Quantifying the efficiency and equity implications of power plant air pollution control strategies in the United States.BACKGROUND: In deciding among competing approaches for emissions control Emissions control may refer to:
depend on, depend upon, devolve on, hinge upon, turn on, ride the potential tradeoffs between efficiency and equity. However, previous health benefits analyses have not formally addressed both dimensions.
OBJECTIVES: We modeled the public health benefits and the change in the spatial inequality Spatial inequality is the unequal distribution of income or services depending on the area or location. The services such as medical or welfare will have even more skills and more range of services. of health risk for a number of hypothetical control scenarios for power plants in the United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. to determine optimal control strategies.
METHODS: We simulated various ways by which emission reductions of sulfur dioxide sulfur dioxide, chemical compound, SO2, a colorless gas with a pungent, suffocating odor. It is readily soluble in cold water, sparingly soluble in hot water, and soluble in alcohol, acetic acid, and sulfuric acid. (S[O.sub.2]), nitrogen oxides Noun 1. nitrogen oxide - any of several oxides of nitrogen formed by the action of nitric acid on oxidizable materials; present in car exhausts
pollutant - waste matter that contaminates the water or air or soil , and fine particulate matter particulate matter
n. Abbr. PM
Material suspended in the air in the form of minute solid particles or liquid droplets, especially when considered as an atmospheric pollutant.
Noun 1. (particulate matter < 2.5 [micro]m in diameter; P[M.sub.2.5]) could be distributed to reach national emissions caps. We applied a source-receptor matrix to determine the P[M.sub.2.5] concentration changes associated with each control scenario and estimated the mortality reductions. We estimated changes in the spatial inequality of health risk using the Atkinson index The Atkinson index (also known as the Atkinson measure) is a measure of economic income inequality developed by Anthony Barnes Atkinson. The distinguishing feature of the Atkinson index is its ability to gauge movements in different segments of the income distribution. and other indicators, following previously derived axioms This is a list of axioms as that term is understood in mathematics, by Wikipedia page. In epistemology, the word axiom is understood differently; see axiom and self-evidence. Individual axioms are almost always part of a larger axiomatic system. for measuring health risk inequality.
RESULTS: In our baseline model, benefits ranged from 17,000-21,000 fewer premature deaths Premature Death occurs when a living thing dies of a cause other than old age. A premature death can be the result of injury, illness, violence, suicide, poor nutrition (often stemming from low income), starvation, dehydration, or other factors. per year across control scenarios. Scenarios with greater health benefits also tended to have greater reductions in the spatial inequality of health risk, as many sources with high health benefits per unit emissions of S[O.sub.2] were in areas with high background P[M.sub.2.5] concentrations. Sensitivity analyses indicated that conclusions were generally robust to the choice of indicator and other model specifications.
CONCLUSIONS: Our analysis demonstrates an approach for formally quantifying both the magnitude and spatial distribution of health benefits of pollution control strategies, allowing for joint consideration of efficiency and equity.
KEY WORDS: environmental justice, equity, particulate matter, power plant, premature mortality, risk assessment. Environ Health Perspect 115:743-750 (2007). doi:10.1289/ehp.9712 available via http://dx.doi.org/ [Online 22 January 2007]
In many settings there are tensions between efficiency and equity in deciding on optimal pollution control strategies. Within the context of benefit-cost analysis benefit-cost analysis
a technique of economic evaluation, particularly for complex projects over a long period of time and involving substantial capital, that takes into account social costs and benefits as well as financial considerations. , efficiency may be related to implementing the least-cost control strategy to achieve a given health benefit, or alternatively, to maximizing net benefits. Similarly, equity can involve procedural fairness (i.e., equal involvement in public proceedings) or equity in the distribution of outcomes (Jacobson et al. 2005). Inequity consists of those inequalities that may be considered unjust UNJUST. That which is done against the perfect rights of another; that which is against the established law; that which is opposed to a law which is the test of right and wrong. 1 Toull. tit. prel. n. 5; Aust. Jur. 276, n.; Hein. Lec. El. Sec. 1080. or unfair
(Macinko and Starfield 2002). Although there are multiple interpretations of these terms, we focus here on efficiency as maximizing the public health benefits of a control measure, and on equality in the distribution of those benefits across at-risk individuals as the dimension of equity that can be included in quantitative analysis Quantitative Analysis
A security analysis that uses financial information derived from company annual reports and income statements to evaluate an investment decision.
Given these definitions, although efficiency is incorporated into any health benefits analysis, equity and related distributional issues are often omitted (Yitzhaki 2003). Most regulatory impact analyses have focused exclusively on aggregate benefits [U.S. Environmental Protection Agency Environmental Protection Agency (EPA), independent agency of the U.S. government, with headquarters in Washington, D.C. It was established in 1970 to reduce and control air and water pollution, noise pollution, and radiation and to ensure the safe handling and (EPA EPA eicosapentaenoic acid.
n.pr See acid, eicosapentaenoic.
n. ) 1999a, 1999b] without formally considering the geographic or demographic distributions of these benefits. In parallel, many studies of equity or environmental justice did not quantify health risks, instead focusing on proximity to sources (Burke 1993; Pollack pollack: see cod.
Either of two commercially important North Atlantic species of food fish in the cod family (Gadidae). and Vittas 1995; Sheppard et al. 1999), emissions (Millimet and Slottje 2002a, 2002b; Perlin et al. 1995), or concentrations (Lopez 2002). Studies that quantified risk inequality (Apelberg et al. 2005; Morello-Frosch and Jesdale 2006) or proposed a framework to do so (Finkel 1990, 1997) focused on characterizing baseline distributions of risk rather than the benefits of control strategies, and the appropriate methodology may differ in this context. The lack of a systematic framework to simultaneously consider efficiency and equity in a decision context may imply that decisions are based largely on maximization of societal benefits without formal consideration of equity implications.
To address these limitations, we developed a framework by which risk inequality could be formally quantified within health benefits analysis (Levy et al. 2006). Briefly, we proposed that quantitative indicators of inequality, similar to those used to measure income inequality, could allow decision makers to construct an optimal efficiency-equality frontier and avoid policies that are dominated across both dimensions. Based on an axiomatic ax·i·o·mat·ic also ax·i·o·mat·i·cal
Of, relating to, or resembling an axiom; self-evident: "It's axiomatic in politics that voters won't throw out a presidential incumbent unless they think his challenger will approach, we selected the Atkinson index (Atkinson 1970) as the most appropriate indicator for health benefits analysis, focusing on the change in this indicator under different control scenarios. Other indicators were considered useful for sensitivity analyses (the Gini coefficient The Gini coefficient is a measure of statistical dispersion most prominently used as a measure of inequality of income distribution or inequality of wealth distribution. It is defined as a ratio with values between 0 and 1: the numerator is the area between the Lorenz curve of the , mean log deviation, and the Theil entropy entropy (ĕn`trəpē), quantity specifying the amount of disorder or randomness in a system bearing energy or information. Originally defined in thermodynamics in terms of heat and temperature, entropy indicates the degree to which a given index).
Quantitative measures of risk-based efficiency and equality may be useful in many contexts, including the evaluation of national-level policies to control emissions from power plants in the United States. In theory these policies could involve site-specific control requirements or cap-and-trade programs. Cap-and-trade programs are designed primarily for economic efficiency but operate under the presumption A conclusion made as to the existence or nonexistence of a fact that must be drawn from other evidence that is admitted and proven to be true. A Rule of Law.
If certain facts are established, a judge or jury must assume another fact that the law recognizes as a logical that health benefits would be similar regardless of the distribution of emissions (Farrell and Lave 2004). However, given differences in atmospheric conditions and population patterns, how emission controls The selective and controlled use of electromagnetic, acoustic, or other emitters to optimize command and control capabilities while minimizing, for operations security: a. detection by enemy sensors; b. mutual interference among friendly systems; and/or c. are distributed geographically could influence the magnitude and distribution of benefits. Sulfur dioxide (S[O.sub.2]) emission trading related to the Title IV Acid Rain Program (U.S. EPA 2007) resulted in greater health benefits than a hypothetical program without trading, based on the geographic distribution of controls (Burtraw and Mansur 1999).
Regardless of efficiency claims, environmental justice advocates and communities housing power plants have expressed concern that unrestricted emission trading does not decrease and may exacerbate environmental inequities (Solomon and Lee 2000). Previous analyses (Corburn 2001; Swift 2001) focused on the possibility of emissions hot spots hot spots
acute moist dermatitis. associated with Title IV and whether low-income or minority populations tended to have lesser emission reductions in proximate proximate /prox·i·mate/ (prok´si-mit) immediate or nearest.
Closely related in space, time, or order; very near; proximal.
immediate; nearest. facilities. While these studies concluded that there were no hot spots, they used a procedural rather than an outcome-based concept of equity and therefore did not address the question of changing patterns of health risks. The benefits analysis of Title IV (Burtraw and Mansur 1999) indicated that certain geographic areas received health benefits while others had health disbenefits. However, without a more formal analysis, it is difficult to determine whether health inequality increased, decreased, or stayed the same, or to ascertain the potential impacts of future policies. Given the framing of the debate about national power plant controls, an outcome-based focus implies that an evaluation of how various distributions of emission controls correspond to changes in health benefits and in the spatial inequality of health risk would be informative for the design of future emission control programs.
In this analysis, we focus on the various ways by which emissions reductions for power plants in the United States could be distributed to meet hypothetical national emissions caps for S[O.sub.2], nitrogen oxides (N[O.sub.x]), and primary fine particulate matter (particulate matter with a diameter < 2.5 [micro]m; P[M.sub.2.5]). For each control scenario, we estimate both the public health benefits and the change in the spatial inequality of health risk. We consider the sensitivity of our conclusions to the pollutants pollutants
see environmental pollution. evaluated, the inequality indicators selected, and other factors.
Control scenarios. Given our objective of evaluating potential efficiency-equality tradeoffs, we needed to construct a number of control scenarios that spanned the efficiency-equality space and were interpretable. First, we established a national target emissions cap for all three pollutants. The Clear Skies Clear Skies could refer to:
CAIR Clean Air Interstate Rule (EPA)
CAIR Center for AIDS Intervention Research
CAIR Changing Attitudes in Recovery
CAIR California Association for Institutional Research ) (U.S. EPA 2005a) called for power plant S[O.sub.2] emissions of 3.5 million tons and N[O.sub.x] emissions of 2.2 million tons by 2015. Alternative proposals have suggested caps of 2.2 million tons of S[O.sub.2] and 1.5 million tons of N[O.sub.x] (U.S. EPA 2001). As power plant emissions in 1999 (the base year for our analysis) were 12.6 million tons of S[O.sub.2] and 5.7 million tons of N[O.sub.x] (U.S. EPA 2003b), we consider 75% reductions in each to be generally representative of proposed regulations. Although primary P[M.sub.2.5] was not incorporated into these proposals, controlling these emissions is plausible, given available technology and fuel options, and we consider a 75% reduction for consistency (but present our findings both with and without primary P[M.sub.2.5] emissions).
For our control scenarios, our objective is not to simulate economic conditions and resulting plant behaviors or to consider the impact of current or pending regulations but simply to consider ways in which an aggregate 75% reduction could theoretically be distributed. We constructed some specified control scenarios that either reflect straightforward control policies or would provide bounding estimates of efficiency or equality regardless of their viability (Table 1). For example, all plants could have 75% emission reductions (scenario A) or all plants could meet a target emission rate per unit heat input, with variable percentage reductions (scenario B).
Scenarios C through P (Table 1) represent bounding values rather than realistic control scenarios and may miss important combinations of emissions reductions. To develop other scenarios, we used a simulation approach. For each pollutant pol·lut·ant
Something that pollutes, especially a waste material that contaminates air, soil, or water. , we allowed each plant to potentially have no change, control to a target emission rate per unit heat input, control halfway between current emissions and the target rate, or control to half the target rate. Or, a plant could shut down, eliminating all emissions. We iterated randomly across these options for all plants, and in each iteration One repetition of a sequence of instructions or events. For example, in a program loop, one iteration is once through the instructions in the loop. See iterative development.
(programming) iteration - Repetition of a sequence of instructions. , retained the scenario if total emissions of each of the three pollutants were within 5% of the target national emissions cap. We constructed 20 of these intermediate control scenarios.
Source-receptor matrix. To link these emission changes with changes in ambient Surrounding. For example, ambient temperature and humidity are atmospheric conditions that exist at the moment. See ambient lighting. concentrations, we apply a source-receptor (S-R S-R Stimulus-Response (Pavlovian psychology)
S-R Set-Reset ) matrix that has been used in previous regulatory impact analyses (U.S. EPA 1997, 1999a). S-R matrix is a reduced-form model that provides the relationship between emissions of P[M.sub.2.5] or particle precursors precursors, (prēkur´srz),
n.pl particles or compounds that precede something. and county-level P[M.sub.2.5] concentrations. It is based on the Climatological cli·ma·tol·o·gy
The meteorological study of climates and their phenomena.
clima·to·log Regional Dispersion dispersion, in chemistry
dispersion, in chemistry, mixture in which fine particles of one substance are scattered throughout another substance. A dispersion is classed as a suspension, colloid, or solution. Model (CRDM CRDM Control Rod Drive Mechanism
CRDM Centre for Rapid Design and Manufacture (Buckinghamshire Chilterns University)
CRDM Cumann Rince Dea Mheasa (Irish dancing organisation) ), a sector-averaged Gaussian dispersion model that includes wet and dry deposition dry deposition
See under acid deposition. and first-order chemical conversion of S[O.sub.2] and N[O.sub.x] to sulfate sulfate, chemical compound containing the sulfate (SO4) radical. Sulfates are salts or esters of sulfuric acid, H2SO4, formed by replacing one or both of the hydrogens with a metal (e.g., sodium) or a radical (e.g., ammonium or ethyl). and nitrate nitrate, chemical compound containing the nitrate (NO3) radical. Nitrates are salts or esters of nitric acid, HNO3, formed by replacing the hydrogen with a metal (e.g., sodium or potassium) or a radical (e.g., ammonium or ethyl). particles.
S-R matrix includes county-specific calibration calibration /cal·i·bra·tion/ (kal?i-bra´shun) determination of the accuracy of an instrument, usually by measurement of its variation from a standard, to ascertain necessary correction factors. factors to adjust initial model outputs to reflect ambient monitoring data. Data from the U.S. EPA Federal Reference Method and Speciation speciation
Formation of new and distinct species, whereby a single evolutionary line splits into two or more genetically independent ones. One of the fundamental processes of evolution, speciation may occur in many ways. Network monitors were spatially interpolated interpolated /in·ter·po·lat·ed/ (in-ter´po-la?ted) inserted between other elements or parts. to county centroids The following diagrams depict a list of centroids. A centroid of an object in , and the ratios between these values and the initial model outputs were used to develop calibration factors (Abt Associates 2006). The calibration factors had a median value Noun 1. median value - the value below which 50% of the cases fall
statistics - a branch of applied mathematics concerned with the collection and interpretation of quantitative data and the use of probability theory to estimate population of 0.9, indicating that relatively little bias was found in initial S-R matrix outputs, although there was some spatial variability Spatial variability is characterized by different values for an observed attribute or property that are measured at different geographic locations in an area. The geographic locations are recorded using GPS (global positioning systems) while the attribute's spatial variability is (5th percentile percentile,
n the number in a frequency distribution below which a certain percentage of fees will fall. E.g., the ninetieth percentile is the number that divides the distribution of fees into the lower 90% and the upper 10%, or that fee level of 0.5, 95th percentile of 1.4, range of 0.11-3.5).
Power plant characteristics. We estimated emissions from the Emissions and Generation Resource Integrated Database (EGRID EGRID Emissions & Generation Resource Integrated Database ; U.S. EPA 2005b) and the National Emission Inventory An emission inventory is an accounting of the amount of air pollutants discharged into the atmosphere. It is generally characterized by the following factors:
NEI Nuclear Energy Institute
NEI National Emission Inventory
NEI Not Enough Information
NEI Netherlands East Indies
NEI Nuevos Estados Independientes ; U.S. EPA 2005c). EGRID contained information on annual N[O.sub.x] and S[O.sub.2] emissions as well as heat input and electricity generation. We used power plant characteristics from 1999 for comparability with other available data. NEI provided information on annual P[M.sub.2.5] emissions. Power plants were omitted from our analysis if they had been deactivated before 1999, if emissions data were unavailable, or if concentration modeling had not been conducted for all three pollutants within S-R matrix. The resulting database included 425 power plants, with total emissions in 1999 of approximately 11.8 million tons of S[O.sub.2], 5.0 million tons of N[O.sub.x], and 600,000 tons of primary P[M.sub.2.5], indicating that our model captures most national power plant emissions.
Demographics The attributes of people in a particular geographic area. Used for marketing purposes, population, ethnic origins, religion, spoken language, income and age range are examples of demographic data. and concentration-response functions. We focus on premature mortality, as it contributed a majority of P[M.sub.2.5]-related benefits in previous health impact analyses (U.S. EPA 1999b, 2004). We derive our concentration-response function from the American Cancer Society American Cancer Society,
n.pr established in 1913, this national volunteer-based health organization is committed to the elimination of cancer through prevention and treatment and to diminishing cancer suffering through advocacy, scholarship, research, cohort study A cohort study is a form of longitudinal study used in medicine and social science. It is one type of study design.
In medicine, it is usually undertaken to obtain evidence to try to refute the existence of a suspected association between cause and disease; failure to refute (Pope et al. 2002), as this study has been used for the primary estimates in other health impact analyses (U.S. EPA 1999b, 2004) and has the largest and most geographically diverse population of available cohort studies.
For all-cause mortality, Pope and colleagues reported that mortality rates increased by 6% (95% confidence interval confidence interval,
n a statistical device used to determine the range within which an acceptable datum would fall. Confidence intervals are usually expressed in percentages, typically 95% or 99%. , 2-11%) for a 10-[micro]g/[m.sup.3] increase in annual average P[M.sub.2.5] concentrations (using average concentrations across the study period), for a population age 30 and older. We collected population data for each county from 2000 Census data (U.S. Census Bureau Noun 1. Census Bureau - the bureau of the Commerce Department responsible for taking the census; provides demographic information and analyses about the population of the United States
Bureau of the Census 2005) and gathered background mortality data for each county from the CDC WONDER CDC WONDER CDC Wide-ranging ON-line Data for Epidemiologic Research database, provided by the Centers for Disease Control and Prevention Centers for Disease Control and Prevention (CDC), agency of the U.S. Public Health Service since 1973, with headquarters in Atlanta; it was established in 1946 as the Communicable Disease Center. (CDC See Control Data, century date change and Back Orifice.
CDC - Control Data Corporation 2005). To provide more stable estimates, all-cause mortality data were aggregated across the years Across The Years is one of a few ultrarunning festivals still taking place in the USA. Founded in 1983 by Harold Sieglaff the race has changed over the years in location as well as organisation. Today the race is held at Nardini Manor about 45 minutes from downtown Phoenix, AZ. 1990-1998.
Inequality indicators. In this section, we briefly describe the Atkinson index and the additional indicators relevant for sensitivity analysis, with more detailed information available in Appendix A and elsewhere (Levy et al. 2006).
The quantitative expression for the Atkinson index is
1-[[1/n][[summation summation n. the final argument of an attorney at the close of a trial in which he/she attempts to convince the judge and/or jury of the virtues of the client's case. (See: closing argument) ].sub.i=1.sup.n]([x.sub.i]/[bar.x])[.sup.1-[epsilon]]][.sup.1/[1-[epsilon]]]
where [x.sub.i] represents the health risk for each individual, n represents the number of individuals affected, and [epsilon] is an explicit inequality parameter ([epsilon] of 0 implies no societal concern about inequality, with increasing values indicating greater aversion a·ver·sion
1. A fixed, intense dislike; repugnance, as of crowds.
2. A feeling of extreme repugnance accompanied by avoidance or rejection. toward inequality). With the Atkinson index, the risk analyst need not decide a priori a priori
In epistemology, knowledge that is independent of all particular experiences, as opposed to a posteriori (or empirical) knowledge, which derives from experience. what the societal viewpoint about inequality should be, and can instead consider if policy decisions are sensitive to the value of [epsilon].
The Atkinson index ranges from 0 to 1, with 0 representing complete equality and 1 representing maximum inequality. Because we are concerned about changes in inequality associated with control strategies, we focus on the difference between the Atkinson index of the precontrol distribution of concentrations or health risks and the Atkinson index given postcontrol concentrations or health risks.
In sensitivity analyses, we also consider the Gini index, the mean log deviation, and the Theil entropy index. The Gini index is defined as one-half the relative mean difference, or the average of the absolute differences between all pairs of values. The Gini index has a number of limitations in the context of health benefits analysis (Levy et al. 2006) but allows us to consider sensitivity to the approach for individual comparisons and aggregation. The mean log deviation is the average of the logarithm logarithm (lŏg`ərĭthəm) [Gr.,=relation number], number associated with a positive number, being the power to which a third number, called the base, must be raised in order to obtain the given positive number. of the ratio between the mean health risk and the individual health risks [x.sub.i]. The Theil entropy index is similarly structured, averaging the product of the ratio between the individual health risks [x.sub.i] and the mean health risk and the logarithm of this ratio. Both these terms are in the same family of indicators as the Atkinson index and capture similar general concepts but without an explicit inequality aversion parameter and with other limitations (Levy et al. 2006). More detail about the calculation of the inequality indicators is provided in Appendix A.
Sensitivity analyses. Although quantitative uncertainty analysis is beyond the scope of this analysis, we test the sensitivity of our conclusions to key model assumptions. For our base case, we quantify mortality benefits considering control of S[O.sub.2], N[O.sub.x], and P[M.sub.2.5] jointly and using the Atkinson index to quantify spatial inequality. A decision must also be made about the relevant baseline against which to compare changes in mortality rates. Omission of baseline distributions of risk would lead to somewhat arbitrary determinations of inequality (Levy et al. 2006), but multiple baselines could be considered--all-cause mortality, P[M.sub.2.5]-related mortality, or power plant P[M.sub.2.5]-related mortality could be the outcome for which policymakers would hope to reduce inequality across the population with this hypothetical regulation. We consider P[M.sub.2.5]-related mortality in our base case.
For our sensitivity analyses, we consider pollutants separately and jointly, model tradeoffs for concentrations and health effects, and consider different definitions of baseline and different inequality indicators. We also present results calculating the inequality of the change in risk rather than the change in the inequality of risk: Atkinson (precontrol--postcontrol) rather than Atkinson (precontrol)-Atkinson (postcontrol). This approach effectively ignores baseline conditions and is not theoretically justified but helps us understand whether this erroneous erroneous adj. 1) in error, wrong. 2) not according to established law, particularly in a legal decision or court ruling. approach leads to different conclusions. We present our primary results with [epsilon] = 0.75 for the Atkinson index, an illustrative il·lus·tra·tive
Acting or serving as an illustration.
Adj. 1. value in the middle of the range typically found in the literature (Atkinson 1970; Kawachi and Kennedy 1997) but test values across a broad range.
Figure 1 presents the spatial patterns of annual average P[M.sub.2.5] concentrations across the United States as well as the S[O.sub.2] emission rates of the power plants in our analysis. Most of the high-emitting power plants are in the eastern United States, where P[M.sub.2.5] concentrations are generally elevated.
We first consider the scenarios to simultaneously control S[O.sub.2], N[O.sub.x], and primary P[M.sub.2.5], and apply the Atkinson index with [epsilon] = 0.75, calculating inequality based on changes in mortality risk from a baseline of P[M.sub.2.5]-related mortality. As indicated in Figure 2, the estimated public health benefits of the policies range from approximately 17,000 to 21,000 fewer premature deaths per year across control scenarios. Of this total, approximately 14,000-17,000 are associated with secondary sulfate particles. Given this, it is not surprising that the scenario with the greatest benefits (scenario C) involves controlling the plants with the highest health benefits per ton of S[O.sub.2] emissions first. Policies requiring uniform emission reductions or for each plant to reach a target emission rate tend to fall in the middle of the efficiency spectrum, similar to the intermediate control scenarios.
As the y-axis in Figure 2 represents the Atkinson index for postcontrol conditions subtracted from the Atkinson index for precontrol conditions, positive values indicate reductions in inequality and points toward the upper right represent more efficient and more equitable outcomes. Scenarios with greater health benefits generally also most reduce spatial inequality (Figure 2). This is because the power plants with maximum population exposure reductions per unit emissions of S[O.sub.2] tend to be in the areas with highest ambient P[M.sub.2.5] concentrations (Figure 3). The two policies on the optimal frontier involve controlling the plants with the highest health benefits per ton of S[O.sub.2] emissions first (scenario C) or controlling the plants with the highest background P[M.sub.2.5] concentration first (scenario I)--whether one prefers one policy over another depends on one's willingness to trade efficiency for equality. All other policies are strictly dominated.
Within our sensitivity analyses, we first considered the application of the Atkinson index with different values of [epsilon] as well as the other inequality indicators, holding other assumptions as in Figure 2. Of note, comparing the absolute values of the different inequality indicators to one another is not directly interpretable; the key question is whether the optimal policies are robust to the choice of indicator. Although there was some modest reordering re·or·der
v. re·or·dered, re·or·der·ing, re·or·ders
1. To order (the same goods) again.
2. To straighten out or put in order again.
3. To rearrange.
v. of control strategies, the general conclusions remained robust, with only scenarios C and I on the optimal frontier (Figure 4). We present results for [epsilon] ranging from 0.25 to 3 (the range generally used in the literature), but conclusions are similar for higher values as well.
Considering the influence of the choice of baseline highlights some important issues (Figure 5). Although the optimal strategies are identical for different mortality-related baselines, the Atkinson index changes to a greater extent for power plant P[M.sub.2.5]-related mortality. Postcontrol power plant-related P[M.sub.2.5] mortality is close to zero in some locations, and the Atkinson index and other indicators are sensitive to near-zero values. Of greater significance is the fact that ignoring baseline conditions leads to substantially different conclusions, in which the scenarios previously considered to most improve equality are now considered to be least equitable. This is because scenarios such as C and I focus controls in geographic areas that have elevated baseline exposures and risks, so that the benefits are spread less uniformly but serve to reduce existing inequalities.
We additionally examined whether the conclusions differed when considering concentrations rather than health effects (with population-weighted concentration change as the efficiency measure and inequality in concentrations as the equity measure), with no significant difference in the findings (results not shown). Omission of primary P[M.sub.2.5] emissions from the analysis, which more closely mirrors some of the proposed national cap-and-trade programs, led to similar conclusions (Figure 6). Not surprisingly, the optimal policies differed if only single pollutants were considered (i.e., controlling only N[O.sub.x] emissions), but the findings similarly illustrated bounding estimates for efficiency by controlling the maximum/minimum health benefits per unit emissions and bounding estimates for equality by controlling the power plants in high/low ambient P[M.sub.2.5] settings first.
Finally, if we allow multiple parameters to vary simultaneously, our conclusions are largely unaffected. For example, under all combinations of inequality indicators, choice of baseline, and use of concentrations or health risks (controlling all three pollutants), scenario I remains the most equitable, whereas scenario C remains the most efficient.
Discussion and Conclusion
Our analysis demonstrates good concordance concordance /con·cor·dance/ (-kord´ins) in genetics, the occurrence of a given trait in both members of a twin pair.concor´dant
n. between national power plant emission reduction patterns that maximize health benefits and those that best reduce spatial inequality in the distribution of air pollution-related risks. This concordance will not always exist. It is clear that reducing risks for the highest-risk individual first would both maximize efficiency and minimize inequality, presuming pre·sum·ing
Having or showing excessive and arrogant self-confidence; presumptuous.
pre·suming·ly adv. no differences in the costs or feasibility of controls. However, pollution control strategies are targeted at sources rather than at individuals. In this context, tradeoffs are likely, as the factors that influence efficiency differ from the factors that influence equality. Our finding is based on the spatial coincidence between population risk reductions (largely a function of downwind down·wind
In the direction in which the wind blows.
downwind population density at long distance) and individual risk reductions (largely a function of high ambient P[M.sub.2.5] concentrations close to the power plant). As shown in Figure 6, this coincidence is stronger for some pollutants (S[O.sub.2]) than for others (N[O.sub.x]).
We also demonstrated within our analysis that these conclusions were robust across numerous model configurations as long as baseline conditions are appropriately incorporated. In particular, the optimal policy choices did not vary with [epsilon]; if the conclusions were sensitive to [epsilon], follow-up studies would be needed to determine the values that best capture priorities of stakeholders Stakeholders
All parties that have an interest, financial or otherwise, in a firm-stockholders, creditors, bondholders, employees, customers, management, the community, and the government. and decision makers.
Another interesting finding is that the difference in health benefits across the control scenarios is small in relative terms, with only a 22% difference between the minimum and maximum benefits. This can be attributed to the fact that the emission reductions are substantial enough to require controls at many facilities, reducing the variation between scenarios in spite of larger variations in plant-specific benefits (Figure 3). That being said, a 22% difference does reflect an absolute difference of nearly 4,000 deaths per year, which could be significant in determining optimal policies. In addition, if not all power plants were controlled at the same time, the differences between the scenarios would increase if discount rates were applied to benefits in future years.
Although our findings are generally robust, a number of limitations are important to recognize. First, we have only addressed one dimension of equity, by focusing on spatial variability in county-level mortality risks with a national focus. More conventionally, equity considerations in an environmental justice context consider racial and ethnic disparities, which are omitted from this analysis. Inclusion of effect modifiers such as educational attainment Educational attainment is a term commonly used by statisticans to refer to the highest degree of education an individual has completed.
The US Census Bureau Glossary defines educational attainment as "the highest level of education completed in terms of the (Pope et al. 2002) or evaluation of morbidity outcomes with known demographic patterning could significantly influence spatial patterns of risk (Levy et al. 2002) and any conclusions about equity, especially if methods are used to decompose de·com·pose
v. de·com·posed, de·com·pos·ing, de·com·pos·es
1. To separate into components or basic elements.
2. To cause to rot.
1. inequality between and within different subpopulations (Levy et al. 2006). Although these factors are clearly important, much of the outcome-based debate related to national power plant control strategies has revolved re·volve
v. re·volved, re·volv·ing, re·volves
1. To orbit a central point.
2. To turn on an axis; rotate. See Synonyms at turn.
3. around spatial equity. In general, the equity measure utilized should be the one most informative to the decision-maker within the context of the policy question. In applications in which other dimensions Other Dimensions is a collection of stories by author Clark Ashton Smith. It was released in 1970 and was the author's sixth collection of stories published by Arkham House. It was released in an edition of 3,144 copies. of equity are central, particularly those involving mobile sources (where the spatial extent of impact is lesser and local socioeconomic so·ci·o·ec·o·nom·ic
Of or involving both social and economic factors.
of or involving economic and social factors
Adj. 1. and demographic factors may be more influential), other measures should be used.
In addition, for our results to be useful for decision making, the costs of control need to be included, with realistic control strategies rather than bounding values and randomly-generated scenarios. With plant-specific control costs, we could compare net monetized benefits with changes in the spatial inequality of risk (noting that cost information cannot be used directly in our inequality indicator). Considering other dimensions of equity, such as the distribution of costs across power plant companies or consumers, would lead to a more comprehensive and relevant analysis, and methods should be developed to synthesize To create a whole or complete unit from parts or components. See synthesis. these elements into a single decision framework.
Our findings are also dependent on the validity of S-R matrix. Although S-R matrix is simplified relative to state-of-the-science dispersion models, it has yielded similar health impact estimates as more advanced models (Abt Associates et al. 2000; Levy et al. 2003). It also has the benefit of explicit calibration with ambient monitoring data. Moreover, given the numerous sources and control scenarios in our analysis, a more intensive model would have been infeasible. We can corroborate To support or enhance the believability of a fact or assertion by the presentation of additional information that confirms the truthfulness of the item.
The testimony of a witness is corroborated if subsequent evidence, such as a coroner's report or the testimony of other our modeling to a limited extent by comparison with similar analyses of the benefits of national cap-and-trade programs. For example, the U.S. EPA analysis of CAIR used CMAQ CMAQ Congestion Mitigation & Air Quality (Improvement Program, ISTEA)
CMAQ Community Multiscale Air Quality Model (US EPA) to estimate benefits of 17,000 fewer premature deaths per year, with population-weighted P[M.sub.2.5] concentration reductions of about 1.2 [micro]g/[m.sup.3] (U.S. EPA 2005d). Our corresponding estimates (for S[O.sub.2] and N[O.sub.x] control only) of 15,000-18,000 fewer premature deaths and 1.3-1.6 [micro]g/[m.sup.3], for a slightly more stringent emissions cap, compare favorably fa·vor·a·ble
1. Advantageous; helpful: favorable winds.
2. Encouraging; propitious: a favorable diagnosis.
3. with these estimates, although this validates our efficiency measures to a greater degree than our equity measures (which rely on spatial concentration patterns). S-R matrix also does not include the influence of N[O.sub.x] emissions on ozone formation. Including ozone-related health benefits could theoretically influence our findings, although previous studies have shown that P[M.sub.2.5] dominates monetized benefits (U.S. EPA 2005d).
In addition, although we conducted multiple sensitivity analyses, some alternative assumptions could have significantly influenced our findings. In particular, if definitive information were available about the relative toxicity of different particle constituents, our conclusions could differ. That being said, Figure 6 demonstrates that control scenario I is on the optimal frontier for all pollutants and therefore would be robust across different toxicity assumptions. Alternative assumptions about concentration-response function nonlinearities or regional differences in concentration-response functions could also have important effects. In particular, thresholds in the concentration-response function would reduce the benefits outside the Midwest, potentially enhancing the differences between control scenarios but likely not changing the optimal control scenarios. Nonlinearities and large variations in baseline risks would also lead to greater differences between concentration-based conclusions and risk-based conclusions, thereby enhancing the importance of risk-based indicators. As the epidemiologic evidence did not provide strong support for any of these factors, we did not formally incorporate them into sensitivity analyses, but they could be considered in future analyses as the evidence base evolves. Of note, other uncertain parameters (like the magnitude of the concentration-response relationship) would not influence the core conclusions about optimal control strategies. More generally, formal uncertainty analysis related to both efficiency and equity measures would be required for any future decision making in this setting.
A final concern is related to the inequality indicators themselves. Although the indicators we used agree with an axiomatic approach proposed previously (Levy et al. 2006), there are some limitations. The parameter [epsilon] in the Atkinson index most influences sensitivity to low values, but in a health risk inequality context, we are more concerned about high values, so this represents an indirect mechanism for expressing concern about different segments of the risk distribution. We also observed the sensitivity of all indicators to values near zero, which can be influential given certain definitions of baseline. Because of these issues, development of novel inequality indicators specific to health benefits analysis may be warranted, although our conclusions were not sensitive to the statistical formulation of the inequality indicator.
More generally, although our framework helped to identify policies on the optimal frontier and policies that were strictly dominated, it is difficult to know to what extent decision-makers should be willing to trade off a given increase in health benefits for a given decrease in an inequality indicator. Further research is needed into the interpretation of small changes in inequality.
Limitations aside, our analysis provides some useful insights. First, our scenarios provide both bounding values and an indication of the types of targeted control strategies that would be most beneficial. For example, if the initial allocation of permits in a cap-and-trade program were weighted to encourage greater emission reductions in zones with high concentrations or high health benefits per unit emissions, it would increase the likelihood of both maximizing health benefits and minimizing spatial inequality in PM-related risk. More generally, our analysis provides insight about the power plants that are the best candidates for controls from a health benefits and health equality perspective. Coupled with control cost information, these insights could be used to design an optimal control regimen regimen /reg·i·men/ (rej´i-men) a strictly regulated scheme of diet, exercise, or other activity designed to achieve certain ends.
1. . Finally, from a methodologic perspective, we have demonstrated the viability of developing efficiency-equality tradeoff frontiers in the context of health benefits analysis. These tools can be applied retrospectively (i.e., to Title IV) or prospectively to determine optimal policy options, taking into account both efficiency and equality.
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Jonathan I. Levy, Andrew M. Wilson,* and Leonard M. Zwack
Department of Environmental Health, Exposure Epidemiology and Risk Program, and Harvard Center for Risk Analysis, Harvard School of Public Health The Harvard School of Public Health is (colloquially, HSPH) is one of the professional graduate schools of Harvard University. Located in Longwood Area of the Boston, Massachusetts neighborhood of Mission Hill, next to Harvard Medical School and Cambridge, Massachusetts, , Boston, Massachusetts “Boston” redirects here. For other uses, see Boston (disambiguation).
Boston is the capital and most populous city of Massachusetts. The largest city in New England, Boston is considered the unofficial economic and cultural center of the entire New , USA
Address correspondence to J.I. Levy, Harvard School of Public Health, Department of Environmental Health, Landmark Center
Landmark Center in Boston, Massachusetts is a commercial center situated in an art deco building built in 1929 for Sears, Roebuck and Company. 4th Floor West, Room 404K, 401 Park Dr., Boston, MA 02215 USA. Telephone: (617) 384-8808. Fax: (617) 384-8859. E-mail: email@example.com
*Current address: Fidelity Investments Fidelity Investments is a group of privately held companies in the financial services industry. It is made up by two independent but closely cooperating companies, Fidelity Management and Research Corporation (FMR Co. , Inc., Boston, MA USA.
We thank D. McCubbin and D. Latimer as well as the Clean Air Task Force for facilitating access to the S-R matrix.
This study was funded by the National Science Foundation (SES-0324746).
A.M.W., who is presently employed by Fidelity Investments, Inc., was employed by Harvard University Harvard University, mainly at Cambridge, Mass., including Harvard College, the oldest American college. Harvard College
Harvard College, originally for men, was founded in 1636 with a grant from the General Court of the Massachusetts Bay Colony. when this work was performed. All other authors declare they have no competing financial interests.
Received 12 September 2006; accepted 22 January 2007.
Table 1. Specified control scenarios for power plant simulation. Scenario Definition A 75% reductions in S[O.sub.2], N[O.sub.x], and primary P[M.sub.2.5] from all plants B Reductions in S[O.sub.2], N[O.sub.x], and primary P[M.sub.2.5] from all plants to meet the average target emissions in pounds per million Btu, with plants currently below the target constrained to no emissions increases C Elimination of plants until all caps are met, starting from the highest health benefit per unit emissions of S[O.sub.2], going down D Elimination of plants until all caps are met, starting from the highest health benefit per unit emissions of nitrogen dioxide (N[O.sub.2]), going down E Elimination of plants until all caps are met, starting from the highest health benefit per unit emissions of P[M.sub.2.5], going down F Elimination of plants until all caps are met, starting from the lowest health benefit per unit emissions of S[O.sub.2], going up G Elimination of plants until all caps are met, starting from the lowest health benefit per unit emissions of N[O.sub.2], going up H Elimination of plants until all caps are met, starting from the lowest health benefit per unit emissions of P[M.sub.2.5], going up I Elimination of plants until all caps are met, starting from the highest background P[M.sub.2.5] concentration, going down J Elimination of plants until all caps are met, starting from the lowest background P[M.sub.2.5] concentration, going up K Elimination of plants until all caps are met, starting from the highest S[O.sub.2] emitters, going down L Elimination of plants until all caps are met, starting from the highest N[O.sub.2] emitters, going down M Elimination of plants until all caps are met, starting from the highest P[M.sub.2.5] emitters, going down N Elimination of plants until all caps are met, starting from the lowest S[O.sub.2] emitters, going up O Elimination of plants until all caps are met, starting from the lowest N[O.sub.2] emitters, going up P Elimination of plants until all caps are met, starting from the lowest P[M.sub.2.5] emitters, going up
As indicated in the text, we use four inequality indicators within our analysis. We apply the Atkinson index for our primary analysis, and we use the Gini coefficient, the mean log deviation, and the Theil entropy index for sensitivity analyses. In each case we apply the indicator to the precontrol distribution of risks, then to the postcontrol distribution of risks, with the difference between these values used to construct the efficiency-equality frontiers. Within this appendix, we provide an illustrative calculation for each of the indicators (including multiple values of [epsilon] for the Atkinson index).
The formulas for the four inequality indicators are listed below:
Atkinson index 1-[[1/n][[summation].sub.i=1.sup.n]([x.sub.i]/[bar.x])[.sup.1-[epsilon]]][.sup.1/[1-[epsilon]]],
where [epsilon] = inequality aversion (range from 0 to infinity),
Gini index [[1/[n.sup.2]][[summation].sub.i=1.sup.n][[summation].sub.j=1.sup.n]|[x.sub.i] - [x.sub.j]|]/2[mu],
Mean log deviation [1/n][[summation].sub.i=1.sup.n]ln([mu]/[x.sub.i]), and
Theil entropy index [1/n][[summation].sub.i=1.sup.n]([x.sub.i]/[mu])ln([x.sub.i]/[mu]).
Now suppose there were 10 geographic regions affected by a control strategy, with the baseline and postcontrol distributions of risk as presented in Table A1. Note that the baseline risks roughly correspond to the deciles of P[M.sub.2.5]-related mortality risks in our analyses, and the three control scenarios are meant to illustrate the implications of controls focused on the bottom, middle, and top of the distribution (with approximate 10% risk reductions). For simplicity, we presume pre·sume
v. pre·sumed, pre·sum·ing, pre·sumes
1. To take for granted as being true in the absence of proof to the contrary: We presumed she was innocent. equal numbers of people in each risk bin.
Table A2 shows the resulting values of each of the inequality indicators, including the Atkinson index for multiple values of [epsilon].
First, it should be noted that the absolute values are less significant than the relative differences between the precontrol and postcontrol scenario. The Atkinson index can take on any value from 0 to 1, depending on the value of [epsilon], and the other three inequality indicators represent different conceptualizations of equity.
In all cases, controlling risks at the bottom of the distribution (the lower-risk individuals) led to an increase in the inequality indicators, implying increased inequality of risk. Similarly, in all cases, controlling risks at the top of the distribution (the higher-risk individuals) led to a decrease in the inequality indicators, implying reduced inequality of risk.
Controlling risks in the middle of the distribution was seen as beneficial for some inequality measures and not for others. In particular, inequality increased according to according to
1. As stated or indicated by; on the authority of: according to historians.
2. In keeping with: according to instructions.
3. the mean log deviation, the Theil entropy index, Gini coefficient, and Atkinson index for [epsilon] = 0.5. For higher values of [epsilon], inequality according to the Atkinson index decreased. This can be explained by the fact that, for higher values of [epsilon], the Atkinson index most heavily penalizes large differences between low values and the mean, and the "control in the middle" scenario has lessened the distance between the mean and the bottom of the distribution, although it has simultaneously increased the distance between the mean and the top of the distribution. As indicated in the text, this emphasizes that the Atkinson index is a somewhat indirect measure for capturing concern about high-risk individuals, as changes in [epsilon] most directly indicate the degree of concern about low-risk individuals.
Table A1. Baseline and postcontrol distributions of risk. Baseline Risk, control at: Decile risk Bottom Middle Top 1 3.4 x [10.sup.-4] 3.1 x 3.4 x 3.40 x [10.sup.-4] [10.sup.-4] [10.sup.-4] 2 6.8 x [10.sup.-4] 6.1 x 6.8 x 6.80 x [10.sup.-4] [10.sup.-4] [10.sup.-4] 3 8.0 x [10.sup.-4] 7.2 x 8.0 x 8.00 x [10.sup.-4] [10.sup.-4] [10.sup.-4] 4 8.9 x [10.sup.-4] 8.9 x 8.0 x 8.90 x [10.sup.-4] [10.sup.-4] [10.sup.-4] 5 9.9 x [10.sup.-4] 9.9 x 8.9 x 9.90 x [10.sup.-4] [10.sup.-4] [10.sup.-4] 6 1.1 x [10.sup.-3] 1.1 x 1.0 x 1.10 x [10.sup.-3] [10.sup.-3] [10.sup.-3] 7 1.2 x [10.sup.-3] 1.2 x 1.1 x 1.20 x [10.sup.-3] [10.sup.-3] [10.sup.-3] 8 1.3 x [10.sup.-3] 1.3 x 1.3 x 1.20 x [10.sup.-3] [10.sup.-3] [10.sup.-3] 9 1.4 x [10.sup.-3] 1.4 x 1.4 x 1.30 x [10.sup.-3] [10.sup.-3] [10.sup.-3] 10 1.8 x [10.sup.-3] 1.8 x 1.8 x 1.60 x [10.sup.-3] [10.sup.-3] [10.sup.-3] Table A2. Values of each of the inequality indicators. Baseline Risk, control at: Inequality indicators risk Bottom Middle Top Atkinson, [epsilon] = 0.5 0.038 0.044 0.040 0.032 Atkinson, [epsilon] = 1.5 0.127 0.146 0.127 0.112 Atkinson, [epsilon] = 3 0.282 0.319 0.272 0.259 Atkinson, [epsilon] = 5 0.445 0.483 0.426 0.423 Mean log deviation 0.084 0.097 0.085 0.072 Theil 0.072 0.083 0.077 0.061 Gini 0.207 0.222 0.215 0.185