Airborne ParticulateParticle Size:Statistical DescriptionInitial Physiological Deposition SiteAirborne Sampling Simulation...
Particle Size Statistics                           2
Site of Deposition Depends on AerodynamicParticle Size or Aerodynamic Diameter (AD)• AD is determined by the settling  vel...
Definitions• Mass Median Aerodynamic Diameter  (MMAD) – The AD where 50% of the  aerosol is of larger AD and 50% smaller. ...
Example: Typical In-plant aerosol     from a “dusty” Plastic Powder•    MMAD = 10 microns•    GSD = 2•    50th percentile ...
99.99                                   99.9                                                  AEROSOLPercentage of Mass in...
Aerosol Distribution MMAD = 10µ and GSD = 2.0                  Typical for In-Plant Handling                  “Dusty” Plas...
Definitions/Classifications• PNOC – airborne particulate not otherwise  classified• PSP – poorly soluble airborne particul...
Initial Physiological  Deposition Site                        9
10
11
Airborne SamplingSimulation             12
BREATHING ZONE SAMPLINGAirborne Mass is measured in the breathing zone of the worker,which is an imaginary hemisphere of a...
14
THREE MEASUREMENT/SIMULATION CLASSES       OF AIRBORNE PARTICULATE              DOSE/EXPOSURE• INHALABLE: any particle tha...
INHALABLE MASSACGIH operational definition of the proportion of TOTALAirborne Aerosol Mass in the breathing zone (BZ) fora...
ISO TR 7708 Inspirable    ACGIH InhalableParticle Aerodynamic                           Mass Fraction        Particle Mass...
THORACIC DUSTACGIH Mathematical definition of proportion ofinhalable particulate per AD size that is depositedanywhere wit...
Particle     Thoracic ParticleAerodynamic     Mass (TPM) (%)Diameter (µm)     0                100     2                 9...
RESPIRABLE PARTICULATE MASSACGIH operational definition for proportion ofinhalable particulate per AD size class that will...
Particle          BMRC                 ACGIHAerodynamic     Respirable Particle   Respirable ParticleDiameter (µm)    Mass...
Sampling Devices                   22
37mm Closed Faced Cassettes    For “Total” Aerosol                              23
37mm Cassette showing open-faced option                                          24
Inlet of an open-faced filter                                25
37 mm filter in a Cyclone                            26
27
Inhalable Dust Sampler                         28
29
30
British Medical Research Council (BMRC)penetration curve for respirable particlesshowing 50% cut point at 5µm.            ...
Sampling Bias                32
33
34
PSP and Lung Effects                   35
PSP RESPIRABLE                    vs.     Non-Respirable Aerosol Particulate• NON-RESPIRABLE: Insoluble Airborne Particula...
Oberdorster, G: Toxicokinetics and Effects of Fibrous and Nonfibrous Particles, Inhalation Toxicology, 14: 29-56, 2002  Pu...
Oberdorster (op. cit.)“Morrow (1988) hypothesized – based on athorough evaluation of a number of long-term inhalation stud...
Oberdorster (op. cit.)“He [Morrow] estimated that a phagocytizedparticle volume of about 6% of the normalmacrophage volume...
Oberdorster (op. cit.)“Indeed, plotting the retained particle volumein lungs of rats after long-term exposure todifferent ...
Oberdorster (op. cit.)                         41
What Specifically Does Morrow Say About theData and its Implications for PNOC – WELs ?• “The results illustrate a progress...
Morrow (op. cit.)• “…dust overloading represents a serious,  confounding complication to the toxicological  assessment, on...
Morrow’s Arguments for a PNOC Respirable Mass   WEL of less than 1 mg/m3 (Morrow op. cit.)• For UNIT DENSITY Particles  (1...
Continuation of Morrow’s Arguments for a PNOC   Respirable Mass WEL of less than 1 mg/m3                  (Morrow op. cit....
Morrow RecommendationModify any unit density PNOC WEL relativeto the density of the material in question.For example, Port...
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Particulate seminar

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Michael Jayjock's lecture.
Refers to: Morrow, P.E. et al: Chronic Inhalation Study Findings as the basis for Proposing a New Occupational Dust Exposure Limit, International Journal of Toxicology March/April 1991 10: 279-290.

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Particulate seminar

  1. 1. Airborne ParticulateParticle Size:Statistical DescriptionInitial Physiological Deposition SiteAirborne Sampling Simulation & BiasSampling DevicesPSP and Lung Effects Michael A. Jayjock, Ph.D. CIH 1
  2. 2. Particle Size Statistics 2
  3. 3. Site of Deposition Depends on AerodynamicParticle Size or Aerodynamic Diameter (AD)• AD is determined by the settling velocity of the particle in normal air.• Any Particle with aerodynamic diameter of X falls at the same speed as a UNIT DENSITY SPHERE with X diameter. 3
  4. 4. Definitions• Mass Median Aerodynamic Diameter (MMAD) – The AD where 50% of the aerosol is of larger AD and 50% smaller. The AD at the 50th percentile.• Geometric Standard Deviation (GSD): A measure of the width (or dispersion) of the distribution. AD at the 84th percentile divided by the AD at the 50th percentile 4
  5. 5. Example: Typical In-plant aerosol from a “dusty” Plastic Powder• MMAD = 10 microns• GSD = 2• 50th percentile AD = 10 microns• 84th percentile AD = 20 microns• 16th percentile AD = 5 microns Compare to 50% “cut point for respirable particulate of 4 or 5 microns – only about 10% of the airborne K120n is respirable 5
  6. 6. 99.99 99.9 AEROSOLPercentage of Mass in Particles 99 MMAD = 10, GSD = 2.0 Less than Stated Size 90 70 50 30 10 MMAD = 10 1 0.1 0.01 1 10 100 Aerodynamic Diameter (microns) 6
  7. 7. Aerosol Distribution MMAD = 10µ and GSD = 2.0 Typical for In-Plant Handling “Dusty” Plastic Powder 7
  8. 8. Definitions/Classifications• PNOC – airborne particulate not otherwise classified• PSP – poorly soluble airborne particulate• Lung Overload – dose rate of particulate that exceeds the normal rate of clearance leading to an even lower rate (or cessation) of clearance and secondary toxicity as a result.• Particulate with Inherent Toxicity – particulate that when in contact with pulmonary tissue can injure that tissue irrespective of overload. 8
  9. 9. Initial Physiological Deposition Site 9
  10. 10. 10
  11. 11. 11
  12. 12. Airborne SamplingSimulation 12
  13. 13. BREATHING ZONE SAMPLINGAirborne Mass is measured in the breathing zone of the worker,which is an imaginary hemisphere of approximately 30 cm,extending in front of their face and measured from the midpoint ofan imaginary line joining the ears (see diagram below). 13
  14. 14. 14
  15. 15. THREE MEASUREMENT/SIMULATION CLASSES OF AIRBORNE PARTICULATE DOSE/EXPOSURE• INHALABLE: any particle that penetrates/deposits past the nose and mouth.• THORACIC: particles that penetrate/deposit anywhere within the lung airways and the gas- exchange region• RESPIRABLE: particles that penetrate/deposit exclusively into the gas-exchange region or pulmonary region of the deep lung. 15
  16. 16. INHALABLE MASSACGIH operational definition of the proportion of TOTALAirborne Aerosol Mass in the breathing zone (BZ) forany aerodynamic diameter that will be Depositedanywhere in the respiratory tree including the nose andmouth. SI(d) = 50% x (1 + e-0.06d ) for 0 < d ≤ 100µm where SI(d) = collection efficiency for particles with aerodynamic diameter d in µm. 16
  17. 17. ISO TR 7708 Inspirable ACGIH InhalableParticle Aerodynamic Mass Fraction Particle Mass (IPM) Diameter (µm) (%) (%) 0 100 100 1 - 97 2 - 94 5 - 87 10 73 77 20 - 65 30 52 58 40 - 54.5 50 - 52.5 60 34 - 100 20 50 185 0 Not defined 17
  18. 18. THORACIC DUSTACGIH Mathematical definition of proportion ofinhalable particulate per AD size that is depositedanywhere within the lung airways and the gas-exchange region. 18
  19. 19. Particle Thoracic ParticleAerodynamic Mass (TPM) (%)Diameter (µm) 0 100 2 94 4 89 6 80.5 8 67 10 50 12 35 14 23 16 15 18 9.5 20 6 25 2 19
  20. 20. RESPIRABLE PARTICULATE MASSACGIH operational definition for proportion ofinhalable particulate per AD size class that willbe deposited deposited in the gas-exchangeregion. 20
  21. 21. Particle BMRC ACGIHAerodynamic Respirable Particle Respirable ParticleDiameter (µm) Mass (RPM) (%) Mass (RPM) (%) 0 100 100 1 98 97 2 92 91 3 82 74 4 68 50 5 50 30 6 28 17 7 0 9 8 - 5 10 - 1 21
  22. 22. Sampling Devices 22
  23. 23. 37mm Closed Faced Cassettes For “Total” Aerosol 23
  24. 24. 37mm Cassette showing open-faced option 24
  25. 25. Inlet of an open-faced filter 25
  26. 26. 37 mm filter in a Cyclone 26
  27. 27. 27
  28. 28. Inhalable Dust Sampler 28
  29. 29. 29
  30. 30. 30
  31. 31. British Medical Research Council (BMRC)penetration curve for respirable particlesshowing 50% cut point at 5µm. 31
  32. 32. Sampling Bias 32
  33. 33. 33
  34. 34. 34
  35. 35. PSP and Lung Effects 35
  36. 36. PSP RESPIRABLE vs. Non-Respirable Aerosol Particulate• NON-RESPIRABLE: Insoluble Airborne Particulate that is deposited in Upper Respiratory Track (ciliated region and above) will go to GI track and be excreted quickly.• RESPIRABLE: Insoluble Airborne particulate that penetrates to the deep lungs (pulmonary region) has a much longer residence time in the lung; thus, chronic exposure is more subject to lung “over-load” effect. 36
  37. 37. Oberdorster, G: Toxicokinetics and Effects of Fibrous and Nonfibrous Particles, Inhalation Toxicology, 14: 29-56, 2002 Pulmonary Retention Kinetics and Effects ofPoorly Soluble Particulate of Low Toxicity (PSP) “…if the deposition rate of the inhaled particles exceeds their mechanical clearance rate…, the retention half-time is significantly increased, reflecting an impaired or prolonged alveolar macrophage-mediated clearance function with accumulation of lung burden.” 37
  38. 38. Oberdorster (op. cit.)“Morrow (1988) hypothesized – based on athorough evaluation of a number of long-term inhalation studies with particles in rats –that the impairment of alveolar macrophage-mediated clearance is due to a volumetricoverloading of the macrophages resultingeventually in a failure to actively moveparticles toward the mucociliary escalator.”{emphasis added} 38
  39. 39. Oberdorster (op. cit.)“He [Morrow] estimated that a phagocytizedparticle volume of about 6% of the normalmacrophage volume signals the beginning ofthe impaired function, and when 60% of thenormal alveolar macrophage volume is filledwith phagocytized particles its clearancefunction will completely cease.” 39
  40. 40. Oberdorster (op. cit.)“Indeed, plotting the retained particle volumein lungs of rats after long-term exposure todifferent particle types against measuredclearance rates demonstrated the correlationbetween clearance rate and retained dustvolume convincingly, as is show in Figure 3.”{emphasis added} 40
  41. 41. Oberdorster (op. cit.) 41
  42. 42. What Specifically Does Morrow Say About theData and its Implications for PNOC – WELs ?• “The results illustrate a progressive decrease in alveolar clearance rates once an excessive pulmonary burden is attained.”• “In this context, loss of mobility represents a failure of particulate clearance to proceed, leading to increased intersitialization of particles and to the induction of a host of dysfunctional and pathologic conditions of a seemingly generic nature.” [emphasis added] Morrow, P.E. et al: Chronic Inhalation Study Findings as the basis for Proposing a New Occupational Dust Exposure Limit, J of Am. Coll. Tox, 10, 2, 1991 42
  43. 43. Morrow (op. cit.)• “…dust overloading represents a serious, confounding complication to the toxicological assessment, one in which the intrinsic toxicity of the test material is either masked or modified by the nonspecific effects of dusts on macrophage transport.”• “The foregoing resume of studies indicates that overloading effects on dust clearance can be expected to occur with any persistently retained dust…” 43
  44. 44. Morrow’s Arguments for a PNOC Respirable Mass WEL of less than 1 mg/m3 (Morrow op. cit.)• For UNIT DENSITY Particles (1 mg/m3)(7.2m3/day)(240days/365days) = 4.7 mg/day• Assuming a clearance half life of 200 days (k = 0.0035/day) THEN (0.0035/day) (Burden) = 4.7 mg/day• Lung Burden = 1340 mg/1000g Lung• Values > 1mg/g lung are associated with overload in the Rat. 44
  45. 45. Continuation of Morrow’s Arguments for a PNOC Respirable Mass WEL of less than 1 mg/m3 (Morrow op. cit.)• Breathing rate of 7.2 m3/day is NOT conservative.• Clearance rate assumed for humans is typical but it is NOT conservative.• Xerox Corporation’s HHRC recommended and Xerox Corporation implemented an internal respirable PNOC limit of 0.4 mg/m3 in 1990. 45
  46. 46. Morrow RecommendationModify any unit density PNOC WEL relativeto the density of the material in question.For example, Portland Cement has a densityof about 3.15 g/cc. Any PNOC WEL forthese particles should be increased by thedensity of the particle; that is, the 8 hourWEL should be 3.1 times higher than the unitdensity WEL of 3.1 mg/m3. 46

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