gasses (1)

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• Particulates

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The Nature of Particulates

• Particulates made up of solids liquids
• Particle size is a critical factor in industrial
  hygiene
• respirable v non-respirable
• size measured in microns
• gases vapors .0002 - .01microns (µ)
• tobacco smoke .01 - 0.4 µ
• metal dusts fumes .001 - 50 µ
• Smallest particle visible w/ optical microscope
  oil immersion lens .25 µ

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Types of Particulates

• Dusts dry airborne solids from mechanical
  action (grinding, cutting, etc.)
• Fumes fine solid aerosol particles produced
  from the condensation of vaporized solid material
  (welding, .
• Mists droplet aerosols produced from bulk
  liquid by mechanical processes
• Smoke air suspended particles (usually from
  combustion)
• Fibers are elongated particles with length much
  greater than width.

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Hazards of Particulates

• Damage to lung lining from inhalation
• pneumoconiosis fibrous hardening
• cancer
• Systemic reactions
• metal fume fever
• blood absorption (biologically active)
• sensitization/allergic reactions
• infections
• irritation
• radioactive damage

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Exposure Factors

• Type of particulate
• nuisance dust
• Asbestos
• Silica
• Length of exposure (sometimes years)
• Concentration
• how much is in the air
• Particle size (key factor)

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Particle Size

• Aerodynamic size particle behavior in air
  depends on density, size, shape. A particle
  with aerodynamic size of 10u may not have an
  actual size of 10u but behaves like a spherical
  particle, unit density and 10u diameter.
• Surface area
• important role in hazard severity
• e.g. chunk of coal wont light, but dust in air
  will explode
• a cube 1cm/side 6cm2 cut into smaller cubes
  1µ/side, surface area 6m2

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Airborne Particles

• Size (microns)
• .25
• .5
• 1.00
• 2.00
• 5.00

• Time to Fall 1 Foot (sec.)
• 590
• 187
• 54
• 14.5
• 2.5

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Respiratory Deposition

• Visible dust (? 50µm) is usually less hazardous
  than non-visible dust (lt 50µm)
• Large particles filter out in nose throat
• Particle Size Deposition in Lungs
• ? 5µm Retained in upper resp
  tract
• .5 - 5.0µm Deposited in small airways
• .1 - .5µm Mostly exhaled, not
  deposited
• lt.1 µm Deposits readily by
  Brownian motion.

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Dust Sampling

• Use air pumps and filters
• Gravimetric measurement
• results reported in mg/m3
• Pump 2 lpm 1 mg dust/8 hrs
• 2 x 480 min 960 liters
• or 1 mg/m3
• Asbestos is measured in number of fibers/cc
• use microscopy to characterize
• OSHA limits 0.1 fiber/cc 8 hr TWA
• 1.0 fiber/cc 30 min short term excursion limit
  (STEL)

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Respirable Dust

• Cyclone used to separate respirable dust from
  total dust
• Traps only respirable dust on filter

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Respiratory Damage

• Pneumoconiosis accumulation of dust in lung and
  tissue reaction to its presence (coal, silica,
  asbestos, etc.)

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Biological Reactions

• Systemic Toxicity
• particles absorbed by blood affect target organ
• Most metal dusts (cadmium, mercury)
• Metal Fume Fever
• inhalation of fine (lt0.1 - 1.0 µm) particles of
  zinc, magnesium, copper
• flu like symptoms which subside in 24 - 48 hrs,
  w/ no permanent effects
• may experience symptoms after return from vacation

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Biological Reactions

• Allergic or Sensitization Reaction
• typically organic dusts (flour, wood, grains)
• may cause asthmatic reaction (constriction of
  bronchial tubes)
• Bacterial Fungal Infections
• dusts containing active organisms
• found in organic materials
• Irritants
• alkalis, acid mists
• Tissue Damage - radioactive materials

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Silica (SO2 )

• Crystalline form can cause silicosis
• Crystalline silica in foundries, glass
  manufacturing, granite rock quarries, tunneling,
  mining, sand blasting
• Silicosis fibrotic condition of the lung
  fibrosis doesnt allow O2 and CO2 to pass as
  fibrosis builds up, volume of lung available for
  gas exchange decreases
• Fibrosis will occur after exposure ceases

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Silicosis Symptoms

• Symptoms
• cough, wheezing, non-specific chest illness
• lung function tests demonstrate reduced capacity
• chest x-rays may show silica nodules in lung
• most cases chronic
• TLV 0.1 mg/m3 OSHA has complex formula which
  comes out the same
• Current analytical methods w/ x-ray diffraction
  allow direct analysis for silica

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Acute Effects

• Acute
• 8 to 18 months to develop after first exposure
• rapidly developing silicosis
• occurs in abrasive soap powder manufacture sand
  blasting
• pneumoconiosis, survival relatively short after
  onset
• dyspnea, coughing, wheezing, no nodulation

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Chronic Effects

• Chronic Effects
• develops after several years of exposure
• occurs in mining, foundries those for acute
• dyspnea, getting progressively worse
• x-ray shows nodulation, TB common complication
• apparently not significant in cancer causation

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Asbestos

• Group of magnesium and iron silicates
• Pyroxenes most common form in U.S. includes
  chrysoltile
• other group are the amphiboles which include
  amosite, crocidolite, tremolite, anthophylite and
  actinolite.
• Chrysotile curly or serpentine form of asbestos
• most common
• thought to be less toxic than other forms
• Amosite rod like structure
• thought to be one of most toxic forms
• Tremolite naturally occurring in talc

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Asbestos Related Diseases

• Asbestosis
• scarring of lung tissue
• reduces lung function
• like silica is degenerative after exposure ceases
• Mesothelioma
• thickening of lung lining
• nearly unique to asbestos
• untreatable illness, nearly always fatal
• Lung cancer synergistic w/ tobacco smoking

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Asbestos Regulations

• EPA has banned in U.S.
• OSHA PEL based on lowest detectable level, not
  safe exposure
• Requires medical surveillance, training, specific
  controls measures

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Other Diseases and Toxic Dusts

• Beryllium - toxic to respiratory system
• Black Lung disease - exposure to coal dust
• Siderosis - exposure to iron oxide
• Biologically active dusts
• organic dusts, bacteria, molds, fungus
• associated with indoor air quality problems
• Legionnaires disease
• allergies, asthma

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Hazard Control

• Substitution
• sand blasting use non-silica material
• asbestos cellulose based insulation
• Work Practices
• wet methods, containment, HEPA filters
• Personal Protective Equipment
• respirators air supplied hoods HEPA filters
• Medical Surveillance
• x-rays pulmonary function exposure history