Health Impact and Control of Particulate Matter

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Health Impact and ControlofParticulate Matter

• Larry Olson, Ph.D.
• Arizona State University
• Phoenix, Arizona USA

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What is Particulate Matter?

• Not a single pollutant (like CO or O3)
• Atmospheric Particulate Matter (PM)
• Natural or Anthropogenic
• Finely dispersed liquid or solid aerosols
• Different Chemical Composition
• Primary or Secondary
• Fine or Coarse
• Size and composition of PM are critical in
  determining health effects.

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Primary vs Secondary

• Primary PM if it exists in same chemical form in
  which it was generated.
• Natural sources sea spray, windblown dust,
  volcanic emissions
• Anthropogenic sources traffic, mining,
  construction, power plant emissions
• Secondary PM if atmospheric reactions of
  precursor gases form a larger condensate that
  form new particles, or if gas condenses on
  existing particles. Can also have natural and
  anthropogenic sources.

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Primary vs Secondary (cont)

• Secondary PM
• Anthropogenic sources more important, especially
  in urban areas. Examples
• Oxidation of sulfur from fuels (diesel, gasoline,
  coal) generates sulfates.
• Condensation of VOCs on existing PM
• Natural sources include oxidation of (CH3)2S
  formed by sea phytoplankton to sulphates and
  reaction of ammonia to form ammonium salts

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Dose from PM

• Rather than use actual size, common to use AED
  (aerodynamic equivalent diameter). Allows
  comparison of different size, shapes,
  densities.
• Dose from inhaled PM depends upon
• Concentration and exposure duration
• Anatomy of respiratory tract
• Ventilation parameters
• Particle size, hygroscopic nature, and solubility
  of PM

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Absorption of PM

• PM gt 100 ?m AED have low probability of entering
  respiratory system
• Upper respiratory system characterized by high
  velocities and sharp directional changes.
  Inertial impact most important for PM gt 1 ?m AED
• Gravitational settling becomes more important in
  lower TB region (smaller airways)
• Surprisingly, new studies show deposition of
  ultra-fine PM (lt 0.1 ?m AED) is similar to coarse
  PM (gt 10 ?m AED). Nasal ET efficient filter.
• Deposition at minimum for 0.2 lt PM lt 1 ?m AED

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Clearance Mechanisms

• Deposited PM can be cleared from respiratory
  tract completely or translocated to another site.
• Clearance
• Coughing and sneezing
• Mucociliary transport
• Dissolution and absorption into blood/lymph
  system
• Translocation
• Endocytosis and phagocytosis
• Interstitial passage
• Alveolar clearance generally much longer

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Regulatory Action

• Initial regulatory actions were directed at TSP
  (total suspended particulates). TSP lt 25-45 ?m.
• Later revised to PM10 (meaning PM 10 ?m). This
  occurred in U.S. in 1987 and in the EU as a whole
  in 1999, although stds differed in individual
  countries)
• Based upon more recent studies showing a greater
  risk associated with fine PM, U.S. EPA
  promulgated new PM2.5 std in 1997. CAFÉ
  currently working on possible revisions to PM10
  std by 2004.

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Coarse and Fine PM

• Coarse PM (U.S. EPA defines as between 2.5-10 ?m)
  more likely to be formed by mechanical action
  (crushing, grinding, or abrasion)
• Can be either natural or anthropogenic
• Fungal spores, pollen, sea spray, volcanic
  emissions are examples of natural sources
• Mining and agriculture examples of anthropogenic
  sources.

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Coarse and Fine PM (cont)

• Fine PM (defined as 0.1 2.5 ?m)
• Primarily derived from combustion sources
• Nucleation of volatilized material or
  condensation of gases on existing particulates
• Organic compounds constitute 10-70 of dry PM2.5.
  Transformation in atmospheric particulates not
  well understood.

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Coarse and Fine PM (cont)

• Size affects how far PM can be transported in
  atmosphere.
• Fine particles have long lifetimes (days or
  weeks) and can travel thousands of km. More
  uniform distribution. Not easily traced to
  source.
• Coarse particles normally travel only tens of km
  and have atmospheric lifetimes of hours. Thus
  more localized effects.

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Toxicology of PM

• Most animal studies have used much higher
  concentrations of PM than ambient air.
• Most have used PM10 or PM2.5 as cutoffs. Few
  studies on PM2.5-10 or PM1.
• Effects of PM inhalation
• Lung inflammation and injury
• Cough, phlegm, chest tightness, wheezing
• Cardiovascular impairment and death
• Pulmonary hypertension and right heart
  enlargement
• Arrhythmias

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Toxicology of PM (cont)

• Composition plays a role.
• Volcanic dusts from Mount St Helens relatively
  inert compared to urban PM.
• Organic fractions of diesel PM linked to effects
  on immune system. Not yet known whether other
  combustion sources have similar effects.
• Except for diesel, few studies on effects of
  organic constituents of PM. Typically, these are
  poorly characterized, heterogeneous complex
  mixtures.
• Mechanisms by which PM exerts toxicity not
  understood.

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Epidemiological Studies

• Measurable associations with PM exposure and and
  mortality rates.
• Morbidity studies document relationship between
  PM exposure and emergency room or hospital
  admissions, changes in pulmonary function, low
  birth weights, etc.
• On-going difficulty in assigning causal agent for
  observed effect.
• For example, even if diesel exhaust is
  implicated, is it the NO, SO2 absorbed on PM, or
  organic PM that is causal agent?

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Epidemiological Studies (cont)

• Highest risk
• Elderly
• Cardiopulmonary disease
• Respiratory ailments (e.g. pneumonia or asthma)

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Anthropogenic Sources of PM

• Stationary Sources
• Fuel combustion for electric utilities
• Industrial processes (e.g. metals, minerals,
  petrochemicals, wood products)
• Agricultural mills and elevators
• Soil cultivation
• Burning of biomass for heating and cooking

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Comparison of PM Sources

• Mobile Sources
• On road gasoline and diesel fuel vehicles
• Off road Construction equipment, aircraft,
  boats, etc.
• Comparison of Sources
• Natural Larger, more oddly shaped particles
• Anthropogenic Smaller, more spherical particles
• Difference in composition as well. Next slide
  shows data from two particulate studies conducted
  by Arizona State University in Phoenix.

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Particulate Composition
Element PAFEX I PAFEX II
S 3.7 45.4
Si 40.1 8.0
Na 9.0 6.7
Cu 3.8
Al 2.8
Ca 8.5 1.7
Fe 16.7 1.1
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• Disturbed Vacant Land
• Agricultural Windblown Dust 14.9
• Agricultural Dust 3.3
• Other Area Sources 3.9
• Residential Wood Burning 0.5

• Construction/Earthmoving Dust 23.4
• Construction Trackout 13.0
• Nonroad Engine Exhaust 4.3
• Construction Windblown Dust 2.3

• Paved Road Dust 17.7
• Unpaved Road Dust 12.9
• Onroad Vehicle Exhaust 2.3

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2006 PM-10 Emission Reductions From Committed
Control Measures
Strengthening and better enforcement of fugitive
dust control rules1- Construction dust
19.1
Strengthening and better enforcement of fugitive
dust control rules1- Trackout paved road dust
9.7
5.9
Reduce emissions from unpaved roads and alleys
1.8
0.9
0.5
0.5
0.2
lt0.1
PM-10 episode thresholds
lt0.1
Restaurant charbroiler controls
lt0.1
lt0.1
Pre-1988 heavy-duty diesel vehicle standards
lt0.1
Coordinate traffic signal systems
1In addition, the emission reduction includes
Dust Control Plans for Construction/Land,
Clearing and Industrial Sites2In addition, the
emission reduction includes Dust Abatement and
Management Plan for State Lands 3In addition, the
emission reduction includes Reduced Particulate
Emissions from Unpaved Shoulders on Targeted
Arterials
ES-7
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0.5
lt0.1
lt0.1
lt0.1
Source Revised MAG 1999 PM-10 Plan
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Conclusions

• Both natural and anthropogenic sources of
  particulate matter are important contributors.
• PM2.5 or fine particulates are more likely to
  be from anthropogenic combustion sources.
• Non-stationary sources are contribute
  disproportionately to particulates.
• PM2.5 are an increasing health concern because
  they penetrate to lower respiratory system where
  they are not easily cleared.

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Conclusions

• Toxicological effects of PM include lung
  inflammation and cardiovascular impairment.
• Measurable relationship between PM exposure and
  morbidity and mortality rates.
• Mechanisms by which PM exert effects not well
  understood.
• Transportation control strategies for PM are
  difficult and expensive.