND PNEUMOCONIOSES

• Diseases (cont.)
• Pneumoconiosis
• Caused by small particles that collect in the
  alveolar areas of the lung.
• Scarring (fibrosis) of the lung tissue results
  from inflammatory response to these particles.
• The disease is progressive
• Symptoms increase as time passes

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DUSTS AND PNEUMOCONIOSES

• Diseases (cont.)
• Silicosis
• Pneumoconiosis caused by exposure to crystalline
  silica
• Observed among miners since the times of the
  Greeks and Romans.
• In Bernardino Ramazzini, the founder of
  occupational medicine, wrote,
• We must not underestimate the maladies that
  attack stonecutters, sculptors, quarrymen, and
  other such workers. When they hew and cut marble
  underground or chisel it to make statues and
  other objects, they often breathe in the rough,
  sharp, jagged splinters that glance off."

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DUSTS AND PNEUMOCONIOSES

• Diseases (cont.)
• Silicosis (cont.)
• The nations worst industrial disasters
• Work began on the Hawks Nest Tunnel near Gauley
  Bridge, West Virginia, in 1930
• At least 476 workers died over the next 5 years
  from silicosis
• Death toll could be as high more than 700
• Factors which contributed to the disaster
• Rock with a high silica content
• New power equipment which created more dust
• Dire financial conditions of the Great Depression
• Desire for profits regardless of the human cost
• http//www.wvculture.org/history/wvhs122.html

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Jackleg pneumatic drill
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DUSTS AND PNEUMOCONIOSES

• Diseases (cont.)
• Silicosis (cont.)
• Disease mechanisms
• Macrophages die after ingesting silica particles,
• Cellular contents cause Inflammation and fibrosis
  
• Process repeats when new macrophages ingest
  particles
• Silica was recently identified as a carcinogen.
• Silica exposure continues to be a serious hazard.
  
• More than one million U.S. workers are exposed
• Mining, abrasive blasting, and construction
• More than 250 die annually
• OSHA and NIOSH have increased awareness and
  enforcement
• http//www.osha-slc.gov/SLTC/silicacrystalline/ind
  ex.html
• http//www.cdc.gov/niosh/topics/silica/default.htm
  l

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1996 CDC report on silicosis mortality emphasizes
the continuing importance of this disease.
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DUSTS AND PNEUMOCONIOSES

• Diseases (cont.)
• Asbestosis
• A pneumoconiosis caused by exposure to asbestos
  fibers.
• Small fibers penetrate the lung to the alveolar
  space, where they have an action similar to
  silica.
• Macrophages die after ingesting fibers longer
  than 5 µm in length, leading to a continual
  process of fibrosis.

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DUSTS AND PNEUMOCONIOSES

• Diseases (cont.)
• Berylliosis
• Caused by chronic exposure to beryllium
• Also known as chronic beryllium disease
• Acute exposure can cause irritation, chest pain,
  difficulty breathing
• http//chppm-www.apgea.army.mil/documents/FACT/64-
  003-0302.pdf

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DUSTS AND PNEUMOCONIOSES

• Diseases (cont.)
• Metal Fume Fever
• Flu-like condition caused by inhalation of metal
  fumes.
• The most common cause is exposure to zinc oxide
  fumes from galvanizing operations, or cutting of
  galvanized steel.
• Symptoms usually are worse when workers return
  after a period away from the job, after vacation
  or weekends, etc.

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DUSTS AND PNEUMOCONIOSES

• Diseases (cont.)
• Polymer Fume Fever
• Similar to metal fume fever, but it is caused by
  exposure to fumes from Teflon (PTFE).
• Caused when workers cut Teflon-lined drums with a
  cutting torch
• Other situations where they breathe fumes from
  heated Teflon.
• NIOSH investigated a case where workers were
  exposed when they smoked contaminated cigarettes
  
• http//www.cdc.gov/mmwr/preview/mmwrhtml/00051631.
  htm

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DUSTS AND PNEUMOCONIOSES

• Diseases (cont.)
• Cancer
• Cancer may be caused by exposure to particulates.
  
• Lung cancer from asbestos exposure and possibly
  by other mineral fibers.
• Synergistic effect between smoking and asbestos
  exposure.
• Mesothelioma, cancer of the lining of the lung
• Caused by exposure to asbestos fibers.
• Other mineral fibers may cause cancers
• High levels of mesothelioma in Turkey where
  non-asbestos fibrous minerals are found.
• Silica also has recently been identified as a
  carcinogen

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DUSTS AND PNEUMOCONIOSES

• Diseases (cont.)
• Control
• Dust exposure controlled by wetting, ventilation,
  or by the use of personal protective equipment.
• Substitution is often the best bet for abrasive
  blasting with silica
• Slag products may contain hazardous metals.
• OSHA online silica advisor at
  http//www.osha-slc.gov/SLTC/etools/silica/index.h
  tml details control methods for silica exposure.
• OELs for allergic responses are set to prevent
  initial sensitization.

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Characteristics of particles
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DUSTS AND PNEUMOCONIOSES

• References
• http//www.cdc.gov/niosh/77_181.html
  Occupational Diseases a Guide to Their
  Recognition
• http//www.cdc.gov/niosh/86-102.html ,
  Occupational Respiratory Diseases