Evaluating the Health Benefits of Air Pollution Reductions: Recent Developments at the U.S. EPA

Bryan J. Hubbell

U.S. EPA, Office of Air Quality Planning and Standards

Innovative Strategies and Economics Group

Overview Background Morbidity and Mortality: The Tip of the Iceberg Age and WTP for Reduced Mortality Risk Why It Is Difficult to Value Morbidity More

Completely The Need for Better Communication Between

Economists and Epidemiologists Concluding Remarks

Background

Evaluations of health benefits have been a major component of the regulatory impact analyses for recent air pollution regulations Tier 2/Gasoline Sulfur Heavy Duty Engine/Diesel Fuel NOx SIP Call (Ozone Transport Rule)

Executive Order 12866: Requires EPA to evaluate the costs and benefits of major regulations (>$100 million in costs).

Background

Many health and environmental effects are still not quantifiable Changes in ecosystem function Chronic changes in lung function Health impacts of air toxics

There are numerous uncertainties embedded in any health benefits analysis: Emissions baselines and changes Air quality changes Population projections Epidemiology Economic valuation

Background Important remaining issues in the

measurement and valuation of: Chronic health effects including mortality

and respiratory diseases Full impact of acute morbidity effects Health effects from exposure to air toxics

The Tip of the Iceberg

As posed by Dr. Pearce – “Why are health benefits high?”

How high should health benefits be?

Two relevant questions:

The Tip of the Iceberg In our most recent analysis for the HD Engine rule, we

estimated annual benefits in 2030: $70 billion in total monetized benefits ($1999, adjusted for

income growth) 8,300 premature mortalities avoided 5,500 incidences of chronic bronchitis avoided 361,000 asthma attacks avoided 1.5 million lost work days avoided Visibility, agriculture, and other health benefits

$200 per person, less than ½ percent of 2030 per capita income.

Excludes many non-health benefits and benefits of CO and air toxic reductions.

The Tip of the Iceberg

Absolute size driven by Strong concentration-response relationship High VSL ($8 million in income adjusted 1999$)

Relative size driven by Large absolute estimate Low values placed on morbidity effects

Health benefits are dominated by premature mortality

Why EPA’s Estimates Might Be Low Selection of low C-R function for PM

chronic exposure mortality Focus on first-order morbidity effects,

ignoring possible long-term “ripple” effects. Failure to account for behavioral responses. Lack of health effect models for air toxics.

Age and WTP for Reduced Mortality Risks

While there are several differences between the labor market studies EPA uses to derive a VSL and the air pollution context to which the VSL is applied, population age is among the most important.

The economics community in the U.S. has not reached consensus on the appropriateness of adjusting VSL for age differences, although they have rejected the VSLY approach.

Age and WTP for Reduced Mortality Risks

EPA did not adjust for age in the primary estimate of mortality benefits for the HD Engine rule.

Provided sensitivity analyses based on ratios of age-adjusted WTP derived from Jones-Lee (1989) and Jones-Lee (1993).

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Jones-Lee (1989)Ratios

Figure 1. Age-specific WTP Ratios and HD Engine Rule Mortality Benefits

Data Available No Data Available

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Jones-Lee (1993)Mortality Benefits

Jones-Lee (1989)Mortality Benefits

Figure 2. Impact of Age-specific WTP on HD Engine Premature Mortality

Reduction Monetized Benefits

Why It Is Difficult to Value Morbidity More Completely Lack of suitable studies for specific

endpoints Reliance on benefits transfer Use of cost-of-illness approach

Asthma Example Asthma attacks are ill-defined health endpoints Understood by asthmatics, but no clear clinical definition.

Severity is heterogeneous over population. Epidemiology solution is to break endpoint into

component symptoms. More difficult for economists to handle

Hard to place some symptom measures in valuation framework Potential for double-counting Problems with pooling dissimilar endpoints

Asthma Example Other problems in measuring and valuing

reductions in asthma symptoms: Lack of WTP and cost-of-illness studies for

asthma symptoms Measurement of baseline incidence rates Projection of baseline prevalence rates

The Need for Better Communication Between Economists and Epidemiologists

Economists have tended to be end-users Early involvement in study design can

improve usability of study results Economists would like more focus on:

Controls for behavioral responses Representativeness of the study location The shape of the C-R function, including

thresholds or non-linearities

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Assumed Effect Threshold (Annual Mean PM2.5 (ug/m3))

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Sensitivity of HD Engine/Diesel Fuel Rule Mortality Reduction Benefits to Assumed Health Effect Thresholds

40%

The Need for Better Communication Between Economists and Epidemiologists Need to find endpoints that match well with economic

valuation Ozone and outdoor exercise performance Economic context of clinical measures such as FEV1 or heart

rate variability Need to find linkages between clinical bioindicators and

economically significant endpoints FEV1 Asthma Attacks HRV Heart Attacks

Need to examine non-traditional endpoints, such as premature onset of diseases.

Concluding Remarks Epidemiology is an essential tool and input into the

process of analyzing the health benefits of federal regulations

We must address some of the key gaps in our understanding of health benefits of air pollution Effects of changes in chronic exposures Shapes of C-R functions “Ripple” effects of acute morbidity Behavioral responses to air pollution Lack of health functions for air toxics

Concluding Remarks Needs for Benefits Analysis

C-R functions that are applicable to changes in pollution at varying baseline levels

Integrated design of epidemiology and valuation studies

“Best Estimate” C-R functions for air toxics Principles for extrapolation

Ongoing Efforts Several analyses of EPA’s health benefits methodology

are underway General Accounting Office: Use of Precautionary Assumptions

in Health Risk Assessments and Benefits Estimates and Truth in Regulating Act

National Academy of Sciences: Estimating the Health-Risk-Reduction Benefits of Proposed Air Pollution Regulations

Science Advisory Board: Valuation of Reduced Mortality Risks from Air Pollution

Useful Websites The Costs and Benefits of the Clean Air Act: 1990 to 2010

http://www.epa.gov/air/sect812/ The Heavy Duty Engine/Diesel Fuel Regulatory Impact Analysis

http://www.epa.gov/otaq/diesel.htm EPA Science Advisory Board

http://www.epa.gov/sab Joint EPA/SAB Workshop on Benefits of Reductions in Exposure to Hazardous Air

Pollutants: Developing Best Estimates of Dose-Response Functions http://www.epa.gov/ttn/ecas/meetings/coverhap.html

Health Effects Institute http://www.healtheffects.org

General Accounting Office Report on Use of Precautionary Assumptions in Health Risk Assessments and Benefits Estimates

http://www.gao.gov/docdblite/summary.php?accno=164183&rptno=GAO‑01‑55 Harvard Center for Risk Analysis

http://www.hcra.harvard.edu/