&EPA
United a*K
Envirainwnlal Protection
Agency
Welfare Risk and Exposure Assessment for
Ozone
Second External Review Draft
Executive Summary
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EPA-452/P-14-003 c
February 2014
Welfare Risk and Exposure Assessment for Ozone
Second External Review Draft
Executive Summary
U.S. Environmental Protection Agency
Office of Air and Radiation
Office of Air Quality Planning and Standards
Health and Environmental Impacts Division
Risk and Benefits Group
Research Triangle Park, North Carolina 27711
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DISCLAIMER
This draft document has been prepared by staff from the Risk and Benefits Group, Health and
Environmental Impacts Division, Office of Air Quality Planning and Standards, U.S. Environmental
Protection Agency. Any findings and conclusions are those of the authors and do not necessarily reflect
the views of the Agency. This draft document is being circulated to facilitate discussion with the Clean
Air Scientific Advisory Committee to inform the EPA's consideration of the ozone National Ambient
Air Quality Standards.
This information is distributed for the purposes of pre-dissemination peer review under
applicable information quality guidelines. It has not been formally disseminated by EPA. It does not
represent and should not be construed to represent any Agency determination or policy.
Questions related to this preliminary draft document should be addressed to Travis Smith, U.S.
Environmental Protection Agency, Office of Air Quality Planning and Standards, C539-07, Research
Triangle Park, North Carolina 27711 (email: smith.jtravis@epa.gov).
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Welfare Risk and Exposure Assessment
Ozone, Second External Review Draft
(January 2014)
Executive Summary
SUMMARY CONCLUSIONS
The goals for this welfare risk and exposure
assessment (REA) include (i) characterizing
ambient ozone (O3) exposure and its relationship
to ecological effects, and (ii) estimating the resulting
impacts to several ecosystem services. We quantitatively
characterize the impact of ambient O3 exposures on two
important ecological effects - biomass loss and visible
foliar injury - and quantitatively estimate impacts to the
following ecosystem services: regulating services
including carbon sequestration and pollution removal;
provisioning services including timber production and
agricultural harvesting; and cultural services such as
recreation. We conduct both national-scale and case
study analyses for these two ecological effects, and we
also qualitatively assess impacts on additional ecosystem
services, including hydrologic cycle, pollination
regulation, and fire regulation (regulating services);
commercial non-timber forest products and insect damage
(provisioning services); and aesthetic and non-use values
(cultural services). For each of these analyses, we use a
biologically-relevant cumulative, seasonal form for O3
exposure, the W126 metric, which is measured as ppm-
hrs.
For biomass loss, the Clean Air Scientific
Advisory Committee (CASAC) recommended that EPA
should consider options for W126 standard levels based
on factors including a predicted one to two percent
biomass loss for trees and a predicted five percent loss of
crop yield. Small losses for trees on a yearly basis
compound over time and can result in substantial biomass
losses over the decades-long lifespan of a tree. For trees,
the annual W126 index values leading to a one percent
biomass loss range from approximately 4 to 10 ppm-hrs
and leading to a two percent biomass loss range from
approximately 7 to 14 ppm-hrs. For crops, the annual
W126 index values leading to a five percent biomass loss
range from approximately 12 to 17 ppm-hrs. The
recommended biomass loss benchmark for crops occurs at
higher W126 index values than for trees, suggesting that
potential alternative standards that are protective of trees
will also be protective of crops.
Unlike for biomass, CASAC did not recommend
a benchmark for foliar injury. In general, however, the
results of several foliar injury analyses demonstrate a
similar pattern - the proportion of biosites1 showing foliar
injury increases steeply with W126 index values up to
approximately 10 ppm-hrs and is relatively constant at
W126 index levels above 10 ppm-hrs. While the
proportion of biosites with foliar injury differs, this
general pattern of response to W126 is seen in the foliar
injury analyses stratified by soil moisture, by year, and by
geographic region.
In this REA, we analyzed the changes in risk
across several potential alternative standard levels after
adjusting air quality to just meet the existing standard2
and just meet alternative secondary standard levels.
Overall, the largest reduction in O3-related welfare risk
occurs when moving from recent ambient conditions to
just meeting the existing standard. Some welfare
exposures and risks remain after just meeting the existing
standard and in many cases, just meeting potential
alternative standard levels results in reductions in those
remaining exposures and risks.
INTRODUCTION
The U.S. Environmental Protection Agency (EPA)
is conducting a review of the national ambient air
quality standards (NAAQS) for O3 and related
photochemical oxidants. This draft welfare REA focuses
on assessments to inform consideration of the review of
the secondary (welfare-based) NAAQS for O3. This draft
REA, which is the second draft for this NAAQS review,
provides an assessment of exposure and risk associated
with recent ambient concentrations of O3 and potential
secondary standards. The REA builds on analyses done
for the previous NAAQS review completed in 2008,
expands the characterization of risk of ecological effects,
and adds consideration of impacts to ecosystem services.
1 A biosite is a plot of land on which data is collected
regarding the incidence and severity of visible foliar
injury on a variety of O3.sensitive plant species.
2 The existing secondary standard for O3 is set identical to
the primary standard at a level of 0.075 ppm (75 ppb),
based on the annual fourth-highest daily maximum 8-hour
average concentration, averaged over three years.
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Welfare Risk and Exposure Assessment
Ozone, Second External Review Draft
(January 2014)
Executive Summary
The REA also focuses on improving the characterization
of the overall confidence in the risk estimates, including
related uncertainties, by improving on the methods and
data used in the previous analyses.
CONCEPTUAL FRAMEWORK
Ecosystem services are distinct from other
ecosystem products and functions because there is
human demand for these services. In the
Millennium Ecosystem Assessment, ecosystem services
are classified into four main categories:
• Provisioning — products obtained from
ecosystems, such as the production of food and
water.
• Regulating — benefits obtained from the
regulation of ecosystem processes, such as the
control of climate and disease.
• Cultural — the nonmaterial benefits that people
obtain from ecosystems through spiritual
enrichment, cognitive development, reflection,
recreation, and aesthetic experiences.
• Supporting — those services necessary for the
production of all other ecosystem services, such
as nutrient cycles and crop pollination.
In the previous review of the secondary NAAQS
for O3, EPA focused the welfare risk assessment on
estimating changes in biomass loss in forest tree species
and yield loss in agricultural crops, quantifying foliar
injury risk, and qualitatively considering effects on
ecosystem services. In this review, EPA expanded the
analysis to consider the broader array of impacts on
ecosystem services resulting from known effects of O3
exposure on ecosystem functions. This expansion
includes quantifying the risks not just to ecosystems, but
also to the aspects of public welfare that depend on those
ecosystems, i.e., ecosystem services. Figure ES-1
illustrates the relationships between the ecosystem
services and aspects of public welfare that depend on
those services.
ECOSYSTEM SERVICES
Provisioning
FOOD
FRESH WEB
WOOD AND FIBER
FUEL
CONSTITUENTS OFWELL-BEING
Security
PERSONAL SAFETY
SECURE RESOURCE ACCESS
SECURITY FROM DISASTERS
Supporting
NUTRIENT CYCLING
SOIL FORMATION
PRIMARY PRODUCTION
Regulating
CLIMATE REGULATION
FLOOD REGULATION
DBEASE REGULATION
WATER PURIFICATION
Cultural
AESTHETIC
SPIRITUAL
EDUCATIONAL
RECREATIONAL
Basic material
for good life
ADEQUATE LIVEUHOOOS
SUFFICIENT NUTRITIOUS FOOD
SHELTER
ACCESS TO GOODS
Health
STRENGTH
FEELING WELL
ACCESSTOCLEANAIR
AND WATER
Freedom
of choice
and action
OPPORTUNE TO BE
ABLE TO ACHIEVE
WHATANINDMDUAL
VALUES DOING
AND BEING
LIFE ON EARTH-BIODIVERSITY
Good social relations
SOCIAL COHESION
MUTUAL RESPECT
ABIUTYTOHELP OTHERS
Source: Millennia Ecosystem Assessment
Figure ES-1 Linkages Between Ecosystem Services
Categories and Components of Human Weil-Being (MEA,
2005)
AIR QUALITY CONSIDERATIONS
The air quality information and analyses for this
review build upon those in prior reviews and
include: (1) summaries of recent ambient O3 data;
(2) application of a methodology to extrapolate measured
O3 concentrations to areas without monitors, including
natural areas, such as national parks, that are important to
a welfare effects assessment; and (3) adjustment of air
quality to show the distributions of O3 when just meeting
existing or potential alternative secondary standards. We
use estimates of O3 exposure (measured as W126) (see
the text box for a description of the W126 metric) to
assess exposures and ecological risks associated with
recent ambient conditions and just meeting the existing
and alternative
standards. While
the existing O3
monitoring
network has a
largely urban
focus, to address
ecosystem impacts
of O3, it is equally
important to focus
The W126 metric is a seasonal sum of
hourly O3 concentrations, designed to
measure the cumulative effects of O3
exposure on vulnerable plant and tree
species. The W126 metric uses a
sigmoidal weighting function to place less
emphasis on exposure to low
concentrations and more emphasis on
exposure to high concentrations.
ES-2
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Welfare Risk and Exposure Assessment
Ozone, Second External Review Draft
(January 2014)
Executive Summary
on monitoring in rural areas. The extent of monitoring
coverage in non-urban areas has not significantly changed
since the previous review. Figure ES-2 shows the current
O3 monitoring coverage in the U.S. - both urban and non-
urban sites. To estimate O3 exposure in areas without
monitors, particularly those gaps left by a sparse rural
monitoring network in the western U.S., we use a spatial
interpolation technique called Voronoi Neighbor
Averaging (VNA) to create an air quality surface for the
contiguous U.S. for each year from 2006 to 2010 and a
surface for a 3-year average of 2006-2008 data.
We also consider the changes in W126 index
values after adjusting O3 concentrations to just meet the
existing standard and potential alternative W126 standard
levels of 15, 11, and 7 ppm-hrs. After adjusting the
monitor values, we generate another 3-year average
national-scale VNA surface for just meeting the existing
standard. We then further adjust monitor data to just meet
potential alternative W126 standard levels of 15, 11, and
7 ppm-hrs. The adjusted surfaces are used as inputs to
several assessments, including the geographic analysis to
assess the effects of insect damage related to foliar injury,
the national- and case study-scale biomass loss
assessments, and the national park case studies for foliar
injury. For the national-scale and screening-level foliar
injury analyses, to better match the air quality data with
short-term soil moisture data, we use the surfaces for the
individual years from 2006 through 2010.
RISK TO VEGETATION AND ECOSYSTEMS
In this welfare REA, we quantified the impact of O3
exposure on two categories of ecological effects: (1)
relative biomass loss for trees and crops, and (2)
visible foliar injury. The results of these ecological
assessments are inputs to ecosystem service assessments,
which are described in more detail in the subsequent
sections.3
In this welfare REA, we do not quantify insect damage
resulting from O3 exposure. In the next Section, Risk to
Ecosystem Services, we briefly discuss the ecosystem
services associated with insect damage on tree stands and
timber production, including the overlap of areas with
The first step in assessing biomass loss for tree
seedlings and crops is to identify the range of W126 index
values corresponding to benchmarks recommended by
CAS AC. To compare different levels of biomass loss to
different W126 index values, we plot the concentration-
response (C-R) functions for 12 tree species and 10 crops
as a function of the percent biomass loss against varying
index values of W126. For a one percent biomass loss in
tree seedlings, the estimated annual W126 index values
are between 4 and 10 ppm-hrs; for a two percent biomass
loss in tree seedlings the estimated annual W126 index
values are between 7 and 14 ppm-hrs; and for a five
percent biomass loss for crops the estimated annual W126
index values are between 12 and 17 ppm-hrs. In general,
estimates of biomass loss in tree seedlings are comparable
to mature trees with a few exceptions. Next, we use these
C-R functions to determine the range of biomass loss
associated with just meeting the existing and potential
alternative W126 standards in analyses of individual
species as well as combined analyses of individual
species.
To assess foliar injury at a national scale and
identify potential benchmarks, we applied a national data
set on foliar injury from the U.S. Forest Service's (USFS)
Forest Health Monitoring Network, which monitors the
potential impacts of O3 on our nation's forests. Our
analyses provide results using both the presence/absence
of foliar injury and elevated levels foliar injury. We also
conduct analyses across years and different soil moisture
categories. Over 81 percent of biosites in USFS's data set
showed no visible foliar injury. Generally, the results of
all of these foliar injury analyses demonstrate a similar
pattern - the proportion of biosites showing foliar injury
increases steeply with W126 index values up to
approximately 10 ppm-hrs and is relatively constant at
W126 index levels above 10 ppm-hrs. We use these
results to derive W126 benchmarks for visible foliar
injury for six scenarios representing the full range of
percentages of biosites showing visible foliar injury (i.e.,
any injury and elevated injury), including five scenarios
considering soil moisture. For the "base scenario", the
benchmark represents the point above which there
higher W126 concentrations and risk of bark beetle
infestation.
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Welfare Risk and Exposure Assessment
Ozone, Second External Review Draft
(January 2014)
Executive Summary
• SLAMS
• CASTNET
• NCORE/PAMS
* SPMS/OTHER
Figure ES-2 U.S. Ambient O3 Monitoring Sites in Operation During 2006-2010
The map shows the location of all U.S. O3 monitors operating during the 2006-2010 period. The gray dots, which make up over 80 percent of the O3 monitoring network, are "State and Local
Monitoring Stations" (SLAMS) monitors that are largely operated by state and local governments and largely focused on urban areas. The blue dots highlight two important subsets of the SLAMS
network: "National Core" (NCore) multipollutant monitoring sites and the "Photochemical Assessment Monitoring Stations" (PAMS) network. The green dots represent the Clean Air Status and Trends
Network (CASTNET) monitors, which are focused on rural areas. In 2010, there were about 80 CASTNET sites operating, with sites in the Eastern U.S. being operated by EPA and sites in the Western
U.S. being operated by the National Park Service (NFS). The black dots represent Special Purpose Monitoring Stations" (SPMS), which include about 20 rural monitors as part of the "Portable O3
Monitoring System" (POMS) network operated by the NFS.
ES-4
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Welfare Risk and Exposure Assessment
Ozone, Second External Review Draft
(January 2014)
Executive Summary
was a consistent percentage (17.7 percent) of biosites
showing foliar injury, regardless of soil moisture. This
analysis suggests that reductions in W126 index values at
or above this benchmark (W126 > 10.46 ppm-hrs) are
unlikely to substantially reduce the prevalence of foliar
injury. Similarly, this analysis suggests that reductions in
W126 index values below the base scenario benchmark
are likely to relatively sharply reduce the prevalence of
foliar injury. We also looked at alternative scenarios
based on three different categories of soil moisture and
the W126 index values associated with four different
prevalences (e.g., 5%, 10%, 15% and 20% of biosites) of
any foliar injury, and a final scenario based on a 5 percent
prevalence of foliar injury index greater than or equal to
5. In total, we evaluated 13 different W126 benchmarks
associated with the six foliar injury risk scenarios. The
W126 benchmarks across the six scenarios range from
3.05 ppm-hrs (five percent of biosites, normal moisture,
any injury) up to 46.87 ppm-hrs (five percent of biosites,
dry, elevated injury). These results suggest that soil
moisture plays a role in foliar injury, potentially
indicating that drought may provide some protection from
foliar injury. In addition, we see similar patterns when
the foliar injury analysis is stratified by year and
geographic region.
Figure ES-3 shows the pattern seen in the foliar injury
analyses stratified by soil moisture category.
Biosite Index -• 0
Figure ES-3 Cumulative Proportion of Sites with Any
Visible Foliar Injury Present, by Soil Moisture
Category
RISK TO ECOSYSTEM SERVICES
F Figure ES-4 illustrates the overall relationships
between some of the ecological effects of O3
exposure and the associated ecosystem services
impacts. While we estimate the impact of ambient O3
exposures on biomass loss and foliar injury and the
associated ecosystem services, because of a lack of
sufficient data, methods, or resources we qualitatively or
semi-quantitatively assess additional ecosystem services
potentially affected.
Ecological Effects
'I'.i'iui.iv. L"v. (Chapter 6)
• Midi Injiiiy (Chapter7)
Supporting Services
• Prinui v1 Productivity
Regulating Services
• (. di bun Veqwesu dliun
* I'ullulion Kemovdl
Cultural Services
KeuejlkmjIU'A*
Provisioning Services
Agricultural Harvest
Timber Production
Additional Assessments
Supporting Services
* Soil Formation
• (.ommiinitv Structure
• hiiiKii, i'Hiiiur.lrilv
Regulating Services
Nutrient Cycling
Water Regulation
Pollination
I lie K
Cultural Services
Aesthetic Services
Non Use Values
Provisioning Services
[used Damage
•Non Timber Uses
Figure ES-4 Relationship between Ecological Effects
of O3 Exposure and Ecosystem Services
Ecosystem Services Affected by Biomass Loss
Ecosystem services most directly affected by
biomass loss include: (1) provision of food and
fiber (provisioning), (2) carbon storage
(regulating), (3) pollution removal (regulating), and (4)
habitat provision for wildlife, particularly habitat for
threatened or endangered wildlife (supporting). We
conduct national-scale and case-study scale analyses to
estimate the ecological effect of biomass loss on several
ecosystem services. Figure ES-5 provides a schematic of
the relationships between the ecological effect of biomass
loss and the analyses conducted to quantify the ecosystem
services affected.
ES-5
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Welfare Risk and Exposure Assessment
Ozone, Second External Review Draft
(January 2014)
Executive Summary
Ambient
I Ozone
i Exposure
\fttlptlf4]
Ecological Effect
BionuHLosi
^^
Provisioning Services
•Non-Timber Uses
* Commercial Non-Tim W
ForcslPr&ducte
• Informal Frftrwmy at" Nf>n-
Timbei Forest Products
V
Ecosystem Level Effects
•Weighted Biomass
Loss
• SpecicsDivc-rsity
• frimmimlP/Sliiirtiire
• E'.'.'iiil-m 'uiHtioimig
,
\
-^~
**r-
iTree
BtJKiiUtini', Service*
•Carbon Sequestration
•Pollution Removal
• Chartism Pollution Removal
^ L J ^'
FASOMGHG
I
Provisioning Services
•Timber Production
•Qianfesin NatoMl Vidd and Prices
• Impacts Mi Producers ard
Consumers
•Agricultural Harvest
i Criarjjssin NaGor.al Yield and Prices
•taipKRvi Pradunnaid
Consumers
Regulating Services
•Carbon Sequestration
•Ndliuiidl Ciidiige^iiiCdiboii
i 5eijueslrabon
Figure ES-5 Conceptual Diagram of Relationship of
Relative Biomass Loss to Ecosystem Services [The
dashed box indicates those services for which direct
quantification was not possible.]
Using the Forest and Agricultural Optimization
Model with Greenhouse Gases (FASOMGHG), we
quantify the effects of biomass loss on
timber production, agricultural
harvesting, and carbon sequestration in
a national-scale analysis.5 The analysis
provided results for nine U.S. climate
regions based on National Oceanic and
Atmospheric Administration (NOAA)
National Climate Data Center (NCDC)
regions (see Figure ES-6 below). We
consider these regions appropriate for our analyses
because geographic patterns of both O3 and plant species
are driven by climactic features such as temperature and
FASOMGHG is a national-scale model that provides a
complete representation of the U.S. forest and agricultural
sectors' impacts of meeting alternative standards.
FASOMGHG simulates the allocation of land over time
to competing activities in both the forest and agricultural
sectors.
precipitation patterns. We use the O3 C-R functions for
tree seedlings and crops to calculate relative yield loss,
which is equivalent to relative biomass loss. Because the
forestry and agriculture sectors are related, and trade-offs
occur between the sectors, we also calculate the resulting
market-based welfare effects of O3 exposure in the
forestry and agriculture sectors.
Because most areas have W126 index values
below 15 ppm-hrs after just meeting the existing O3
standard, yield losses for commercial timber production
are below one percent, with the exception of the
Southwest, Southeast, Central, and South regions. For
agricultural harvest, the largest yield changes occur
between recent ambient conditions and just meeting the
existing standard. Under recent ambient conditions, the
West, Southwest, and Northeast regions generally have
the highest yield losses at between 6.5 and 15 percent for
winter wheat. Relative yield losses for winter wheat are
less than one percent at potential alternative standard
levels of 15, 11, and 7 ppm-hrs. For soybeans, yield
losses above 1 percent remain after just meeting 15 ppm-
hrs in the Southwest and Central regions. Yield losses are
below one percent after just meeting 11 and 7 ppm-hrs.
Changes in yield are also associated with
changes in consumer and producer/farmer surplus. The
overall effect of changes in yield on forest ecosystem
productivity depends on the
composition of forest stands
and the relative sensitivity
of trees within those stands.
Overall effect on
agricultural yields and
producer and consumer
surplus depends on the (1)
ability of producers/farmers
to substitute other crops that are less O3 sensitive, and (2)
responsiveness of demand and supply. Economic impacts
from just meeting the existing and alternative standards
were similar between the forestry and agricultural sectors
~ consumer surplus generally increased in both sectors
because higher productivity under lower W126 index
values increased total yields and reduced market prices.
Because the quantity demanded for most forestry and
agricultural commodities is not highly responsive to
Welfare economics focuses on the optimal allocation of
resources and goods and how those allocations affect
total social welfare. Total welfare is also referred to as
economic surplus, which is the overall benefit a society,
composed of consumers and producers, receives when a
good or service is bought or sold, given a quantity
provided and a market price. Economic surplus is
divided into two parts: consumer and producer surplus.
ES-6
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Welfare Risk and Exposure Assessment
Ozone, Second External Review Draft
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Executive Summary
changes in price, producer surplus often declines. In
some cases, lower prices reduce producer profits more
than can be offset by higher yields. For example, in 2040
the year with maximum changes in consumer and
producer surplus, after just meeting the existing standard,
the total producer surplus in the forestry
sector is estimated to be $133 billion and
total consumer surplus is estimated to be
$935 billion. When adjusting to meeting
alternative standards of 15, 11, and 7
ppm-hrs, consumer surplus increases
$597 million, $712 million, and $779
million (i.e., 0.06, 0.08, and 0.08
percent), respectively, while producer
surplus decreases $839 million, $858
million, and $766 million, (i.e., about 0.6
percent), respectively. (All estimates are
in 2010$.)
Consumer surplus is the difference between what a
consumer would be willing to pay for a product and the price
they have to pay for the product. For example, assume a
consumer goes out to buy a CD player and he/she is willing to
spend $250. When the shopper finds that the CD player is on
sale for $150, economists would say that this shopper has a
consumer surplus of $100, e.g., the difference between the
$150 sale price and the $250 the consumer was willing to
spend.
Biomass loss due to O3 exposure
can reduce carbon sequestration, and
shifts between the forestry and
agricultural sector can also affect carbon
sequestration. Because most areas have
W126 index values below 15 ppm-hrs after just meeting
the existing O3 standard, a potential alternative standard
of 15 ppm-hrs does not appreciably increase carbon
sequestration. The majority of the enhanced carbon
sequestration potential is in the forest biomass increases
over time under potential alternative standards of 11 and 7
ppm-hrs. On an annual basis, carbon sequestration at 11
ppm-hrs is increased by about 20 million metric tons per
year relative to just meeting the existing O3 standard,
which is equivalent to taking about 4 million cars off the
road.6 Carbon sequestration at 7 ppm-hrs is increased by
about 53 million metric tons per year relative to just
meeting the existing standard, which is the equivalent of
taking approximately 11 million cars off the road.
In the case-study scale analyses, we use the iTree
model to estimate the impact of biomass loss on tree
growth and ecosystem services such as carbon
sequestration and pollution removal provided by urban
forests in five urban areas over a 25-year period.7
Relative to just meeting the existing standard, three of the
urban areas (Atlanta, Chicago, and the urban areas of
Tennessee) show gains in carbon sequestration at
potential
alternative
standard levels of
11 and 7 ppm-hrs.
For example,
relative to just
meeting the
existing standard,
Chicago gains
about 6,400 tons
of carbon
sequestration per
year at 7 ppm-hrs,
and the urban
areas of
Tennessee gain
about 8,800 tons
of carbon
sequestration per year at 11 ppm-hrs and 20,000 tons of
carbon sequestration per year at 7 ppm-hrs. These same
three areas show gains in pollution removal (i.e., O3,
carbon monoxide, nitrogen dioxide, and sulfur dioxide) at
potential alternative standard levels of 11 and 7 ppm-hrs
compared to meeting the existing standard. For example,
relative to just meeting the existing standard, Chicago
gains about 2,300 metric tons of pollution removal
annually at 11 ppm-hrs and 6,500 metric tons of pollution
removal annually at 7 ppm-hrs, and the urban areas of
Tennessee gain about 5,300 metric tons of pollution
removal annually at 11 ppm-hrs and 11,700 metric tons of
pollution removal annually at 7 ppm-hrs.
Producer surplus refers to the benefit, or profit, a producer
receives from providing a good or service at a market price
when they would have been willing to sell that good or service
at a lower price. For example, if the amount the producer is
willing to sell the CD player for is $75, and the producer sells
the CD player for $150, the producer surplus is $75, e.g., the
$150 sale price less the $75 price at which the producer was
willing to sell.
6 As calculated by the EPA Greenhouse Gas
Equivalencies Calculator, available at
http://www.epa.gov/cleanenergv/energv-
resources/calculator.html.
7 The iTree model is a peer-reviewed suite of software
tools provided by USFS.
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Figure ES-6 Map of the 9 NOAA Climate Regions used in the National-Scale Air Quality Adjustments
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Executive Summary
Syracuse and Baltimore do not realize gains in carbon
sequestration or pollution removal, because W126 index
values almost meet the alternative standards of 15, 11,
and 7 ppm-hrs in those areas.
We qualitatively describe the potential effects of
O3 on other (non-timber) forest products that are
harvested for commercial or subsistence activities,
including edible fruits, nuts, berries, and sap; foliage,
needles, boughs, and bark; grass, hay, alfalfa, and forage;
herbs and medicinals; fuelwood, posts and poles; and
Christmas trees. According to the ISA, O3 exposure
causes biomass loss in sensitive woody and herbaceous
species, which in turn could affect forest products used
for arts, crafts, and florals. For example, Douglas Fir and
Red Alder, among others, are used on the Pacific Coast
for arts and crafts, particularly holiday crafts and
decorations. Foliar injury impacts on O3-sensitive plants
would potentially affect the harvest of leaves, needles,
and flowers from these plants for decorative uses. The
visible injury and early senescence caused by O3 in some
evergreens may also reduce the value of a whole tree such
as Christmas trees. Likewise, O3 can reduce the harvest of
edible fruits, nuts, berries, and sap in O3-sensitive plants.
According to the U.S. Census Bureau, the industry sector
for forest nurseries and gathering of forest products
employed 2,098 people, accounting for an annual payroll
of $71 million (2006$) with an average annual income of
$34,155).
Ecosystem Services Affected by Visible Foliar
Injury
The ecosystem services most likely to be affected
by O3-induced visible foliar injury are aesthetic
value and outdoor recreation (cultural services),
which depend on the perceived scenic beauty of the
environment. Studies of Americans' perception of scenic
beauty show that people tend to have reliable preferences
for forests and vegetation with fewer damaged or dead
trees and plants. Many outdoor recreation activities
directly depend on the scenic value of the area, in
particular scenic viewing, wildlife watching, hiking, and
camping. These activities are enjoyed by millions of
Americans every year and generate millions of dollars in
economic value. According to the National Survey on
Recreation and the
Environment, some
of the most popular
outdoor activities
are walking,
including day
hiking and
backpacking;
camping; bird
watching; wildlife
watching; and nature
viewing. Total
expenditures across
wildlife watching
activities, trail-based activities, and camp-based activities
are approximately $200 billion dollars annually. Figure
ES-7 shows the relationship between foliar injury and the
analyses to assess affected ecosystem services.
Bags of ponderosa pine (Pinus ponderosa C.
Lawson var. ponderosa) cones gathered in central
Oregon for arts, crafts, and floral markets.
Courtesy: U.S. Department of Agriculture
Ecological Effect
Visible Foliar Injury
Ecosystem level Effects
• National-kale Analysis of Foliar Injury
Cultural Services
•Recreational Use
•National Values of Trip and
Equipment-Related Expenditures
forWildlife-WatchingJraiUnd
Camping Activities
' Screening-level Assessment
of Foliar Injury in National
Parks
Cultural Services
•Recreational Use
• For 3 National Parks Case Studies,
Data on Activities, Travel and Local
Expenditures, and Local Economic
Impact
V ;
Figure ES-7 Relationship between Visible Foliar
Injury and Ecosystem Services
Enjoyment of recreation in national parks can be
adversely affected by visible foliar injury, and national
parks are designated as special areas in need of protection.
In a screening-level assessment at 214 national parks, we
apply the benchmarks from the national analysis of foliar
ES-9
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Welfare Risk and Exposure Assessment
Ozone, Second External Review Draft
(January 2014)
Executive Summary
injury to six scenarios representing a range of percentages
of biosites showing visible foliar injury. Based on lists
from the National Park Service, 95 percent of the parks in
this assessment contain at least one O3-sensitive species.
Generally, benchmark scenarios corresponding to higher
percentages of biosites showing foliar injury show fewer
parks that exceed the benchmark criteria for those
scenarios. During 2006 to 2010, 58 percent of parks
exceeded the benchmark W126 corresponding to the base
scenario (W126>10.46 ppm-hrs, 17.7 percent of biosites,
without consideration of soil moisture, any injury) for at
least three years. The analyses suggest that in order to
substantially reduce the risk of foliar injury in these parks,
the W126 index values would need to be reduced to be
below 10.46 ppm-hrs. In addition, 98 percent, 80 percent,
68 percent and 2 percent of parks would exceed the
benchmark criteria corresponding to the 5 percent, 10
percent, 15 percent, and 20 percent prevalence scenarios
for at least 3 years within the 2006-2010 period. For the
elevated injury scenario, 34 percent of parks would
exceed the benchmark criteria (five percent of biosites,
multiple moisture categories, elevated foliar injury) for at
least three years. Because the screening-level assessment
relies on annual estimates of W126 index values and soil
moisture, we cannot fully evaluate just meeting the
existing and alternative standards because they are based
on the 3-year average air quality surfaces. However, we
can observe that after adjusting the W126 surfaces to just
meet the existing standard (3-year average), all of the 214
parks are below 10.46 ppm-hrs, which corresponds to the
annual W126 benchmark criteria for the base scenario.
We also assess foliar injury at a case-study scale.
Specifically, we assess O3-exposure risk at three national
parks - Great Smoky Mountains National Park, Rocky
Mountain National Park, and Sequoia/Kings National
Parks. For each park, we assess the potential impact of
Os-related foliar injury on recreation (cultural services) by
considering information on visitation patterns,
recreational activities and visitor expenditures. We
include percent cover of species sensitive to foliar injury
and focus on the overlap between recreation areas within
the park and alternative W126 standard levels.
Mount Le Conte, Summer
Great Smoky Mountains National Park
Courtesy: NPS
http://www.nps.gov/grsm/photosmultimedia/index.
htm
In the Great Smoky Mountains National Park,
there are 37 sensitive species across vegetative strata, and
2011 visitor spending exceeded $800 million. Seasonal
O3 concentrations in the park have been among the
highest in eastern U.S. - under recent ambient conditions,
44 percent of the park has W126 index values above 15
ppm-hrs. After adjustments to just meeting the existing
standard of 75 ppb, no area in the park exceeds an
alternative W126 standard level of 7 ppm-hrs. Rocky
Mountain National Park has seven sensitive species,
including Quaking Aspen. In 2011, visitor spending at
the park was over $170 million. Under recent ambient
conditions, all of the park has W126 index values above
15 ppm-hrs. When adjusted to just meeting the existing
standard, 59 percent of the park would have W126 index
values between 7 and 11 ppm-hrs. When adjusted to just
meeting an alternative W126 standard level of 15 ppm-
hrs, no area in the park exceeds an alternative W126
standard level of 7 ppm-hrs. In Sequoia/Kings National
Parks, there are 12 sensitive species across vegetative
strata, and 2011 visitor spending was over $97 million.
When adjusted to just meet the existing standard, no area
in the park exceeds an alternative W126 standard level of
7 ppm-hrs.
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Welfare Risk and Exposure Assessment
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Executive Summary
Additional Ecosystem Services Affected
Because of a lack of data, methods, or resources
we qualitatively or semi-quantitatively assess
additional ecosystem services potentially
affected, including cultural, supporting,
regulating, and provisioning services. Cultural services
include non-use values that can be directly or indirectly
impacted by O3 exposure. When people value a resource
even though they may never visit the resource or derive
any tangible benefit from it, they perceive an existence
value. When the resource is valued as a legacy to future
generations, bequest value exists. Additionally, there
exists an option value to knowing that you may visit a
resource at some point in the future. The National Survey
on Recreation and the Environment (NSRE) is an ongoing
survey of a random sample of adults over the age of 16 on
their interactions with the environment.8 NSRE data
indicate that Americans have very strong preferences for
existence, option, and bequest values related to forests -
90 to 97 percent of survey respondents indicated it is
moderately,
very, or
extremely
important to
them to
maintain existence values, to maintain option values, and
to maintain bequest values.
The supporting service of community
composition, or structure, is affected by O3 exposure
because some species are more resistant to the negative
effects of O3 and are able to out-compete more susceptible
species. Changes in community composition underlie
possible changes in associated services such as herbivore
grazing, production of preferred species of timber, and
preservation of
habitat for
unique or
endangered
communities
Between 90 and 97 percent of NSRE survey
respondents stated that maintaining existence,
option, or bequest values is moderately, very, or
extremely important to them.
Between 93 and 96 percent of NSRE survey
respondents stated that provision of habitat
for wild plants and animals is moderately,
very, or extremely important to them.
or species.
8 The NSRE is conducted by the U.S. Forest Service.
Additional information can be located at
http://www.srs.fs.usda.gov/trends/nsre-directory/.
The NSRE provides data on the values that survey
respondents place on the provision of habitat for wild
plants and animals - between 93 and 96 percent of survey
respondents indicated it is important to them to preserve
wildlife habitat, to preserve unique wild plants and
animals, and to protect rare or endangered species.
Regulating services include air quality, water
quantity and quality, climate, erosion, fire regulation, and
pollination regulation. Regulation of the water cycle can
be adversely affected by the effects of O3 on plants.
Studies of O3-impacted forests in eastern Tennessee in or
near the Great Smoky Mountains has shown that ambient
O3 exposures resulted in increased water use in O3-
sensitive species, which led to decreased modeled late-
season stream flow in those watersheds. Ecosystem
services potentially affected by such a loss in stream flow
could include habitat for species (e.g., trout) that depend
on an optimum stream flow or temperature. Additional
downstream effects could potentially include a reduction
in the quantity and/or quality of water available for
irrigation or drinking and for recreational use. Ninety-one
percent of NSRE respondents ranked water quality
protection as either an extremely or very important benefit
of wilderness.
Fire regime regulation is also negatively affected
by O3 exposure. For example, O3 exposure may
contribute to forest susceptibility to wildfires in southern
California by increasing leaf turnover rates and litter,
increasing fuel loads on the forest floor. In a case-study
scale analysis, we develop maps that overlay the mixed
conifer forest area of California with (i) areas of moderate
or high fire risk and recent W126 index values and (ii) air
quality adjusted to just meet existing and alternative
standard levels. The highest fire risk and highest W126
levels overlap with each other, as well as with significant
portions of mixed conifer forest. Under recent conditions,
over 97 percent of mixed conifer forest area has W126
index values over 7 ppm-hrs and fire risk, and 74 percent
has W126 index values over 15 ppm-hrs and fire risk.
After just meeting the existing standard, almost all of the
mixed conifer forest area with fire risk is below 7 ppm-
hrs. At the alternative standard level of 15 ppm-hrs, less
than one percent of the fire risk area is above 7 ppm-hrs.
At alternative standard levels of 11 and 7 ppm-hrs, all of
the fire risk area is below 7 ppm-hrs.
ES-11
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Welfare Risk and Exposure Assessment
Ozone, Second External Review Draft
(January 2014)
Executive Summary
O3 exposure results in increased susceptibility to
infestation by some chewing insects, including the
southern pine beetle and western bark beetle. These
infestations can cause economically significant damage to
tree stands and the
associated timber
production
(provisioning
service). In the
short-term, the
immediate
increase in timber
supply that results
from the
additional
harvesting of
Southern Pine Beetle Damage
Courtesy: Ronald F. Billings, Texas Forest
Service. Bugwood.org
damaged timber depresses prices for timber and benefits
consumers. In the longer-term, the decrease in timber
available for harvest raises timber prices, potentially
benefitting producers. The USFS reports timber
producers have incurred losses of about $1.4 billion
(2010$), and wood-using firms have gained about $966
million, due to beetle outbreaks between 1977 and 2004.
We develop maps that overlay the forest areas at risk of
basal area loss from pine beetle infestation with W126
index values. After just meeting the existing standard,
most of the pine beetle risk area is below 7 ppm-hrs. At
the alternative standard level of 15 ppm-hrs, all of the
pine beetle risk area is less than 7 ppm-hrs.
CONCLUSIONS
his welfare REA provides analyses that further inform
the following policy-relevant questions9: (1) in
Tconsidering alternative standards, to what extent do
alternative levels reduce estimated exposures and welfare
risks attributable to O3; (2) what range of alternative
standard levels should be considered based on the
scientific information evaluated in the ISA, air quality
analyses, and the welfare REA; and (3) what are the
important uncertainties and limitations in the evidence
and assessments and how might those uncertainties and
limitations be taken into consideration in identifying
alternative secondary standards for consideration. To
develop information to help inform these questions, we
quantify ecological effects based on the relationship with
the W126 metric and assess the associated impacts on
ecosystem services. For some ecosystem services, such
as commercial non-timber forest products, recreation, and
aesthetic and non-use values, we qualitatively assess
potential impacts to services.
For biomass loss, a one to two percent loss for
trees corresponds to an annual W126 index value of 4 to
14 ppm-hrs, and a five percent loss for crops corresponds
to an annual W126 index value of 12 to 17 ppm-hrs. For
visible foliar injury, across all biosites, the proportion of
biosites showing injury generally levels off around a
W126 index value of 10 ppm-hrs; however, for biosites
with greater than normal soil moisture, the proportion of
sites with damage can be greater.
We estimate that some exposures and risks
remain after just meeting the existing standard and that in
many cases, just meeting potential alternative standard
levels results in reductions in those exposures and risks.
Overall, the largest reduction in O3 exposure-related
welfare risk occurs when moving from recent ambient
conditions to just meet the existing secondary standard of
75 ppb. When adjusting for meeting the existing
standard, only two of the nine U.S. regions have W126
index values remaining above 15 ppm-hrs (West ~ 18.9
ppm-hrs and Southwest - 17.7 ppm-hrs). Four regions
(East North Central, Northeast, Northwest, and South)
would meet 7 ppm-hrs, and two regions (Southeast and
West North Central) have index values between 9 and 12
ppm-hrs (Southeast - 11.9 ppm-hrs and West North
Central - 9.3 ppm-hrs). At an alternative standard of 15
ppm-hrs, ambient O3 exposure and related risk are not
appreciably different than they are after just meeting the
existing standard. Meeting alternative standard levels of
11 ppm-hrs and 7 ppm-hrs results in smaller risk
reductions compared to the decreases in risk from meeting
the existing standard relative to recent conditions.
9 The policy-relevant questions were identified in the
Integrated Review Plan for the Ozone National Ambient
Air Quality Standards.
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United States Office of Air Quality Planning and Standards Publication No. EPA-452/P-14-003 c
Environmental Protection Health and Environmental Impacts Division February 2014
Agency Research Triangle Park, NC
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