54046 Federal Register / Vol. 70, No. 176 / Tuesday, September 13, 2005 / Notices 

and the corresponding one-time total 

cost to all respondents will be $24,800. 

Since this information collection is 

voluntary and does not involve any 

special equipment, respondents will not 

incur any capital or operation and 

maintenance (O&M) costs. 

Burden means the total time, effort, or 

financial resources expended by persons 

to generate, maintain, retain, or disclose 

or provide information to or for a federal 

agency. This includes the time needed 

to review instructions; develop, acquire, 

install, and utilize technology and 

systems for the purposes of collecting, 

validating, and verifying information, 

processing and maintaining 

information, and disclosing and 

providing information; adjust the 

existing ways to comply with any 

previously applicable instructions and 

requirements; train personnel to be able 

to respond to a collection of 

information; search data sources; 

complete and review the collection of 

information; and transmit or otherwise 

disclose the information. 

Dated: September 2, 2005. 

Deborah Y. Dietrich, 

Director, Office of Emergency Management. 

[FR Doc. 05–18091 Filed 9–12–05; 8:45 am] 

BILLING CODE 6560–50–M 

ENVIRONMENTAL PROTECTION 

AGENCY 

[FRL–7968–8] 

Science Advisory Board Staff Office; 

Notification To Convene Workgroups 

of Experts for Rapid Consultative 

Advice on Scientific and Technical 

Issues From Hurricane Katrina 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Notice. 

SUMMARY: The EPA Science Advisory 

Board (SAB) Staff Office announces its 

intent to convene workgroups of experts 

drawn from the U.S. EPA SAB, the 

Clean Air Scientific Advisory 

Committee, and the Advisory Council 

on Clean Air Compliance Analysis 

(chartered advisory committees), their 

standing committees, subcommittees, 

and advisory panels to provide rapid 

consultative advice on scientific and 

technical issues in the aftermath of 

Hurricane Katrina. 

FOR FURTHER INFORMATION CONTACT: 

Members of the public who wish to 

obtain information about the rapid 

consultative advice process and projects 

may contact Dr. Anthony F. 

Maciorowski, Associate Director for 

Science, Science Advisory Board Staff 

Office, by telephone at (202) 343–9983; 

by e-mail at 

maciorowski.anthony@epa.gov; or by 

mail at the U.S. EPA, Science Advisory 

Board (1400F), 1200 Pennsylvania 

Avenue, NW, Washington, DC 20460. 

SUPPLEMENTARY INFORMATION: The SAB 

was established by 42 U.S.C. 4365 to 

provide independent scientific and 

technical advice, consultation, and 

recommendations to the EPA 

Administrator on a technical basis for 

Agency positions and regulations. The 

SAB anticipates that the scope and scale 

of environmental destruction in 

Mississippi, Louisiana and Alabama 

will lead EPA Program Offices and 

Regions to request advice on an array of 

scientific and technical issues. Rapid 

consultative advice from nationally 

recognized scientists and engineers will 

assist the Agency in developing and 

implementing timely and scientifically 

appropriate responses to Hurricane 

Katrina induced destruction and 

contamination along the Gulf Coast. 

To expedite the development of 

advice on Hurricane Katrina related 

issues, the SAB Staff Office will 

convene workgroups of technical 

experts drawn from the U.S. EPA SAB, 

the Clean Air Scientific Advisory 

Committee, the Advisory Council on 

Clean Air Compliance Analysis 

(chartered advisory committees), their 

standing committees, subcommittees, 

and advisory panels. Workgroup 

members will be invited to serve based 

on their scientific and technical 

expertise, knowledge, and experience; 

availability and willingness to serve; 

absence of financial conflicts of interest; 

and scientific credibility and 

impartiality. Due to critical mission and 

schedule requirements, there is 

insufficient time to provide the full 15 

days notice in the Federal Register prior 

to advisory committee meetings, 

pursuant to the final rule on Federal 

Advisory Committee Management 

codified at 41 CFR 102–3.150. 

Therefore, information on the 

workgroup consultations will be posted 

on the SAB Web site at http:// 

www.epa.gov/sab as they are available. 

Dated: September 8, 2005. 

Vanessa Vu, 

Director, EPA Science Advisory Board Staff 

Office. 

[FR Doc. 05–18227 Filed 9–12–05; 8:45 am] 

BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

[OAR–2003–0032; FRL–7965–4] 

Interim Guidance on Control of Volatile 

Organic Compounds in Ozone State 

Implementation Plans 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Notice of interim guidance on 

SIP development. 

SUMMARY: The Environmental Protection 

Agency (EPA) encourages States to 

consider recent scientific information 

on the photochemical reactivity of 

volatile organic compounds (VOC) in 

the development of State 

implementation plans (SIPs) designed to 

meet the national ambient air quality 

standard (NAAQS) for ozone. This 

interim guidance summarizes recent 

scientific findings, provides examples of 

innovative applications of reactivity 

information in the development of VOC 

control measures, and clarifies the 

relationship between innovative 

reactivity-based policies and EPA’s 

current definition of VOC. This interim 

guidance does not change any existing 

rules. 

DATES: This interim guidance is 

effective on September 13, 2005. 

ADDRESSES: EPA has established a 

docket for this action under Docket ID 

No. OAR–2003–0032. All documents in 

the docket are listed in the EDOCKET 

index at http://www.epa.gov/edocket. 

Although listed in the index, some 

information may not be publicly 

available, i.e., Confidential Business 

Information (CBI) or other information 

whose disclosure is restricted by statute. 

Certain other material, such as 

copyrighted material, is not placed on 

the Internet and will be publicly 

available only in hard copy form. 

Publicly available docket materials are 

available either electronically in 

EDOCKET or in hard copy at the Docket 

ID No. OAR–2003–0032, EPA/DC, EPA 

West, Room B102, 1301 Constitution 

Ave., NW., Washington, DC. The Public 

Reading Room is open from 8:30 a.m. to 

4:30 p.m., Monday through Friday, 

excluding legal holidays. The telephone 

number for the Public Reading Room is 

(202) 566–1744, and the telephone 

number for the Air Docket is (202) 566–

1742. 

FOR FURTHER INFORMATION CONTACT: 

William L. Johnson, Office of Air 

Quality Planning and Standards, Air 

Quality Strategies and Standards 

Division, Mail code C539–02, Research 

Triangle Park, NC 27711, telephone 

(919) 541–5245.; fax number: (919) 541–

Federal Register / Vol. 70, No. 176 / Tuesday, September 13, 2005 / Notices 54047 

0824; e-mail address: 

Johnson.WilliamL@epa.gov. 

SUPPLEMENTARY INFORMATION: 

Outline 

I. General Information 

II. Introduction 

III. Short History of VOC Reactivity Policy 

and Science 

IV. Use of VOC Reactivity in Developing SIPs 

V. Relationship to Existing VOC Exemption 

Policy 

VI. Summary 

I. General Information 

Does This Action Apply to Me? 

You may be an entity affected by this 

interim guidance if you are a State or 

local air pollution control agency that 

has, or is currently developing, an ozone 

SIP containing programs to control VOC 

emissions. Additionally, you may be 

impacted if you use or emit VOCs in 

commercial/industrial/manufacturing 

operations, as well as other consumer/ 

commercial activities. If you have 

questions regarding the applicability of 

this action to a particular entity, consult 

the person listed in the preceding FOR

FURTHER INFORMATION CONTACT section. 

This action does not impose any new 

mandates on States or industry, but 

rather provides information about 

options for meeting Clean Air Act 

mandates that are likely to be more 

effective, and more cost-effective, than 

the measures currently employed in 

most parts of the country. 

II. Introduction 

Ground level ozone, one of the 

principal components of ‘‘smog,’’ is a 

serious air pollutant that harms human 

health and the environment. In April 

2004, EPA designated 126 areas of the 

country as ‘‘nonattainment’’ for the 8- 

hour ozone national ambient air quality 

standards (NAAQS). States and tribes 

are currently revising State 

Implementation Plans (SIPs) in order to 

bring air quality into compliance with 

the 8-hour ozone standard. The Agency 

has proposed that these SIP revisions 

must be submitted to EPA by June 15, 

2007. Certain areas will need to submit 

separate reasonably available control 

technology (RACT) SIP revisions. There 

is final action pending that the Agency 

anticipates will require these revisions 

to be submitted by September 15, 2006. 

Some of the areas designated as 

nonattainment under the 8-hour 

standard have persistent air quality 

problems and will need to employ as 

many cost-effective controls as possible 

to achieve the 8-hour ozone NAAQS as 

expeditiously as practicable but no later 

than by their attainment date. 

The development of measures to 

reduce ozone concentrations is 

complicated by the fact that ozone is not 

directly emitted. It is formed in the air 

by chemical reactions of nitrogen oxides 

(NOX) and VOCs in the presence of heat 

and sunlight. Therefore, ozone SIPs 

must address emissions of these ozone 

precursors. 

There are thousands of individual 

chemical species of VOCs that can react 

to form ozone. It is generally understood 

that not all VOCs contribute equally to 

ozone formation and accumulation. 

Some VOCs react slowly and changes in 

their emissions have limited effects on 

local or regional ozone pollution 

episodes. Some VOCs form ozone more 

quickly, or they may degrade through a 

series of reactions that generates more 

ozone than the reaction pathways of 

other VOCs. Others not only form ozone 

themselves, but also enhance ozone 

formation from other VOCs. The 

photochemical reactivity of a compound 

is a measure of its potential to form 

ozone. By distinguishing between more 

reactive and less reactive VOCs, it 

should be possible to decrease ozone 

concentrations further or more 

efficiently than by controlling all VOCs 

equally. 

Discriminating between VOCs on the 

basis of their contributions to ozone 

formation, or reactivities, is not 

straightforward. Reactivity is not simply 

a property of the compound itself; it is 

a property of both the compound and 

the environment in which the 

compound is found. The absolute 

reactivity of a single compound varies 

with VOC–NOX ratios, meteorological 

conditions, the mix of other VOCs in the 

atmosphere, and the time interval of 

interest. On the other hand, there are 

several scientifically valid methods that 

can be used to develop reactivity 

‘‘scales’’ or weighting approaches based 

on the relative reactivity of different 

VOCs, and there is a high correlation 

between these different methods. 

The promise of a more efficient VOC 

control strategy has led the California 

Air Resources Board (CARB), EPA, and 

other organizations to invest in 

reactivity research. This research has 

produced improved methods for 

discriminating between VOCs on the 

basis of reactivity under a variety of 

conditions. Applying some of the 

lessons of this research, California and 

Texas have developed innovative 

regulations that use VOC reactivity 

information to improve the efficiency or 

effectiveness of VOC controls for 

specific source categories. As States 

develop their 8-hour ozone SIPs, EPA 

encourages them to consider how they 

may incorporate VOC reactivity 

information to make their future VOC 

control measures more effective and 

efficient. 

III. Short History of VOC Reactivity 

Policy and Research 

The issue of VOC reactivity was first 

recognized by EPA in its initial 

guidance to States on the preparation of 

ozone SIPs in 1971. In this initial 

guidance, EPA emphasized the need to 

reduce the total mass of organic 

emissions, but also noted that 

‘‘substitution of one compound for 

another might be useful where it would 

result in a clearly evident decrease in 

reactivity and thus tend to reduce 

photochemical oxidant formation.’’ EPA 

encouraged States to promulgate SIPs 

with organic emission control 

provisions similar to those outlined in 

Los Angeles District’s Rule 66, which 

allowed many VOC species thought to 

have minimal adverse effects to be 

exempted from control. 

The Rule 66 exempt status for many 

of these organic emission species was 

questioned a few years later when 

research results from field studies 

conducted between 1971–1974 revealed 

that pollutant transport conditions were 

capable of enhancing ozone formation 

such that these ‘‘exempt’’ compounds 

were now considered significant ozone 

producers. Thus, in 1977, the EPA 

issued the ‘‘Recommended Policy on 

Control of Volatile Organic 

Compounds,’’ offering its own, much 

more limited list of ‘‘negligibly reactive’’

compounds to be exempted (42 FR 

35314, July 8, 1977). As new 

information about the reactivity of 

different compounds has become 

available, EPA has continued to add to 

the list of negligibly reactive 

compounds following the logic of the 

1977 policy. In 1992, this list of 

negligibly reactive compounds was 

explicitly excluded from the definition 

of VOC when it was codified in 40 CFR 

51.100(s) (57 FR 3941, February 3, 

1992). Since 1977, EPA has designated 

approximately 50 compounds or classes 

of compounds as negligibly reactive and 

has excluded these compounds from the 

regulatory definition of VOC. 

Beginning in the early 1990s, CARB 

has pursued the development of 

regulatory approaches that more fully 

discriminate VOCs on the basis of 

reactivity. In 1991, CARB incorporated 

a reactivity scale for weighting the 

emissions of individual VOC species in 

their low emitting vehicle and clean 

fuels regulation. The scale was designed 

to account for the differences in the 

ozone-forming potential of exhausts 

from gasoline engines and alternative 

fueled vehicles. The scale adopted by 

54048 Federal Register / Vol. 70, No. 176 / Tuesday, September 13, 2005 / Notices 

1Carter, William P. L. ‘‘Development of Ozone 

Reactivity Scales for Volatile Organic Compounds.’’

Journal of the Air and Waste Management 

Association 44 (1994): 881–99. 

2See http://www.cgenv.com/Narsto/ 

reactinfo.html. 

3Carter, William P.L., D.R. Crocker, III, D.R. Fitz, 

L.L. Malkina, K. Bumiller, C.G. Sauer, J.T. Pisano, 

C. Bufalino, and C. Song. ‘‘A New Environmental 

Chamber for Evaluation of Gas-Phase Chemical 

Mechanisms and Secondary Aerosol Formation.’’

Atmospheric Environment accepted for publication, 

July 15, 2005 (in press). 

4Arunachalam, S., R. Mathur, A. Holland, M.R. 

Lee, D. Olerud, and H. Jeffries. ‘‘Investigation of 

VOC Reactivity Assessment with Comprehensive 

Air Quality Modeling.’’ Report to the U.S. 

Environmental Protection Agency, 2003; and Carter, 

William P.L., Gail S. Tonnesen, and G. Yarwood. 

‘‘Investigation of VOC Reactivity Effects Using 

Existing Regional Air Quality Models.’’ Report to 

the American Chemistry Council, Contract SC–

20.0–UCR–VOC–RRWG, 2003. 

5Carter, William P.L., Gail S. Tonnesen, and G. 

Yarwood. ‘‘Investigation of VOC Reactivity Effects 

Using Existing Regional Air Quality Models.’’

Report to the American Chemistry Council, 

Contract SC–20.0–UCR–VOC–RRWG, 2003. 

6 Ibid. 

7Hakami, A., M.S. Bergin, and A.G. Russell. 

‘‘Ozone Formation Potential of Organic Compounds 

in the Eastern United States: A Comparison of 

Episodes, Inventories, and Domains.’’

Environmental Science and Technology 38 (2004): 

6748–59; Hakami, A., M. Arhami, and A.G. Russell. 

‘‘Further Analysis of VOC Reactivity Metrics and 

Scales.’’ Report to the U.S. Environmental 

Protection Agency, 2004; and Derwent, R.G. 

‘‘Evaluation and Characterization of Reactivity 

Metrics.’’ Report to the U.S. Environmental 

Protection Agency, 2004. 

CARB was the Maximum Incremental 

Reactivity (MIR) scale, derived using a 

series of box model simulations with 

varying VOC composition and VOCNOX ratios.1 The MIR scale is 

commonly expressed in units of grams 

of ozone produced per gram of VOC 

emitted. 

Over the course of the 1990s, CARB 

continued to invest in the development 

of reactivity scales and to explore their 

potential regulatory applications. In 

June 2000, CARB adopted an aerosol 

coatings regulation that incorporates an 

updated MIR scale. This regulation is 

described in more detail below. 

Currently, CARB is exploring the use of 

reactivity scales in other programs, 

including regulations for architectural 

coatings. 

In 1998, EPA participated in the 

formation of the Reactivity Research 

Working Group (RRWG), which was 

organized to help develop an improved 

scientific basis for reactivity-related 

regulatory policies.2 All interested 

parties were invited to participate. Since 

that time, representatives from EPA, 

CARB, Environment Canada, States, 

academia, and industry have met in 

public RRWG meetings to discuss and 

coordinate research that would support 

this goal. The RRWG has organized a 

series of research projects that have 

addressed issues such as: 

• The sensitivity of ozone to VOC 

mass reductions and changes in VOC 

composition; 

• The derivation and evaluation of 

reactivity scales using photochemical 

airshed models; 

• The development of emissions 

inventory processing tools for exploring 

reactivity-based strategies; and 

• The fate of VOC emissions and their 

availability for atmospheric reactions. 

This research has led to a number of 

findings that increase our confidence in 

the ability to develop approaches that 

discriminate between VOCs on the basis 

of reactivity. These findings include: 

• State of the art chamber studies at 

low VOC-NOX ratios demonstrate that 

current atmospheric chemistry models 

generally perform as well under ‘‘real 

world’’ conditions as under the high 

concentration scenarios used in their 

development.3

• Substituting emissions of low 

reactivity compounds for emissions of 

high reactivity compounds can be 

effective in reducing 1-hour and 8-hour 

ozone concentrations. Substitutions 

based on equal mass, equal carbon, or 

equal molar concentrations will achieve 

different levels of ozone reduction 

depending on the chemicals being 

substituted. Similar to decreases in mass 

of VOC emissions, reactivity-based VOC 

substitution seems to reduce higher 

concentrations of ozone more than 

lower concentrations of ozone.4

• There are several scientifically valid 

methods that can be used to calculate 

reactivity scales, each with different 

strengths and weaknesses. Although 

there is a high correlation between the 

different methods (even the simplest 

ones), important differences exist in 

their geographical representativeness 

and in the amount of spread between 

low reactivity and high reactivity 

compounds.5

• Using available reactivity scales, it 

is possible to construct a VOC 

substitution scenario that will achieve 

approximately the same ozone 

reductions as reducing the overall mass 

of VOC emissions. However, when 

applied, the substitution scenario may 

increase ozone in some areas and 

decrease ozone in others depending on 

the robustness of the reactivity scale 

used.6

• Several reactivity metrics derived 

with airshed models (such as the 

Maximum Ozone Incremental Reactivity 

to Maximum Incremental Reactivity 

(MOIR-MIR) and Least Squares Relative 

Reactivity (LS-RR)) appear to be robust 

over different regions of the country, 

meteorological episodes, year of 

analysis, averaging times, and models.7

EPA encourages all interested parties 

to continue working through the RRWG 

to improve the scientific foundation of 

VOC reactivity-based regulations. EPA 

will continue to update its guidance to 

States as new information becomes 

available. In the meantime, EPA 

encourages States to take advantage of 

the information that is now available in 

designing future VOC control strategies. 

IV. Use of VOC Reactivity in 

Developing SIPs 

Although the traditional approach to 

VOC control focused on reducing the 

overall mass of emissions may be 

adequate in some areas of the country, 

an approach that discriminates between 

VOCs based on reactivity is likely to be 

more effective and efficient. In 

particular, reactivity-based approaches 

are likely to be important in areas for 

which VOC control is a key strategy for 

reducing ozone concentrations. Such 

areas include: 

• Areas with persistent ozone 

nonattainment problems; 

• Urbanized or other NOX-rich areas 

where ozone formation is particularly 

sensitive to changes in VOC emissions; 

• Areas that have already 

implemented VOC RACT measures and 

need additional VOC emission 

reductions. 

In these areas, there are a variety of 

ways of addressing VOC reactivity in 

the SIP development process, including: 

• Developing accurate, speciated 

VOC emissions inventories. EPA 

encourages States—and particularly 

States with persistent ozone problems—

to develop emissions inventories that 

include emission estimates for 

individual VOC species, as opposed to 

only estimating total VOC mass. This 

type of information may be especially 

useful for identifying emissions of the 

most reactive VOCs in the most VOCsensitive areas. Currently, most States 

collect information on the mass of total 

VOC emissions. For air quality 

modeling purposes, this mass is 

apportioned to individual chemical 

species using EPA-provided profiles for 

each source category. Many industries, 

however, calculate their reported total 

VOC emissions from detailed speciated 

information that they routinely gather 

for other reasons. Where appropriate, 

States may want to gather such detailed 

speciated information and compare it to 

the national default speciation profiles. 

States should also consider emerging 

research on the actual availability of 

VOCs for atmospheric reaction. In 

estimating VOC emissions, especially 

Federal Register / Vol. 70, No. 176 / Tuesday, September 13, 2005 / Notices 54049 

8Reactivity Research Working Group. ‘‘Final 

Proceedings of Workshop on Combining 

Environmental Fate and Air Quality Modeling.’’

Research Triangle Park, NC, 2000. 

9Russell, A.G., J.B. Milford, M.S. Bergin, S. 

McBride, L. McNair, Y. Yang, W.R. Stockwell, and 

B. Croes. ‘‘Urban Ozone Control and Atmospheric 

Reactivity of Organic Gases.’’ Science 269 (1995): 

491–95. 

10California Air Resources Board. ‘‘Initial 

Statement of Reasons for the Proposed 

Amendments to the Regulation for Reducing 

Volatile Organic Compound Emissions from 

Aerosol Coating Products.’’ 2000. 

from coatings, solvents, and consumer 

products, it is often assumed that the 

entire volatile fraction is emitted and 

available for photochemical reaction, 

unless captured by specific control 

equipment. In some situations, however, 

otherwise volatile compounds may be 

trapped in liquid or solid phases or 

adhere to surfaces such that they are not 

actually released to the atmosphere. 

Once emitted into the atmosphere, 

VOCs may also be scavenged by rain, 

form particles, or deposit on surfaces.8

Taking this behavior into account 

should lead to more accurate VOC 

emissions inventories and 

photochemical modeling. It may also 

allow States to consider volatility 

thresholds or other approaches designed 

to reflect atmospheric availability in 

certain types of regulatory programs. 

• Prioritizing control measures using 

reactivity metrics. Most States prioritize 

control measures for implementation 

based on the cost effectiveness of 

controlling the total mass of VOCs (i.e., 

$/ton). Using reactivity metrics and 

speciated VOC emission information, it 

is possible to calculate cost effectiveness 

on the basis of relative ozone formation 

(i.e., $/ozone decreased). By controlling 

the most reactive source categories first, 

a State may be able to decrease the total 

cost of reaching attainment. For 

example, Russell, et al.9 found that in 

Los Angles, selecting VOC controls on 

the basis of reactivity would decrease 

the cost of achieving any given level of 

ozone reduction as compared to a massbased strategy up to a certain level of 

reduction. As more controls are 

required, the cost of strategies optimized 

on a reactivity basis converge with the 

cost of mass-based strategies as all the 

available controls are applied in both 

cases. 

• Targeting emissions of highlyreactive VOC compounds with specific 

control measures. With speciated 

emissions information, a State may 

develop control measures that 

specifically target sources of the most 

highly reactive VOCs. In the HoustonGalveston area, a comprehensive field 

study revealed that fugitive or episodic 

releases of several highly reactive 

compounds (e.g., ethylene, propylene, 

1,3-butadiene, and butenes) from 

petroleum refining and petrochemical 

facilities have contributed significantly 

to exceedances of the ozone NAAQS. In 

2002, after consultation with the local 

industry, the Texas Commission on 

Environmental Quality (TCEQ) issued 

rules targeting emissions of these highly 

reactive VOCs from four processes: 

fugitive releases, flares, process vents, 

and cooling towers. These first rules 

emphasized additional monitoring, 

record keeping, and enforcement rather 

than establishing individual unit 

emission limits. In 2004, TCEQ adopted 

a cap-and-trade program for ethylene 

and propylene emissions from flares, 

vents, and cooling towers in Houston. 

Under this program, each site is 

assigned a daily and yearly emissions 

cap. Non-highly reactive VOC emissions 

may be used to offset highly reactive 

VOC emissions up to a limit of 5% of 

the facility’s initial cap. The non-highly 

reactive VOC emission offsets are 

discounted based on the ratio of the 

reactivity of the offsets to the reactivity 

of propylene. EPA has proposed 

approval of some facets of the Texas 

rules for the control and monitoring of 

highly reactive VOCs (70 FR 17640), and 

the Agency expects to propose action on 

other program elements, such as the 

cap-and-trade program, in the near 

future. Although EPA has not completed 

its review of the SIP revisions provided 

by Texas for the Houston-Galveston 

area, it does seem clear that targeting 

these highly reactive compounds for 

additional control will achieve 

substantial ozone benefit and is more 

cost effective than a rule targeting all 

VOCs. 

• Encouraging VOC substitution and 

composition changes using reactivityweighted emission limits. For some VOC 

source categories, such as paints, 

coatings, adhesives, and other 

formulated products, manufacturers 

may have the flexibility to change 

product formulations so as to change the 

composition as well as the mass of the 

VOC emissions. In some cases, changing 

the composition of the VOC emissions 

may be less costly and allow for better 

product performance than decreasing 

the mass of VOC emissions, while also 

providing greater benefits for ozone 

control. In 2000, CARB found that 

manufacturers were having difficulty 

meeting California’s stringent massbased VOC emission limits for aerosol 

coatings.10 After extensive study and 

consultations with stakeholders, CARB 

replaced the mass-based emission limits 

for aerosol coatings with reactivityweighted emissions limits, using a 

version of the MIR scale. CARB gathered 

VOC composition and sales information 

from manufacturers to create VOC 

emission profiles for different categories 

of aerosol coatings products. Using this 

composition information, CARB 

calculated the MIR-weighted emission 

limits that would achieve the same 

ozone reduction as would have been 

achieved by the existing mass-based 

emission limits. To determine 

compliance with the reactivity-weighted 

limits, the weight percent of each 

individual VOC in the product is 

multiplied by its corresponding MIR 

value and then summed for all VOCs in 

the product. All VOCs with MIR values, 

including those that are considered 

‘‘negligibly reactive’’ under the national 

policy, are included in the calculation. 

For complex mixtures, such as mineral 

spirits, CARB performed analyses to 

assign appropriate MIR values for 

different mixtures. CARB intends to 

review and, as appropriate, update the 

reactivity scale used in the rule to 

incorporate the latest scientific 

information. EPA has proposed 

approval of this rule for inclusion in 

California’s SIP (70 FR 1640, January 7, 

2005) and expects to finalize this 

approval in the near future. EPA and 

CARB view this rule as an important 

opportunity to gather additional 

information about the effectiveness and 

practical implementation issues 

associated with a reactivity-based 

program. 

V. Relationship to Existing VOC 

Exemption Policy 

Although a continuous reactivity 

scale is likely to be the most effective 

approach for regulating VOCs in many 

areas of the country, such an approach 

is more difficult to develop and 

implement than traditional mass-based 

approaches because reactivity-based 

programs carry the extra burden of 

characterizing and tracking the full 

chemical composition of VOC 

emissions. In addition, although most 

existing VOC control programs do not 

discriminate between individual VOCs 

based on reactivity, they continue to 

provide significant ozone reduction 

benefits and will remain in place unless 

and until they are replaced by programs 

that achieve the same or greater benefits. 

Under virtually all existing programs, 

EPA and States exclude certain 

negligibly reactive compounds from the 

regulatory definition of VOC and thus 

exempt them from regulation as ozone 

precursors. This exemption policy 

serves two important purposes: 

(1) Because EPA does not give VOC 

reduction credit for programs that 

54050 Federal Register / Vol. 70, No. 176 / Tuesday, September 13, 2005 / Notices 

11Carter, William P. L., Gail S. Tonnesen, and G. 

Yarwood. ‘‘Investigation of VOC Reactivity Effects 

Using Existing Regional Air Quality Models.’’

Report to the American Chemistry Council, 

Contract SC–20.0–UCR–VOC–RRWG, 2003. 

reduce emissions of negligibly reactive 

compounds, control efforts are focused 

on emissions that contribute 

significantly to the formation and 

accumulation of ozone. The Agency 

continues to believe that it is not 

appropriate, and would be misleading, 

to give VOC reduction credit to States or 

industries for reducing emissions of 

compounds that have little or no effect 

on ozone concentrations. 

(2) Because negligibly reactive 

compounds are not subject to regulation 

as VOCs, industry has an incentive to 

use negligibly reactive compounds in 

place of higher reactivity compounds. 

The exemption approach also creates a 

strong incentive for industry to invest in 

the development of negligibly reactive 

compounds and low reactivity 

formulations. The Agency continues to 

believe that the substitution of ‘‘VOCexempt’’ compounds for regulated VOCs 

is an effective ozone control strategy, 

even though it is not as effective or 

efficient as the use of a continuous 

reactivity scale to encourage optimal 

substitutions in terms of ozone control. 

Because the current exemption 

approach continues to serve these 

purposes, EPA will continue its efforts 

to identify negligibly reactive 

compounds and exclude them from the 

federal regulatory definition of VOC. 

The Agency expects that such 

compounds will also be exempt from 

state VOC control programs, with 

exceptions made for specific reactivitybased rules such as the CARB aerosol 

coatings rule. 

Since 1977, EPA has used the 

reactivity of ethane as the threshold of 

negligible reactivity. Compounds that 

are less reactive than or equally reactive 

to ethane have been deemed negligibly 

reactive. Compounds that are more 

reactive than ethane continue to be 

considered reactive VOCs and subject to 

control requirements. The selection of 

ethane is based on a series of smogchamber experiments that underlies the 

1977 policy. In these experiments, 

various compounds were injected into a 

smog chamber at a molar concentration 

that was typical of the total molar 

concentration of VOCs in Los Angeles 

ambient air at the time (4 ppmv). NOX

was injected into the chamber at a 

concentration of 0.2 ppm, and as the 

chamber was exposed to sunlight, the 

maximum ozone formed in the chamber 

was measured. The maximum ozone 

formed in the chamber was compared to 

the level of the NAAQS, which at the 

time was 0.08 ppm of oxidants. Propane 

was the most reactive compound tested 

that did not cause a maximum ozone 

concentration greater than 0.08 ppm. 

Ethane was somewhat less reactive than 

propane. Based on these experiments, 

the Agency determined that ethane 

should be used as the benchmark for 

identifying compounds whose potential 

contribution to ozone formation was 

below regulatory concern. 

A more recent modeling study 

conducted under the auspices of the 

RRWG replicated the essence of the 

1970s smog chamber experiments using 

a state-of-the-art airshed model of the 

eastern United States. In this study, 

Carter et al. replaced all anthropogenic 

VOC emissions with ethane and found 

that ozone formation decreased almost 

as much as when all anthropogenic 

emissions of VOC were removed. When 

anthropogenic emissions were removed 

or when they were replaced with 

ethane, the model still predicted ozone 

concentrations greater than the level of 

the NAAQS due to emissions of NOX

and biogenic VOCs.11

The metric used to compare the 

reactivity of a specific compound to that 

of ethane has varied over time. The 

primary metric for comparison has been 

kOH, the molar rate constant for 

reactions between the subject 

compound and the hydroxyl radical 

(OH). In several cases, EPA has also 

looked at comparisons of MIR values 

expressed on both a molar and a mass 

basis. Comparing MIR values on a molar 

basis versus a mass basis can lead to 

different conclusions about whether a 

compound is less reactive or more 

reactive than ethane. In two cases, 

acetone (60 FR 31633, June 16, 1995) 

and tertiary butyl acetate (69 FR 69293, 

November 29, 2004), EPA has exempted 

compounds based on the finding that 

the compounds are less reactive than 

ethane when compared using 

incremental reactivity values expressed 

on a mass basis, even though they were 

more reactive on a molar basis. 

The molar comparison is more 

consistent with the original smog 

chamber experiments, which compared 

equal molar concentrations of 

individual VOCs, that underlie the 

selection of ethane as the threshold. The 

mass-based comparison is consistent 

with how MIR values and other 

reactivity metrics are applied in 

reactivity-based emission limits. The 

mass-based comparison is slightly less 

restrictive than the molar-based 

comparison in that a few more 

compounds qualify as negligibly 

reactive. 

Given the two goals of the exemption 

policy articulated above, the Agency 

believes that ethane continues to be an 

appropriate threshold for defining 

negligible reactivity. Furthermore, in 

light of the second goal of encouraging 

environmentally beneficial 

substitutions, EPA believes that a 

comparison to ethane on a mass basis 

strikes the right balance between a 

threshold that is low enough to capture 

compounds that significantly affect 

ozone concentrations and a threshold 

that is high enough to exempt some 

compounds that may usefully substitute 

for more highly reactive compounds. 

When reviewing compounds that 

have been suggested for VOC-exempt 

status, EPA will continue to compare 

them to ethane using kOH expressed on 

a molar basis and MIR values expressed 

on a mass basis. Consistent with past 

practice, the Agency will consider a 

compound to be negligibly reactive as 

long as it is equal to or less reactive than 

ethane based on either one of these 

metrics. The Agency will also consider 

other reactivity metrics that are 

provided with adequate technical 

justification, such as metrics based on 

airshed modeling. States may also wish 

to identify VOC exemptions in their 

SIPs in order to encourage VOC 

substitutions that would reduce ozone 

formation. 

In the past, concerns have sometimes 

been raised about the potential impact 

of a VOC exemption on environmental 

endpoints other than ozone 

concentrations, including fine particle 

formation, air toxics exposures, 

stratospheric ozone depletion, and 

climate change. EPA has recognized, 

however, that there are existing 

regulatory and non-regulatory programs 

that are specifically designed to address 

these issues, and the Agency continues 

to believe that the impacts of VOC 

exemptions on environmental endpoints 

other than ozone formation will be 

adequately addressed by these 

programs. The VOC exemption policy is 

intended to facilitate attainment of the 

ozone NAAQS, and questions have been 

raised as to whether the Agency has 

authority to use its VOC policy to 

address concerns that are unrelated to 

ground-level ozone. Thus, in general, 

VOC exemption decisions will continue 

to be based solely on consideration of a 

compound’s contribution to ozone 

formation. However, if the Agency 

determines that a particular VOC 

exemption is likely to result in a 

significant increase in the use of a 

compound and that the increased use 

would pose a significant risk to human 

health or the environment that would 

not be addressed adequately by existing 

programs or policies, EPA reserves the 

Federal Register / Vol. 70, No. 176 / Tuesday, September 13, 2005 / Notices 54051 

right to exercise its judgment in 

deciding whether to grant an exemption. 

In all but one of the past exemption 

decisions, EPA has exempted negligibly 

reactive VOCs from recordkeeping and 

reporting requirements as well as 

control requirements. Concerns have 

been raised that even negligibly reactive 

compounds, if present in sufficient 

quantities, can contribute significantly 

to ozone formation over large spatial 

scales. Without recordkeeping and 

reporting requirements, States and EPA 

have no regular mechanism for 

maintaining adequate emissions 

inventories of negligibly reactive 

compounds or tracking their collective 

contribution to ozone concentrations. 

One approach for addressing this issue 

would be to require recordkeeping and 

reporting of all negligibly reactive VOC 

emissions. The Agency recognizes, 

however, that efforts to develop State 

and local inventories of such emissions 

are a relatively low priority compared to 

other activities that are likely to be more 

important for reducing ozone 

concentrations. In particular, as noted 

above, efforts to develop speciated 

emissions inventories should be focused 

on highly reactive compounds because 

programs targeted at controlling 

emissions of these compounds are likely 

to be more effective than simply 

regulating all VOCs equally. 

Another approach that would allow 

policymakers to track potential 

increases in emissions of negligibly 

reactive compounds would be to ask 

manufacturers who are responsible for 

VOC exemption petitions to provide 

EPA with periodic estimates of the 

magnitude and distribution of emissions 

of the exempted compound. Although 

such an approach would not provide 

detailed information about the location 

of such emissions, this type of spatial 

definition is relatively unimportant for 

compounds with negligible reactivity. 

The Agency believes that parties 

submitting VOC exemption requests 

may be able to provide emissions 

estimates that are sufficient for purposes 

of tracking the potential effects of VOCexempt compound emissions on 

regional air quality. The Agency may 

consider such an approach in the future. 

VI. Summary 

EPA encourages States, and 

particularly those with persistent ozone 

nonattainment problems, to consider 

recent scientific information on VOC 

reactivity and how it may be 

incorporated into the development of 

ozone control measures. Using reactivity 

information, States may be able to 

improve the effectiveness and efficiency 

of their VOC control policies. EPA 

encourages all interested parties to 

continue to work through the RRWG to 

improve the scientific foundation for 

reactivity-based regulatory approaches. 

Although most existing VOC control 

programs do not discriminate between 

individual VOCs based on reactivity, 

they continue to provide significant 

ozone reduction benefits and will 

remain in place unless and until they 

are replaced by programs that achieve 

the same or greater benefits. Therefore 

EPA will continue its policy of granting 

VOC exemptions for compounds that 

are negligibly reactive. EPA will 

continue to evaluate new scientific 

information regarding VOC reactivity 

and will update this interim guidance as 

appropriate. This interim guidance does 

not change any existing rules. 

List of Subjects in 40 CFR Part 51 

Environmental protection, 

Administrative practice and procedure, 

Air pollution control, Intergovernmental 

relations, Nitrogen dioxide, Ozone, 

Particulate matter, Reporting and 

recordkeeping requirements, Volatile 

organic compounds. 

Dated: August 25, 2005. 

Jeffrey R. Holmstead, 

Assistant Administrator for Air and 

Radiation. 

[FR Doc. 05–18015 Filed 9–12–05; 8:45 am] 

BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

[FRL–7967–8] 

Clean Water Act Section 303(d): 

Availability of List Decisions 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Notice of availability. 

SUMMARY: This action announces the 

availability of EPA decisions identifying 

water quality limited segments and 

associated pollutants in Nevada to be 

listed pursuant to Clean Water Act 

Section 303(d)(2), and requests public 

comment. Section 303(d)(2) requires 

that states submit and EPA approve or 

disapprove lists of waters for which 

existing technology-based pollution 

controls are not stringent enough to 

attain or maintain state water quality 

standards and for which total maximum 

daily loads (TMDLs) must be prepared. 

On September 1, 2005, EPA partially 

approved and partially disapproved 

Nevada’s 2004 submittal. Specifically, 

EPA approved Nevada’s listing of 205 

water body-pollutant combinations, and 

associated priority rankings. EPA 

disapproved Nevada’s decisions not to 

list 98 water body-pollutant 

combinations. EPA identified these 

additional water bodies and pollutants 

along with priority rankings for 

inclusion on the 2004 Section 303(d) 

list. 

EPA is providing the public the 

opportunity to review its decisions to 

add waters and pollutants to Nevada 

2004 Section 303(d) list, as required by 

EPA’s Public Participation regulations. 

EPA will consider public comments in 

reaching its final decisions on the 

additional water bodies and pollutants 

identified for inclusion on Nevada’s 

final lists. 

DATES: Comments must be submitted to 

EPA on or before October 13, 2005. 

ADDRESSES: Comments on the proposed 

decisions should be sent to David 

Smith, TMDL Team Leader, Water 

Division (WTR–2), U.S. Environmental 

Protection Agency Region IX, 75 

Hawthorne Street, San Francisco, CA 

94105, telephone (415) 972–3416, 

facsimile (415) 947–3537, e-mail 

smith.davidw@epa.gov. Oral comments 

will not be considered. Copies of the 

proposed decisions concerning Nevada 

which explain the rationale for EPA’s 

decisions can be obtained at EPA Region 

9’s Web site at http://www.epa.gov/ 

region9/water/tmdl/index.html by 

writing or calling Mr. Smith at the above 

address. Underlying documentation 

comprising the record for these 

decisions is available for public 

inspection at the above address. 

FOR FURTHER INFORMATION CONTACT: 

David Smith at (415) 972–3416 or 

smith.davidw@epa.gov. 

SUPPLEMENTARY INFORMATION: Section 

303(d) of the Clean Water Act (CWA) 

requires that each State identify those 

waters for which existing technologybased pollution controls are not 

stringent enough to attain or maintain 

State water quality standards. For those 

waters, States are required to establish 

TMDLs according to a priority ranking. 

EPA’s Water Quality Planning and 

Management regulations include 

requirements related to the 

implementation of Section 303(d) of the 

CWA (40 CFR 130.7). The regulations 

require states to identify water quality 

limited waters still requiring TMDLs 

every two years. The lists of waters still 

needing TMDLs must also include 

priority rankings and must identify the 

waters targeted for TMDL development 

during the next two years (40 CFR 

130.7). 

Consistent with EPA’s regulations, 

Nevada submitted to EPA its listing 

decisions under section 303(d)(2) on 

June 2, 2004. Nevada submitted