February 8, 2010

Submitted via www.regulations.gov to Docket No.: EPA-HQ-OAR-2007-0352

Subject: Proposed Primary National Ambient Air Quality Standard (NAAQS) for 

Sulfur Dioxide, 74 Fed. Reg. 64810 (December 8, 2009

Dear Sir or Madam:

The Edison Electric Institute (EEI) submits the attached comments on the Environmental 

Protection Agency (EPA) proposed Primary National Ambient Air Quality Standard 

(NAAQS) for Sulfur Dioxide (SO2).

EEI is the association of shareholder-owned electric companies, international affiliates 

and industry associates worldwide. Our U.S. members serve 95 percent of the ultimate 

customers in the shareholder-owned segment of the industry, and represent 

approximately 70 percent of the U.S. electric power industry. The electric power sector 

generates approximately one-half of the nation’s power using the nation’s large coal 

resources, at relatively low cost to support the U.S. economy and millions of jobs. 

The electric power sector has invested tens of billions of dollars to reduce its SO2

emissions from over 17 million tons in 1980 to about 6 million tons in 2009, despite a 70 

percent increase in both coal-based and fossil-based electricity generation over the same 

time period. Further progress in reducing SO2 emissions will come from compliance with 

the Clean Air Interstate Rule (CAIR) and a revised Phase 2 CAIR plus likely co-benefits 

from Maximum Achievable Control Technology (MACT) standards for hazardous air 

pollutants and revision of other NAAQS.

EPA is currently moving forward with many regulations affecting the power industry. 

Air quality regulations facing the power industry include the short-term SO2 standard; 

CAIR and a revised Phase 2 CAIR; new NAAQS for nitrogen dioxide, ozone and 

QUINLAN J. SHEA III

Executive Director, Environment
particulate matter; the Regional Haze/Best Available Retrofit Technology rule; and a 

MACT regulation. Other power sector regulatory programs will address coal ash, water 

quality, cooling water withdrawal, and greenhouse gases. The industry, electric 

customers and the U.S. economy cannot afford to implement stringent rules, such as for a 

new SO2 standard, that do not provide real benefits. Further, a tight new short-term SO2

standard could undermine EPA’s marquee Clean Air Act (CAA) program, i.e., the 1990 

CAA amendments Acid Rain Program SO2 cap-and-trade system.

EEI supports regulation that provides real benefits. However, this proposal provides very 

little benefit as indicated by EPA’s own Regulatory Impact Analysis, which shows that 

the cost of the proposal far outweighs the direct SO2 reduction benefits. EEI believes that 

setting a 1-hour standard in the range of 50-100 ppb is not supported by the scientific 

evidence. 

EPA also requested comment on a standard of 150 ppb. If the Agency decides that it 

must establish a new 1-hour standard, EEI recommends a standard of no less than 150 

ppb, and agrees with the Agency that it should revoke the current 24-hour and annual 

primary SO2 standards. 

EEI appreciates the opportunity to provide comments. Questions may be directed to John 

Kinsman (202-508-5711 or jkinsman@eei.org).

Sincerely,

Quinlan J. Shea, III

QJS:jk
1

COMMENTS OF THE EDISON ELECTRIC INSTITUTE 

PROPOSED PRIMARY NATIONAL AMBIENT AIR QUALITY STANDARD 

(NAAQS) FOR SULFUR DIOXIDE, 74 Fed. Reg. 64810 (December 8, 2009)

Docket No. EPA-HQ-OAR-2007-0352

FEBRUARY 8, 2010

The Edison Electric Institute (EEI) submits these comments on the proposed Primary 

National Ambient Air Quality Standard (NAAQS) for Sulfur Dioxide (SO2). EPA seeks 

comment on a new one-hour ambient air standard for SO2 with a recommended range of 

50-100 parts per billion (ppb), while also accepting comments on an alternative range for 

concentrations as high as 150 ppb. 

ELECTRIC SECTOR SO2 EMISSIONS HAVE BEEN DRAMATICALY

REDUCED 

The electric power sector has been reducing emission, especially SO2, for decades while 

meeting the nation’s ever-increasing demand for energy. These emission reductions have 

produced environmental benefits. Electric companies and their customers have invested

tens of billions of dollars to reduce emissions. As emission levels go lower and lower, 

questions about the optimal level of emissions that should be allowed become more 

highly debated and the cost for every incremental emission reduction becomes higher and 

higher. 

The power generation sector has been monitoring SO2 emissions continuously at every 

plant for at least 15 years. No other sector can so accurately characterize its emissions 

and such data.
2

The electric power sector has cut SO2 emissions deeply. Using the EPA Clean Air 

Markets Division website (Quick Reports), 1power sector SO2 emissions have declined 

from 17.3 million tons (1980) to 15.7 million tons (1990) to 11.2 million tons (2000) to 

7.6 million tons (2008). This equates to a 56 percent reduction from 1980 to 2008, 

despite a 70 percent increase in both coal-based and fossil-based electricity generation 

over the same time period (according to the Energy Information Administration). 2

The updated and likely more stringent version of CAIR, to be finalized by mid-2011, will 

require a substantial additional investment by the power generation sector to reduce SO2

emissions. In preparation for meeting new CAIR requirements, based on preliminary 

data it appears that power sector SO2 emissions in 2009 declined significantly from 2008 

levels, from 7.6 million tons to closer to 6 million tons. Further progress in reducing SO2

emissions will come from compliance with Maximum Achievable Control Technology 

(MACT) standards for hazardous air pollutants and revision of other NAAQS.

SO2 REDUCTIONS HAVE BENEFITED AIR QUALITY AND THE 

ENVIRONMENT 

A recent EPA report on Air Quality Trends 3evaluates national air quality and emissions 

trends since 1980. National SO2 emissions (the total from all sources, including electric 

power plants) are down 56 and 51 percent, respectively, from 1980 and 1990 to 2008.

National SO2 concentrations (the average monitored level in the outside air) have 

declined 71 and 59 percent, respectively, from 1980 and 1990 to 2008.

Environmental progress has resulted. EPA’s October 2009 report “2008 Environmental 

Results” 4on the environmental benefits of the acid rain program, finds that emission 

 

1

 http://camddataandmaps.epa.gov/gdm/index.cfm?fuseaction=emissions.wizard

2

 http://www.eia.doe.gov/emeu/aer/pdf/pages/sec8_8.pdf

3

 http://www.epa.gov/airtrends/aqtrends.html

4

 http://www.epa.gov/airmarkets/progress/ARP_3.html
3

reductions (from power plants and other sources) have led to the following improvements 

in air quality as measured between the two periods of 1989-1991 and 2006-2008:

Average sulfate concentrations in ambient air have decreased by 38 percent in the 

Mid-Atlantic, 44 percent in the Midwest, 43 percent in the Northeast, and 28 percent 

in the Southeast;

Decreases in wet deposition of sulfate averaged more than 30 percent for the eastern 

United States; and 

Total sulfur deposition (wet plus dry deposition) declined about 40 percent.

IMPACTS OF THE PROPOSED RULE ON THE ELECTRIC POWER SECTOR

The proposed rule is very important to the power generation sector, which emits about 60 

percent of domestic industrial SO2 emissions. The proposal comes as EPA is currently 

moving forward on many other air quality regulations facing the power industry --- CAIR

and a revised Phase 2 CAIR; new NAAQS for nitrogen dioxide, ozone and particulate 

matter; the Regional Haze/Best Available Retrofit Technology rule; and Maximum 

Achievable Control Technology (MACT) standards --- plus regulatory programs 

addressing coal ash, water quality, cooling water withdrawal, and greenhouse gases. The 

industry, electric customers and the U.S. economy cannot afford to implement stringent 

rules that do not provide real benefits. 

A tight new short-term SO2 standard could undermine EPA’s marquee Clean Air Act 

(CAA) program – the 1990 CAA amendments Acid Rain Program SO2 cap-and-trade 

system. This trading system established the paradigm supporting market-based 

approaches of all kinds, because it has been extremely successful from both 

environmental and cost-effectiveness perspectives. To undo this landmark EPA program 

with a highly-questionable and unnecessary short-term SO2 standard would do damage to 

the entire concept of market-based control programs.
4

EPA’S REGULATORY ANALYSIS DOES NOT SUPPORT THE PROPOSED 1-

HOUR STANDARD 

EPA’s Regulatory Impact Analysis for this proposed standard 5shows that almost none 

of the proposed rule benefits would come from reducing adverse health effects associated 

with SO2. Virtually all of the benefits come from EPA assuming secondary benefits are 

related to possible reductions in particulate matter concentrations. 

The calculations indicate that at least 99.97% of the benefits are not from direct control of 

SO2. For example, at the most stringent standard alternative (50 ppb) the maximum 

assumed national annual benefits are $12 million from lower SO2 concentrations. By 

contrast, the associated benefits estimated to result from associated reductions in 

particulate matter levels are $41 billion. Thus, the RIA finds 3,400 times the level of 

benefit from assumed indirect reductions in particulate matter than from reductions of 

SO2. 

Impacts of SO2 emissions on health risks associated with particulates should be 

considered separately in the pending particulate matter NAAQS proceeding, for which 

EPA is scheduled to issue a proposal in November 2010 and a final decision by July 

2011.

If EPA continues to rely upon particulate matter co-benefits to drive its NAAQS costbenefit justifications, it should acknowledge more directly that such benefits are highly 

uncertain. Regarding particulate matter health effects, the Electric Power Research 

Institute (EPRI) has implemented state-of-the-air studies, including ARIES, which 

indicate that claims regarding health effects attributed to particulate matter sulfates are 

questionable, while other components in the PM mass such as elemental carbon (EC) and 

organic carbon are more important than assumed. EPRI also questions premature 

mortality assumptions. 6 

 

5

 http://www.epa.gov/ttn/ecas/regdata/RIAs/pso2full11-16-09.pdf

6

 EPRI in a February 2009 document entitled “PM2.5 Reductions and Impact on Premature Death: An EPRI 

Perspective Issue Brief” concludes, regarding estimates of premature mortality attributed to particulate 

matter, that 
5

It is inappropriate for EPA, rule after rule, to claim particulate matter co-benefits as a 

major, if not dominant part of the benefit equation. This leads to a situation where the 

benefits probably are at least quadruple-counted (i.e., particulate matter co-benefits are or 

likely will be factored into benefit calculations for the SO2, nitrogen dioxide, and ozone 

NAAQS; the upcoming CAIR Phase 2 rule; and perhaps even the power sector MACT 

rule).

As for cost-effectiveness, the agency has not set forth a cogent path forward assessing the 

impacts of revising one standard on concentrations of other pollutants. All six NAAQS 

are being reviewed within a short amount of time and presumably all will be tightened. 

EPA should consider when setting standards and in implementation rules/guidance that 

 

“However, one number does not reflect the high degree of uncertainty associated with each step of 

the analysis. A more appropriate way to express potential health impacts would be to use a range. 

Since some models in some studies do not find a statistically significant effect of PM2.5 on 

mortality, the effects range could even include zero.” 

EPRI in a document entitled Particulate Matter Toxicology (September 2008) asks “What have we learned 

through toxicology about the relative toxicity of different PM components?” and concludes regarding our 

current state of knowledge on the health effects attributable to different PM components: 

“Sulfate and acid aerosols: There is little evidence for sulfate-related health effects except at high 

concentrations (in the mg/m3range, several orders of magnitude higher than ambient air 

concentrations), where some effects on pulmonary function have been noted. Some strong acids 

(for example, H2SO4) can cause pulmonary effects, but again, in the mg/m3concentration range.”

EPRI in a December 2009 document entitled “Air Quality Health Effects Research: Current Status”, 

concludes that: 

“Substantial progress has been made in understanding the effects of air pollution. EPRI research 

has helped to lead the way in demonstrating that all PM components are not equally toxic, and 

today there is a growing consensus that EC is one of the most important components in explaining 

health responses to PM. Because EC itself is relatively inert, it is likely that any signal observed 

with this component reflects an association with a pollutant that varies with EC because it is 

emitted from the same source(s). For example, the signal could be due to particle-phase organic 

compounds emitted from diesel engines, which are a major source of EC. 

EPRI’s research has also made it clear that the focus cannot only be on PM; pollutant gases are 

also tied to health responses and could explain some of the responses that have been attributed to 

PM. In particular, the organic gases (i.e., volatile or semi-volatile organic compounds; VOCs and 

SVOCs) need to be considered more comprehensively. This seems particularly important, since as 

mentioned above, EC and some of these VOCs and SVOCs are emitted from the same source. 

Therefore, considering both in a holistic and integrative manner may lead to valuable insights into 

the causative components of air pollution. Clearly, this understanding is critical so that regulation 

can focus on those sources emitting the most harmful pollutants.”
6

significant interactions will occur for air quality and implementation decisions, which 

will complicate, if not undermine, planning and compliance measures. 

While cost is not a consideration in establishing a NAAQS, the Administrator can make 

her own policy judgment weighing the benefits when establishing a NAAQS. Supreme 

Court Justice Breyer, in Whitman v. American Trucking Association, emphasized the 

considerable latitude the EPA Administrator has in setting a NAAQS at a level that will 

have small public health risks when viewed in the context of the many other factors that 

influence health.

PROJECTED HEALTH EFFECTS OF EXPOSURE TO SO2 DO NOT SUPPORT 

THE 1-HOUR STANDARD.

EPA clearly focuses its concerns and proposal on protecting exercising asthmatics from 

elevated short-term SO2 exposures. The health response, which occurs rarely, is small, 

transient and quickly reversed. Identical effects commonly occur in response to a variety 

of situations such as moderate exercise, exposure to cold, or everyday stress. Effects are 

very small compared. There is no effect on healthy individuals from SO2 concentrations 

at or close to those that occur in ambient air. EPA states in the proposal that there is little 

evidence supporting a long-term effect and thus proposes to, after establishing a 1-hour 

standard, revoke the 24-hour and annual SO2 standards.

The Utility Air Regulatory Group (UARG) will submit detailed comments on the 

scientific justification for the proposed standards. UARG raises many important issues, 

several of which EEI discusses briefly below. EEI supports the comments of UARG on 

the proposed rule. 

Regarding clinical studies, there is no real change in the underlying data from the 

previous SO2 NAAQS review in 1996, but rather an EPA shift in interpretation of the 

studies. EPA takes an unwarranted jump to assume that responses to higher SO2 are 

worse for more severe asthmatics, a conclusion refuted by a study that EPA itself uses to 

support aspects of its proposal (Linn et al., 1987). 
7

Regarding epidemiology studies, the issue of confounding remains very important and 

EPA continues to undervalue the uncertainties of measurement error, modeling 

deficiencies, and co-pollutant effects (i.e., when numerous air pollutants are present, what 

appears to be an impact from one may in fact be an impact of another). Co-pollutant 

impacts cannot be evaluated when modeling efforts include only one pollutant and 

exclude others, which is the case in many of the studies EPA relies upon. UARG in its 

comments also notes that the proposed rule relies heavily on studies with slightly positive 

findings that are at the same time not statistically significant. 

Finally, the magnitude of the possible effects of SO2 is very small. UARG in its 

comments notes that EPA discussed in its Risk and Exposure Analysis (REA) a modeling 

study for Greene County, Missouri which found that 0.4 percent of exercising 

(moderately or greater) asthmatic children experienced a single lung function response 

over the course of an entire year at current air quality levels or at 50-100 ppb SO2, 

compared to 0.5 percent at 150 ppb SO2. There appears to be little difference in health 

benefits for a 50-100 ppb standard compared to a 150 ppb standard and EPA’s risk 

assessment does not suggest that any of the standards under consideration would 

significantly reduce risks to asthmatics and asthmatic children from those associated with 

SO2 levels currently found in ambient air.

Taken together, these comments demonstrate that EPA does not have a sufficient basis to 

choose a 50-100 ppb standard. The CAA requires that health effects be projected with a 

reasonable degree of scientific certainty. The Agency’s review and utilization of the 

information contained in the Integrated Science Assessment and the Risk and Exposure 

Assessment do not meet the requirements of the CAA and EPA’s promulgation of a final 

standard within the range proposed would be more stringent than necessary and thus 

arbitrary and capricious.

MONITORING AND OTHER ISSUES

EEI concurs with UARG comments regarding monitoring, data interpretation and 

exceptional events aspects of the proposed rule.
8

CONCLUSION

EEI supports regulation that provides real benefits. However, this proposal provides very 

little benefit as indicated by EPA’s own Regulatory Impact Analysis, which shows that 

the cost of the proposal far outweighs the direct SO2 reduction benefits. EEI believes that 

setting a 1-hour standard in the range of 50-100 ppb is not supported by the scientific 

evidence. 

EPA also requested comment on a standard of 150 ppb. If the Agency decides that it 

must establish a new 1-hour standard, EEI recommends a standard of no less than 150 

ppb, and agrees with the Agency that it should revoke the current 24-hour and annual 

primary SO2 standards.