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Particulates Chapter 8

Particulates Chapter 8. Background. Particulate matter considered an aerosol when suspended in air. Size range of particulates from <100-<1 μg Agricola (1491-1555) & Ramazzini described hazards of aerosols in mining. Alice Hamilton in early 20 th century Particulates also hazardous by skin

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Particulates Chapter 8

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  1. ParticulatesChapter 8

  2. Background • Particulate matter considered an aerosol when suspended in air. • Size range of particulates from <100-<1 μg • Agricola (1491-1555) & Ramazzini described hazards of aerosols in mining. • Alice Hamilton in early 20th century • Particulates also hazardous by skin • Soot • Nuisance dusts is least hazardous • PM 10 • Particulate matter 10 μm

  3. Types of Particulate Matter • Dusts • Produced by mechanical action on larger pieces of the material • Mists • Droplets of liquid created by breaking liquid into small particles • Fume • Formed by evaporation and rapid condensation of metal vapor

  4. Types of Particulate Matter • Smoke • Products of incomplete combustion of organic materials • Biological agents • Include and living and nonliving agents that may be allergenic, toxigenic or infectious

  5. Selected Hazardous Particulates • Asbestos • Asbestosis, cancer • Beryllium • Berylliosis, cancer • Bacteria • Humidifier fever • Cotton dust • Byssinosis

  6. Particulate Size Determination • Aerodynamic (equivalent) diameter • Diameter of a unit-density sphere having the same gravitational-settling velocity as the particle in question • Aerodynamic diameter takes into account the shape, roughness, and aerodynamic drag of the particle. • Used for movement of particles through a gas

  7. Particulate Size Determination Workers are not exposed to single particles but rather to large masses of particles suspended in air (particle clouds). Particle clouds may be: • Monodisperse • Composed of airborne particulates with a single size or a small range of sizes • e.g. fog from boiling acid; welding fumes • Polydisperse • Composed of airborne particulates of many different sizes • e.g. sand blasting; paint spraying

  8. Factors that Influence Toxicity of Inhaled Substances • Inhalable particulate mass • A particle which is deposited anywhere in the human respiratory tract • Thoracic particulate mass • A particle which is deposited anywhere within the lung airways and the gas-exchange region of the human respiratory tract • Respirable particulate • A particle which is deposited in the gas-exchange region of the human respiratory tract

  9. Selected Hazardous Particulates • Diesel exhaust • Lung cancer • Lead & compounds • CNS, blood • Nickel • Nasal cancer • Pesticides • CNS, cancer • Cadmium, Chromium, Cobalt, Manganese • Cancer, CNS, pneumoconiosis

  10. Particulate Deposition Mechanisms • 1. Inertial impaction • 2. Interception • 3. Sedimentation (settling) • 4. Electrostatic attraction • 5. Diffusion (Brownian movement)

  11. Particulate Deposition • Inertial impaction • Follows Newton’s Law • “a mass in uniform motion tends to remain in motion unless acted upon by outside force”. • Cause the particulate to impact when direction of stream is changed. • Impaction is directly proportional to the density of the particle, square of its diameter, and the velocity of the moving aerosol

  12. Particulate Deposition • Interception • Particle follows air stream fairly closely but contacts surface of lung and sticks • Most effective for mid-size particulates

  13. Particulate Deposition • Sedimentation • All particles are acted upon by gravity • Dependent upon the particle’s mass • Particle movement is resisted by aerodynamic drag created by the particle moving downward • The terminal rate of settling (Vt) for most particles can be calculated by Vt = g/m3 x 980 cm/sec2 x Cf x d2 1.8 x 10-4 g/cm/sec x dynamic shape factor

  14. Particulate Deposition • Electrostatic attraction • Charged particles are attracted to opposite charge • Not important in lung deposition but in sampling and collection

  15. Particulate Deposition • Diffusion (Brownian Movement) • very small particles wiggle around randomly and settle out when they bump on a surface. • Very small & slow moving particles favors deposition by diffusion

  16. Critical Factors in Determining Exposure • Chemical & biological composition • Crystalline, structural, & isotopic forms of particles • Shape of particles • Size of particles • Dose- concentration vs duration • Pre-existing health or genetic status • Concurrent exposure to other toxic agents

  17. Chemical & Biological Composition • Chemical composition can be primary concern • Lead, cadmium, silica, smoke composition,radiological particles, etc. • Biological organisms • Type and numbers

  18. Crystalline, Structural, Isotopic Nature • Silica dust • “free crystalline silica” • Diatomaceous earth • Fumed silica • Silica gel • Smokes, soots, organic origin • Radioisotopes

  19. Shape of Particle • Asbestos • Fibrous shape • Length and width play a role in PEL and TLV • Aspect ratio • Silica has three dimensional crystalline shape or structure • Particles can also have shapes including • Uneven pellet shapes • Rock-like shapes • Round • Flat • Oblong

  20. Size of Particle • Toxicity of some particles is heavily dependent upon size • Equivalent aerodynamic diameter is what IH is concerned about • Predicts how the particle will behave when inhaled and where it will be deposited in lungs • PM10 are particles of 10 m which are respirable. • 2.5 m are very respirable.

  21. Dose vs. Duration • Concentration in the air is one of if not the most important factors for exposure • Some materials have very small PELs and others have large PELs • Asbestos vs Silica • Beryllium exposure in occupational setting is 200 times less than in general public • Just as important for exposure to many materials is the duration of exposure • Metal fume fever is acute exposure vs cancer or asbestosis which is chronic

  22. Pre-Existing or Genetic Status • PELs/TLVs are set for healthy workers • Susceptibility of individuals is not taken into account when setting these levels • Some medical evaluation is done as in pre-employment physicals and medical history

  23. Concurrent Exposures • Exposures do not normally occur in isolation • Some exposures follow the same route but have very different effects on body • Some materials may also be additive, synergistic or potentiators • Lead & thallium can be additive as they have similar toxic effects • When the exposures are measured together, the TWA fractions of the exposure limits are added, if total is >1.0 than overexposure has occurred • Asbestos & smoking are synergistic- multiplier effect

  24. Biological Reactions • Pulmonary irritants • Pulmonary edema • Acute or chronic bronchitis • Allergic sensitization • Fibrosis • Emphysema • Systemic toxicity • Lymphatic toxicity • Infection • Oncogenesis • Metal fume fever

  25. Air Sampling & Analysis • Sampling for particulates is a fundamental activity by IH’s • Determine exposure vs PEL/TLV • Microbiological sampling is generally area sampling using plates or impingers • Breathing zone sampling • Personal • Sampling pump and cassette attached to worker • Area sampling • Area where workers are • Sampling pump and cassette placed in area • New instantaneous instruments to measure total, PM10 and PM2.5

  26. Air Sampling • Size selective particle sampling on filters for either gravimetric or microscope counting of fibers • Respirable dust is collected on a filter (37mm) using a cyclone set up • Gravimetric analysis • Asbestos is collected on smaller filter • 25 mm

  27. Biological Monitoring • Biological monitoring for individuals is used to determine absorbed dose. • Urine • Blood • Exhaled air • Hair • Nail • Feces

  28. Silica • Produces silicosis from the free silica found in crystallized silica such as sand • Quartz PEL (mg/m3), respirable dust

  29. Asbestos • Produces several diseases • Asbestosis • Lung cancer • Mesothelioma • Cancer of • Stomach • Colon • Rectum • PEL (f/cc) = 0.2 f/cc – 2 f/cc

  30. Lead • Produces lead poisoning • Acute exposure • Systemic poisoning and seizures • Chronic exposure • Damages blood-forming bone marrow and the urinary, reproductive, and nervous systems • PEL (µg/m3) • 50 µg/m3

  31. Beryllium • Causes severe systemic disease • Acute exposure • Chemical pneumonitis • Chronic exposure • Berylliosis • PEL (µg/m3) • 2.0 µg/m3

  32. Coal Dusts • Causes • Coal workers’ pneumoconiosis • Black Lung • Chronic bronchitis • Silicosis • Free silica in coal dust • Regulated by MSHA • Standard of 2.0 mg/m3 • OSHA regulates coal dust away from mines • PEL = 2.4 mg/m3 of respirable dust • containing < 5% free silica • if free silica is >5% • PEL same as free silica

  33.  Toxic Dusts and Fumes • Welding fumes • Produce metal fume fever • PEL is dependent on type of metal • Zinc has PEL (fume) • 5 mg/m3

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