Multipollutant Air Quality Management:A Critical Review

George M. Hidy

William T. PennellA&WMA 103rd Annual Conference and Exhibition

Calgary, Alberta, Canada

June 23,2010

Introduction and Overview

Motivation:2004 NRC Assessment

Air Quality Management in the United States--NARSTO evaluated and extended the concept for

North America

Current practice constrains our ability to meet future challenges:

• Increasingly strict ambient standards• Health effects of air toxics—integrated with criteria

pollutants• Apparent lack of risk thresholds• Environmental justice and “hot-spots”• Ecosystem effects• Regional influence and long-range transport• Climate change

System could evolve to one that strives to--

• Identify the most significant cumulative exposures, risks, and uncertainties based on pollutant mixtures.

• Take a multipollutant approach to controlling emissions that pose the most significant risks

• Take an airshed-based approach optimizing pollutant reductions to minimize exposure risk to multipollutants arising from local, regional, national, and international sources

• Emphasize results over process, create a system for evaluating the effectiveness of control measures, and dynamically adjust and correct actions as they are implemented

Charge to Assessment Team

• Assess the state of knowledge and the multipollutant assessment tools for achieving a risk-based air quality management approach that incorporates means for assessing the effectiveness of management actions (accountability)

• Provide recommendations for enhancement of capabilities and knowledge needing improvement

Assessment Chairs and Expertise

• George Hidy (Envair/Aerochem)• Jeff Brook (Environment Canada)• Ken Demerjian (State University of New York at Albany)• Luisa Molina (MIT and Molina Center for Energy and the

Environment)• Rich Scheffe (EPA)• Bill Pennell (NARSTO -ex-officio)• A large group of contributors in the relevant sciences.

Approach

• Query health and ecosystem effects scientists regarding their information needs for risk reduction from multipollutant exposure– Vital information for estimating exposure and dose– Improved effects exposure-response; especially the

effects of exposure to pollutant mixtures• Assess the ability of the atmospheric-

environmental sciences to meet these needs– Existing resources– Improved methods (chemical characterization, modeling

and monitoring) for assessing exposure– Improved information on emissions and atmospheric

composition at point of exposure

Features of Risk- and Results-Based Air Quality Management

• Administrative coordination– All air pollutants and climate-forcing agents considered in

concert– Reviews of standards coordinated and placed on compatible

schedules– Plans for achieving goals coordinated

• Risk-based decision making– Priority on reducing exposures that represent the greatest

risks

• Accountability

Transitioning to a Risk- and Results-Based Approach

• Level 1: focus on attainment of individual ambient standards

• Level 2: attainment of individual standards, but with increasing attention to co-benefits from coordinated emissions reductions

• Level 3: decisions based on achieving greatest risk reduction based on single-pollutant exposure-dose-response relationships

• Level 4: decisions based on achieving greatest risk reduction based on multipollutant exposure-dose-response relationships

Where Are We Now?

• Level 2 is clearly achievable -- given appropriate planning and resources

• Level 3 is attainable given significant improvements in exposure characterization, but determination of relative risk is problematic unless there are significant differences pollutant exposure and potency

• Attaining Level 4 will require substantial advances in our understanding of the consequences of exposure to multiple pollutants and our ability to simplify multipollutant exposure assessment

Accounting for Problems of “Global” Change

Future air quality management could be complicated by three global-scale influences

• Large -scale Transport of long-lived pollutants or pollutant precursors resulting from increased global emissions

• Changes in emissions resulting from actions taken to mitigate anthropogenic climate change, including substitution of technologies

• Changes in atmospheric chemistry, biogenic emissions, and meteorological conditions resulting from climate change—climate change increasingly included in pollutant regulation?

These factors could affect strategies for managing air quality, but current estimates of impacts are “small” and extend to a long term (> 50 years).

The “Climate Penalty”

Tools and Priorities

Emissions Air QualityHuman

Exposure

EcosystemExposure

EcosystemEffects

Human HealthEffects

RiskCharacterization

ValuationManagement

Options(Policy)

Global ChangeExamples

The Toolbox for Multipollutant Strategies

• Tools to support multipollutant AQ strategies are well known with understanding of –– Atmospheric Physicochemical Processes

• Multipollutants derive from sources and atmospheric chemistry

– Measurements of Ambient Concentrations and Exposure Estimation

• What’s there is fundamental! Criteria and Toxics

– Emissions Characterization• Primary sources –magnitude, location, reactivity and futures

– System or Air Quality Modeling• Present and future space and time

– Linking Exposure to Effects• Exposure (Concentration) and Response Humans and Ecosystems

Integrating Complexity for Relative Risk

Light AbsorbingPhotolytic

Phase: Gas/Aerosol

TargetedFunctional Groups

Water Solubility

Chemical LifetimeReactivity

Particle Size

Thermal Dissociation

CP – HAPSPrecursor

Environmental Variables:Solar Radiation, Temperature, Relative Humidity

Analysis of Relative Risk –Priority Setting

• The Current Approach Deals with Pollutants Separately.– Formal Risk Analysis Methods Exist, but are Data Limited.

• A Risk-Based Framework Needs to be Able to Differentiate Risks for Priority Setting.

• What Are the Criteria?– Population vs. Individual Risk– Cost and Benefit

• What’s Missing?– Dose-Response of mixtures?– Critical Elements—Toxicity and Concentration or Exposure?

• Are There Practical Measures for Risk Priorities Within the Present Regulatory Frameworks?– Some Demonstrations Focused on Cost-Benefit

Accountability is Important

Parallelism Between Risk Analysis, AQ Management and Accountability

Paradigm

Goal Setting Strategy Audit Action

Emissions

Exposure

Effects

Emiss. Inv.

Model exposure

Effects

Emiss. Change

Ambient Measure

Exposure

Effects

How Far Can We Take Accountability

• Accountability is a Sequence of Assessment Beginning with Emissions, Tracing through Ambient Exposure Conditions to health or Ecological Response

• Do Changes in Emissions Result in Improvements in Public Health?

• Examples can be extracted from Records of Progress.– Ozone and Oxidants– Particles– HAPs, including Mercury

Trends in O3 –Los Angeles

Trends in Ambient OzoneRegional O3 (AL,GA,MS, FL) Don’t Follow NOx Emissions or

NMHC Emissions Changes

0

10

20

30

40

50

60

70

80

90

100

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

Year

Mea

n A

nnua

l 4th

Hig

hest

O3

(ppb

v)

0

100

200

300

400

500

600

700

800

900

EG

U N

Ox

Em

issi

ons

(100

0 to

ns p

er y

ear)

Mean Annual 4th Max O3 EGU NOx Emissions

The Case of Particulate Matter

• Trends in Emissions and Ambient Concentration

• Outdoor Concentrations are exposure– Exposure complexity– Some PM is Indoor-

Outdoor• Some PM is Not• Assume Outdoor a

Surrogate!

• Health Effects and PMx– Intervention Experiments– Historical Health Change

PM Health Effects—Response to Change

• Accountability—The End Game• Intervention Studies

– A Series of Studies – Utah Steel Mill Shutdown (Pope et al, 1989;Ghio, 2004) – U. S. Southwest- 1960s Smelter Strike (Pope et al., 2007)– Hong Kong Fuel Switch (Hedley et al., 2002)– Dublin Coal Use (Clancy et al., 2002)

• Long Term Changes with Ambient Air Quality– Reanalysis of the 6 Cities Study (Laden et al., 2006)– PM2.5 and Life Expectancy (Pope et al., 2009)

Opportunities for Multipollutant Management

• Working within the Current Regulations– Streamlining Administrative Direction, including Adjusting

Parallel Schedules for Implementing Emission Reductions.

– Expand Knowledge of Emissions and Air Chemistry to Integrate Criteria Pollutants and Air Toxics.

– Use Risk-Based Goal Setting--Support with More Systematic Concentration --Response Portfolio.

– Encourage Prescription of Accountability Chain in Regulatory Process.

– Incorporate Feedback from Accountability Analyses into Planning and Implementing Strategies, including Progressive Changes.

For the Future

• Develop a Framework for Grouping Pollutants within Common sources, Chemistry and Biological Response for Addressing Strategies.

• Test Concepts for Risk Prioritization and Adopt These in Complex Emission Reduction Strategies.

• Establish Refined Health and Ecological Effects Programs to Address Relative Risk.

• Explore Improving Opportunities to Obtain Management Relevant Feedback from the Accountability Chain.

• Review Monitoring and Measurement Programs to Estimate Their Effectiveness in Providing Multipollutant Characterization Beyond Regulated Pollutants.