Health Impact and Control of Particulate Matter

1. Health Impact and ControlofParticulate Matter Larry Olson, Ph.D. Arizona State University Phoenix, Arizona USA

2. 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.

3. 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.

4. 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

5. 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

8. 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

10. 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

12. 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.

13. 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.

14. 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.

15. 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.

16. 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

17. 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.

18. 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?

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

20. 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

21. 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.

22. Particulate Composition

24. 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%

25. 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% <0.1% PM-10 episode thresholds <0.1% Restaurant charbroiler controls <0.1% <0.1% Pre-1988 heavy-duty diesel vehicle standards <0.1% 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

26. 0.5% <0.1% <0.1% <0.1% Source: Revised MAG 1999 PM-10 Plan

27. 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.

28. 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.