&EPA
United a*K
Envirainwnlal Protection
Agency
Welfare Risk and Exposure Assessment for
Ozone
Final
Executive Summary
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EPA-452/P-14-005c
August 2014
Welfare Risk and Exposure Assessment for Ozone
Final
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 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.
Questions on this document should be addressed to Dr. Bryan Hubbell at the U.S.
Environmental Protection Agency, Office of Air Quality Planning and Standards, 109 TW Alexander
Drive, C504-02, Research Triangle Park, North Carolina 27711 or email — hubbell.bryan@epa.gov.
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Welfare Risk and Exposure Assessment
for Ozone, Final
(August 2014)
Executive
Summary
SUMMARY CONCLUSIONS
The goals for this welfare1 risk and exposure
assessment (REA) include (i) characterizing
ambient ozone (Os) 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 Os
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 protect trees will also
protect 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 biosites2 showing foliar
injury increases steeply with W126 index values up to
approximately 10 ppm-hrs and is relatively constant
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 and by year.
In this REA, we analyzed the changes in Os
exposure and risk after adjusting air quality to just meet
the existing standard3 and to just meet potential
alternative secondary standard levels. Overall, the largest
reduction in Os-related ecological effects and associated
ecosystem services occurs when moving from recent
ambient conditions to just meeting the existing standard.
Exposures and risks remaining after just meeting the
existing standard, in many cases, can be reduced when
just meeting potential alternative standard levels.
INTRODUCTION
The U.S. Environmental Protection Agency (EPA)
is conducting a review of the national ambient air
quality standards (NAAQS) for Os and related
photochemical oxidants. This welfare REA presents
assessments to inform consideration of the review of the
secondary (welfare-based) NAAQS for Os. This REA
provides an assessment of exposure and risk associated
with recent ambient concentrations of Os and potential
alternative secondary standards. The REA builds on
1 A secondary, or welfare-based, standard provides public welfare
protection, including protection against decreased visibility and against
damage to animals, crops, vegetation, and buildings.
2 A biosite is a plot of land on which data was collected regarding the
incidence and severity of visible foliar injury on a variety of O3-sensitive
plant species.
3 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 fourth-highest
daily maximum 8-hour average concentration, averaged over three
years.
ES-1
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Welfare Risk and Exposure Assessment
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(August 2014)
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. 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 Os, 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 Os
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 public welfare.
Executive
Summary
ECOSYSTEM SERVICES
Provisioning
FOOD
FRESHWATER
WOOD AND RBER
FUEL
CONSTITUENTS OFWELL-BEING
Supporting
- NUTRIENT CYCLING
SOIL FORMATION
i PRIMARY PRODUCTION
Regulating
CLIMATE REGULATION
FLOOD REGULATION
DISEASE REGULAT10M
WATER PURIFICATION
Cultural
AESTHETIC
SPIRITUAL
EDUCATIONAL
Security
PERSONAL SAFETY
SECURE RESOURCE ACCESS
SECURITY FROM DISASTERS
Basic material
for good life
ADEQUATE LIVELIHOODS
SUFFICIENT NUTRITIOUS FOOD
Freedom
of choice
and action
LIFE ON EARTH - BIODIVERSITY
SHELTER
ACCESS TO GOODS
Health
STRENGTH
FEELING WELL
ACCESS TO CLEAN AIR
AND WATER
OPPOBTUNITY TO BE
ABLE TO ACHIEVE
WHAT AN INDIVIDUAL
VALUES DOING
AND BEING
Good social relations
SOCIAL COHESION
MUTUAL RESPECT
'ABIUTYTOHELPOTHEflS
Source: Millennium Ecosystem Assessment
Figure ES-1 Linkages Between Ecosystem Services
Categories and Components of Human Well-Being (MEA,
2005)
AIR QUALITY CONSIDERATIONS
The air quality information and analyses in this
REA build upon those in prior reviews and
include: (1) summaries of recent ambient Os
monitoring data; (2) an extrapolation of measured Os
concentrations to areas without monitors, including
natural areas that are important to public welfare, such as
national parks; and (3) adjustment of air quality to just
meet the existing standard and potential alternative
secondary
standards.
We use
estimates of
Os exposure
(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 Os monitoring network has a largely urban focus,
to address ecosystem impacts of Os, it is equally
important to focus on monitoring in rural areas. The
extent of monitoring coverage in non-urban areas has not
significantly changed since the previous review. Figure
The W126 metric is a seasonal sum of
hourly Os concentrations, designed to
measure the cumulative effects of Os
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
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Executive
Summary
ES-2 shows the current Os monitoring coverage in the
U.S. - both urban and non-urban sites. To estimate Os
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 Os 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. When adjusting air quality to just meet the
existing standard, only two of the nine U.S. regions
remain 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) are between 9 and 12 ppm-hrs (Southeast - 11.9
ppm-hrs and West North Central - 9.3 ppm-hrs).
The adjusted surfaces are used as inputs to
several assessments, including the geographic analysis to
assess the potential overlap between areas with elevated
Os and areas with elevated risks of fire and insect damage,
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. We do not quantify fire or insect damage
resulting from Os exposure. In the Risk to Ecosystem
Services section, we briefly discuss the ecosystem
services associated with fire and insect damage on tree
stands and timber production, and show the overlap of
areas with higher W126 concentrations and higher risk of
bark beetle infestation and fire risk.
The first step in assessing biomass loss for tree
seedlings and crops is to identify the range of W126 index
values corresponding to annual percent biomass loss
benchmarks recommended by CASAC using exposure-
response (E-R) functions for 12 tree species and 10 crops,
for which sufficient information is available. The
estimated annual W126 index values are between 4 and
10 ppm-hrs for a one percent biomass loss in tree
seedlings, between 7 and 14 ppm-hrs for a two percent
biomass loss in tree seedlings, and between 12 and 17
ppm-hrs for a five percent biomass loss for crops. In
general, estimates of annual percent biomass loss in tree
seedlings are comparable to mature trees with a few
exceptions. Next, we use these E-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 Forest
Health Monitoring Network (FHM), which monitors the
potential impacts of Os on our nation's forests. Our
analyses identify the presence/absence of foliar injury.
We also conduct analyses across years and different soil
moisture categories. Over 81 percent of FHM biosites
showed no visible foliar injury. Generally, the results 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 above 10 ppm-hrs.
For biosites with greater than normal soil moisture, more
biosites showed injury. Figure ES-3 shows the pattern
seen in the foliar injury analyses stratified by soil
moisture category. In addition, we see similar patterns
when the foliar injury analysis is stratified by year.
ES-3
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Welfare Risk and Exposure Assessment
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Executive
Summary
SLAMS
CASTNET
NCORE/PAMS
SPMS/OTHER
Figure ES-2 U.S. Ambient O3 Monitoring Sites in Operation During 2006-20104
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
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Executive
Summary
Biosites with Foliar Injury
20
W126 (ppm-hrs)
Figure ES-3 Cumulative Proportion of Sites with Any
Visible Foliar Injury Present, by Soil Moisture
Category
Using the foliar injury benchmarks derived from
the national scale analysis, we applied a screening-level
approach using Os exposure and soil moisture data for 214
parks in the contiguous U.S. All scenarios assessed in the
screening-level assessment reflect the special status of
parks as areas designated for protection, and thus apply
benchmarks corresponding to the presence of any visible
foliar injury. We use these results to derive W126
benchmarks for visible foliar injury for five scenarios
representing the full range of percentages of biosites
showing visible foliar injury, including four scenarios
considering soil moisture. For the fifth scenario, or "base
scenario", the benchmark is the W126 index value where
the slope of exposure-response relationship changes for
all FHM biosites in all soil moisture categories. We
looked at scenarios based on three different categories of
soil moisture (i.e., wet, normal, dry) and the W126 index
values associated with four different prevalences of any
foliar injury (e.g., 5 percent, 10 percent, 15 percent and 20
percent of biosites). In total, we evaluated ten different
W126 benchmarks associated with the five foliar injury
risk scenarios. The W126 benchmarks across the
scenarios range from 3.05 ppm-hrs (five percent of
biosites, normal moisture, any injury) up to 24.61 ppm-
hrs (15 percent of biosites, dry, any injury). These results
suggest that soil moisture plays a role in foliar injury,
potentially indicating that drought may provide some
protection from foliar injury.
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 Os
exposures on biomass loss and foliar injury and the
Ecological Effects
• E'.i' im.^ Ui'.-. [Chapter 6)
* I "!MI Injury [Chapter 7)
Supporting Sgrvkes
' Primary Productivity
f
Regulating Services
j * Carbon Sequestration
/[ * Pollution Removal
'j\^ J
c ~\
^""^^ Cultural Services
T • Recreational Use
/ V
/
( ^
Provisioning Services
• Agi itu Elu ral Harve-sl
"•Timber Production
V J
Additional Assessments
Supporting Services
• Soil formation
• Community Structure
- Primary Productivity
Regulating Services
• Nulrient Cycling
• Water Regulation
• Pollination
• fire Regulation
* Aesthetic Services
• Non-Use Values
Provisioning Services
* tiiwc! Daiiugp
* Non-Umber Uses
Figure ES-4 Relationship between Ecological Effects
of Os Exposure and Ecosystem Services
associated ecosystem services, because of a lack of
sufficient data, methods, or resources we qualitatively or
semi-quantitatively assess additional ecosystem services
potentially affected.
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
ES-5
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Welfare Risk and Exposure Assessment
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(August 2014)
Executive
Summary
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.
Provisioning Services
• Non-Timber Uses
• Commercial Non-Timber
Forert Products
• Informal Economy ol Non-
Timber Forest Products
Ecosystem-level Effects
• Weighted Biomass
Loss
•Species Diversity
•Com m unity Structure
•Ecosystem functioning
Regulating Services
•Carbon Sequestration
Sequestration in 5 Urban Areas
•Pollution Removal
• Changes In Pollutio
\jn 5 Urban Areas
Provisioning Services
• Timber Production
• Impacts on Producers and
Consumers
•Agricultural Harvest
• Changes In National Yield a
• Impact* on Producers and
Regulating Services
• Carbon Sequestration
• National Charges In Carbon
Sequestration
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 Os and plant species
are driven by climatic features such as temperature and
precipitation patterns. We use the Os E-R functions for
tree seedlings and crops to calculate relative yield loss,
which equates to relative biomass loss. Because the
forestry and agriculture sectors are linked, and trade-offs
occur between the sectors, we also calculate the resulting
market-based welfare effects of Os exposure in the
forestry and agriculture sectors.
Because most areas are below 15 ppm-hrs after
adjusting Os distributions to just meet the existing
standard (based on reducing nationwide emissions of
NOx), 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 effects on
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.
5 FASOMGHG is a national-scale model that provides a complete
representation of the U.S. forest and agricultural sectors' impacts of just
meeting alternative standards. FASOMGHG simulates the allocation of
land over time to competing activities in both the forest and agricultural
sectors.
ES-6
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Welfare Risk and Exposure Assessment
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Executive
Summary
Figure ES-6 Map of the 9 NOAA Climate Regions used in the Welfare Risk and Exposure Assessment
ES-7
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Welfare Risk and Exposure Assessment
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Summary
agricultural yields and producer and consumer surplus
depends on the (1) ability of producers/farmers to
substitute other crops that are less Os sensitive, and (2)
responsiveness of demand and supply. The overall
economic effect of reduced Os exposure on the forestry
and agricultural sectors from just meeting the existing and
alternative standards were
similar between the 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 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 adjusting air quality to 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 air quality to just meet alternative W126
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 $766 million, (i.e., about 0.6 percent), respectively.
(All estimates are in 2010$ for the U.S. only.)
Biomass loss due to Os exposure can reduce
carbon sequestration, and shifts between the forestry and
agricultural sector can also affect carbon sequestration.
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.
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 $70, and the
producer sells the CD player for $150, the producer surplus is
$80, e.g., the $150 sale price less the $70 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/energy-
resources/calculator.html.
Because most areas have W126 index values below 15
ppm-hrs after just meeting the existing Os standard, a
potential alternative standard of 15 ppm-hrs does not
appreciably increase carbon sequestration (meeting the
existing 8-hour standard of 75 ppb increases carbon
sequestration by 2,972 million metric tons per year). 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
Os 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 i-
Tree 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 study 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
7 The i-Tree model is a peer-reviewed suite of software tools provided
by the U.S. Forest Service that provides urban forestry analysis.
ES-8
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Executive
Summary
carbon sequestration per year at 7 ppm-hrs. These same
three areas show gains in pollution removal (i.e., Os,
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. Syracuse and
Baltimore do not realize gains in carbon sequestration or
pollution removal because the 2006-2008 W126 index
values almost meet the alternative standard levels in those
areas.
We qualitatively describe the potential effects of
Os 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. Ozone 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
Bags of ponderosa pine cones (Pinus ponderosa C.
Lawson var. ponderosa) gathered in central Oregon for
arts, crafts, and floral markets.
Courtesy: U.S. Department of Agriculture
others, are used on the Pacific Coast for arts and crafts,
particularly holiday crafts and decorations. Foliar injury
impacts on Os-sensitive plants would potentially affect
the harvest of leaves, needles, and flowers from these
plants for decorative uses. Visible foliar injury and early
senescence caused by Os in some evergreens may also
reduce the value of a whole tree such as Christmas trees.
Likewise, Os can reduce the harvest of edible fruits, nuts,
berries, and sap in Os-sensitive plants. According to the
U.S. Census Bureau, the industry sector for forest
nurseries and gathering of forest products employed 2,098
people with an annual payroll of $71 million (2006$).
Ecosystem Services Affected by Visible Foliar
Injury
The ecosystem services most likely to be affected
by Os-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,8 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.
8 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. The NSRE is conducted by the U.S.
Forest Service. Additional information can be located at
http://www.srs.fs.usda.gov/trends/nsre-directorv/.
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Welfare Risk and Exposure Assessment
for Ozone, Final
(August 2014)
Ecological Effect
Visible Foliar Injun,
Ecosystem Level Effects
frfldlife-Walchi»g.TrjiUd
Camping AttviGes
•Recreational Use
'FwSHafwalMsCaseStute,
Dili wActtvi to, Travel and Loul
Impact
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 areas designated for protection. In a screening-
level assessment at 214 national parks, we apply the
W126 benchmarks from the national analysis of foliar
injury using FHM biosite data to five scenarios
(representing the full range of percentages
of biosites showing visible foliar injury)
in order to provide an indication of the
risk of visible foliar injury in each park.
Based on lists from the National Park
Service, 95 percent of the parks in this
assessment contain at least one Os-
sensitive species. Generally, scenarios for
higher percentages of FHM biosites
showing foliar injury have fewer parks
that exceed the benchmarks for those
scenarios across multiple years. During
2006 to 2010, 58 percent of parks
exceeded the W126 benchmark
corresponding to the base scenario
Executive
Summary
(W126>10.46 ppm-hrs, all biosites in all soil moisture
categories) for at least three years. In addition, 98
percent, 80 percent, 68 percent and 2 percent of parks
would exceed the benchmark criteria corresponding to the
prevalence scenarios (i.e., 5 percent, 10 percent, 15
percent, and 20 percent) for at least 3 years within the
2006-2010 period.9 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
air quality 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
for the base scenario.
We also assess foliar injury at three national
parks - Great Smoky Mountains National Park, Rocky
Mountain National Park, and Sequoia/Kings Canyon
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.
In the Great Smoky Mountains National Park,
there are 37 sensitive
species across
vegetative strata, and
2011 visitor spending
exceeded $800 million.
Seasonal Os
concentrations in the
park have been among
the highest in eastern
U.S. -underrecent
ambient conditions, 44
percent of the park was
above 15 ppm-hrs.
After adjustments to
Mount Le Conte, Summer
Great Smoky Mountains National Park
Courtesy: NPS
http://www.nps.gov/grsm/photosmultimedia/index.htm
just meet the existing
3 The prevalence scenarios are also discussion on page ES-5.
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Welfare Risk and Exposure Assessment
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Executive
Summary
standard of 75 ppb, no area in the park exceeds 7 ppm-
hrs. Rocky Mountain National Park has seven sensitive
species, including Quaking Aspen. In 2011, visitor
spending was over $170 million. Under recent ambient
conditions, all of the park is above 15 ppm-hrs. When
adjusted to just meet the existing standard, 59 percent of
the park would be between 7 and 11 ppm-hrs. When
adjusted to just meet an alternative standard level of 15
ppm-hrs, no area in the park exceeds 7 ppm-hrs. In
Sequoia/Kings Canyon 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 7
ppm-hrs.
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 Os 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. Surveys indicate that
Americans have very strong preferences for existence,
bequest, and option 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 Os exposure
because some species are more resistant to the negative
effects of Os 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 or species. 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 Os on plants.
Studies of Os-impacted forests in eastern Tennessee in or
near the Great Smoky Mountains has shown that ambient
Os exposures resulted in increased water use in O3-
sensitive species, which decreased late-season stream
flow modeled 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 potentially
negatively affected by Os exposure. For example, Os
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 areas of moderate or high fire risk and (i) recent
W126 index values and (ii) air quality adjusted to just
meet existing and alternative standard levels. The areas
with 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 with high fire risk
had W126 values over 7 ppm-hrs, and 74 percent had
W126 values over 15 ppm-hrs. After just meeting the
existing standard, almost all of the mixed conifer forest
area with high fire risk is below 7 ppm-hrs. At the
alternative standard level of 15 ppm-hrs, less than one
percent of the high fire risk area is above 7 ppm-hrs. At
ES-11
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Welfare Risk and Exposure Assessment
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(August 2014)
Executive
Summary
; } '•. -1 \ ' ' \
Southern Pine Beetle Damage
Courtesy: Ronald F. Billings, Texas
Bugwood.org
j •* 1
Forest Service.
alternative standard levels of 11 and 7 ppm-hrs, all of the
high fire risk area is below 7 ppm-hrs.
Os exposure may increase 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
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 U.S. Forest Service 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 high pine beetle risk area is below 7
ppm-hrs. At the alternative standard level of 15 ppm-hrs,
all of the high pine beetle risk area is less than 7 ppm-hrs.
CONCLUSIONS
This welfare REA provides analyses that further
inform the following policy-relevant questions10:
(1) in considering alternative standards, to what
extent do alternative levels reduce estimated exposures
and welfare risks attributable to Os; (2) what range of
alternative standard levels should be considered based on
the scientific information evaluated in the Integrated
Science Assessment, 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.
The analyses in this REA found 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 Os exposure-related welfare risk
occurs when moving from recent ambient conditions to
just meet the existing standard. This finding should be
considered in the context of potential uncertainties in the
actual responsiveness of W126 values in all areas to the
emissions reductions used in the adjustments to just meet
the existing standard. Keeping these potential
uncertainties in mind, at an alternative standard level of
15 ppm-hrs, ambient Os 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.
Despite uncertainties inherent in any complex,
quantitative analysis, the overall body of scientific
evidence underlying the ecological effects and associated
ecosystem services evaluated in this welfare REA is
strong, and the methods used to quantify associated risks
are scientifically sound.
10 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-14-005c
Environmental Protection Health and Environmental Impacts Division August 2014
Agency Research Triangle Park, NC
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