- On January 7, 2010, the EPA announced on its web site
its proposal to strengthen the national ambient air quality standards
for ground-level ozone. The EPA's proposal decreases the 8-hour
primary ozone standard level, designed to protect
public health, to a level within the range of 0.060-0.070 parts
per million (ppm). EPA is also proposing to establish a distinct
cumulative, seasonal secondary standard, referred
to as the W126 index, which is designed to protect
sensitive vegetation and ecosystems, including forests, parks,
wildlife refuges, and wilderness areas. Dr. Lefohn, A.S.L. &
Associates' President, developed and proposed the W126 index
over 20 years ago as a metric that could be used to protect vegetation
from ozone exposure. EPA is proposing to set the level of the
W126 secondary standard within the range
of 7-15 ppm-hours. The proposed revisions result from a reconsideration
of the identical primary and secondary ozone standards set at
0.075 ppm in March 2008. The EPA accepted written comments until
March 22. The Agency's decision was planned to be made in August
2010. However, on August 20, the Agency announced that it will
delay its announcement to on or around the end of October. For
identifying violating counties for the 2006-2008 period for the
proposed human health and vegetation ozone standards, please
visit our maps webpage. Please note that for the
8-h ozone standard, there will be more counties that violate
the standard than the US EPA has estimated due to the selection
methodology that the Agency utilizes in identifying monattainment
areas. For more information, please join A.S.L. & Associates
in the Discussion area on Facebook.
As part of the
proposed changes to the current 8-hour ozone human health standard,
the EPA estimates that the percentage of violating counties with
monitors for the 0.060, 0.065, and 0.070 ppm thresholds would
be 96%, 90%, and 76%, respectively. For the 3-year average of
the annual maximum 3-month cumulative 12-hour W126 secondary
ozone standard, the EPA estimates that the percentage of violating
counties with monitors for the 7 and 15 ppm-hour thresholds would
be 91% and 31%, respectively.
Some of the
background concerning the events that led to the EPA's Administrator's
decision on revising the 8-hour ozone standard helps in better
understanding the process. On
March 12, 2008, the EPA Administrator announced a decision on
the human health and vegetation ozone standards. At that time,
EPA revised the 8-hour "primary" ozone standard, designed
to protect public health, to a level of 0.075 parts per million
(ppm). The previous standard, set in 1997, was 0.08 ppm. EPA
decided not to adopt the cumulative exposure index as the vegetation
standard (i.e., secondary ozone standard). Although the EPA Administrator
recommended the W126 index as the secondary ozone standard,
based on advice from the White
House (Washington
Post, April 8, 2008; Page D02), the EPA Administrator made the
secondary ozone standard the same as the primary 8-hour average
standard (0.075 ppm). On May 27, 2008, health and environmental
organizations filed a lawsuit arguing that the EPA failed to
protect public health and the environment when it issued in March
2008 new ozone standards. On March 10, 2009, the US EPA requested
that the Court vacate the existing briefing schedule and hold
the consolidated cases in abeyance. EPA requested the extension
to allow time for appropriate EPA officials that are appointed
by the new Administration to review the Ozone NAAQS Rule to determine
whether the standards established in the Ozone NAAQS Rule should
be maintained, modified, or otherwise reconsidered. On September
16, 2009, the EPA announced it would reconsider the 2008 national
ambient air quality standards (NAAQS) for ground-level ozone
for both human health and environmental effects. The Agency planned
to propose any needed revisions to the ozone standards by December
2009 and issue a final decision by August 2010. In December,
the EPA changed its announcement date to January 6, 2010.
- The range of suggested
values for the W126 standard is mainly based on the recommendations
that were made at a Workshop that took place in Raleigh, North
Carolina in 1996. To better understand what took place at this
workshop, please click here. The EPA recommends an accumulation
over a 12-hour (8 am 8 pm) exposure period over a 3-month
period giving greater weight to exposures at higher levels of
ozone. Our analyses and peer-reviewed published papers indicate
that such a secondary
ozone standard, in the proposed form, would overestimate vegetation
effects. For information about why the use of a 12-hour versus
a 24-hour accumulation period would contribute
to the inconsistency problem of the W126 index, please click here. You can learn more about the subject
of vegetation effects by visiting our Table of Contents web page.
- For several
years, A.S.L. & Associates has had an on-going effort to
better understand the range and frequency of occurrence of background
ozone levels that may not be affected by emission reduction strategies.
In a paper published
in May 2001, the research team consisting of Allen Lefohn, Samuel
Oltmans, Tom Dann, and Hanwant Singh discussed that background
ozone levels were higher and that the natural short-term variability
was more frequent and greater than previously believed. The authors
are associated with the following institutions: A.S.L. &
Associates, NOAA, Environment Canada, and NASA, respectively.
In our 2001 paper, we concluded that hourly levels greater than or equal to 50 ppb occur
more frequently as a result from natural sources than previously
believed. In
2006, the US EPA defined Policy-Relevant
Background (PRB) for ozone as those concentrations that would
occur in the United States in the absence of anthropogenic emissions
in continental North America (i.e., the United States, Canada,
and Mexico). PRB concentrations include contributions from (1)
natural sources everywhere in the world and (2) anthropogenic
sources outside the United States, Canada, and Mexico. In 2008,
we published results, using empirical data, confirming that at
some locations in the US, PRB ozone concentrations are greater
than or equal to 50 ppb. In
late September 2009, the National Research Council released the
report, Global Sources of Local Pollution. In the report,
the Committee states that modeling and analysis supports the
finding that Policy-Relevant Background (PRB) is 20-40 ppb for
the United States. Unfortunately, the NRC conclusion does not
agree with the peer-review literature using empirical data that
hourly averaged PRB ozone concentrations are greater than or
equal to 50 ppb. Although
spatially low-resolution models have been exercised and indicate
that the conclusions reached by Lefohn et al. (2001) are
incorrect, our current research and the results published by
other research groups support the conclusions reached by Lefohn
et al. (2001) that PRB ozone concentrations are greater
than or equal to 50 ppb at both high- and low-elevation monitoring
sites. Clearly, low-resolution models are unable to adequately
capture the important processes that are important for characterizing
PRB and therefore, underestimate policy relevant background concentrations.
An Internet-based slide
presentation
is available for purposes of previewing our paper. Also please
be sure to check out the answer to our quiz that identifies
the month in which the highest 8-hour daily maximum concentration
occurred for the 4 remote ozone monitoring sites. Additional
information on background ozone concentrations can be found in
the Air Quality Analyses section of our Table of Contents. In-depth
discussions are provided on this very important topic.
- As of June 7,
2010, EPA announced that the number of nonattainment areas are
50 ozone (8-hour 1997 standard), 1 carbon monoxide, 9 sulfur
dioxide, 46 PM-10, 39 PM-2.5 (1997 Standard), 31 PM-2.5 (2006
Standard), and 2 lead in the United States. There are no NO2
nonattainment areas in the United States. Maps of the ozone,
carbon monoxide, sulfur dioxide, PM-10, and PM-2.5 nonattainment
areas are available for review and download.
- EPA released its design value findings on air quality on October 15, 2009 and concluded
for the period 2006-2008:
|
31 of the 126 areas originally
designated nonattainment for the 8-hour O3 National Ambient Air
Quality Standard (NAAQS) failed to meet the 1997 8-hour O3 NAAQS
for the period 2006-2008 (see Table); |
|
1 of the areas originally designated nonattainment
had incomplete data (see
Table); |
|
1 additional unclassifiable/attainment areas
failed to meet the O3 NAAQS in 2006-2008 (see Table); |
|
As of July 31, 2009, 59 of the 126 areas originally
designated nonattainment for the 8-hour O3 NAAQS are classified
as maintenance areas, meaning they have been redesignated to
attainment (see
Table); |
|
Fifteen of the original 39 areas designated
nonattainment for the PM2.5 NAAQS in April, 2005 (using 2001-2003
data) failed to meet the annual PM2.5 NAAQS in 2006-2008. Seventeen
of the original 39 nonattainment areas met the annual NAAQS in
2006-2008. The remaining seven areas have insufficient data to
allow a determination of compliance with respect to the annual
PM2.5 NAAQS in 2006-2008; in each of these seven areas, one or
more sites for which compliance cannot be determined for 2006-2008
clearly violated the NAAQS in a previous period (e.g., for 2005-2007)
(see Table); |
|
Thirty-one areas were designated nonattainment
for the 24-hour PM2.5 NAAQS in September, 2008. Twenty-eight
of these 31 areas failed to meet the NAAQS with 2006-2008 data.
The other three areas are shown to have incomplete data with
respect to the 24-hour PM2.5 NAAQS; in each of these three areas,
one or more sites for which compliance cannot be determined for
2006-2008 clearly violated the NAAQS in a previous period (e.g.,
for 2005-2007) (see
Table); |
|
Four counties outside of existing (previous
and new) PM2.5 nonattainment areas violated one or both PM2.5
NAAQS in 2006-2008 (see
Table)
- Two counties, outside of existing nonattainment
areas, did not meet the PM2.5 annual NAAQS (see Table); and
- Three counties, outside of existing nonattainment
areas, did not meet the PM2.5 24-hour NAAQS. (One county violated
both the annual and the 24-hour NAAQS with 2006-2008 data (see Table).
|
- On
EPA's web site (www.epa.gov/airtrends/ozone.html), the Agency
summarized in June 2009 trends for the periods 1980-2008 and
1990-2008. Figures 1 and 2 below have been reproduced from the
Agency's current website. There has been a flattening effect
over time, where the peak O3 concentrations were reduced in the
early years but then modest improvements in the mid-level values
since the 1990s. Based on EPA's calculations, on a national basis,
O3 levels have not changed much over the past several years.
Lefohn, Shadwick, and Oltmans (2008) have recently statistically
quantified in the peer-reviewed journal, Atmospheric Environment,
this observation for the period 1980-2005 and 1990-2005. Please
see publications list for the citation.
Table 1 below lists the changes over the past several years.
Figure 1. National 8-hour Ozone Air Quality Trend, 1980-2008.
Based on annual fourth highest daily maximum 8-hour ozone concentration
trended over the period of time.
(Source: www.epa.gov/airtrends/ozone.html)
Figure 2. National 8-hour Ozone Air Quality Trend, 1990-2008.
Based on annual fourth highest daily maximum 8-hour ozone concentration
trended over the period of time.
(Source: www.epa.gov/airtrends/ozone.html)
Table 1. Comparison
of trending by US EPA for two exposure metrics for several time
periods.
|
Exposure Metric |
1980-2005 |
1980-2006 |
1980-2007 |
1980-2008 |
1990-2005 |
1990-2006 |
1990-2007 |
1990-2008 |
|
2nd Highest 1-Hour Average |
-28% |
-29% |
-29% |
-32% |
-12% |
-14% |
-14% |
-18% |
|
4th Highest 8-Hour Average |
-20% |
-21% |
-21% |
-25% |
-8% |
-9% |
-9% |
-14% |
As indicated above, Lefohn et al. (2008)
published their trending findings for surface ozone monitoring
sites across the United States. Using statistical trending on
a site-by-site basis of the (1) health-based annual 2nd highest
1-hour average concentration and annual 4th highest daily maximum
8-hour average concentration and (2) vegetation-based annual
seasonally corrected 24-hour W126 cumulative exposure index,
they investigated temporal and spatial statistically significant
changes that occurred in surface ozone in the United States for
the periods 1980-2005 and 1990-2005. For more information about
the Lefohn et al. (2008) findings, please click
here.
Since 1997, we have
been discussing the "piston" effect in the peer-reviewed
literature (see publications listing).
In 1997, we predicted that there would be a leveling off of improvements
in O3 concentrations as O3 emission precursors were reduced.
Our prediction apparently has been verified by the EPA's analysis.
The "piston" effect, as described in the peer-review
literature and on this web site, affects
the ability of the nation to attain the 8-hour ozone standard
and in some cases, the 1-hour standard. As we discussed in our
original paper, the peak hourly average concentrations (i.e.,
hourly average concentrations greater than or equal to 0.10 ppm)
are reduced much faster than the mid-level concentrations (i.e.,
0.06-0.099 ppm). In the most recent EPA Ozone Criteria Document
(2006), the Agency notes "The highest O3 concentrations
have tended to decrease over the past 15 years, while there has
been little change in O3 concentrations near the center of the
distribution." The document notes that this is consistent
with results published in Europe. Interesting, the Agency notes
in the document that there has been an increase in O3 concentrations
at the lower levels throughout the monitoring period, which is
consistent with data obtained in Europe, showing that O3 minima
increased during the 1990s because of reduced titration of O3
by reaction with NO in response to reductions in NOx emissions.
Based on our published findings, the EPA has attempted to take
into consideration the "piston" effect by utilizing
theoretical rollback models that allow the higher hourly average
ozone concentrations to be reduced at a faster rate than the
mid-level values. Clearly the "piston" effect heavily
influences the Nation's ability to attain the 8-hour ozone standard.
We discuss more about the "piston" effect and how it
affects the attainability of the ozone standard in our concerns
web area.
Trends in 8-hour
design values are calculated using three consecutive years of
air monitoring data. EPA compares design values to its national
air quality standards to determine whether they are met. Figure
3 illustrates trends for the original 126 designated nonattainment
areas for ozone for the 3-year periods from 1999 to 2005. As
of June 5, 2009, there were 55 nonattainment areas for ozone.
Figure 3. Eight-hour ozone design value trends for the
original 126 designated ozone nonattainment areas for the 3-year
periods from 1999 to 2005.
(Source: www.epa.gov/airtrends/ozone.html)
Because the design
value is calculated as a three-year average of the 4th highest
8-hour value, the effects of the low ozone years of 2003 and
2004 appear to have affected the 2002-2004 and the 2003-2005
design value calculations. Maps has been
created that compares for the U.S. and Canada the 2002-2004,
2003-2005, 2004-2006, and 2005-2007 periods for the 4th highest
8-hour ozone concentration.
- On
EPA's web site (http://www.epa.gov/airtrends/aqtrends.html),
the Agency summarizes emission trends for the period 1980-2008.
The tables below are the most current estimates provided by EPA
on its web page as of October 2009.
National Emissions Estimates
(fires and dust excluded)
For Common Pollutants and their Precursors
|
1980 |
1985 |
1990 |
1995 |
2000 |
2005 |
2008 |
|
Carbon Monoxide (CO) |
178 |
170 |
144 |
120 |
102 |
93 |
78 |
|
Lead |
0.074 |
0.023 |
0.005 |
0.004 |
0.003 |
0.002 |
0.002 |
|
Nitrogen Oxides (NOx) |
27 |
26 |
25 |
25 |
22 |
19 |
16 |
Volatile Organic
Compounds (VOC) |
30 |
27 |
23 |
22 |
17 |
18 |
16 |
Particulate Matter (PM)
PM10
PM2.5 |
6
NA |
4
NA |
3
2 |
3
2
|
2
2
|
2
1
|
2
1
|
|
Sulfur Dioxide (SO2) |
26 |
23 |
23 |
19 |
16 |
15 |
11 |
Totals |
267 |
250 |
220 |
191 |
161 |
148 |
124 |
Notes:
1. In 1985 and 1996 EPA refined its methods for estimating emissions.
Between 1970 and 1975, EPA
revised its methods for estimating PM emissions.
2. The estimates for 2005 and beyond are from the final version
2 of the 2005 NEI.
3. For CO, NOx, SO2 and VOC emissions, fires are excluded because
they are highly variable; for
direct PM emissions both fires and dust are excluded.
4. PM estimates do not include condensable PM.
5. EPA has not estimated PM2.5 emissions prior to 1990.
6. The 1999 estimate for lead is used for 2000, and the 2002
estimate for lead is used for 2005 and
2008.
7. PM2.5 emissions are not added when calculating the total because
they are included in the PM10
estimate.
Source: http://www.epa.gov/airtrends/sixpoll.html
Percent Change
in Air Quality
|
Pollutant |
1980 versus 2008 |
1990 versus 2008 |
|
CO |
-79 |
-68 |
|
Ozone (8-hour) |
-25 |
-14 |
|
Lead |
-92 |
-78 |
|
Nitrogen Dioxide |
-46 |
-35 |
|
PM10 (24-hour) |
-- |
-31 |
|
PM2.5 (Annual) |
-- |
-19 |
|
PM2.5 (24-hour) |
-- |
-20 |
|
Sulfur Dioxide |
-71 |
-59 |
Notes:
1. --- Trend data not available
2. PM2.5 air quality based on data since 2000
3. Negative numbers indicate improvements in air quality
Source: http://www.epa.gov/airtrends/aqtrends.html
Percent Change
in Emissions
|
Pollutant |
1980 versus 2008 |
1990 versus 2008 |
|
CO |
-56 |
-46 |
|
Lead |
-99 |
-79 |
|
Nitrogen Oxides |
-40 |
-35 |
|
VOC |
-47 |
-31 |
|
Direct PM10 |
-68 |
-39 |
|
Direct PM2.5 |
-- |
-38 |
|
Sulfur Dioxide |
-56 |
-51 |
Notes:
1. --- Trend data not available
2. Direct PM10 emissions for 1980 are based on data since 1985
3. Negative numbers indicate reductions in emissions
Source: http://www.epa.gov/airtrends/aqtrends.html
- On February
24, 2009, the U.S. Court of Appeals for the D.C. Circuit remanded
the National Ambient Air Quality Standards (NAAQS) for fine particulate
matter (PM2.5) to EPA for reconsideration of the annual level
of the standard (which EPA left at 15 micrograms per cubic meter
(µg/m3)) and reconsideration of the secondary PM2.5 NAAQS.
With respect to the annual PM2.5 NAAQS, the court held that the
agency failed to explain adequately why an annual level
of 15 µg/m3 is requisite to protect the public health,
including the health of vulnerable subpopulations, while providing
an adequate margin of safety. 42 U.S.C.§ 7409(b)(1).
For the secondary standards, the court held that EPA unreasonably
concluded that the NAAQS are adequate to protect the public welfare
from adverse effects on visibility. The court denied petitions
for review of the primary daily standard for coarse PM and the
petition for review of EPAs revocation of the primary annual
standard for coarse PM. The Court opinion can be read by clicking
here.
On September
21, 2006, EPA announced with regard to primary standards for
fine particles (generally referring to particles less than or
equal to 2.5 micrometers (µm) in diameter, PM2.5) that
it revised the level of the 24-hour PM2.5 standard to 35 micrograms
per cubic meter (µg/m3) and retained the level of the annual
PM2.5 standard at 15 µg/m3. With regard to primary standards
for particles generally less than or equal to 10 µm in
diameter (PM10), EPA retained the 24-hour PM10 and revoking the
annual PM10 standard. With regard to secondary PM standards,
EPA made them identical in all respects to the primary PM standards,
as revised. The issue of reliability of the epidemiological time-series
methodologies continued to be of concern to the Administrator.
The Administrator noted in his decision that there were many
sources of uncertainty and variability inherent in the inputs
to the assessment and that there was a high degree of uncertainty
in the resulting PM2.5 risk estimates. Such uncertainties generally
related to a lack of clear understanding of a number of important
factors, including, for example, the shape of concentration-response
functions, particularly when, as here, effect thresholds can
neither be discerned nor determined not to exist; issues related
to selection of appropriate statistical models for the analysis
of the epidemiologic data; and the role of potentially confounding
and modifying factors in the concentration-response relationships.
For those interested in the possible violation areas for the
revised 24-hour PM-2.5 standard based on 2004-2005 data, please
click
here.
- On December
22, 2008, EPA designated areas throughout the United States as
"nonattainment" and "unclassifiable/attainment"
for the 24-hour national air quality standard (35 ug/m3) for
fine particulate matter (PM2.5). The EPA designated 211 counties
or parts of counties as nonattainment. These nonattainment areas
include counties with monitors violating the standards and nearby
areas that contribute to that violation. A map of the EPA's PM2.5
designations for nonattainment can be reviewed by clicking
here.
For a comparison of the violators for the PM2.5 annual standard
(2005-2007) and the PM2.5 24-hour average standard (35 ug/m3),
please
click here.
- In December 2008, we presented at the AGU Fall Conference
in San Francisco a summary of one of our several research efforts
dealing with changes in tropospheric ozone levels. The talk was
presented at the Tropospheric Gaseous Composition in the Regional
and Global Perspective 1 - A11F-03 session. The title of
our presentation was: "Tropospheric Ozone Changes from Surface
and Ozonesonde Observations." The research was presented
by the lead author, Samuel Oltmans, NOAA Earth System Research
Laboratory Global Monitoring Division, Boulder, Colorado. The
talk explored the following:
- What are the implications
from this record of observations?
- Are the records consistent
in regions with multiple records?
- At what geographic scale
can conclusions about trends be drawn (global, hemispheric, regional)?
and
- Are changes related to
precursor emissions, transport variability, stratospheric input?
Based on our analyses,
our conclusions are
- In the Northern Hemisphere,
there is a different pattern of long-term changes between North
America, Europe, and Japan;
- Over North America there
does not appear to be a significant increase over the 30 years
of measurements, although there have been shorter term fluctuations;
- Western Europe saw the
largest increases prior to 1990 but a significant decrease in
growth rates (and in some cases declines) over the past 15 years
over continental Europe;
- In Japan, increases were
primarily prior to the mid 1980s, but with recent increases in
Okinawa;
- In the Southern Hemisphere
mid latitudes, at Cape Point, Cape Grim, and Lauder, ozone has
increased significantly with the increases coming primarily in
the austral spring;
- In Hawaii (North Pacific
tropics), increases appear to be associated with decadal transport
shifts;
- The tropical south Pacific
(Samoa) has not shown significant changes in tropospheric ozone;
and
- At the South Pole, earlier
declines have reversed so that overall there has been almost
no change.
Some possible implications
of recent (i.e., 30 year) observed changes are
- The relationship between
emission changes and longer term hemispheric and global tropospheric
ozone changes is not adequately understood;
- The climate forcing of
tropospheric ozone changes over the recent past is still very
uncertain; and
- It will be difficult to
assess the climate forcing reductions that can be gained by reducing
tropospheric ozone with the current network of observations.
Co-authors of the research
study are A. Lefohn, J. Harris, H.-E. Scheel, E. Brunke, H. Claude,
D. Tarasick, I. Galbally, G. Bodeker, J. Davies, T. Koide, B.
Johnson, C. Meyer, F. Schmidlin, E. Cuevas, A. Redondas, P. Simmonds,
and B. Buchman.
Over the past several years,
there have been several articles quoting other sources indicating
that surface ozone concentrations are increasing everywhere.
Our most current research results do not support this claim.
Our research continues to monitor the status of worldwide ozone
levels by performing sophisticated analyses using surface ozone
and ozonesonde data. Previous peer-reviewed papers on background
ozone trends that we have published are
Oltmans S. J., Lefohn A.
S., Scheel H. E., Harris J. M., Levy H. II, Galbally I. E. ,
Brunke E. G., Meyer C. P., Lathrop J. A., Johnson B. J., Shadwick
D. S., Cuevas E., Schmidlin F. J., Tarasick D. W., Claude H.,
Kerr J. B., Uchino O., and Mohnen V. (1998) Trends of ozone in
the troposphere. Geophysical Research Letters. 25:139-142.
Oltmans S. J., Lefohn A.
S., Harris J. M., Galbally I., Scheel H. E., Bodeker G., Brunke
E., Claude H., Tarasick D., Johnson B.J., Simmonds P., Shadwick
D., Anlauf K., Hayden K., Schmidlin F., Fujimoto T., Akagi K.,
Meyer C., Nichol S., Davies J., Redondas A., and Cuevas E. (2006)
Long-term changes in tropospheric ozone. Atmospheric Environment.
40:3156-3173.
- Canada has identified the ozone concentrations for
the 4th highest 8-hour levels for 2004-2006 for the U.S. and
Canada. Maps are available that compare the U.S.
and Canada for the 2002-2004, 2003-2005, 2004-2006, and 2005-2007
periods for your review.
- A.S.L.
& Associates has estimated the nonattainment areas for a
daily PM-2.5 standard of 35 ug/m3. For the 2004-2005 period,
A.S.L. & Associates estimates that there will be 441 counties
that violate a possible short-term standard of 35 ug/m3. A map
is provided to illlustrate the violation areas. To review the
map, please visit our maps web page.
- Sometimes policymakers
do not pay careful attention to the technical details associated
with important scientific topics. For example, EPA indicated
in April 2004 in its report, The Ozone Report - Measuring
Progress Through 2003, that for the period 1990 - 2003, six
locations experienced statistically significant increases in
ozone: Great Smoky Mountains (Tennessee) in the eastern United
States and Mesa Verde (Colorado), Rocky Mountain (Colorado),
Craters of the Moon (Idaho), Canyonlands (Utah), and Yellowstone
(Wyoming) in the West.
Yellowstone National
Park is a relatively remote site for ozone monitoring in the
United States. The greatest frequency of ozone concentrations
greater than or equal to 0.05 ppm occurs in the spring, which
we believe implies a natural stratospheric contribution to the
site. We have not observed trends in ozone in the park since
the beginning of monitoring. Our ozone trending analysis includes
data through 2005. Our review of the latest data for 2006 indicate
that no statistically significant ozone trends would be identified
for Yellowstone National Park if the additional year were included
in our analysis. We pointed out several years ago that EPA's
trending results were due to a change in the physical location
of the actual ozone monitor. In 1996, the monitoring site was
changed and this resulted in two distinct sets of data being
generated. Based on our analysis, EPA should not have combined
the two sets of data for trends analysis in its April 2004 report.
EPA, in its latest estimates of trending at national parks, did
not attempt to identify a trend for the Yellowstone National
Park site for the period 1990 - 2004 because of the change in
physical location (EPA, 2006 - see page AX3-113). The
scientific information showing the changes in the monitoring
site and the effects on trends from 1987 through 2001 is available
for review.
In May 2006, the
U.S. National Park Service provided on its web site (http://www2.nature.nps.gov/air/) the results
of its 2005 Annual Performance and Progress Report: Air Quality
in National Parks report. Based on air quality data covering
the period 1995-2004, the National Park Service announced that
both Yellowstone National Park and Glacier National Park are
experiencing statistically significant increases in ozone concentrations.
This finding contradicts our own peer-reviewed published analyses
(Oltmans et al. 2006) and the information provided in
EPA's Ozone Criteria Document published in 2006. Although EPA
did not attempt to determine an ozone trending for Yellowstone
National Park for the scientific reasons detailed above, the
Agency did report that no statistically significant trend was
observed at Glacier National Park for the period 1990-2004. Thus,
our most recent trending analyses (Oltmans et al., 2006)
and EPA's analysis agree that no trend appears to exist at Glacier
National Park. In addition, our most recent analysis (Oltmans
et al., 2006) also shows no trending at Yellowstone National
Park. We believe there are clear reasons for the discrepancy
between the results presented by the National Park Service and
those by EPA and A.S.L. & Associates. Based on our review
of the National Park Service analysis of ozone data, we believe
that at this time, no trends in surface ozone are occurring at
either Yellowstone National Park or Glacier National Park. For
additional information, please
review our technical comments.
Oltmans S. J., Lefohn A. S., Harris
J. M., Galbally I., Scheel H. E., Bodeker G., Brunke E., Claude
H., Tarasick D., Johnson B.J., Simmonds P., Shadwick D., Anlauf
K., Hayden K., Schmidlin F., Fujimoto T., Akagi K., Meyer C.,
Nichol S., Davies J., Redondas A., and Cuevas E. (2006) Long-term
changes in tropospheric ozone. Atmospheric Environment. 40:3156-3173.
U.S. Environmental Protection
Agency (2006) Air Quality Criteria for Ozone and Related Photochemical
Oxidants. Research Triangle Park, NC: Office of Research and
Development; report no. EPA/600/R-05/004af.
- Review the areas that exceeded the EPA's PM-2.5 standards
based on 2006-2008 data.
- Review the areas that exceeded the EPA's 8-hour ozone
standard based on 2006-2008 data.
- Our research team has used ordinary kriging
to develop surface ozone models for the years 1982 to 2006. Our
most recent work has included the kriging of the W126 integrated
and the N100 exposure indices. To read more about our Team's
use of kriging to spatially characterize surface ozone , please
visit our kriging web page.
- Over the past 10 years, A.S.L. & Associates and
its consultants have commented on the strengths and weaknesses
associated with the mathematical and statistical methodologies
used in epidemiological studies to link exposure with human health
effects. Many of the statistical caveats raised throughout the
PM and Ozone Criteria Documents and the PM and Ozone Staff Papers
indicate a pattern of inconsistent results that is troubling.
Examples of the growing pattern of inconsistent and inconclusive
findings include the following:
- Instability of PM mortality
effect estimates resulting from different model specifications
of weather effects and time trends.
- Instability of PM effect
estimates resulting from different selections of monitoring sites
within cities.
- Increased heterogeneity
of PM effect estimates across cities.
- Greater diversity of findings
among studies and across study areas.
- Contradictory results
from mortality displacement studies.
- PM effect lags that are
inconsistent across cities and across studies.
- Exposure-response relationships
that are inconsistent across cities and across studies.
- Inconsistencies between
short-term and long-term effect studies, such as respiratory
effects of fine particles.
- Contradictory findings
among long-term studies.
Additional details about
the Team's epidemiological concerns are discussed on our epidemiological
concerns web page. The
Team's comments on the first draft of the PM Staff Paper were
submitted to EPA in October 2003. To read more about our concerns
about the first draft, please visit our web page.
- On April 5, 2005, the Environmental Protection Agency
(EPA) modified its original 225 nonattainment counties (including
the District of Columbia) for the PM-2.5 standard. The number
of nonattainment counties has been changed to 208. A map is available that identifies the nonattainment areas.
Further information can be obtained from EPA's web
site.
EPA
announced on April 15, 2004 that it has designated 474 counties
as nonattainment for the 8-hour ozone standard. There were 126
nonattainment areas. The most recent update shows an adjustment
to these numbers. A map is available to view the locations
of nonattainment counties. We do have concern
that while the number of violation areas of the ozone standard
is great, the public may not be at as much risk as the EPA estimates.
In addition, the standard will be difficult and in many cases
impossible to attain due to the "piston" effect. An
Internet-based slide
presentation is available
that explains the effect. Additional information about the effect
can be found in the Table
of Contents section
of this web site.
- Sometimes science
and politics mixed together become science fiction. Such is the
case that occurred, when in September 2002, many newspapers across
the United States printed a story summarizing the report, Code
Red: America's Five Most Polluted National Parks, which described
The Great Smoky Mountains as the nation's most polluted national
park, with air quality rivaling that of Los Angeles. For the
period 1997-2001, the report claims that the annual ozone exposure
was higher at Great Smoky Mountains National Park than at Los
Angeles, California. There is a serious technical problem associated
with the report and the report's conclusions are flawed. Please
read "The Rest of the Story."
- In 2000, Haywood County, NC experienced its 4th highest
8-hour
ozone concentration at 0.085 ppm.
On May 1, a daily maximum 8-hour average concentration of 0.089
ppm was experienced. A detailed meteorological
analysis suggests
that stratospheric ozone played an important role in this ozone
episode.
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