Technical & Policy Issues with 

EPA’s Proposed Ozone NAAQS

June 18, 2010

American Petroleum Institute

Presentation to:

Environmental Protection Agency

Washington, D.C. 

1
Recommendation

Maintain EPA’s Scheduled 2013 Ozone Review

 complete a thorough review of all new health studies to 

address unanswered questions on health effects from 

the last review

 consider new data on ozone background levels / 

international transport

 Assess utility and applicability of a secondary standard 

in the W126 form

2
Discussion Issues

 Human Health Impacts are overstated and more 

uncertain than presented in the proposed rule

 Policy Relevant Background (PRB) is higher than EPA 

estimates and therefore the risk assessment overstates 

the potential benefits of a lower standard

 The evidence does not establish that a secondary 

NAAQS more stringent and with a different form than the 

primary standard is warranted

3
Background

 EPA reconsidering 2008 decision that lowered ozone 

NAAQS

 EPA proposes to again lower the standard to 60 - 70 ppb 

based on:

 the scientific record from the last review 

 Provisional Assessment of Recent Studies (PARS) on Health 

and Ecological Effects of Ozone Exposure of new data

 EPA concluded that PARS does not “materially change 

any of the broad scientific conclusion regarding health 

effects of ozone made in the 2007 AQCD”

 A more comprehensive review of new studies suggests an alternate 

conclusion

4
Continuing Concerns with 

EPA’s 2008 Ozone Review

 EPA reanalyzed published studies and reached different conclusions 

not supported by the author (Adams 2006)

 EPA excluded well conducted studies without justification

 Schildcrout (2006): reports ozone does not exacerbate asthma

 Giradot (2006): reports no effects of ozone in highly exposed hikers 

 Kamps (2001) finds as unreliable lung function measurement test used in key EPA studies

 EPA relied on conflicting hypothesis to explain inconsistent results

 Mortimer 2004, Delfino 2002: reached different conclusions on asthmatic symptoms in children

 Mortimer 2004, Ross 2002: reached different conclusions on time of day for lung function changes 

 In both cases, EPA accepts conflicting hypothesis to explain inconsistent results 

 EPA used individual responses in clinical study designed to assess 

group effects: Adams 2006

 EPA failed to recognize limitations of observational studies

 Use of ambient measurements as surrogate for personal exposure; single pollutant models

 EPA deviated from established medical criteria in defining adverse 

effect

5
New Health Data Challenges 

EPA 2010 Conclusions1

 EPA states pulmonary function effects occur at 60 ppb 

but...

 New clinical study (Schelegle 2009) confirms no effects at 60 ppb transient non-adverse effects at 

70 ppb

 EPA claimed asthma exacerbation occurs at current 

levels but...

 3 of 4 new studies report no association, including an EPA-sponsored study not cited in the PA 

(O’Connor 2008) that relies on improved measuring methods

 EPA concluded airway inflammation/respiratory morbidity 

occurs at current levels, but...

 All new studies (3) on airway inflammation report no association

 Results of new studies on respiratory morbidity continue to be mixed 

 EPA concluded cardiac hospital admissions occur at 

current ozone levels, but...

 7 of 8 new studies in PA plus one large study (HEI 2009 NMMAPS) not cited by PA report no 

association 

 EPA concluded acute mortality occurs at current ozone 

levels, but...

 New studies not in PA (HEI 2009, Smith 2009, Stylianou 2009) do not support case for acute 

mortality link 

6

1

In the proposed rule, EPA makes several key conclusions but indicates new research is needed to reduce

uncertainties. In the examples presented, significant new research is already available. 
Concerns with EPA Approach 

to Determine PRB

 EPA defines Policy Relevant Background (PRB) as 

concentration that would occur in the US in the absence 

of anthropogenic emissions in continental North America 

(US, Canada, and Mexico) 

 EPA assesses risks to human health and environmental 

effects from O3levels in excess of PRB

 EPA asserts PRB to be 15-35 ppb based on GEOSCHEM modeling

 Modeled PRB is far too low in comparison to monitored 

values.

7
Impact of PRB on Acute 

Mortality Estimates1

Number of Deaths 

Attributable to Ozone > 

GEOS-CHEM PRB

Number of Deaths 

Attributable to Ozone > 

40 ppb PRB

Percent Reductions If 

Using 40 ppb rather 

than GEOS-CHEM for 

PRB Assumption

Atlanta 6.5 0.3 95%

Cleveland 37.4 4.3 88%

Detroit 37.9 1.8 95%

Houston 22.7 1.5 94%

Los Angeles 38.5 0.1 99%

Sacramento 11.0 0.2 98%

St. Louis 4.4 0.3 93%

8

1Risks estimated using risk specific coefficients from Bell et al. 2004, at exact attainment of the 0.084 ppm NAAQS, average of 2002 and 2004 data (CRA, 

2007) 
CASTNET Data Indicate Many Rural Areas 

Will Exceed a 60-70 ppb NAAQS1

9

1VValues are three-Year Average of Fourth Highest Daily Maximum 8-Hour Average Ozone Concentrations (ppb)

in various National Parks for 2006–2008

Yellowstone 

Rocky Mt. 

Acadia 

Blackwater 

Great Smokey

Kane National Forest

Big Bend Monmouth Cave 

Lassen

Volcano 

Yosemite 

Petrified Forest

Grand Canyon 

Sequoia 

Joshua Tree 

Konza Prairie
Transport Issue Must be 

Considered1

 Increasing emissions from Asia are outpacing reductions in the U.S. 

 Asia NOx emissions increased 44% (55% in China) during 2001-2006 while ozone precursors 

from the U.S. decreased by more than a third in 1985-2008

 Recent studies estimate that Asia emissions have contributed up to 

17 ppb to tropospheric ozone levels over 1984-2008

 Trend will continue and increase tropospheric ozone 0.7 ppbv per year

 Intrusion of tropospheric ozone in spring significantly increases ground level ozone in the 

west and midwest regions of the U.S. 

 Key conclusion: ozone transport hindering attainment in U.S.

10 1Statements, data, conclusions presented are from Cooper et al. (2010). 
 Sole reliance on modeling

 Global emission inventory which is 

out of date

 Large grid size of the model

 Determined for only 12 US cities

 Looked at average of only part of a 

year verses the statistic of the 

standard

 Does not vary by season or 

elevation

 PRB should be reevaluated before 

setting a new ozone NAAQS

 PRB should be reevaluated using all 

available data and tools

 monitoring, upper air measurements, 

modeling, and satellite 

 A new global inventory accounting for 

increased emissions from Asia

 Use a smaller grid size

 PRB should be assessed for a 

broader and more diverse geographic 

region than 12 cities and for the full 

year

 PRB should use the same form as the 

NAAQS (4th highest 8-hr average from 

a full year’s data)

 PRB should vary by:

 Season

 Elevation

 Perhaps geographical location 11

Concerns with 

EPA’s Approach to 

Determine PRB

Recommendations 

for Improving the 

PRB Determination
A Separate Secondary Ozone 

NAAQS is Not Warranted

 W126 index lacks a strong biological basis, its relevance 

to biological responses in the real world is speculative.

 Any protection provided by any W126 indication would not be 

nationally uniform.

 Peer-reviewed research concluded W126 greatly overestimated 

the negative response to ozone and . . . the growing season 4th

highest daily maximum 8-hour average ozone concentration index 

had high statistical significance and a much greater association 

with biological endpoints. (Percy et. al. 2006)

 CASAC Feb 19 letter recommends ”EPA collect 

information and seek additional research that could be 

used to inform continued refinement of the [W126] 

standard” ... W126 is not ready 

12
Conclusions for the Proposed 

Lower Ozone NAAQS

 New and existing health studies do not support EPA’s 

conclusion that the ozone standard must be lowered

 The benefits of a lower ozone NAAQS are questionable 

 the large majority of new and existing studies show no effects at current ozone 

levels

 most of EPA’s health impacts in both their Risk and Exposure Assessment and 

Regulatory Impact Assessment are estimated to occur at levels below the 

standard and down to EPA’s assumed PRB levels of 15-35 ppb

 since EPA has underestimated PRB, the health benefits of alternate standards 

are vastly over-stated, particularly at lower alternate NAAQS levels 

 The ozone standard should not be changed until a full 

review of the new science on health effects, background 

ozone levels and W126 limitations occurs as scheduled 

in 2013

 Lots of technical and regulatory uncertainty with the 

implementation leaving a substantial downside for the 

economy and jobs

13
Background

14
15
Not Attaining the Current 75 ppb Standard

Monitored MSAs and Non-Urban Counties Exceeding 75 ppb 

( 682 Counties; Based on 2006-2008 Data)

16
17

EPA Data Show Lowest 10% Ozone Values Have Resisted Changed 

Despite Aggressive Control Program

Year 10th Percentile

1980 0.069

1981 0.070

1982 0.069

1983 0.072

1984 0.071

1985 0.069

1986 0.070

1987 0.074

1988 0.077

1989 0.070

1990 0.070

1991 0.068

1992 0.068

1993 0.066

1994 0.069

1995 0.072

1996 0.071

1997 0.066

1998 0.071

1999 0.072

2000 0.067

2001 0.069

2002 0.069

2003 0.069

2004 0.064

2005 0.065

2006 0.064

2007 0,061

2008 0.064 http://www.epa.gov/airtrends/ozone.html

1980 to 2008 : ~10% decrease in 10th Percentile Values
18

Average Levels of Ozone in the U.S. Continue to Decline

18
19

Remote Area Nonattainment?

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5 Ozone (ppb)

3-Year Average of 4th Highest 8-Hour Ozone Concentration 

Cannyonland

Centenial

Mesa Verde

Pinedale

Rocky Mnt colocated

Rocky Mnt 

Theor Roosevelt

Duchesne

Gothic

Yellowstone

(Hanna et al, 2010)
20

Model Evaluation

20

30

40

50

60

70

80

J F M A M J J A S O N D MDA8 O3 (ppbv)

CAMCHEM

 ECHAM5

 EMEP

 FRSGCUCI

 GEMAQ-EC 

GEMAQ-v1p0 

 GEOSChem-v07 

 GEOSChem-v45 

 GISS-PUCCINI

 GMI-v02f 

INCA-vSSz 

 LLNL-IMPACT

 MOZARTGFDL

 MOZECH

 OsloCTM2 

TM5-JRC

OBS

Ensemble

Models vs. Obs: Mtn. West Region

Wide spread in 

individual models, but 

ensemble represents 

observations quite well,

However... 

GEOSChem 

significantly under 

estimates observations

30

40

50

60

70

80

M A M

MDA8 O3 (ppbv)

Ensemble +/- 1SD

Obs

Ensemble mean

Mtn. West Region: MAM

r

2

 = 0.47

Mean SD 90th 

percentile

Exceedance 

Days

Obs 55.2 5.2 61.6 0

Ensemble 52.1 3.7 57.4 0

Correlations are generally 

strongest in East & weaker 

in West

Models have large (+) 

biases in summer that are 

largest in the East

Reidmiller, AGU, 2008; in prep for JGR

(Fiore, 2009)
21

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

0

2 0

4 0

6 0

8 0

100

120

140

160

Percent Change in Exposure

Ozone concentration (ug/m3)

Elevation (ft)

Effect of Elevation on Ozone Mass Exposure for 75 ppb 

ug/m3

percent change

Effect of Elevation on Ozone Mass Exposure

 The form of the standard in ppm does not change with elevation 

 Are ozone health effects a function of ozone mass or ozone concentration? 

 In elevated terrain, the mass exposure to ozone is reduced

 Ozone health effects should be evaluated as a function of elevation and the 

form of the standard changed if appropriate.

 EPA has revised the reference conditions for the PM10 standard

(Stoeckenius, 2009)
Underestimating PRB Results in a 

Significant Over-Estimation of Health Impacts

• Using a PRB only 5 ppb higher than base case resulted in a decrease in estimated 

accidental acute mortality of >50%1

– e.g. Houston: decreased from 18 to 8 per 100,000 using Bell (2004)

– e.g L.A.: decreased from 24 to 9 per 100,000 using Bell (2004) 

• Decrease of mortality of this magnitude (50%) is equal to EPA’s estimate for meeting 

the most stringent standard (64/4) versus the current standard (84/4)2

• Impact of alternate PRB on risk estimates is greater at lower alternate standards1

• The reason EPA’s estimates of hospital admissions were higher in their 2008 vs.1997 

review was EPA used a PRB of 0.015-0.035 vs. 0.04 ppm, resp.3

• Conclusion: EPA must reassess PRB and correct their health impact estimates 

before a decision is made on the NAAQS 

1EPA 2007 Policy Assessment Document for Ozone page 5-82 and table 5C-18

2EPA 2007 Policy Assessment Document for Ozone page 5-96

3EPA 2007 Policy Assessment Document for Ozone page 5-92

22
23

References

23

Adams W. et al. (2006). Comparison of chamber 6.6-h exposures to 0.04-0.08 ppm ozone via square-wave and triangular 

Profiles on pulmonary responses. Inhal. Toxicol. 8(2):127-136.

Cooper et al. (2010). Increasing springtime ozone mixing ratios in the free troposphere over western North America.

Nature 463: 344-348. 

Delfino et al. (2002). Association of asthma symptoms with peak particulate air pollution and effect modification by 

Anti-inflammatory medication use. Env. Health Persp. 110(10:607-617.

Fiore et al. (2009). Multi-model estimates for intercontinental transport of ozone pollution in the northern hemisphere (and uncertainties therein), 

presentation January 21, 2009, http://www.gfdl.noaa.gov/cms-filesystem-action/user_files/aff/presentation_ppts/fiore_gfdl_jan09.ppt

HEI (2009). Air Pollution and Health: a European and North American Approach (APHENA). HEI Report 142. 

Kamps A. et al. (2001). Peak flow diaries in childhood asthma are unreliable. Thorax 56:180-182 

Mortimer et al. (2002). The effect of air pollution on inner-city children with asthma. Eur. Resp. J. 19:699-705. 

O’Connor et al. (2008). Acute respiratory health effects of air pollution on children with asthma in U.S. inner cities. J. 

Allergy Clin. Immunol. 12: 1133-9

Schelegle et al. (2009). 6.6 Hour inhalation of ozone concentrations from 60 to 87 ppb in health humans. Am. J. Resp. Crit. Care Med. 164:505-517. 

Smith et al. (1999). Threshold dependence of mortality effects for fine and coarse particles in Phoenix, Arizona. J. Air Waste Management 

Association 50: 1467-1379. 

Schildcdrout et al. (2006). Ambient air pollution and asthma in children: an eight city analysis. Am. J. Epi. 164(5): 505-17. 

Smith et al. (2009). Reassessing the relationship between ozone and short-term mortality in U.S. urban communities. 

Inhalation Toxicology 29:37-61. 

Stoeckenius et al. (2010, 2010). Air quality modeling study for the four corners region and addendum. Environ Int. Corp Report. August 2009 and 

January 2010. http://www.nmenv.state.nm.us/aqb/4c/Modeling.htlm. 

Stylinaou and Nicolich (2009). Cumulative effects and threshold levels in air pollution mortality: data analysis of nine large

US cities using the NMMAPS dataset. Environmental Pollution 157:2216-2223.