Human Health Effects of Particulate Matter (PM)

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Human Health Effects of Particulate Matter (PM)

• Nathan Pechacek, M.S.
• Toxicology Section
• Texas Commission on Environmental Quality
• 512-239-1336
• npechace_at_tceq.state.tx.us

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PM10 100 ug/m3 PM2.5 20 ug/m3
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PM10 400-1000 ug/m3, PM2.5 60-140 ug/m3
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Presentation Outline

• Background information
• Health effects
• Challenges of epidemiological studies
• Sensitive populations
• Research needs
• Summary

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Background Information on PM and the Respiratory
System
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Particulate Matter

• Complex substance
• Sources
• Composition
• Size
• Travel distance
• Time spent airborne

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-reference Brook, et al. 2004
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Human Respiratory System
-reference USEPA, 2004
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PM Deposition in the Respiratory System
-reference USEPA, 2003
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PM Deposition in the Respiratory System

• One of the major determinants for responses
• Deposited PM can accumulate, translocate, and be
  removed
• Acute effects best represented by deposited dose
• Chronic effects best represented by retained dose

• Mechanisms
• Interception
• Impaction
• Electrostatic interaction
• Sedimentation
• Diffusion
• Site of deposition affects
• Severity of local damage
• Potential for systemic effects
• Clearance mechanisms

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PM Clearance Mechanisms

• Often classified as absorptive or nonabsorptive
• Mechanisms
• Sneezing
• Nose wiping and blowing
• Coughing
• Mucociliary transport
• Dissolution and absorption in blood/lymph
• Uptake by cells
• Time for clearance ranges from minutes to years

-reference modified from Schlesinger, 1995
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Health Effects of PM
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Historical PM Events of Health Significance

• Meuse Valley, Belgium 1930
• PM from coal combustion
• 63 dead, 6000 ill
• Donora, Pennsylvania 1948
• PM from zinc smelter
• 20 dead, 7000 hospitalized out of a town of
  14,000
• London, UK 1952
• PM from combustion, air inversion
• 3500-4000 deaths estimated originally, revised to
  12,000 potential deaths

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Types of PM Health Studies

• Types of studies
• Epidemiological
• Controlled human exposures
• Animal
• Molecular/Cellular/Tissue
• Consistency and coherence of data

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PM Components/Parameters of Potential Interest
For Health

• Size
• Surface area
• Number
• Acidity
• Metals
• Elemental and organic carbon

• Mass
• Size distribution
• Ions
• Bioaerosols
• Other specific toxic constituents

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General Comments on PM Health Effects

• Effects may be from the inherent toxicity of the
  individual components of PM and/or toxicity due
  to general PM characteristics
• Emphasis on PM that reaches the lungs (?PM10)
• Recent focus on health effects of PM2.5
• Health effects can result from PM ?PM10 (e.g.
  TSP)
• Effects are generally believed to be less severe
  unless high inherent particle toxicity or
  overloading occurs
• Temporary irritation to the eyes, nose, and
  throat is a common potential effect
• Both acute and chronic PM exposures are a concern
• Health effects associated with PM are nonspecific

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Respiratory Effects of PM

• Acute symptoms irritation, coughing, wheezing,
  difficulty taking deep breaths
• Inflammation
• Decreased lung function (FEV1, FVC)
• Aggravate existing respiratory diseases (e.g.
  asthma, bronchitis, other COPD)
• Increases airway reactivity (response to stimuli)
• Increases susceptibility to respiratory
  infections
• Chronic exposure to some types of PM may result
  in an increased risk of respiratory cancers such
  as lung cancer
• ex. Diesel exhaust PM

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PM Cardiac Effects Challenging Toxicologists
To Think Differently
My toxicologists are better trained than this
cat!!!
Otto
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Cardiac Effects of PM

• Change in blood chemistry
• Can increase blood viscosity which may lead to
  clotting
• Inflammation disrupts cell function and activates
  platelets, which can rupture blood vessel plaques
• Leads to clotting
• Cardiac arrhythmias abnormal heart beats
• Change in heart rate variability (HRV)
• Decrease in HRV is an early warning sign of
  potential heart attacks
• Aggravate existing cardiac diseases
• Can potentially stimulate heart attacks in
  sensitive individuals

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Cardiac Effects of PM Change in Blood Chemistry
Damage
Repair
-reference Nadziejko, et al., 2002
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Modes of Action for Cardiac Effects

• Underlying mechanism(s) not known
• Three proposed modes of action
• Ultrafine PM (PM0.1 ) enters the blood and
  directly exerts effects on the heart
• Pro-inflammatory chemicals triggered in the
  alveolar region that travel in the blood and
  exert toxicity in the heart
• Cardiac effects secondary to respiratory system
  effects
• PM can alter autonomic nervous system control of
  the heart
• Raises the possibility that heart effects are
  independent of adverse respiratory effects
• All three modes are biologically plausible
• Multiple modes may be working or one mode may
  predominate depending on the PM characterization

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Challenges Evaluating Epidemiological Studies
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Association between PM and Heart Attacks
-reference Peters, 2001
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Association between PM and Hospital
Visits/Admissions
-reference USEPA, 2004
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Association between PM and Respiratory Effects
-reference USEPA, 2002
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Association between PM and Cardiovascular Effects
-reference USEPA., 2003
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Issues Concerning PM Epidemiological Studies

• Challenge of quantifying exposure-response
  relationship
• Consistent finding Relatively weak positive
  association that is not always statistically
  significant
• A large number of diverse studies conducted
  (geographical and temporal variety)
• Underlying biological mechanism to support
  epidemiological findings not known
• Progress made on potential modes of action
• Ambient monitoring may not be an accurate
  assessment of personal exposure
• Confounding sources - other air pollutants
  responsible?

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Who is Sensitive to PM

• It is estimated that approximately 1/3 of U.S.
  population is potentially sensitive to PM-related
  health effects
• However, at ambient PM levels the majority of the
  population is not likely to experience health
  effects or experiences temporary, mild effects
• Risk from PM is a continuum
• high early in life
• low during late childhood and early adulthood
• rises as one ages and risk of cardiac and/or
  respiratory disease increases

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Who is Sensitive to PM?

• People with pre-existing cardiac and/or
  respiratory diseases
• Severe cardiac effects can be triggered, some
  effects may be fatal
• Respiratory diseases can be exacerbated
• The elderly
• Greater prevalence of cardiac and respiratory
  diseases
• PM deposition and clearance typically
  with age
• Time to recover from effects may be extended
• Young children
• Developing systems may be more vulnerable
• PM exposure is often higher (e.g. more active
  outdoors)
• Others people active outdoors during elevated
  PM
• Pregnant woman?

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Research Needs

• Determine the best PM parameter(s) for health
  effects
• Improve understanding of the mode/mechanism of
  action
• Concentration-response estimates
• Emerging effects developmental effects
• Role of co-pollutants in eliciting adverse
  effects
• Further understanding of sensitive populations
• Placing risk from ambient PM exposure in context
  with other PM exposures (e.g. indoor, personal)

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Summary

• PM is complex
• Historical events highlight that PM generates
  health effects, some that may be severe
• Importance of PM size when discussing deposition
  and health effects
• Respiratory and cardiac effects emphasized
• Sensitive populations for health effects
• Research needs