Airborne Hazards

1. Airborne Hazards IENG 341 Carter J. Kerk, PhD, PE, CSP, CPE Industrial Engineering Department South Dakota School of Mines Spring 2008

2. Chapter 4 Assignment • Read Chapter 4 • HW4 • Critical Thinking Questions • P. 97 • 1-6 • Due?

3. Outline • Anatomy and function of the lungs • Airborne hazardous materials • Occupational diseases associated with airborne particulates • Oxygen-deficient atmospheres

4. Introduction • Route of entry: Airborne hazards are the most serious concern • Processes: welding, grinding, spraying, hot processes, engine exhausts • Pollen, spores • Lungs: efficient transfer of gases in and out of the body • But also provide a route of entry for hazards

5. Anatomy & Function of the Lungs • Regions of the respiratory tract • Upper (nasopharyngeal) • Middle (tracheobronchial) • Lower (distal) • ACB Plates 91-97

6. Upper (Nasopharyngeal) • Head, nose, nasal passages, sinuses, mouth, tonsils, epiglottis, back of throat • Lined with mucous membrane • Moist, sticky substance captures materials • Many small hairs • Help to trap particles

7. Middle (Tracheobronchial) • Trachea (windpipe), bronchi • Rings of cartilage and muscle • Cartilage provides structural support • Muscles contract to help force air • Coughing, sneezing • Lined with mucous membrane and hairs (cilia) • Cilia move like waves to push mucus and particles upward • Cigarette smoking can paralyze the cilia • Particle-laden mucus is removed by coughing, expectorating, or swallowing

8. Lower (Distal) • Bronchi split (bifurcate) repeatedly into two smaller passages (17 times, 217 = 131,072) called bronchioles • Diameters decrease accordingly • Bronchioles end in microscopic sacs called alveoli (site of gas exchange) • Alveolar membrane is one cell thick (pneumocytes), surrounded by capillaries • Passive diffusion

12. Definition: Microns (Micrometer) • One thousandth of a millimeter • 0.001 mm = 1 mm • Greek letter, m • Useful in discussion of the size of inhaled particles • Visible to human eye • > 100 mm = 0.1 mm = 0.01 cm • Human hair diameter • 5 – 500 mm = 0.005 – 0.5 mm

13. Protective Mechanisms of the Respiratory Tract • Larger particles (>10 mm) • Removed in nose and upper airways • 5 – 10 mm • Captured in tracheal region • 3 – 5 mm • Contact mucus lining in tracheal or bronchi • 0.5 – 3 mm • Can reach alveolar region, but few do

14. Capture of particles • Mucus (moist, sticky) linings • Tortuous pathway • Multitude of branches and splits • Large surface area of the route • Once particles are captured in mucus, they are removed by the mucociliary elevator or ladder • Cough reflex

16. Protection in the Alveolar Region • Primary defense – macrophages (specialized white blood cells) • Engulf foreign objects and attempt to dissolve them • The smallest of particles may pass through cell membranes and lodge between cells (interstitial space)

17. Airborne Hazardous Materials • Aerodynamic Diameter • Useful for comparing particles with irregular shapes (dusts, fibers, etc.) to particles with regular shapes (droplets, mists, etc.) • The diameter of a reference spherical particle with a unit density of one (1) that has the same settling velocity as the contaminant particle

19. Classes of Airborne Materials • Particulates / aerosols • Solid particles, dusts, fibers, mists, droplets, fumes • Gases / vapors • Gaseous contaminants, vapors • Oxygen-deficient atmospheres • < 19.5% oxygen • Combination • Any combination of particulates and/or gases, including oxygen-deficient atmospheres

20. Particulate contaminants • Particulates and aerosols • Individual or discrete masses • (Not gases or vapors) • Aerosols • Liquid droplets or solids that are suspended in air for an extended period of time • Dusts, mists, fumes

21. Dusts (particulates/aerosols) • Aerosols composed of dry particles, fibers, powders • Naturally occurring or from blasting, mining, grinding, polishing, crushing, etc. • Concerned with < 10 mm • Irritation, allergic response, various diseases, cancer, explosions • Silica, coal, grains, sawdust

22. Mists (particulates/aerosols) • Airborne droplets from processes involving liquids (sprays, coolants, cutting fluids, paints, solvents, pesticides, etc.) • Air (or other gas) is introduced into a liquid (usually under pressure), causing the liquid to break apart (aerolize) • Surface tension between molecules causes them to stick together and form droplets • Can cause bacteria to become airborne • Hazards: depends on size, reactivity, solubility, toxicity • Responses: irritation, inflammation, stimulation of mucus production, pulmonary edema (lung fluid), allergic or sensitization response

23. Fumes (particulates/aerosols) • Produced when metals are heated (> 2000 °C) to the point they become a vapor or gas • The hot gas cools once airborne, then condenses to form small particles • Diameters: 0.1 – 100 mm • Processes: welding, cutting torch, sometimes buffing/grinding • CO is not a fume: airborne phase is a gas • Gasoline is not a fume: airborne phase is a vapor

24. Classes of Airborne Materials • Particulates / aerosols • Solid particles, dusts, fibers, mists, droplets, fumes • Gases / vapors • Gaseous contaminants, vapors • Oxygen-deficient atmospheres • < 19.5% oxygen • Combination • Any combination of particulates and/or gases, including oxygen-deficient atmospheres

25. Gases • Air: nitrogen, oxygen, argon, carbon dioxide,water • Oxygen – Carbon Dioxide exchange • Damaging gases: carbon monoxide, acetylene, ammonia, chlorine, hydrogen fluoride, hydrogen sulfide, sulfur dioxide

27. Vapors • Gaseous phase of liquids • Tendency of a liquid to change to a gas depends on its vapor pressure (how quickly it will evaporate and thus breathable) • Higher vapor pressure (faster evaporation) • High VP presents toxicity, asphyxiation, flammable/explosive mixtures

28. Effects of Inhaled Materials • Airborne toxins • Local effects on tissues • Ammonia irritation in respiratory tract • Systemic effects through blood transport • Carbon tetrachloride (liver) • Solubility • More soluble – upper respiratory tract, moist tissue around eyes – ammonia • Less soluble – penetrate to middle and lower respiratory tract – phosgene gas

29. Size-selective Sampling • Recall the relationship between particle size and site deposition? • Thus size-selective sampling becomes important • ACGIH has defined three ranges (or fractions) • Inhalable • Thoracic • respirable

30. Size-Selective Sampling

31. Size-Selective Sampling • Some OSHA PELs are established for the respirable fraction • Example: crystalline silica • Table Z-1, Silicon • Total Dust, 15 mg/m3 • Respirable fraction, 5 mg/m3

32. Occupational Diseases Associated with Airborne Particulates • Pneumoconiosis • Physiological Responses • Mineral Fibers and Other Fibers • Metals • Organic Particles

33. Pneumoconiosis • Reaction of lung tissue to the presence of dust • Inhaled dust may deposit in the lungs, be detectable with x-rays, but with no ill effects • Some dusts cause scarring and damage leading to severe impairment • Silicosis – pneumoconiosis caused by inhaling silica dust • Asbestosis - asbestos • Berylliosis - beryllium • Aluminosis - aluminum

34. Physiological Responses Associated with Inhaled Dust • Increased production of mucus • Engulfment of particles by macrophages • Inflammation of tissues • Edema (swelling) • Formation of fibrous tissues (reticulin, collagen), usually benign • Reticulin – immature red blood cells that don’t mature • Siderosis - iron oxide dust in lungs, reddish discoloration, benign

35. Silicosis • scarring of lungs from crystalline silica • reticulin nodules build up when macrophages engulf the silica particles • When macrophage dies, it released the silica particle and another macrophage engulfs it • Endless cycle which impairs lung function • May lead to hypertension (high blood pressure) and an enlarged heart • May mask the presence of tuberculosis or pneumonia • Silicon dioxide, SiO2: quartz, tridymite, cristobalite, coesite • Must evaluate “respirable fraction” • Study Table Z-3

36. Mineral Fibers and Other Fibers • Asbestos (best known)

37. Metals • Inhalation of metal fumes • One of the oldest known occupational diseases • Agricola, etc. • Aluminum, Lead, Cadmium, Chromium

38. Metals • Inhalation of metal fumes or dust (from grinding, machining, sawing, sanding) • Metal oxides – metal atoms combined with oxygen atoms – can also be inhaled • Iron oxide – rust • Metals differ in their site of effect (see next slide)

40. Metal Fume Fever • Inhalation of metal fumes during welding • Flu-like symptoms that may be mistaken for the flu • Fever, nausea, coughing, wheezing, muscle aches • Cause could be a single metal or a combination of several

41. Aluminum • Inhalation during smelting, refining, metalworking • Aluminum and its oxides used in paints, coatings, ammunition, explosives, abrasives, ceramics • Irritants to respiratory system • Acute exposure – alveolar edema • Chronic exposure – interstitial fibrosis, emphysema (Shaver’s disease, bauxite lung) • Particle damage to cornea • Aluminum is not regulated by OSHA except as a nuisance dust

42. Lead • Frequently encountered • Exposure the lead fume or lead oxide (as a dust) • Mining and smelting • Cutting and welding on surfaces covered with lead-containing paints • Manufacture / recycling of lead-containing batteries • Production of lead-containing paints / coatings

43. Lead Paints / Coatings • Some legislation requires identification of lead-based paint in residential buildings • Hazard to occupants and workers who remove it • Children are particularly susceptible

44. Lead • 90% of lead that enters the body accumulates in the bones • Biological half-life of 10-20 years • 10% accumulates in the liver and kidneys • Lead toxicity • Muscle weakness, insomnia, lassitude, weight loss, colic, constipation, headache, memory loss, anemia, irritability, paralysis of extensor muscles of the wrist, dark line of discoloration on the gums, sterility in men, teratogen hazard for pregnant women

45. Lead Requirements • Airborne lead action level: 35 mg/m3 • Training about hazards and protection • Showers and changing rooms • Monitor levels in workplace air • Provide engineering controls and PPE • Medical surveillance program • Regular blood level tests • 29 CFR 1910.1025 and 1926.69

46. Cadmium • Present in lead and zinc ores • Used in alloys, electroplating, pigments, corrosion-resistant coatings, batteries, fungicides • Inhalation to blood stream to liver and kidneys (damage to renal tubules) • Biological half-life ~20 years • Acute exposure can be fatal • Chronic exposure • anemia, liver & kidney damage, emphysema, heart damage, reproductive system damage, teratogen, carcinogen • 29 CFR 1910.1027

47. Chromium • Smelting, ore extraction, processing, alloy manufacturing • Used in pigments, wood preservative, photographic chemicals, anti-corrosive additives in boilers and cooling systems • Hexavalent (Cr6+) is most hazardous, followed by Trivalent (Cr3+)

48. Hexavalent Chromium (Cr6+) • Irritating and corrosive • Inhalation of dust / metal fumes, mists during electroplating; skin absorption • Exposure symptoms: • coughing, headaches, breathing pain, fever, weight loss, nose ulcers, perforation of nasal septum, chronic bronchitis, skin discoloration, erosion of teeth, increased risk of lung cancer, liver and kidney damage • 29 CFR 1910.1000

49. Organic Particles • Inhalation of some organic particles can lead to lung impairments • Reactive Airway Disease • Tightening of the chest, wheezing, shortness of breath • Byssinosis (cotton, linen, hemp, flax) • Made worse with cigarette smoking • Allergic alveolitis • Inhalation of spores from fungi and molds, protein molecules • Involves small terminal branches of bronchioles, just outside the alveoli • Symptoms: coughing, increased production of mucus, fever, fatigue, muscle aches • Diagnosis can be confused or missed because of similarity to other illnesses such as pneumonia