Health Impact and Controlof

Particulate Matter

Larry Olson, Ph.D.

Arizona State University

Phoenix, Arizona USA

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.

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.

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

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

Absorption of PM PM > 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 > 1 m AED

Gravitational settling becomes more important in lower TB region (smaller airways)

Surprisingly, new studies show deposition of ultra-fine PM (< 0.1 m AED) is similar to coarse PM (> 10 m AED). Nasal ET efficient filter.

Deposition at minimum for 0.2 < PM < 1 m AED

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

Regulatory Action Initial regulatory actions were directed at TSP

(total suspended particulates). TSP < 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.

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.

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.

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.

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

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.

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?

Epidemiological Studies (cont)

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

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

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.

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%

•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%

•Disturbed Vacant Land & Agricultural Windblown Dust 14.9%•Agricultural Dust 3.3%•Other Area Sources 3.9%•Residential Wood Burning 0.5%

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 Lands3In addition, the emission reduction includes Reduced Particulate Emissions from Unpaved Shoulders on Targeted Arterials

Strengthening and better enforcement of fugitive dust control rules1- Construction dust

Strengthening and better enforcement of fugitive dust control rules1- Trackout paved road dust

Reduce emissions from unpaved roads and alleys

PM-10 episode thresholds

Restaurant charbroiler controls

Pre-1988 heavy-duty diesel vehicle standards

Coordinate traffic signal systems

ES-7

19.1%9.7%

5.9%1.8%

0.9%

0.5%

0.2%

<0.1%

<0.1%<0.1%

<0.1%

<0.1%

0.5%

2006 PM-10 Emission ReductionsFrom Committed Control Measures

Source: Revised MAG 1999 PM-10 Plan

<0.1%

<0.1%

<0.1%

0.5%

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.

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.