National Park Service

U.S. Department of the Interior

Natural Resource Program Center

Air Quality in National Parks

2008 Annual Performance & Progress Report

Natural Resource Report NPS/NRPC/ARD/NRR—2009/151
ON THE COVER

Dream Lake, Rocky Mountain National Park, Colorado.

Photo by Debbie Miller.
Air Quality in National Parks

2008 Annual Performance & Progress Report

Natural Resource Report NPS/NRPC/ARD/NRR—2009/151

Natural Resource Program Center

Air Resources Division

PO BOX 25287

Denver, Colorado 80225

September 2009

U.S. Department of the Interior

National Park Service

Natural Resource Program Center

Denver, Colorado
ii Air Quality in National Parks–2008

The National Park Service, Natural Resource Program Center publishes a range of reports that address 

natural resource topics of interest and applicability to a broad audience in the National Park Service and 

others in natural resource management, including scientists, conservation and environmental constituencies, 

and the public. 

The Natural Resource Report Series is used to disseminate high-priority, current natural resource 

management information with managerial application. The series targets a general, diverse audience, and may 

contain NPS policy considerations or address sensitive issues of management applicability.

All manuscripts in the series receive the appropriate level of peer review to ensure that the information is 

scientifically credible, technically accurate, appropriately written for the intended audience, and designed 

and published in a professional manner. This report received informal peer review by subject-matter experts 

who were not directly involved in the collection, analysis, or reporting of the data. Data presented in this 

report were collected and analyzed using methods based on established, peer-reviewed protocols, and were 

analyzed and interpreted within the guidelines of the protocols.

Views, statements, findings, conclusions, recommendations, and data in this report are those of the author(s) 

and do not necessarily reflect views and policies of the National Park Service, U.S. Department of the Interior. 

Mention of trade names or commercial products does not constitute endorsement or recommendation for 

use by the National Park Service.

This report is available from the Air Resources Division of the NPS (www.nature.nps.gov/air) and the Natural 

Resource Publications Management Web site (http://www.nature.nps.gov/publications/NRPM) on the 

Internet. 

Please cite this publication as:

National Park Service, Air Resources Division. 2009. Air quality in national parks: 2008 annual performance 

and progress report. Natural Resource Report NPS/NRPC/ARD/NRR—2009/151. National Park Service, 

Denver, Colorado.

NPS 999/100367, September 2009
 National Park Service iii

Contents

Executive Summary ...............................................................1

Measuring Progress–

Air Quality Goals and Trends ................................................3

Visibility Measures..................................................................................................3

Atmospheric Deposition Measures..........................................................................4

Ozone Measures ....................................................................................................6

Measuring Success–

Assessment of Air Quality Conditions and Trends..............9

Air Quality Condition Results..................................................................................9

Longer Term Trends................................................................................................10

Ozone Exposure .....................................................................................................25

Producing Results–

Information and Collaboration.............................................27

Visibility and Regional Haze:...................................................................................27

Ecosystem Protection Initiatives: .............................................................................27

Assessing Air Pollution Risk to NPS Resources:........................................................27

Natural Resource Condition Assessments................................................................28

Four Corners Air Quality Task Force ........................................................................28

Climate Change......................................................................................................28

Conclusion ..............................................................................30

Appendix A: GPRA Goal Assessment Methodology..........31

Appendix B: Table of Trend Results, 1998–2007.................33

Appendix C: Determination of Air Quality Condition.......41

Appendix D: Ozone W126....................................................50
iv Air Quality in National Parks–2008
 National Park Service 1

The NPS measures progress toward improving park air quality by examining trends for 

key air quality indicators, including:

•	 visibility – which affects how well and 

how far visitors can see; 

•	 atmospheric deposition – which affects 

ecological health through acidification 

and fertilization of soil and surface waters; and

•	 ozone – which affects human health and 

native vegetation.

The NPS monitors one or more of these 

indicators in 57 park units, and there are sufficient data to assess conditions and trends 

in 55 of these parks. In addition, many state 

and local air quality monitoring stations 

are located near enough to parks that the 

data they collect are considered reasonably 

representative of park air quality. As a result, 

air quality conditions and trends have been 

calculated for 181 monitoring locations representing 228 park units.

Air quality trends provide one measure of 

performance and progress. In general, stable 

or improving air quality trends may be considered a sign of success. In accordance with 

the Government Performance and Results 

Act (GPRA), the NPS has established performance goals based on trends, and reports 

annually on progress. These goals are stable 

or improving:

•	 visibility in 95% of NPS reporting parks, 

•	 atmospheric deposition in 75% of NPS 

reporting parks, and 

•	 ozone in 85% of NPS reporting parks.

For this Annual Performance Report, ozone, 

visibility, and deposition data collected 

between 1998 and 2007 were examined.1

 The 

NPS exceeds air quality performance goals 

1. The lag time in data reporting results from quality 

assurance and data analysis procedures. 

for 2008, with 99 percent of the reporting 

parks showing stable or improving trends 

in visibility, 94 percent showing stable or 

improving trends in ozone concentrations, 

and 83 percent showing stable or improving 

trends in atmospheric deposition. 

While improving trends certainly show 

progress, a stable trend in air quality may not 

be sufficient to protect an area already experiencing poor air quality. Current air quality 

conditions are characterized for those park 

units with available trend information to 

identify areas where stable trends may be 

of some concern. Using an index for each 

type of air quality data collected (visibility, 

wet deposition concentrations, and ozone 

concentrations), park air quality is characterized as good, moderate (or cautionary), or of 

significant concern. 

•	 With respect to visibility, 59 percent 

of the parks are in good or moderate 

condition. All of the parks with significant visibility concerns have stable—not 

improving—trends. 

•	 For nitrogen deposition, only 29 percent 

of the parks are in good or moderate 

condition. Of the parks where nitrogen 

deposition is a significant concern, five 

parks have degrading trends, 35 have 

stable trends, and one has an improving 

trend.

•	 For sulfur deposition, 48 percent of the 

parks are in good or moderate condition. 

Of the parks where sulfur deposition is 

a significant concern, six have improving trends and 24 have stable trends. No 

park has a degrading trend with respect to 

sulfur deposition. 

•	 With respect to ozone, 32 percent of the 

parks are in good or moderate condition. 

Among the parks where current ozone 

conditions are of significant concern, 33 

have improving trends, 74 have stable 

trends, and one has a degrading trend.

Executive Summary

The National Park Service works to preserve, protect, enhance, and 

understand air quality and resources sensitive to air quality in the National 

Park System. This is crucial to parks because air pollution affects ecological 

health, scenic views, human health, and visitor enjoyment even at relatively 

low levels.
2 Air Quality in National Parks–2008

Air quality in parks is expected to improve 

as regulations aimed at reducing tailpipe 

emissions from motor vehicles and pollution from electric-generating facilities take 

full effect over the next few years. In addition, states and tribes, with assistance from 

regional planning organizations, are in the 

process of implementing programs to improve visibility in national parks and wilderness areas in response to Environmental 

Protection Agency regulations. Information 

available through the NPS air quality monitoring program has provided a foundation 

and impetus for pollution control programs 

that will benefit parks. The Park Service’s 

ability to offer expert and constructive assistance and advice to regulatory and permitting agencies has stimulated collaborative 

efforts to find creative and cost-effective air 

quality management approaches. 

The images above show clear, moderate, and hazy visbility 

conditions (top to bottom) at Denali National Park and Preserve. 
 National Park Service 3

The NPS Strategic Plan establishes the following air quality goals to meet by 2012:

•	 visibility in 95% of NPS reporting parks 

has remained stable or improved; 

•	 atmospheric deposition in 79% of NPS 

reporting parks has remained stable or 

improved; and

•	 ozone in 89% of NPS reporting parks has 

remained stable or improved. 

The target goals for 2008 were 95 percent 

for visibility, 85 percent for ozone, and 75 

percent for atmospheric deposition. We 

exceeded these goals with 99 percent of the 

reporting parks showing stable or improving trends in visibility, 94 percent showing 

stable or improving trends in ozone concentrations, and 83 percent showing stable or 

improving trends in atmospheric deposition. 

Performance exceeded the goals in part 

because many of the park units included in 

this year’s report are in or near urban areas, 

where pollution control programs have been 

in effect for many years. More detail on how 

trends are calculated appears in Appendix A. 

Progress toward these goals is measured 

annually through target goals. Data from visibility, ozone, and precipitation monitoring 

are used to assess air quality trends. Six total 

measures are used in calculating the goal 

percentages: two are used to measure progress toward the visibility goal, one measure is 

used for the ozone goal, and three measures 

are used for the atmospheric deposition goal. 

Not all parks monitor all six of the indicators. A park is considered to have improving 

or stable air quality if none of the measures 

used for that goal show a statistically significant degrading trend (denoted in red on attached figures and table). A summary of the 

trend results is presented in Table 1 showing 

the numbers of parks in each category that 

had stable, improving, and degrading trends. 

Results of the trend analyses for individual 

parks are shown in Appendix B . Trends that 

have at least a 95% probability of being correct (those with p-values <=0.05) are shown 

in red (degrading trends) and blue (improving trends). Also highlighted in the table are 

trends that have less than a 95% probability, 

but greater than an 85% probability of being 

correct (p-values less than 0.15). They are 

outlined in blue (improving trends) and red 

(degrading trends).

Visibility Measures

The NPS examines the clearest days and 

haziest days to measure visibility conditions2

. 

The Environmental Protection Agency 

(EPA) uses these measures to assess progress 

toward the national goal of remedying any 

existing and preventing any future human 

caused visibility impairment in protected 

Class I areas3

. This year we are able to report 

on 147 parks, both Class I and non-Class I, 

that have representative visibility monitoring and have at least 6 years of visibility data 

available during the period 1998-2007. All 

but one of the parks trended for visibility 

recorded stable or improving trends on both 

clear and hazy days. This means that 99 percent are meeting the visibility goal. On the 

clearest days, 35 parks are showing statistically significant improvement; these parks 

2. The clearest days are defined as the clearest 20% 

of those days each year for which visibility measurements are available, and the haziest days are the haziest 20%.

3. Class I areas include national parks greater than 

6,000 acres and wilderness areas greater than 5,000 

acres that were in existence or authorized as of August 7, 1977. They receive the highest degree of air 

quality protection under the Clean Air Act.

Measuring Progress–Air Quality Goals and Trends

Trend Category Total Parks 

Trended

Stable Trends Improving 

Trends

Degrading 

Trends

Visibility--Clearest Days 147 112 35 0

Visibility--Haziest Days 147 144 2 1

Wet Deposition--Ammonium 58 50 1 7

Wet Deposition--Nitrate 58 45 12 1

Wet Deposition--Sulfate 58 45 13 0

Ozone 161 102 46 13

Table 1. Summary of trend results for national park units with available monitoring data. 

All but one of the parks 

trended for visibility 

(1998–2007) recorded 

stable or improving 

trends on both clear 

and hazy days.
4 Air Quality in National Parks–2008

include Acadia National Park in the eastern 

U.S., and several sites in the northwest U.S., 

California, Colorado Plateau, and the Rocky 

Mountain region. No parks show degrading 

trends on the clearest days. These trends are 

shown in Figure 1. On hazy days, most areas 

are showing stable—not improving—trends. 

Only two parks show statistically significant 

improvement (Mount Rainier and Olympic), 

while one park shows statistically significant 

worsening of visibility (Hawaii Volcanoes). 

Trends on the haziest days are shown in 

Figure 2. 

Atmospheric Deposition Measures

Sulfate, nitrate, and ammonium ions in 

precipitation (rain and snow) are used as indicators of atmospheric deposition, because 

they can be directly linked to ecological 

effects (e.g., acidification of surface waters 

or nutrient enrichment that disrupts natural 

systems). This year we determined trends for 

58 parks that had representative monitoring. 

Table 1 gives the results of the trend analyses 

for wet deposition. 

In 45 areas (78 percent), sulfate concentrations were stable, and 13 showed 

Improving Trend

p <= 0.05

Improving Trend

0.05 < p <= 0.15

Degrading Trend

0.05 < p < =0.15

Degrading Trend

p <= 0.05

No Trend

Trends in Haze Index (Deciview) on Clearest Days

1998-2007

Figure 1. Trends in haze index on the clearest days, 1998-2007. 

Trends in Haze Index (Deciview) on Haziest Days

1998-2007

Improving Trend

p <= 0.05

Improving Trend

0.05 < p <= 0.15

Degrading Trend

0.05 < p < =0.15

Degrading Trend

p <= 0.05

No Trend

Figure 2. Trends in haze index on the haziest days, 1998-2007. 
 National Park Service 5

improvement. No area showed statistically 

significant deteriorating trends (Figure 3). 

Nitrate concentrations are stable or improving in 57 parks and deteriorating in one park 

(Olympic). Trends in nitrate ion concentrations are shown in Figure 4. 

Ammonium, another form of nitrogen, is 

stable in 50 areas (86 percent), with just 

one area showing a statistically significant 

improvement in concentrations. Ammonium 

concentrations are degrading in 7 areas, 

primarily in the intermountain west. Trends 

in ammonium are shown in Figure 5. 

In total, eight parks have deteriorating 

nitrogen loadings: Olympic, Yellowstone, 

Mesa Verde, Mount Rainier, Chiricahua, 

Fort Bowie, Canyonlands, and Capulin 

Volcano. The NPS has shared information 

and concerns about these trends with EPA, 

states, tribes, and stakeholders. As explained 

further below, collaborative efforts are underway to better understand the causes and 

effects of nitrogen loadings and to explore 

options for protecting ecosystem health, if 

necessary. 

Trends in Sulfate Concentrations in Precipitation

1998-2007

Virgin Islands

Improving Trend

p <= 0.05

Improving Trend

0.05 < p <= 0.15

Degrading Trend

0.05 < p < =0.15

Degrading Trend

p <= 0.05

No Trend

Figure 3. Trends in sulfate concentrations in precipitation, 1998-2007.

Trends in Nitrate Concentrations in Precipitation

1998-2007

Virgin Islands

Improving Trend

p <= 0.05

Improving Trend

0.05 < p <= 0.15

Degrading Trend

0.05 < p < =0.15

Degrading Trend

p <= 0.05

No Trend

Figure 4. Trends in nitrate concentrations in precipitation, 1998-2007. 
6 Air Quality in National Parks–2008

Ozone Measures

The NPS calculates ozone trends using 

EPA’s metric for the primary National Ambient Air Quality Standard4

. This standard is 

designed to protect the public health. Of 

the 161 park units that have representative 

ozone monitoring, 148 units have stable or 

improving trends (92 percent). These trends 

are shown in Figure 6. In the East, where 

ozone concentrations in parks like Great 

Smoky Mountains, Mammoth Cave, and 

Shenandoah sometimes reach levels high 

enough to harm human health, the ozone 

trends are largely improving over the past 

ten years. Some western parks also have 

improving trends, while a number of others 

are stable. On the other hand, several parks 

in the West have degrading ozone levels, 

including Death Valley, Mesa Verde, Glacier, 

North Cascades, Chiricahua, Fort Bowie, 

and parks in the San Francisco metropolitan area. As with concerns about increasing 

nitrogen loadings in western parks, the NPS 

has shared information about ozone trends 

with regulatory agencies, and several initiatives are underway to understand causes and 

effects and explore management options.

4. The EPA determines compliance with the ozone 

standard using the 3-year average of the annual 

fourth highest daily maximum 8-hour ozone concentration.

Trends in 3-Year Average 4th-Highest 8-Hour Ozone Concentrations

1998-2007

Improving Trend

p <= 0.05

Improving Trend

0.05 < p <= 0.15

Degrading Trend

0.05 < p < =0.15

Degrading Trend

p <= 0.05

No Trend

Figure 6. Trends in the 3-year average of the annual 4th-highest 8-hour ozone 

concentration, 1998-2007.

Trends in Ammonium Concentrations in Precipitation

1998-2007

Virgin Islands

Improving Trend

p <= 0.05

Improving Trend

0.05 < p <= 0.15

Degrading Trend

0.05 < p < =0.15

Degrading Trend

p <= 0.05

No Trend

Figure 5. Trends in ammonium concentrations in precipitation, 1998-2007.
 National Park Service 7

Researchers look for ozone injury on coneflowers in 

Rocky Mountain National Park, Colorado. The photo on 

the left shows ozone injury to a coneflower leaf.
8 Air Quality in National Parks–2008

The photo at right shows deposition monitoring equipment 

in use at Canyonlands National Park, Utah. This site 

operates under the National Atmospheric Deposition 

Program.

The photo above illustrates the sandstone spires that give 

the Needles district of the park its name.
 National Park Service 9

To assess condition, we first used all available 

monitoring data from NPS, EPA, state, tribal, 

and local monitors over the period 2003-

2007 to estimate air quality parameters for 

the reported park units. We then used these 

estimated values to determine an index for 

each type of air quality data collected (visibility, wet deposition concentrations, and 

ozone concentrations) that assigns the park 

to one of three condition categories where 

air quality is:

Condition Red–a Significant Concern,

Condition Yellow–in Moderate Condition, or

Condition Blue–in Good Condition.

The procedures for estimating the air quality parameters and assigning the condition 

categories are described in Appendix C.

Air Quality Condition Results

Appendix C gives the results of the air quality condition determinations for parks where 

we were also able to derive trend estimates. 

For each park, a blue circle indicates a park 

assigned to the Good category for the indicated air quality parameter, a yellow circle 

indicates the park is assigned to the Moderate (or Caution) category, and a red circle indicates the park is assigned to the Significant 

Concern category. The category symbols in 

the Appendix C table are also overlaid with 

arrows indicating the direction of the trend 

(if any). The arrows represent the trends 

computed from data collected at individual 

monitors (presented in Appendix B), not 

from the methods used to derive the condition estimates. A blue down arrow indicates 

an improving trend, a yellow double-headed 

horizontal arrow indicates no trend, and a 

red up arrow indicates a worsening trend. 

In the case of the nitrogen deposition and 

visibility trends, two trend indicators were 

combined to create one trend arrow, and the 

less favorable trend was chosen to represent 

the site. For nitrogen deposition, if the trend 

in the concentration of either nitrate or 

ammonium is degrading while the other is 

stable or improving, an arrow indicating a 

degrading trend is overlaid on the condition 

symbol. If the trend in one form of nitrogen 

is stable while the other is improving, an 

arrow indicating a stable trend is shown. 

Similarly, trends in visibility on clear days 

and hazy days were combined and overlaid 

on the visibility condition symbol. If a trend 

in one is degrading while a trend in the other 

is stable or improving, an arrow indicating a 

degrading trend is shown for that park, and 

if there is one stable trend and one improving trend, a stable trend is shown. All up 

and down arrows represent trends that have 

at least a 95% probability of being correct 

(those with p-values <=0.05).

The air quality condition results are shown 

graphically on maps in Figures 7-10. Figure 7 

shows the visibility conditions at park units. 

Only Denali in Alaska falls into the Good 

category. Most of the 85 parks in the Moderate category are located in the western 

US, with a few in the upper Midwest near 

the Canadian border. The 59 parks in the 

Significant Concern category are found 

mostly in the eastern US, with two located in 

California. 

Air quality conditions for nitrogen wet 

deposition are shown in Figure 8. Only 

four sites—Denali, Virgin Islands, Canyonlands, and Pinnacles—fall into the Good 

category. There are 13 parks that fall into 

the Moderate category; these are located 

in the southwestern US, Washington State, 

Montana, North Dakota, and Maine. The 

other 41 parks, comprising the majority of 

the monitored parks and located throughout the US, fall into the Significant Concern 

category. Sulfur wet deposition conditions 

are shown in Figure 9. The 28 parks in the 

Measuring Success–

Assessment of Air Quality Conditions and Trends

In addition to determining the trends in air quality, the NPS is interested 

in assessing the current condition of the air resources within NPS units. 

A stable trend in air quality may not be sufficient to protect an area that is 

already experiencing poor air quality.
10 Air Quality in National Parks–2008

Good and Moderate categories are located 

largely in the western US, along with a few in 

the upper Midwest. There are 30 parks in the 

Significant Concern category; they are found 

in the eastern US, Midwest, Colorado, and 

Washington State.

Results for the ozone concentration assessment are shown in Figure 10. The 108 parks 

in the Significant Concern category are concentrated largely on the east and west coasts, 

with a few located near the Great Lakes 

region and eastern Texas. There are 39 that 

fall in the Moderate category; these parks 

are located throughout the US. Only 13 parks 

fall in the Good category, located in Alaska, 

North Dakota, Washington, Oregon, Montana, and the northern coast of California.

Longer Term Trends

The sliding 10-year trend period was originally chosen for trend reporting because 

different monitors began at different times, 

making it difficult to select a single common 

starting point, and because we felt it was important to demonstrate continued progress 

toward achieving air quality improvements. 

It is also valuable, however, to examine 

trends over longer time periods in order 

to assess overall progress made during the 

course of each monitoring program, as well 

as to identify parks that may be of special 

Good Condition

Moderate Condition

Significant Concern

Virgin Islands

Air Quality Condition--Nitrogen Wet Deposition

Figure 8. Air quality condition assessments for nitrogen deposition. Assessments 

were derived from interpolations of nitrogen deposition in precipitation, 2003-2007. 

Good Condition

Moderate Condition

Significant Concern

Air Quality Condition--Visibility

Figure 7. Air quality condition assessments for visibility. Condition assessments 

were derived from interpolations of average visibility conditions, 2003-2007.
 National Park Service 11

concern. For this evaluation we selected inpark monitors with at least 10 years of data 

that had a start data of 1997 or earlier (since 

1998 is the beginning of the current 10-year 

trend period, trends beginning in 1998 and 

later have already been presented). We computed a trend for each of the six indicators 

used for reporting trend results. The results 

of these trends are presented below.

We chose to evaluate long-term progress 

in ozone concentrations using the annual 

4th-highest 8-hour daily maximum ozone 

concentration, rather than the 3-year average of this number that is used by EPA for 

the ozone standard, as the annual value is 

available for a longer span of years. Each 

monitoring location was analyzed over the 

entire record of available data. We required 

that each year have at least 75% of possible 

valid daily 8-hour maximum ozone concentrations during the local ozone season in 

order for it to be used in the trend analysis. 

We generated long-term trends for 27 park 

monitors. The trend results and number of 

available years of data are presented in Table 

2. Statistically significant degrading trends 

were observed at Craters of the Moon, 

Denali, Mesa Verde, and Rocky Mountain. 

Improving trends were found at Cape Cod 

and Pinnacles. No statistically significant 

trends were found for the other 21 parks 

listed in the table. 

Virgin Islands

Good Condition

Moderate Condition

Significant Concern

Air Quality Condition--Sulfur Wet Deposition

Figure 9. Air quality condition assessments for sulfur deposition. Assessments 

were derived from interpolations of sulfur deposition in precipitation, 2003-2007. 

Good Condition

Moderate Condition

Significant Concern

Air Quality Condition--Ozone

Figure 10. Air quality condition assessments for ozone concentration. Assessments 

were derived from interpolated values of the annual 4th-highest 8-hour ozone 

concentrations, 2003-2007. 
12 Air Quality in National Parks–2008

Table 2. Long-term ozone trends from park monitors that have been collecting data since 1997 or earlier. 

Trends in Annual 4th-Highest 8-Hour Daily Maximum Ozone Concentration

Park Slope 

(ppb/year) P-value Number of Valid Years

First Year 

of Data

Last Year of 

Data

Acadia -0.38 0.32 12 1996 2007

Big Bend 0.00 0.46 15 1992 2007

Canyonlands 0.33 0.14 15 1993 2007

Cape Cod -1.00 < 0.01 18 1989 2007

Chamizal 0.13 0.41 16 1992 2007

Chiricahua 0.14 0.15 17 1990 2007

Cowpens -0.33 0.18 19 1989 2007

Craters Of The Moon 0.76 < 0.01 12 1993 2007

Death Valley 0.33 0.06 13 1994 2007

Denali 0.27 0.02 18 1990 2007

Glacier 0.24 0.13 19 1989 2007

Grand Canyon 0.00 0.42 15 1993 2007

Great Basin 0.25 0.14 14 1994 2007

Great Smoky Mountains 0.00 0.53 18 1989 2007

Joshua Tree -0.60 0.17 14 1994 2007

Lassen Volcanic 0.06 0.37 19 1989 2007

Mesa Verde 0.61 0.02 13 1994 2007

Mount Rainier -0.18 0.34 13 1994 2007

North Cascades 0.67 0.11 11 1996 2007

Pinnacles -0.43 0.01 19 1989 2007

Rocky Mountain 0.50 0.02 18 1989 2007

Saguaro 0.00 0.42 19 1989 2007

Sequoia/Kings Canyon -0.07 0.34 19 1989 2007

Shenandoah -0.14 0.34 19 1989 2007

Voyageurs -0.50 0.08 11 1997 2007

Yellowstone -0.11 0.32 11 1997 2007

Yosemite -0.40 0.10 14 1994 2007

Degrading air quality trend, 

statistically significant (p <= 0.05)

Degrading air quality trend, 

not statistically significant (0.05 < p <= 0.15)

Improving air quality trend, 

statistically significant (p <= 0.05)

Improving air quality trend, 

not statistically significant (0.05 < p <= 0.15)
 National Park Service 13

Figure 11. Long-term ozone trends at parks where the annual 4th-highest daily maximum 8-hour ozone concentration 

has been consistently at or above the ozone standard. 

An examination of the time series plots is 

helpful in identifying parks that may be of 

concern despite flat or improving trends. 

Several parks have annual 4th-highest 8-hour 

ozone concentrations that are consistently at 

or above the standard of 75 ppb. These parks 

include Acadia, Great Smoky Mountains, 

Death Valley, Joshua Tree, Sequoia/Kings 

Canyon, and Yosemite (see Figure 11). Several 

other parks with flat trends nonetheless 

have annual values that are very close to the 

standard and sometimes over it, including 

Chamizal, Cowpens, Grand Canyon, Lassen 

Volcanic, Saguaro, and Shenandoah (Figures 

12-17). Canyonlands, Chiricahua, and Great 

Basin have remained largely under the level 

of the standard but are also close to it, and 

there is no indication that ozone is trending 

downward at these locations (Figures 18-20). 
14 Air Quality in National Parks–2008

Figure 12. Figure 13.

Figure 14. Figure 15.

Figure 16. Figure 17.

Figures 12-17 show ozone trends at parks where the annual 4th-highest daily maximum 8-hour ozone 

concentration has been consistently near or above the ozone standard.
 National Park Service 15

Figure 18. Figure 19.

Figure 20.

Figures 18-20 show ozone trends at parks where the annual 

4th-highest daily maximum 8-hour ozone concentration has 

mostly been below, but close to, the ozone standard.
16 Air Quality in National Parks–2008

Figure 22. Levels of the annual 4th-highest 8-hour ozone 

concentration at Rocky Mountain increased from 1989 to 2007.

Figure 21. Levels of the annual 4th-highest 8-hour ozone 

concentration at Mesa Verde increased from 1994 to 2007.

The ozone concentrations at Great Basin are 

of particular concern. The park is located in 

eastern Nevada some distance from population centers and known sources of pollution, 

and its annual 4th-highest 8-hour ozone 

concentrations are higher than expected. 

Great Basin is consistently one of the clearest parks for visibility within the National 

Park Service, with deciview values comparable to relatively clean sites such as Denali, 

which occupies a remote location in Alaska. 

On the haziest days in 2007, Denali had the 

lowest mean deciview of 47 national parks 

(8.8 dv), and Great Basin had the second 

lowest (10.3 dv). Great Basin’s ozone concentrations, however, are considerably higher 

than those in Denali. In 2007, Denali’s 

4th-highest 8-hour ozone concentration was 

the second lowest of 41 monitors located in 

national parks (53 ppb), but Great Basin’s 

4th-highest 8-hour ozone concentration 

ranked in the upper half of the monitors at 

75 ppb, tying with Chamizal and Pinnacles 

for the 16th-highest value. 

Mesa Verde has a statistically significant 

increasing trend over the 1994-2007 period 

and its annual 4th-highest 8-hour ozone 

concentrations are approaching the standard 

(Figure 21). Rocky Mountain also has an 

increasing trend and its annual values have 

been at or near the standard over the last few 

years (Figure 22). The trend at Craters of the 

Moon is increasing, but so far the levels remain below the standard (Figure 23). Denali 

(Figure 24) also exhibits an increasing trend 

over the long term but the increase appears 

to be very slight, and the levels remain well 

below the standard. Cape Cod and Pinnacles 

exhibit statistically significant downward 

trends (Figure 25). Cape Cod’s annual levels 

are still above the standard but are trending 

strongly downwards. Annual 4th-highest 

8-hour ozone concentrations at Pinnacles 

are still near or slightly above the standard 

but are also trending down.

Several eastern parks, including Cowpens, 

Great Smoky Mountains, and Shenandoah, 

experienced a peak in ozone values around 

1998-1999 (Figure 26). As a result, their 

long-term trends are flat, despite trending 

downward over the most recent 10-year 

period. The length of the trend at Mammoth 

Cave is not as long since the site moved in 
 National Park Service 17

Figure 23. Long-term trend in annual 4th-highest 8-hour ozone 

concentration at Craters of the Moon. Despite an increase, ozone 

levels remain below the standard.

Figure 25. Trends in the annual 4th-highest 8-hour ozone 

cocnentration show a decrease at Cape Cod and Pinnacles.

Figure 24. Although the long-term trend in the annual 4thhighest 8-hour ozone concentration showed an increase through 

2007, ozone levels at Denali remain well below the standard.

Figure 26. Long-term ozone trends at several eastern monitoring 

stations show peaks in the annual 4th-highest 8-hour ozone 

concentration in 1998 and 2002. Long-term trends at these 

locations are flat.
18 Air Quality in National Parks–2008

1997, but a similar decrease in concentrations was observed there beginning in 1998. 

Despite this recent improving trend the annual ozone levels at Mammoth Cave remain 

near or above the standard. From other data 

collected at monitors located in this region it 

appears as if a peak in ozone values occurred 

during this time period at some locations 

outside these parks (Figures 27 and 28). 

However, this was not the case everywhere, 

particularly in larger urban areas further to 

the east (Figure 29). 

Long-term visibility trends were also calculated for park visibility monitors with at 

least 10 years of data beginning in 1997 or 

earlier. We calculated trends in deciview on 

the clearest and haziest days for the period of record at 29 locations. The results 

are shown in Table 3. On the clearest days, 

most sites indicated a statistically significant 

improving trend. These locations include: 

Acadia, Badlands, Bandelier, Big Bend, Bryce 

Canyon, Canyonlands, Chiricahua, Crater 

Lake, Denali, Glacier, Great Basin, Great 

Sand Dunes, Guadalupe Mountains, Lassen 

Volcanic, Mesa Verde, Mount Rainier, Petrified Forest, Pinnacles, Point Reyes, Redwood, Rocky Mountain, Shenandoah, Tonto, 

Washington D.C., Yellowstone, and Yosemite. No trend was observed on the best days 

at Great Smoky Mountains, Mammoth Cave, 

or Sequoia. On the haziest days, statistically 

significant improving trends occurred at 

Acadia, Canyonlands, Denali, Great Smoky 

Mountains, Mount Rainier, Pinnacles, Point 

Reyes, Redwood, Shenandoah, and Washington D.C. Statistically significant degrading 

trends were found at Big Bend and Guadalupe Mountains. 

Figures 27-28. Ozone data from some southeastern monitors suggest a peak in 

the annual 4th-highest daily maximum 8-hour ozone concentration around 1998.

Figure 29. A distinct peak in 

the annual 4th-highest 8-hour 

ozone concentration is not 

evident in ozone data from 

monitors near several large 

eastern urban areas.
 National Park Service 19

Trends in Annual Deciview (DV) on Clearest and Haziest Days

Park

Clearest Days Haziest Days

Number of 

Valid Years

First Year 

of Data

Last Year 

Slope of Data

(DV/year) P-value

Slope 

(DV/year) P-value

Acadia -0.18 < 0.01 -0.23 < 0.01 18 1990 2007

Badlands -0.05 0.01 -0.04 0.12 19 1989 2007

Bandelier -0.10 < 0.01 -0.06 0.15 17 1989 2007

Big Bend -0.10 0.01 0.07 0.04 16 1990 2007

Bryce Canyon -0.09 < 0.01 0.05 0.054 17 1990 2007

Canyonlands -0.15 < 0.01 -0.11 < 0.01 18 1990 2007

Chiricahua -0.10 < 0.01 -0.03 0.27 18 1990 2007

Crater Lake -0.18 < 0.01 -0.05 0.34 13 1992 2007

Denali -0.11 < 0.01 -0.11 0.02 19 1989 2007

Glacier -0.12 < 0.01 -0.03 0.27 17 1989 2007

Great Basin -0.14 < 0.01 0.00 0.46 15 1993 2007

Great Sand Dunes -0.08 0.01 -0.01 0.47 19 1989 2007

Great Smoky Mountains -0.07 0.07 -0.12 0.01 18 1990 2007

Guadalupe Mountains -0.08 < 0.01 0.13 0.03 17 1989 2007

Lassen Volcanic -0.10 < 0.01 0.05 0.18 19 1989 2007

Mammoth Cave 0.00 0.54 -0.07 0.17 14 1992 2007

Mesa Verde -0.07 0.02 0.03 0.39 17 1989 2007

Mount Rainier -0.15 < 0.01 -0.38 < 0.01 17 1989 2007

Petrified Forest -0.05 0.02 0.07 0.11 16 1990 2007

Pinnacles -0.13 < 0.01 -0.20 < 0.01 17 1989 2007

Point Reyes -0.07 0.02 -0.12 0.03 16 1989 2007

Redwood -0.14 < 0.01 -0.18 < 0.01 19 1989 2007

Rocky Mountain -0.10 < 0.01 0.02 0.42 17 1991 2007

Sequoia/Kings Canyon -0.06 0.24 -0.18 0.08 10 1994 2007

Shenandoah -0.17 < 0.01 -0.23 < 0.01 17 1990 2007

Tonto -0.12 < 0.01 0.00 0.46 14 1991 2007

Washington -0.21 < 0.01 -0.21 < 0.01 17 1990 2007

Yellowstone -0.07 0.02 0.00 0.57 10 1997 2007

Yosemite -0.08 0.01 0.02 0.42 19 1989 2007

Table 3. Long-term visibility trends from park monitors that have been collecting data since 1997 or earlier. 

Degrading air quality trend, 

statistically significant (p <= 0.05)

Degrading air quality trend, 

not statistically significant (0.05 < p <= 0.15)

Improving air quality trend, 

statistically significant (p <= 0.05)

Improving air quality trend, 

not statistically significant (0.05 < p <= 0.15)
20 Air Quality in National Parks–2008

Figure 30. Figure 31.

Figure 32. Figure 33.

Although a majority of the observed trends 

over the long-term are favorable (either 

improving or not degrading), visibility at 

all parks suffers from at least some impairment, particularly on the haziest days. 

Annual mean deciview values on the haziest days at the 29 NPS locations during the 

period 2005-2007 ranged from 1.5 dv to 22 

dv higher than estimated natural conditions 

and averaged approximately 8.5 dv higher 

than estimated natural conditions. Eastern 

sites such as Acadia, Shenandoah, Great 

Smoky Mountains, and Mammoth Cave 

have consistently experienced annual mean 

deciview values on the haziest days well 

in excess of estimated natural conditions 

(Figures 30-33). Some western parks, such as 

Sequoia, Yosemite, Mount Rainier, and Pinnacles also experience haze levels well above 

estimated natural conditions, although longterm trends at Mount Rainier and Pinnacles 

suggest that conditions on the worst days are 

improving (Figures 34-37). 

Figures 30-33: Visibility monitoring data from Acadia, Shenandoah, Great Smoky Mountains, and 

Mammoth Cave National Parks show annual mean deciview values on the haziest days that are well 

in excess of estimated natural conditions.
 National Park Service 21

Figure 34.

Figure 35.

Figure 36.

Figure 37.

Figures 34-37: Visibility conditions on the haziest days at some 

western parks—including Sequoia, Yosemite, and Mount Rainier 

National Parks and Pinnacles National Monument—show mean 

deciview values above estimated natural conditions; trends suggest improvement at Mount Rainier and Pinnacles.
22 Air Quality in National Parks–2008

Visibility conditions on the best days are 

also impaired, although to a lesser degree. 

At all NPS sites with data during 2005-2007, 

mean deciview values on the clearest days 

ranged from 0.3 to 12 dv above estimated 

natural conditions, and averaged roughly 

3.5 dv above estimated natural conditions. 

All but three of the 29 monitoring locations evaluated for long-term trends show 

statistically significant improving trends on 

the clearest days, while the remaining three 

show no trends. Monitoring locations with 

the greatest differences between measured 

visibility on the clearest days and estimated 

natural conditions include Washington D.C., 

Shenandoah, Mammoth Cave, and Great 

Smoky Mountains (Figures 38-41).

Long-term trends in concentrations of ammonium, nitrate, and sulfate in wet deposition were calculated for in-park monitors 

with 10 years or more of data beginning in 

1997 or earlier. Only data collected from 1994 

and later were considered due to changes 

in measured sulfate and nitrate concentrations that occurred as a result of a change in 

sample handling procedures5

. The results are 

shown in Table 4. There were 27 monitoring 

locations with sufficient data for long-term 

trends. Six of the 27 locations exhibited statistically significant degrading trends in ammonium concentrations (Capulin Volcano, 

Craters of the Moon, Mesa Verde, Rocky 

Mountain, Yellowstone, and Yosemite). Only 

one park (Olympic) observed a statistically 

significant improving trend in ammonium 

concentrations. Statistically significant 

improving trends in nitrate concentrations 

were found at five monitoring locations (Big 

Bend, Buffalo, Indiana Dunes, Isle Royale, 

and Shenandoah); no trends in nitrate 

concentrations were found at the remaining 

monitors. Sulfate concentrations in precipitation improved at ten NPS monitoring locations (Big Bend, Bryce Canyon, Buffalo, Glacier, Guadalupe Mountains, Indiana Dunes, 

Little Bighorn, Mesa Verde, North Cascades, 

and Shenandoah). No long-term trends in 

sulfate concentrations were found at the 

remaining 15 NPS monitoring locations.

5. See NADP data advisory, http://nadp.sws.uiuc.

edu/documentation/advisory.html.

Figure 38. Figure 39.

Figures 38-39: Visibility data from monitors in Washington DC and Shenandoah show that haze levels 

remain above estimated natural conditions on the clearest days, but long-term trends show improvement. 
 National Park Service 23

Figure 40. Long-term trends in visibility on the clearest days 

are flat at Mammoth Cave.

Figure 41. Annual mean deciview trends on the clearest days at 

Great Smoky Mountains.
24 Air Quality in National Parks–2008

Trends in Wet Deposition Concentrations

Park

Ammonium Nitrate Sulfate Number 

of Valid 

Years

First 

Year of 

Data

Last Year 

Slope of Data

μeq/liter/yr P-value

Slope 

μeq/liter/yr P-value

Slope 

μeq/liter/yr P-value

Acadia 0.02 0.43 -0.24 0.06 -0.39 0.06 13 1994 2007

Bandelier 0.31 0.06 0.01 0.52 -0.22 0.13 13 1994 2007

Big Bend -0.45 0.08 -0.47 < 0.01 -0.67 0.01 13 1994 2007

Bryce Canyon 0.48 0.06 0.03 0.50 -0.45 < 0.01 11 1994 2007

Buffalo 0.06 0.43 -0.22 0.05 -0.45 < 0.01 13 1994 2007

Capulin Volcano 0.35 0.02 -0.11 0.30 -0.08 0.43 10 1994 2007

Craters Of The Moon 0.58 0.01 -0.09 0.17 0.06 0.37 14 1994 2007

Denali -0.01 0.50 -0.02 0.33 0.07 0.33 14 1994 2007

Everglades 0.10 0.23 -0.01 0.47 -0.04 0.42 12 1994 2007

Gila Cliff Dwellings 0.39 0.06 0.54 0.18 -0.40 0.14 11 1994 2007

Glacier 0.17 0.06 -0.02 0.46 -0.13 0.03 14 1994 2007

Grand Canyon 0.22 0.14 0.10 0.27 -0.07 0.44 11 1994 2007

Great Basin 0.37 0.08 -0.09 0.43 -0.18 0.054 10 1994 2006

Great Smoky Mountains 0.14 0.30 -0.08 0.12 -0.07 0.50 14 1994 2007

Guadalupe Mountains -0.12 0.38 -0.31 0.10 -1.02 0.01 13 1994 2007

Indiana Dunes 0.02 0.50 -0.64 0.01 -0.99 < 0.01 14 1994 2007

Isle Royale 0.30 0.12 -0.33 0.01 -0.28 0.16 12 1994 2007

Little Bighorn Battlefield 0.14 0.12 -0.26 0.06 -0.25 < 0.01 14 1994 2007

Mesa Verde 0.22 0.03 0.03 0.50 -0.62 < 0.01 14 1994 2007

Mount Rainier 0.01 0.38 0.04 0.18 -0.23 0.08 11 1994 2006

North Cascades -0.03 0.25 -0.04 0.43 -0.10 0.02 13 1995 2007

Olympic -0.03 0.04 0.00 0.57 -0.01 0.50 10 1994 2005

Organ Pipe Cactus 0.65 0.12 0.29 0.23 -0.17 0.23 12 1994 2007

Rocky Mountain 0.56 0.01 0.10 0.37 -0.24 0.06 14 1994 2007

Shenandoah -0.12 0.18 -0.49 0.02 -0.70 0.02 11 1994 2006

Yellowstone 0.53 0.01 0.10 0.18 0.14 0.10 13 1994 2007

Yosemite 0.47 0.03 -0.04 0.47 0.07 0.23 12 1994 2007

Table 4. Long-term deposition trends from park monitors that have been collecting data since 1997 or earlier. 

Degrading air quality trend, 

statistically significant (p <= 0.05)

Degrading air quality trend, 

not statistically significant (0.05 < p <= 0.15)

Improving air quality trend, 

statistically significant (p <= 0.05)

Improving air quality trend, 

not statistically significant (0.05 < p <= 0.15)
 National Park Service 25

Ozone Exposure

In July 2007 the EPA proposed a new secondary ozone standard. Secondary standards 

set limits to protect public welfare, including protection against decreased visibility 

and damage to vegetation and buildings. 

The proposed standard is based upon a 

cumulative sum of hourly ozone concentrations, where the hourly values are weighted 

according to their magnitude6

. This sum 

provides an index of the total amount of 

ozone that plants are exposed to during the 

daytime. The three-month period with the 

highest cumulative exposure index is used 

as the reporting statistic, which is referred 

to as the W126 statistic (more details on 

how this value is calculated are provided in 

Appendix D). The units of the W126 statistic 

are ppm-hours. In making this secondary 

standard proposal, EPA recommended that 

the level of the standard be set somewhere 

in the range of 7-21 ppm-hours, so that the 

annual maximum 3-month cumulative W126 

should be less than that value. EPA proposed 

the new standard on the basis of research 

showing that a cumulative index, rather than 

a maximum value, is the best way to relate 

ozone concentrations to the potential for 

harmful impacts to vegetation. Although 

EPA did not adopt this proposed standard in 

its final ruling, we feel that it is still an important indicator of the potential for damage to 

ozone-sensitive plant species. 

Table 5 shows parks with on-site monitoring that had W126 index values at or above 

7 ppm-hours during 2007. There were 28 

parks that equalled or exceeded this exposure value, which is the lower range 

of the proposed EPA standard. Six parks 

(Sequoia-Kings Canyon, Joshua Tree, Death 

Valley, Yosemite, Great Smoky Mountains, 

and Mammoth Cave) exceeded the upper 

range of 21 ppm-hours. Parks with 3-month 

maximum ozone exposures between 7 and 

21 ppm-hours include Acadia, Badlands, Big 

Bend, Cape Cod, Canyonlands, Chamizal, 

Chiricahua, Congaree, Cowpens, Craters of 

the Moon, Everglades, Great Basin, Grand 

Canyon, Lassen Volcanic, Mesa Verde, 

Petrified Forest, Pinnacles, Rocky Mountain, 

Saguaro, Shenandoah, Wind Cave, Yellowstone, and Zion.

6. See Federal Register Vol. 72 No. 132, 40 CFR 

Part 50, National Ambient Air Quality Standards for 

Ozone; A Proposed Rule, July 11, 2007.

 Monitoring Locations With Maximum 3-Month W126

 Greater Than or Equal to 7 ppm-hrs (2007)

Park Maximum 3-Month 

 W126 (ppm-hrs)

Acadia--Cadillac Mountain 7

Badlands 8

Big Bend 10

Canyonlands 17

Cape Cod 13

Chamizal 13

Chiricahua 14

Congaree 9

Cowpens 7

Craters of the Moon 10

Death Valley 32

Grand Canyon 18

Great Basin 15

Great Smoky Mountains--Cades Cove 12

Great Smoky Mountains--Clingmans Dome 23

Great Smoky Mountains--Cove Mountain 20

Great Smoky Mountains--Look Rock 23

Great Smoky Mountains--Purchase Knob 13

Joshua Tree 52

Lassen Volcanic 15

Mammoth Cave 22

Mesa Verde 17

Petrified Forest 16

Pinnacles 14

Rocky Mountain 20

Saguaro 17

Sequoia and Kings Canyon--Ash Mountain 63

Sequoia and Kings Canyon--Lower Kaweah 53

Shenandoah 13

Wind Cave 12

Yellowstone 10

Yosemite 28

Zion 18

Table 5. Parks with on-site monitoring that had W126 index values equal to 

or greater than 7ppm-hours in 2007. The W126 index provides a useful metric 

for assessing the potential for harm to vegetation due to cumulative ozone 

exposure.
26 Air Quality in National Parks–2008

Members of the Western Airborne Contaminants Assessment 

Project study team take water, fish, and snow samples in 

Denali National Park and Preserve, and sediment samples in 

Glacier National Park. This study looked at eight western parks 

to determine the levels of airborne contaminants in the air, 

snow, water, sediments, lichens, conifer needles, and fish. Air, 

lichen, and conifer needle samples were also collected from an 

additional 12 parks and forests.
 National Park Service 27

Making progress toward meeting park air 

quality goals is challenging because while we 

are given a consultation role under the Clean 

Air Act, the NPS has no direct authority to 

control sources of pollution located outside 

park boundaries. In order to achieve park air 

quality goals, the NPS works collaboratively 

with federal and state air regulatory agencies, as well as neighboring land management agencies, to enhance and protect air 

quality in the parks to greatest extent possible. These goals are also achieved by understanding and sharing information about air 

quality conditions and trends in parks with 

regulatory agencies and the public, which 

supports or helps shape federal and state 

air pollution control programs. Information 

sharing has supported the NPS in fulfilling 

its responsibility under the Clean Air Act 

and led to further collaborative efforts with 

states, tribes, EPA, the private sector, and 

the public aimed at protecting air quality in 

parks. Such efforts include:

Visibility and Regional Haze:

NPS is continuing to consult with states 

on their Regional Haze State Implementation Plans that are designed to improve 

visibility due to long-range transport of 

haze-producing pollutants. States must 

inform the public of federal land manager 

concerns and respond to those concerns 

when they submit the plans for approval to 

the EPA. The visibility protection plans were 

due to EPA from all 50 states in December, 

2007 and must include strategies for making 

reasonable progress toward natural visibility 

conditions. However, due to court actions 

and program concerns, many state plans 

have been delayed. The NPS has focused its 

comments on state actions to retrofit certain 

larger industrial facilities with pollution control devices and the long-term programs that 

states will implement to achieve progress 

towards natural visibility conditions at the 

mandatory Federal Class I parks. We expect 

major reductions in visibility-impairing pollutants as a result of these efforts.

NPS is working closely with the U.S. Fish 

and Wildlife Service and the U.S. Forest Service in reviewing regional haze plans since 

they also manage Class I units. 

Ecosystem Protection Initiatives:

The NPS has been encouraging the use 

of critical loads for atmospheric deposition as indicators of ecological health and 

benchmarks for evaluating the effect of air 

pollution control programs. A critical load 

is an exposure value below which harmful 

environmental effects are not known to occur. In cooperation with EPA, other federal 

land managing agencies, states and others, 

various research, monitoring, and modeling 

approaches to developing critical loads are 

being examined around the country. 

Studies on the ecological effects of air pollution in national parks are currently ongoing 

through agreements with researchers at various universities and other federal agencies. 

Current research projects are underway to 

assess the effects of nitrogen, ozone or mercury deposition on plants, soils or waters in 

three southeast Alaska parks, three National 

Capitol Region parks, five southeastern U.S. 

parks, and in Joshua Tree, Sequoia, Yosemite, Grand Teton, Crater Lake, Acadia, and 

Rocky Mountain National Parks. 

Assessing Air Pollution Risk to NPS 

Resources:

The NPS Inventory and Monitoring Program has enabled broad regional and 

national-scale assessments of air pollution 

effects and resource sensitivities to air quality changes in parks. Private sector contractors have been used to assess air pollution 

risks for 270 national parks. Natural resource 

risk assessments have been completed for 

ozone, and are underway for mercury, acid 

deposition, and nitrogen.

NPS partnered with EPA, the U.S. Geological Survey, the U.S. Forest Service, Oregon 

State University, and University of Washington in the Western Airborne Contaminants 

Assessment Project (WACAP). A final report 

for this six year project was completed in 

2008. The project was developed to determine the risk to ecosystems and food webs 

in 20 western national parks from airborne 

toxic contaminants. NPS is concerned about 

airborne contaminants because they can 

pose serious health threats to wildlife and 

humans, as some of these compounds tend 

Producing Results–Information and Collaboration

Information sharing has 

supported the NPS in fulfilling 

its responsibility under the 

Clean Air Act and led to 

further collaborative efforts 

with states, tribes, EPA, the 

private sector, and the public 

aimed at protecting air 

quality in parks.
28 Air Quality in National Parks–2008

to accumulate in the food chain. Results 

from the project have been published in 

ten different journal articles. Key findings 

include: (1) over 70 agricultural and industrial contaminants from both international 

and local/regional sources are being deposited in western national parks; (2) parks with 

the highest levels of pesticides in snow and 

vegetation are those closest to croplands 

and include Glacier, Rocky Mountain, and 

Sequoia/Kings Canyon National Parks; (3) 

fish in some parks contained contaminant 

levels exceeding human health risk thresholds; and (4) lake sediment records show 

that many contaminants deposited in parks 

are increasing over time.

Fish are currently being sampled and analyzed for contaminant concentrations and 

effects on fish health and condition in 10 

western national parks, as a follow-up to the 

WACAP study.

Natural Resource Condition Assessments

The NPS is conducting assessments to determine the current conditions for important 

natural resources in all parks that are part of 

the NPS Inventory and Monitoring Program. 

Each assessment relies on existing data and 

knowledge, is focused on a park-specific 

subset of important resource indicators, and 

summarizes overall conditions by individual 

park areas. The Air Resources Division is 

providing guidance, data, and information 

to assess air quality conditions for ozone, 

deposition, and visibility as part of the park 

assessments.

Four Corners Air Quality Task Force

The Four Corners region—the intersection 

of the states of Colorado, New Mexico, 

Utah, and Arizona—is home to existing and 

planned oil and gas production and coalfired power plants. These activities result in 

substantial air pollutant emissions. The NPS 

units near this area include Mesa Verde National Park, Arches National Park, Canyonlands National Park, Capitol Reef National 

Park, Bryce Canyon National Park, Grand 

Canyon National Park, Chaco Culture National Historic Park, and Bandelier National 

Monument. 

The states of Colorado and New Mexico initiated a collaborative effort involving Arizona 

and Utah, interested tribes in the area, the 

U.S. Environmental Protection Agency as 

well as federal land management agencies 

(NPS, the Bureau of Land Management, and 

the U.S. Forest Service) to explore air quality 

issues associated with present and future 

air pollutant emissions in the Four Corners 

region. These parties entered into a Memorandum of Understanding that defines an 

Interagency Policy Oversight Group, which, 

in turn, facilitated the Four Corners Air 

Quality Task Force.

The Task Force was open to all interested 

parties to discuss and formulate options to 

address regional air quality issues. The Four 

Corners Air Quality Task Force Final Report 

was issued in November, 2007 and includes 

hundreds of options to reduce air pollution. 

The air quality regulators in the area continue to use the report to develop air quality 

management strategies for the Four Corners 

region.

Climate Change

The Climate Friendly Parks Program was 

funded through July 2009 via an interagency agreement between the National 

Park Service and the EPA. NPS assumes full 

funding for the program in August 2009. The 

program encourages and enables national 

parks to develop strategies to reduce their 

greenhouse gas emissions. The program also 

entails a commitment on the part of participating parks to educate the public about 

what actions the park is taking to mitigate 

emissions. Over 89 parks are participating in the program and more are gearing 

up to ‘do their part.’ NPS interpreters have 

been working in partnership with National 

Aeronautics and Space Administration and 

other scientists to develop climate change 

training materials and interpretive products such as brochures and exhibits. NPS, 

in cooperation with EPA, Bureau of Land 

Management, Fish and Wildlife Service, U.S. 

Forest Service, the National Aeronautics 

and Space Administration, the National 

Oceanic and Atmospheric Administration, 

and the U.S. Geological Survey, developed a 

product entitled Climate Change: Wildlife & 

Wildlands, a Toolkit for Formal and Informal 

Educators. The new kit is designed for classroom teachers and for informal educators in 

parks, refuges, forest lands, nature centers, 
 National Park Service 29

zoos, aquariums, science centers, etc., and is 

designed for the middle school level. The kit 

will aid educators in teaching how climate 

change is affecting our nation’s wildlife and 

public lands, and how everyone can become 

“climate stewards.” The toolkit is available 

online at http://www.globalchange.gov/

resources/educators/toolkit. 

The information, expertise and management concerns that the NPS brings to many 

external decision making arenas have made a 

difference in the past and will continue to in 

the future. 

Group photo from a Western Regional Air Partnership meeting, Glacier National Park, Montana. 

The NPS participates in this regional haze planning group along with other federal land managers, 

federal agencies, states, and tribes. 
30 Air Quality in National Parks–2008

Conclusion

An examination of available trend data in and near National Park Service 

units suggests that progress is being made in some areas of park air 

quality. 

Sulfate concentrations in deposition are 

trending lower in many areas, and no statistically significant increasing trends were 

found. Nitrate concentrations in deposition also appear to be trending downward, 

particularly at eastern monitoring stations 

over the last 10 years. Visibility on the best 

days is also improving in many areas, and 

conditions are remaining stable or improving on the worst days in most areas. Ozone 

concentrations are trending downward at 

many areas, particularly in the East over the 

last 10 years.

Despite these improvements there are 

significant challenges remaining. Ammonium concentrations in wet deposition are 

trending higher in many areas, particularly 

in the West. Ozone concentrations are also 

trending higher in some areas in the West 

over the last 10 years. In addition, ambient 

ozone concentrations remain near or above 

the standard at many locations. Some parks 

in more remote areas such as Great Basin 

and Mesa Verde are experiencing surprisingly high ozone concentrations. Ozone 

exposures are also high at many parks, 

creating the potential for harmful impacts to 

ozone sensitive species. Visibility is impaired 

to some degree at all units where it is being 

measured, and remains considerably higher 

than the target natural conditions in many 

places, particularly on the haziest days. Furthermore, conditions estimates at park units 

across the country show quite a few parks 

where conditions for ozone, visibility, and 

deposition are of significant concern, and 

relatively few that are considered to be in 

good condition. The National Park Service 

will continue its work to understand the 

causes of air quality impairment at its units, 

and maintain its collaborative efforts with 

states and other agencies in order to improve 

park air quality.
 National Park Service 31

The National Park Service (NPS) recently completed the FY 2008 performance assessment for the Servicewide air quality 

program as required by GPRA. The NPS evaluates performance based on a few air quality goals established by the NPS.

Long Term NPS Air Quality Goal

The NPS Strategic Plan establishes the following air quality goals for reporting parks to meet by September 30, 2012:

•	 Ia3A--visibility in 95% of NPS reporting parks has remained stable or improved; 

•	 Ia3B--ozone in 89% of NPS reporting parks has remained stable or improved; 

•	 Ia3C--atmospheric deposition in 79% of NPS reporting parks has remained stable or improved.

Intermediate goals have been established for each of the years from FY 2008 through FY 2011. The FY 2008 target percentages are 95 percent for goal Ia3A, 85 percent for goal Ia3B, and 75 percent for goal Ia3C. All three goals were met or exceeded 

for FY 2008.

NPS Goal Ia3 Performance Indicators

Determining progress toward meeting NPS Goal Ia3 requires an assessment whether park air quality is stable or improving. 

Assessing performance for this goal is based on a 10-year trend of three performance indicators: visibility, atmospheric deposition, and ozone. Six measures are used to assess performance under the three indicators. 

Visibility: Two measures are used to assess this indicator. Particle measurements made at or near 147 NPS units were used 

to calculate the annual reconstructed atmospheric extinction in deciviews for both clear and hazy days. (Extinction depends 

on the mass and chemical composition of the particles and is a quantitative measure of how the passage of light through the 

atmosphere is affected by air pollutants.) The visibility goal Ia3A was met at 99 percent of reporting parks in FY 2008.

Ozone: This goal is evaluated by determining the 10-year trend in the 3-year average of the annual 4th-highest 8-hour ozone 

concentration, which is the statistic used for the National Ambient Air Quality Standard for ozone. Ozone measurements 

made in or near 161 parks were used to evaluate this measure. The ozone goal Ia3B was met at 94 percent of reporting parks 

in FY 2008.

Atmospheric Deposition: Three measures were used to assess this goal. Annual precipitation-weighted means of sulfate, 

nitrate, and ammonium ion concentrations at or near 58 NPS areas were trended to gauge air quality for this indicator. 

Changes in ammonium ion concentration in precipitation were included in the wet deposition indicator beginning in 2004 

because ammonium contributes to total nitrogen deposition and data indicate that ammonium concentrations are increasing 

at a faster rate than nitrate ion concentrations alone. The atmospheric deposition goal Ia3C was met at 83 percent of reporting parks in FY 2008.

Significance Levels Refined: The method used to determine statistical significance of trends was modified to use a value 

more commonly used in the literature. In past trend reporting, we had used a significance level of 0.15, meaning there was a 

15 percent chance that we could wrongly conclude that there was a trend when in fact the change was due to chance. We decided to change the significance level to 0.05, which is commonly used by many researchers. This reduces the chance that we 

would incorrectly conclude that there is a trend from 15 percent to 5 percent. 

Calculating Progress: To calculate the service-wide percentages to compare with the air quality goals, we first performed a 

trend analysis for each of the above six air quality measures (2 visibility, 1 ozone, and 3 atmospheric deposition) over a tenyear period. The FY2008 analysis used 1998-2007 data and required each monitoring site to have a minimum of six years of 

data in this 10-year period. Calendar year 2008 data were not used in this FY2008 analysis because all of that year’s data were 

not available. There is typically at least a three to six month lag between the time the data are collected in the field and when 

they are validated and available for analysis. Our trend time period is a sliding 10-year window and will change to 1999-2008 

for next year’s analysis. A sliding 10-year trend window was chosen rather than a variable length trend from a single fixed 

Appendix A: GPRA Goal Assessment Methodology

FY 2008 Annual Performance Report: Government Performance and 

Results Act (GPRA)Air Quality Goals Ia3A, Ia3B, and Ia3C 
32 Air Quality in National Parks–2008

baseline year because individual parks began monitoring in different years and thus there is no individual fixed baseline year 

that can be applied to all parks. Trends were computed using a non-parametric technique that does not require any assumptions about the distribution of the data. This method was described by Theil (1950). In this method all possible ordered pairs 

of points are compared and the differences are computed. Each positive difference is recorded as a +1, each negative difference is recorded as a -1, and the sum of the +1 and +1 values is computed. This sum is then used to determine the probability 

that the observed differences could have occurred by chance as a result of random fluctuations in the time series. The EPA 

has also used this method to determine trends in air quality data (see http://www.epa.gov/visibility/report/APPd.pdf). 

A few parks operate more than one ozone, visibility, or deposition monitor. We considered data from all monitoring sites at a 

park and if, for example, any one of the ozone monitors at a park showed a statistically significant degrading trend, the park 

was considered as not meeting the goal for that measure. In past years’ analyses, the same park monitoring site was used for 

the trend analysis, even if other park site monitoring data were available. Initially when the GPRA air quality goal reporting 

started, we chose to use the park monitoring site with the longest period of data collection. Monitoring at parks with multiple 

sites has occurred long enough for there to be more than one park monitor that can be used for trend analysis. In addition, 

some park units that do not have monitors within their borders have more than one nearby monitor with sufficient data for 

trend analysis. Here also if one of the nearby monitors indicated a degrading trend we chose that monitor to represent the 

park unit in this report. In all cases if a monitor exists within a park for a particular measure and that monitor has sufficient 

data for trending we chose the in-park monitor over any nearby monitors.

In this report, we include information from deposition or ozone monitors within 10 miles of the boundary of that park. For 

a particulate (visibility) monitor, we required that it lie within 100 km (approximately 60 miles) of a park unit and within 130 

meters in elevation of the park’s minimum or maximum elevation in order to be considered representative of that park. This 

is consistent with the Interagency Monitoring for Visual Environments (IMPROVE) program, which considers IMPROVE 

monitors within 100 km of a Class I area to be representative of that area for monitoring progress under the Regional Haze 

Rule program. In some cases where parks do not have monitors within their borders and are located very close together, 

particularly in urban areas, these parks have been grouped together and represented by a single nearby monitor. These areas 

include the San Francisco, Washington D.C., Boston, New York City, Philadelphia, and Baltimore metropolitan areas. They 

also include the following non-urban parks: Charles Pinckney National Historic Site and Fort Sumter National Monument; 

Eisenhower National Historic Site and Gettysburg National Military Park; the parks included in the North Cascades Complex (North Cascades National Park, Lake Chelan National Recreation Area, and Ross Lake National Recreation Area); Fort 

Washington and Piscataway Parks; and Fort Caroline National Memorial and Timucuan Ecological and Historic Preserve.

A park is considered to have improving or stable air quality for each of the three measures if none of the trends used to assess that measure shows a statistically significant degrading trend. This means that for a park to be assessed as have stable or 

improving air quality with respect to visibility it must have stable or improving trends on both the clearest and haziest days. 

In addition, for a park to be considered to have met the air quality goal for atmospheric deposition it must have stable or 

improving trends for deposition of nitrate, ammonium, and sulfate. The tabulated values (Appendix B) include the slope or 

change in the measure per year and a level of statistical significance (p-value). Slopes with p values at 0.05 or less are considered statistically significant. The number of NPS areas not showing statistically significant deterioration in each of the 

performance indicators at the 0.05 level of significance is divided by the total number of NPS units with monitoring in that 

indicator to calculate a system-wide percentage. The three resulting percentages are then compared to the target percentages 

for the three GPRA goals.

References 

Kendall, M. G. and J. D. Gibbons. 1990. Rank Correlation Methods. 5th ed. Edward Arnold: London. 

Thiel, H. 1950. A rank-invariant method of linear and polynomial regression analysis, III. Proceedings of the Koninklijke Nederlandse Akademie van Wetenschappen A 53: 1397–1412. 
 National Park Service 33

Individual Park 1998-2007 Trend Results

Park

Visibility Atmospheric Deposition Ozone

Clear Days Hazy Days Ammonium Nitrate Sulfate

Average 3-Yr 4th 

High 8-Hour

dv/yr p-value dv/yr p-value

μeq/liter 

/yr p-value

μeq/liter 

/yr p-value

μeq/liter 

/yr p-value ppb/yr p-value

Abraham Lincoln Birthplace 0.01 0.54 0.05 0.24

Acadia -0.11 <0.01 -0.08 0.15 0.09 0.18 -0.50 0.022 -0.44 0.18 -0.71 0.19

Allegheny Portage Railroad - -2.38 <0.01

Antietam 0.01 0.46 -0.14 0.24 -1.60 0.068

Appalachian 0.10 0.14 0.10 0.36 0.43 0.054 -0.02 0.36 0.65 0.19 0.57 0.11

Appomattox Court House -0.10 0.50 -0.17 0.39

Arches -0.20 <0.01 -0.08 0.19

Aztec Ruins -1.50 0.028

Badlands -0.07 0.11 -0.15 0.15

Baltimore Metropolitan 

Area Parks 0.01 0.46 -0.14 0.24 -1.20 <0.01

 Fort McHenry

 Hampton

Bandelier -0.15 <0.01 -0.18 0.36 0.10 0.54 -1.01 0.060 -0.71 0.038

Bent’s Old Fort 1.09 0.11 -0.11 0.36 0.04 0.50

Big Bend -0.29 0.038 -0.28 0.060 -0.24 0.38 -0.52 0.09 -0.37 0.18 -0.29 0.24

Big Cypress 0.33 0.12 -0.30 0.50

Big Hole -0.07 0.23 2.03 0.23

Big Thicket -0.86 0.15

Biscayne 0.33 0.12 -0.30 0.50 -0.67 0.15

Appendix B: Table of Trend Results, 1998–2007

Trends in individual park air quality, for 1998-2007, are shown below. Data used to calculate these 

trends came from air quality monitors that are inside park boundaries, within 10 miles of parks (for 

ozone and deposition), and within 100 kilometers of parks (for visibility). Red indicates a degrading trend and blue indicates an improving trend. Statistically significant trends, shown with solid 

backgrounds, have at least a 95% probability that they did not occur by chance (p-values <=0.05). 

Also shown are trends that have an 85% to 95% probability that they did not occur by chance (pvalues from 0.05 to 0.15); these trends are are indicated by colored outlines.

Degrading air quality trend, 

statistically significant (p <= 0.05)

Degrading air quality trend, 

not statistically significant (0.05 < p <= 0.15)

Improving air quality trend, 

statistically significant (p <= 0.05)

Improving air quality trend, 

not statistically significant (0.05 < p <= 0.15)
34 Air Quality in National Parks–2008

Individual Park 1998-2007 Trend Results

Park

Visibility Atmospheric Deposition Ozone

Clear Days Hazy Days Ammonium Nitrate Sulfate

Average 3-Yr 4th 

High 8-Hour

dv/yr p-value dv/yr p-value

μeq/liter 

/yr p-value

μeq/liter 

/yr p-value

μeq/liter 

/yr p-value ppb/yr p-value

Black Canyon Of The 

Gunnison -0.13 <0.01 -0.10 0.24

Blue Ridge 0.10 0.14 0.13 0.18 -1.29 <0.01

Booker T Washington -0.10 0.50 -0.17 0.39

Boston Metropolitan Area 

Parks -0.20 0.23 -0.25 0.23 0.13 0.38 -0.51 0.18 -1.11 0.060 -0.80 0.28

 Adams

 Boston African 

 American

 Boston Harbor Islands

 Boston

 Frederick Law Olmsted

 John F Kennedy

 Longfellow

 Minute Man

 Saugus Iron Works

Bryce Canyon -0.13 <0.01 0.13 0.19 0.62 0.14 -0.21 0.36 -0.42 0.054

Buffalo 0.08 0.36 -0.10 0.30 0.25 0.31 -0.29 0.038 -0.40 0.038

Canaveral -0.10 0.31 -0.31 0.060 -0.54 0.038

Canyonlands -0.20 <0.01 -0.08 0.19 0.60 0.038 -0.04 0.54 -0.13 0.24 -0.13 0.24

Cape Cod -0.20 0.23 -0.25 0.23 -1.33 0.014

Capitol Reef -0.13 <0.01 0.13 0.19

Capulin Volcano 0.78 0.015 -0.23 0.50 0.08 0.28

Carlsbad Caverns -0.13 <0.01 -0.20 0.15

Catoctin Mountain -0.37 0.14 -0.43 0.14

Cedar Breaks -0.13 <0.01 0.13 0.19

Central High School 0.43 0.15

Chamizal -0.56 0.078

Channel Islands -1.00 0.023

Charles Pinckney/

Fort Sumter -0.02 0.54 -0.13 0.46

 Charles Pinckney

 Fort Sumter

Chattahoochee River -1.14 0.054

Chesapeake & Ohio Canal 0.01 0.46 -0.14 0.24 -0.14 0.45
 National Park Service 35

Individual Park 1998-2007 Trend Results

Park

Visibility Atmospheric Deposition Ozone

Clear Days Hazy Days Ammonium Nitrate Sulfate

Average 3-Yr 4th 

High 8-Hour

dv/yr p-value dv/yr p-value

μeq/liter 

/yr p-value

μeq/liter 

/yr p-value

μeq/liter 

/yr p-value ppb/yr p-value

Chiricahua -0.13 0.014 -0.10 0.15 1.72 <0.01 0.63 0.19 0.06 0.50 0.33 <0.01

Congaree -1.50 0.028

Cowpens -2.60 <0.01

Crater Lake -0.10 <0.01 -0.28 0.20

Craters Of The Moon -0.23 0.12 0.05 0.50 0.64 0.054 -0.15 0.15 0.08 0.43 0.25 0.19

Cumberland Gap 0.11 0.38 -0.80 0.012 -1.29 0.18 -1.43 0.054

Cumberland Island -0.12 0.15 -0.07 0.15

Curecanti -0.13 <0.01 -0.10 0.24

Cuyahoga Valley -1.00 0.054

Dayton Aviation Heritage -2.00 <0.01

De Soto 0.00 0.50

Death Valley -0.06 0.068 0.02 0.50 0.43 <0.01

Delaware Water Gap -0.12 0.36 -0.97 <0.01 -0.99 0.11

Denali -0.10 0.11 0.00 0.57 -0.04 0.43 -0.08 0.30 0.10 0.24 0.00 0.43

Eleanor Roosevelt -1.83 0.078

Eugene O’Neill -0.21 <0.01 0.15 0.45 -1.00 <0.01

Everglades 0.33 0.12 -0.30 0.50 0.30 0.13 0.11 0.38 -0.11 0.38

Fire Island -2.00 0.068

First Ladies -0.14 0.23 -0.04 0.50 -1.29 0.036

Fort Bowie -0.13 0.014 -0.10 0.15 1.72 <0.01 0.63 0.19 0.06 0.50 0.33 <0.01

Fort Donelson -0.10 0.36 0.35 0.23

Fort Frederica -0.12 0.15 -0.07 0.15 -1.50 <0.01

Fort Pulaski -1.00 0.023

Fort Union Trading Post -0.20 0.054 0.20 0.20

Fort Vancouver 0.00 0.43

Fredericksburg 

& Spotsylvania 0.01 0.46 -0.14 0.24 -1.33 <0.01

Friendship Hill -1.67 0.14

George Rogers Clark 0.21 0.31 -0.54 <0.01 -0.53 0.24 -1.40 <0.01

George Washington 

Birthplace 0.01 0.46 -0.14 0.24

Gettysburg/Eisenhower -0.37 0.14 -0.43 0.14 -0.15 0.38 -1.81 <0.01 -1.17 0.090 -1.75 0.036

 Eisenhower

 Gettysburg
36 Air Quality in National Parks–2008

Individual Park 1998-2007 Trend Results

Park

Visibility Atmospheric Deposition Ozone

Clear Days Hazy Days Ammonium Nitrate Sulfate

Average 3-Yr 4th 

High 8-Hour

dv/yr p-value dv/yr p-value

μeq/liter 

/yr p-value

μeq/liter 

/yr p-value

μeq/liter 

/yr p-value ppb/yr p-value

Gila Cliff Dwellings -0.20 <0.01 -0.13 0.38 0.36 0.12 -0.03 0.50 -0.70 0.068

Glacier -0.12 0.089 -0.15 0.20 0.21 0.15 -0.12 0.30 -0.14 0.078 1.00 <0.01

Glen Canyon -0.02 0.55 0.00 0.55

Grand Canyon -0.02 0.55 0.00 0.55 0.27 0.36 -0.08 0.55 -0.11 0.45 0.00 0.24

Grand Teton -0.07 0.060 0.00 0.50

Grant-Kohrs Ranch -0.28 0.068 0.20 0.28

Great Basin -0.20 <0.01 -0.03 0.43 0.44 0.07 -0.20 0.50 -0.03 0.50 0.00 0.43

Great Egg Harbor River 0.08 0.18 0.07 0.46 -2.00 <0.01

Great Sand Dunes -0.13 0.014 -0.15 0.11

Great Smoky Mountains -0.13 0.11 -0.14 0.078 0.19 0.30 -0.29 0.054 -0.22 0.36 -1.67 <0.01

Guadalupe Mountains -0.13 <0.01 -0.20 0.15 -0.24 0.13 -0.71 0.038 -1.69 <0.01

Gulf Islands -1.13 0.023

Haleakala -0.02 0.50 0.10 0.28

Harpers Ferry 0.01 0.46 -0.14 0.24

Harry S Truman -1.00 0.14

Hawaii Volcanoes -0.13 0.39 0.87 0.015

Hohokam Pima -1.00 0.14

Home Of Franklin D 

Roosevelt -1.83 0.078

Indiana Dunes 0.22 0.15 -0.70 0.11 -0.97 0.11 -1.50 <0.01

Isle Royale -0.10 0.14 0.06 0.45 0.41 0.27 -0.38 0.14 -0.32 0.20

James A Garfield -1.25 <0.01

Jean Lafitte 0.00 0.50

Jefferson 0.20 0.24

John D Rockefeller Jr -0.07 0.060 -0.13 0.24

John Muir -0.21 <0.01 0.15 0.45 -0.75 0.078

Johnstown Flood -2.43 <0.01

Joshua Tree -0.10 0.19 -0.33 0.068 -0.75 0.36

Kalaupapa -0.02 0.50 0.10 0.28

Kennesaw Mountain -2.80 0.068

Keweenaw -0.10 0.14 0.06 0.45 0.41 0.27 -0.38 0.14 -0.32 0.20

Knife River Indian Villages -0.25 0.24

Lake Clark 0.00 0.64 -0.40 0.23

Lake Mead 0.00 0.57
 National Park Service 37

Individual Park 1998-2007 Trend Results

Park

Visibility Atmospheric Deposition Ozone

Clear Days Hazy Days Ammonium Nitrate Sulfate

Average 3-Yr 4th 

High 8-Hour

dv/yr p-value dv/yr p-value

μeq/liter 

/yr p-value

μeq/liter 

/yr p-value

μeq/liter 

/yr p-value ppb/yr p-value

Lassen Volcanic -0.13 0.078 -0.18 0.30 -1.00 0.036

Lava Beds -0.10 0.28 -0.45 0.12

Lincoln Home -0.71 0.023

Little Bighorn Battlefield -0.14 0.19 -0.46 <0.01 -0.29 0.036

Mammoth Cave 0.01 0.54 0.05 0.24 -3.00 <0.01

Manassas 0.01 0.46 -0.14 0.24 -1.40 <0.01

Martin Luther King Jr -2.40 0.023

Mesa Verde -0.17 <0.01 -0.09 0.30 0.25 0.036 -0.40 0.30 -0.73 0.014 0.67 0.023

Minuteman Missile -0.07 0.11 -0.15 0.15 0.80 0.19 -0.21 0.36 -0.42 0.036

Mississippi -0.33 0.24

Mojave -0.10 0.19 -0.33 0.068

Monocacy 0.01 0.46 -0.14 0.24 -1.80 <0.01

Morristown -1.50 0.078

Mount Rainier -0.09 0.18 -0.50 <0.01 0.11 <0.01 0.08 0.39 -0.35 0.035 0.75 0.11

Mount Rushmore -0.13 0.089 0.06 0.36

Natchez -1.00 <0.01

Natchez Trace -0.20 0.14 0.10 0.36 -0.17 0.15 -0.09 0.36 -0.47 0.036 -1.00 <0.01

Natural Bridges -0.20 <0.01 -0.08 0.19

New Bedford Whaling -0.20 0.23 -0.25 0.23 -1.00 0.036

New York Metropolitan 

Area Parks 1.00 0.39

 African Burial Ground

 Castle Clinton

 Edison

 Federal Hall

 Gateway

 General Grant

 Governors Island

 Hamilton Grange

 Saint Paul’s Church

 Statue Of Liberty

 Theodore Roosevelt

 Birthplace

Nez Perce -0.07 0.23 2.03 0.23
38 Air Quality in National Parks–2008

Individual Park 1998-2007 Trend Results

Park

Visibility Atmospheric Deposition Ozone

Clear Days Hazy Days Ammonium Nitrate Sulfate

Average 3-Yr 4th 

High 8-Hour

dv/yr p-value dv/yr p-value

μeq/liter 

/yr p-value

μeq/liter 

/yr p-value

μeq/liter 

/yr p-value ppb/yr p-value

North Cascades Complex -0.07 0.39 -0.04 0.50 0.02 0.36 -0.10 0.19 -0.14 0.036 0.75 0.023

 Lake Chelan

 North Cascades

 Ross Lake

Ocmulgee -3.23 <0.01

Olympic -0.10 0.14 -0.40 0.028 -0.03 0.39 0.06 0.015 -0.07 0.50

Organ Pipe Cactus 0.17 0.45 -0.49 0.36 -0.11 0.45

Palo Alto Battlefield 0.00 0.43

Pecos -0.15 <0.01 -0.18 0.36

Petersburg -1.50 0.014

Petrified Forest -0.10 0.054 0.00 0.57

Petroglyph 0.00 0.36

Philadelphia Metropolitan 

Area Parks 0.08 0.18 0.07 0.46 -1.13 0.15

 Edgar Allan Poe

 Independence

 Thaddeus Kosciuszko

Pictured Rocks 0.03 0.36 0.26 0.089

Pinnacles -0.20 0.031 -0.14 0.14 0.08 0.36 -0.04 0.50 0.04 0.36 -1.00 <0.01

Piscataway/

Fort Washington -0.14 0.45

 Fort Washington

 Piscataway

Point Reyes -0.21 <0.01 0.15 0.45

Prince William Forest 0.01 0.46 -0.14 0.24 -0.75 0.014

Redwood -0.11 0.078 -0.10 0.30

Richmond -1.38 <0.01

Rocky Mountain -0.10 0.036 -0.05 0.36 0.45 0.19 0.01 0.50 -0.26 0.11 0.33 0.15

Roger Williams 0.17 0.36

Sagamore Hill -1.00 0.054

Saguaro -0.07 0.50 -0.17 0.23 0.33 0.19

Saint Croix -0.94 0.031 -1.04 0.031 -0.80 0.031 -0.50 0.24

Saint Croix Island -0.13 0.023 -0.10 0.19

Saint-Gaudens 0.00 0.57
 National Park Service 39

Individual Park 1998-2007 Trend Results

Park

Visibility Atmospheric Deposition Ozone

Clear Days Hazy Days Ammonium Nitrate Sulfate

Average 3-Yr 4th 

High 8-Hour

dv/yr p-value dv/yr p-value

μeq/liter 

/yr p-value

μeq/liter 

/yr p-value

μeq/liter 

/yr p-value ppb/yr p-value

Salem Maritime -0.20 0.23 -0.25 0.23 -0.78 0.054

San Antonio Missions -0.45 0.054

San Francisco Bay Area 

Parks -0.21 <0.01 0.15 0.45 0.25 0.036

 Fort Point

 Golden Gate

 Muir Woods

 Rosie the Riveter 

 WWII Home Front

 San Francisco Maritime

Santa Monica Mountains 1.80 0.15

Saratoga 0.00 0.57

Sequoia & Kings Canyon -0.14 0.19 -0.13 0.28 0.00 0.57

Shenandoah -0.05 0.38 0.13 0.18 -0.18 0.36 -0.54 0.14 -1.22 0.089 -2.00 <0.01

Sleeping Bear Dunes -0.61 0.14 -1.45 0.028 -0.91 0.068 -1.00 <0.01

Springfield Armory 0.00 0.50

Steamtown -1.60 <0.01

Sunset Crater Volcano -0.02 0.55 0.05 0.39

Theodore Roosevelt -0.30 <0.01 0.10 0.50 0.40 0.39 -0.26 0.39 -0.06 0.50 0.00 0.36

Theodore Roosevelt 

Inaugural 0.17 0.43

Thomas Stone 0.01 0.46 -0.14 0.24

Timpanogos Cave -1.00 <0.01

Timucuan/Fort Caroline -0.12 0.15 -0.07 0.15 -0.25 0.36

 Fort Caroline

 Timucuan

Tonto -0.15 0.031 -0.10 0.27

Tumacácori -0.07 0.50 -0.17 0.23

Tupelo -2.25 <0.01

U S S Arizona -0.83 <0.01

Ulysses S Grant -1.13 0.089

Upper Delaware -0.12 0.36 -0.97 <0.01 -0.99 0.11

Valley Forge -1.50 <0.01

Vanderbilt Mansion -1.83 0.078

Virgin Islands 0.07 0.24 -0.07 0.31 0.08 0.46
40 Air Quality in National Parks–2008

Individual Park 1998-2007 Trend Results

Park

Visibility Atmospheric Deposition Ozone

Clear Days Hazy Days Ammonium Nitrate Sulfate

Average 3-Yr 4th 

High 8-Hour

dv/yr p-value dv/yr p-value

μeq/liter 

/yr p-value

μeq/liter 

/yr p-value

μeq/liter 

/yr p-value ppb/yr p-value

Voyageurs -0.07 0.20 0.10 0.27 -0.40 0.054

Walnut Canyon -0.20 0.39 0.05 0.39

Washington Metropolitan 

Area Parks 0.01 0.46 -0.14 0.24 -0.14 0.45

 Arlington House

 Carter G. Woodson

 Home

 Clara Barton

 Ford’s Theatre

 Frederick Douglass

 Greenbelt

 George Washington

 Lyndon Baines Johnson

 Mem. Grove

 Mary McLeod Bethune

 Council House

 National Mall 

 & Memorial Parks

 National Mall

 Pennsylvania Avenue

 Rock Creek

 Theodore Roosevelt

 Island

 Washington

 President’s Park 

 (White House)

 Wolf Trap

Weir Farm -0.67 0.11

Whiskeytown -0.13 0.078 -0.18 0.30 -2.13 0.023

William Howard Taft -1.00 0.07

Wilson’s Creek 0.00 0.64 -0.20 0.14

Wind Cave -0.13 0.089 0.06 0.36

Yellowstone -0.07 0.060 -0.13 0.24 0.72 0.022 0.06 0.46 0.14 0.13 -0.25 0.19

Yosemite -0.09 0.24 -0.08 0.43 0.02 0.45 -0.36 0.054 -0.10 0.27 0.00 0.50

Zion -0.13 <0.01 0.13 0.19
 National Park Service 41

To assess condition, we first used all available monitoring data over the period 2003-2007 to generate interpolations for the 

continental United States. Monitors used included NPS, EPA, state, tribal, and local monitors. These interpolations allowed 

us to derive estimates of the air quality parameters at NPS units located within the continental United States, including those 

without on-site monitoring. (Since there were not sufficient monitors to generate interpolations outside the continental US, 

on-site monitoring data were used to derive the condition category estimates for Denali, Virgin Islands, Hawaii Volcanoes, 

and Haleakala.) We then used these interpolated values to determine an index for each type of air quality data collected 

(ozone concentrations, wet deposition concentrations, and visibility) that assigns the park to one of three condition categories:

 Condition Red: Air Quality is a Significant Concern

Condition Yellow: Air Quality is in Moderate Condition

Condition Blue: Air Quality is in Good Condition

The interpolated values were then used to assign parks to condition categories using the following procedures.

Visibility Condition 

Individual park scores for visibility were based on the deviation of the current Group 50 visibility conditions from estimated 

Group 50 natural visibility conditions1

, where Group 50 is defined as the mean of the visibility observations falling within the 

range from the 40th through the 60th percentiles. For parks within the continental US, current visibility was estimated from 

the interpolation of the five-year averages of the Group 50 visibility. For sites outside the continental US, five-year averages 

were computed from on-site data. Visibility in this calculation is expressed in terms of a haze index2

 in deciviews (dv). As the 

haze index increases, the visibility worsens. The visibility condition is expressed as:

Visibility Condition = current Group 50 visibility – estimated Group 50 visibility under natural conditions

Condition Blue was assigned to parks with a visibility condition 

estimate of less than two dv above estimated natural conditions. 

Parks with visibility condition estimates ranging from two to eight 

dv above natural conditions were considered to be in moderate 

condition, and parks with visibility condition estimates greater than 

eight dv above natural conditions were considered to have a significant concern. The dv ranges of these categories, while somewhat 

subjective, were chosen to reflect as nearly as possible the variation 

in visibility conditions across the monitoring network.

Atmospheric Deposition Condition

Park scores for current condition of atmospheric deposition were based on wet deposition because dry deposition data was 

not available for most areas. Wet deposition for sites within the continental US was calculated by multiplying nitrogen (N) or 

sulfur (S) concentrations in precipitation by a normalized precipitation amount.3

 (For sites outside the continental US, where 

interpolations could not be calculated and normalized precipitation amounts were not available, five-year averages of on-site 

deposition were used. Deposition data were obtained from the National Atmospheric Deposition Program.) Several factors 

were considered in rating deposition condition, including natural background deposition estimates and deposition effects on 

ecosystems. Estimates of natural background deposition for total deposition are approximately 0.25 kilograms per hectare 

per year (kg/ha/yr) in the West and 0.50 kg/ha/yr in the East for either N or S. For wet deposition only, this is roughly equivalent to 0.13 kg/ha/yr in the West and 0.25 kg/ha/yr in the East.4

 Certain sensitive ecosystems respond to levels of deposition 

on the order of 3 kg/ha/yr total deposition, or about 1.5 kg/ha/yr wet deposition.5

1. The natural visibility conditions used in this treatment are those visibility conditions that have been estimated to exist in a given area in the absence of human-caused visibility impairment. These estimates were determined in accordance with with the EPA’s Guidance for Estimating Natural 

Visibility Conditions Under the Regional Haze Rule, EPA-454/B-03-005

2. The Haze Index is a measure of visibility derived from calculated light extinction (EPA-454/B-03-005).

3. Normalized 30-year precipitation values from the PRISM database were used to calculate deposition in order to minimize interannual variation 

in deposition caused by interannual fluctuations in precipitation (http://www.ocs.orst.edu/prism/).

4. The proportion of wet to dry deposition varies by location but, in general, wet deposition is approximately one-half of total deposition.

5. Fenn et al. 2003. BioScience 53: 404-420; Krupa 2002. Environmental Pollution 124: 179-221

Appendix C: Determination of Air Quality Condition

Visibility Condition Difference from Estimated 

Natural Condition (dv)

Red > 8

Yellow 2-8

Blue < 2
42 Air Quality in National Parks–2008

Evidence indicating that wet deposition amounts less than 1 kg/ha/

yr cause ecosystem harm is not currently available. Therefore, parks 

with wet deposition less than 1 kg/ha/yr were considered to be in 

good condition for deposition; parks with 1-3 kg/ha/yr were considered to be in moderate condition; and parks with greater than 3 kg/

ha/yr were considered to have a significant concern for deposition. 

Scores for parks with ecosystems potentially sensitive to N or S6

 were 

adjusted up one category (e.g., a park with N deposition from 1-3 kg/

ha/yr that contains N-sensitive ecosystems was assigned the condition “red”).

Ozone Condition

The ozone standard was used as a benchmark for rating current ozone air quality. This standard was revised in 2008 in order 

to be more protective of human health. To attain this standard, the 3-year average of the fourth-highest daily maximum 

8-hour average ozone concentrations measured at each monitor within an area over each year must not exceed 75 parts per 

billion (ppb). To derive an estimate of the current ozone condition at parks, the five-year average of the annual 4th-highest 

8-hour ozone concentration was determined for each park from the interpolated values described above. If the resulting 

five-year average was greater than or equal to 76 ppb then Condition Red was assigned to that park. Condition Yellow for 

ozone was assigned to parks with average five-year 4th-highest 8-hour ozone concentrations from 61 to 75 ppb (concentrations greater than 80 percent of the standard). Condition Blue for ozone was assigned to parks with average five-year ozone 

concentrations less than 61 ppb (concentrations less than 80 percent of the standard).

In addition to the standard, vegetation sensitivity was considered for park 

condition. Data show that some plant species7

 are more sensitive to ozone 

than humans and the ozone standard is not protective of some vegetation. 

Ozone injury to vegetation has been documented at a number of parks, 

including Great Smoky Mountains NP, Shenandoah NP, and Sequoia/

Kings Canyon NPs. A risk assessment completed in 2004 rated parks at low, 

moderate, or high risk for ozone injury to vegetation, based on presence of 

sensitive plant species, ozone exposures8

, and environmental conditions, i.e., 

soil moisture. For this report, parks that were evaluated at high risk were 

moved into the next condition category (e.g., a park with an average ozone 

concentration of 72 ppb, but judged to be at high risk for vegetation injury, 

would move from the category “yellow” for ozone to “red”).

6. Ecosystems that are considered potentially sensitive to N or S deposition include high-elevation ecosystems in the West, upland areas in the 

East, areas on granitic bedrock, coastal and estuarine waters, arid ecosystems, and some grasslands.

7. Lists of ozone sensitive species, by park, are available from NPSpecies (https://science1.nature.nps.gov/npspecies/).

8. The ozone risk assessment for injury to vegetation was based on ozone exposures over the growing seasons from 1995-1999. The ozone exposure metrics are described in the ozone risk assessments at http://www2.nature.nps.gov/air/Pubs/ozonerisk.htm.

.

Ozone Condition Ozone concentration

Red ≥ 76 ppb

Yellow 61-75 ppb

Blue ≤ 60 ppb

Nitrogen/Sulfur 

Deposition Condition Wet Deposition (kg/ha/yr)

Red > 3

Yellow 1-3

Blue < 1
 National Park Service 43

Air Quality Condition Air Quality Trend

Red–Significant Concern Degrading

Yellow–Moderate Concern Stable

Blue–Good Condition Improving

Visibility 

Nitrogen 

Deposition

Sulfur 

Deposition Ozone

Abraham Lincoln Birthplace

Acadia

Adams

African Burial Ground

Allegheny Portage Railroad

Antietam

Appomattox Court House

Appalachian

Arches

Arlington House

Aztec Ruins

Badlands

Bandelier

Bent's Old Fort

Big Bend

Big Cypress

Big Hole

Biscayne

Big Thicket

Black Canyon Of The Gunnison

Blue Ridge

Boston African American

Boston Harbor Islands

Boston

Booker T Washington

Bryce Canyon

Buffalo

Park

Condition and Trend Symbol
44 Air Quality in National Parks–2008

Visibility 

Nitrogen 

Deposition

Sulfur 

Deposition Ozone

Park

Condition and Trend Symbol

Castle Clinton

Cape Cod

Canaveral

Canyonlands

Capitol Reef

Catoctin Mountain

Carlsbad Caverns

Capulin Volcano

Carter G. Woodson Home

Cedar Breaks

Chamizal

Chattahoochee River

Chiricahua

Channel Islands

Chesapeake & Ohio Canal

Charles Pinckney

Central High School

Clara Barton

Congaree

Cowpens

Crater Lake

Craters Of The Moon

Cumberland Gap

Cumberland Island

Curecanti

Cuyahoga Valley

Dayton Aviation Heritage

Denali

De Soto

Death Valley

Delaware Water Gap

Edgar Allan Poe

Edison
 National Park Service 45

Visibility 

Nitrogen 

Deposition

Sulfur 

Deposition Ozone

Park

Condition and Trend Symbol

Eisenhower

Eleanor Roosevelt

Eugene O'Neill

Everglades

Federal Hall

Fire Island

First Ladies

Fort Bowie

Fort Caroline

Fort Donelson

Fort Frederica

Fort McHenry

Fort Point

Fort Pulaski

Fort Sumter

Ford's Theatre

Fort Union Trading Post

Fort Vancouver

Fort Washington

Frederick Douglass

Friendship Hill

Frederick Law Olmsted

Fredericksburg & Spotsylvania

Gateway

General Grant

George Rogers Clark

Gettysburg

George Washington Birthplace

Gila Cliff Dwellings

Glacier

Glen Canyon

Golden Gate

Governors Island
46 Air Quality in National Parks–2008

Visibility 

Nitrogen 

Deposition

Sulfur 

Deposition Ozone

Park

Condition and Trend Symbol

Great Basin

Grand Canyon

Greenbelt

Great Egg Harbor River

Grant-Kohrs Ranch

Great Sand Dunes

Great Smoky Mountains

Grand Teton

Gulf Islands

Guadalupe Mountains

George Washington

Harpers Ferry

Hamilton Grange

Haleakala

Hampton

Hawaii Volcanoes

Home Of Franklin D Roosevelt

Harry S Truman

Independence

Indiana Dunes

Isle Royale

James A Garfield

Jefferson

Jean Lafitte

John D Rockefeller Jr

John F Kennedy

Johnstown Flood

John Muir

Joshua Tree

Kennesaw Mountain

Keweenaw

Knife River Indian Villages

Lava Beds
 National Park Service 47

Visibility 

Nitrogen 

Deposition

Sulfur 

Deposition Ozone

Park

Condition and Trend Symbol

Lake Chelan

Lake Mead

Lassen Volcanic

Little Bighorn Battlefield

Lincoln Home

Longfellow

Lyndon Baines Johnson Memorial Grove

Mammoth Cave

Martin Luther King Jr

Mary McLeod Bethune Council House

Manassas

Mesa Verde

Minute Man

Minuteman Missile

Mississippi

Mojave

Monocacy

Mount Rainier

Morristown

Mount Rushmore

Muir Woods

Natural Bridges

National Mall & Memorial Parks

National Mall

Natchez

Natchez Trace

New Bedford Whaling

Nez Perce

North Cascades

Ocmulgee

Olympic

Organ Pipe Cactus

Palo Alto Battlefield
48 Air Quality in National Parks–2008

Visibility 

Nitrogen 

Deposition

Sulfur 

Deposition Ozone

Park

Condition and Trend Symbol

Pennsylvania Avenue

Pecos

Petrified Forest

Petersburg

Petroglyph

Hohokam Pima

Pinnacles

Pictured Rocks

Piscataway

Point Reyes

Prince William Forest

Redwood

Richmond

Rock Creek

Ross Lake

Rocky Mountain

Rosie the Riveter WWII Home Front

Roger Williams

San Antonio Missions

Saint Croix

Saint Croix Island

San Francisco Maritime

Saint-Gaudens

Saguaro

Sagamore Hill

Saugus Iron Works

Salem Maritime

Santa Monica Mountains

Saint Paul's Church

Saratoga

Sequoia & Kings Canyon

Shenandoah

Sleeping Bear Dunes
 National Park Service 49

Visibility 

Nitrogen 

Deposition

Sulfur 

Deposition Ozone

Park

Condition and Trend Symbol

Springfield Armory

Steamtown

Statue Of Liberty

Sunset Crater Volcano

Theodore Roosevelt Island

Thaddeus Kosciuszko

Theodore Roosevelt Birthplace

Theodore Roosevelt Inaugural

Theodore Roosevelt

Thomas Stone

Timpanogos Cave

Timucuan

Tonto

Tumacácori

Tupelo

Ulysses S Grant

Upper Delaware

Valley Forge

Vanderbilt Mansion

Virgin Islands

Voyageurs

Walnut Canyon

Washington

Weir Farm

President's Park (White House)

Whiskeytown

Wind Cave

Wilson's Creek

William Howard Taft

Wolf Trap

Yellowstone

Yosemite

Zion
50 Air Quality in National Parks–2008

Appendix D: Ozone W126

Calculation of the Ozone W126 Statistic

In July 2007 the EPA proposed a new secondary ozone standard. The proposed standard was based upon a cumulative sum 

of hourly ozone values, where the hourly values are weighted according to their concentrations. The weighted value is usually referred to as the W126 statistic. Each hourly index value is computed by multiplying the hourly concentration (O3) by 

the weighting function as given by the following equation:

( )















+ ∗ = 126∗− 3 3

44031

1 *126 O

e

OW

The hourly index values are then summed over the daylight hours from 8am to 8pm for each 3-month period during the local 

ozone season. The three-month period with the highest cumulative W126 value is the annual standard-related summary statistic, and it is expressed in ppm-hours. For a month to be valid, it must have hourly ozone values available for at least 75% of 

possible hours. The W126 index is then adjusted for missing hourly data by multiplying it by the ratio of the number of possible hours to the available hours. Months with fewer than 75% of possible hourly ozone measurements are not considered. 
The Department of the Interior protects and manages the nation’s natural resources and cultural heritage; provides scientific and other 

information about those resources; and honors its special responsibilities to American Indians, Alaska Natives, and affiliated Island 

Communities.

NPS 999/100367, September 2009 
National Park Service

U.S. Department of the Interior

Natural Resource Program Center 

Air Resources Division

PO BOX 25287

Denver, Colorado 80225

www.nature.nps.gov/air

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