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CFR Citation: 40 CFR Parts 51 and 59

RIN ID: RIN 2060-AN69

EPA ID: [EPA-HQ-OAR-2006-0971; FRL-8498-6]

NOTICE: Part III

DOCUMENT ACTION: Final rule.

SUBJECT CATEGORY: National Volatile Organic Compound Emission Standards for Aerosol Coatings

DATES: Effective Date: This final rule is effective March 24, 2008. The incorporation by reference of certain publications listed in the rule is approved by the Director of the Federal Register as of March 24, 2008.

DOCUMENT SUMMARY: This action promulgates national emission standards for the aerosol coatings (aerosol spray paints) category under section 183(e) of the Clean Air Act (CAA). The standards implement section 183(e) of the CAA, as amended in 1990, which requires the Administrator to control volatile organic compounds (VOC) emissions from certain categories of consumer and commercial products for purposes of reducing VOC emissions contributing to ozone formation and ozone nonattainment. This regulation establishes nationwide reactivitybased standards for aerosol coatings. States have previously promulgated rules for the aerosol coatings category based upon reductions of VOC by mass; however, EPA has concluded that a national rule based upon the relative reactivity approach will achieve more reduction in ozone formation than may be achieved by a massbased approach for this specific product category. This rule will better control a product's contribution to ozone formation by encouraging the use of less reactive VOC ingredients, rather than treating all VOC in a product alike through the traditional massbased approach. We are also revising EPA's regulatory definition of VOC. This revision is necessary to include certain compounds that would otherwise be exempt in order to account for the reactive compounds in aerosol coatings that contribute to ozone formation. Therefore, certain compounds that would not be VOC under the otherwise applicable definition will count towards the applicable reactivity limits under this final regulation. The initial listing of product categories and schedule for regulation was published on March 23, 1995 (60 FR 15264). This final action announces EPA's final decision to list aerosol coatings for regulation under Group III of the consumer and commercial product category for which regulations are mandated under section 183(e) of the CAA.

SUMMARY: Environmental Protection Agency,

SUPPLEMENTAL INFORMATION

Entities Potentially Affected by This Action. The entities potentially affected by this regulation encompass all steps in aerosol coatings operations. This includes manufacturers, processors, wholesale distributors, or importers of aerosol coatings for sale or distribution in the United States, or manufacturers, processors, wholesale distributors, or importers who supply the entities listed above with aerosol coatings for sale or distribution in interstate commerce in the United States. The entities potentially affected by this action include:
NAICS code Examples of regulated Category \a\ entities Paint and Coating Manufacturing.. 32551 Manufacturing of lacquers, varnishes, enamels, epoxy coatings, oil and alkyd vehicle, plastisols, polyurethane, primers, shellacs, stains, water repellant coatings. All Other Miscellaneous Chemical 325998 Aerosol can filling, Production and Preparation aerosol packaging Manufacturing. services.
\a\ North American Industry Classification System http://www.census.gov/ epcd/www/naics.html.

This table is not intended to be exhaustive, but rather provides a guide for readers regarding entities likely to be affected by this action. To determine whether you would be affected by this action, you should examine the applicable industry description in section I.E of the promulgation preamble. If you have any questions regarding the applicability of this action to a particular entity, consult the appropriate EPA contact listed in the FOR FURTHER INFORMATION CONTACT section of this notice.

Docket. The docket number for the National Volatile Organic Compounds Emission Standards for Aerosols Coating (40 CFR part 59, subpart E) is Docket ID No. EPAHQOAR20060971.

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World Wide Web (WWW). In addition to being available in the docket, an electronic copy of the final rule is also available on the WWW. Following the Administrator's signature, a copy of the final rule will be posted on EPA's Technology Transfer Network (TTN) policy and guidance page for newly proposed or promulgated rules at http:// www.epa.gov/ttn/oarpg. The TTN provides information and technology exchange in various areas of air pollution control.

Judicial Review. Under section 307(b)(1) of the Clean Air Act (CAA), judicial review of the final rule is available only by filing a petition for review in the U.S. Court of Appeals for the District of Columbia Circuit by May 23, 2008. Under CAA section 307(b)(2), the requirements established by this final action may not be challenged separately in any civil or criminal proceedings brought by EPA to enforce these requirements.

Section 307(d)(7)(B) of the CAA further provides that ``only an objection to a rule or procedure which was raised with reasonable specificity during the period for public comment (including any public hearing) may be raised during judicial review.'' This section also provides a mechanism for EPA to convene a proceeding for
reconsideration, ``if the person raising the objection can demonstrate to EPA that it was impracticable to raise such an objection [within the period for public comment] or if the grounds for such objection arose after the period for public comment (but within the time specified for judicial review) and if such objection is of central relevance to the outcome of the rule.'' Any person seeking to make such a demonstration to EPA should submit a Petition for Reconsideration to the Office of the Administrator, U.S. EPA, Room 3000, Ariel Rios Building, 1200 Pennsylvania Ave., NW., Washington, DC 20460, with a copy to both the person(s) listed in the preceding FOR FURTHER INFORMATION CONTACT section, and the Air and Radiation Law Office, Office of General Counsel (Mail Code 2344A), U.S. EPA, 1200 Pennsylvania Ave., NW., Washington, DC 20004.

Organization of This Document. The information presented in this notice is organized as follows:
I. Background

A. The Ozone Problem

B. Statutory and Regulatory Background

C. Photochemical Reactivity

D. Role of Reactivity in VOC/Ozone Regulations

E. The Aerosol Coating Industry
II. Summary of the Final Standards and Changes Since Proposal

A. Applicability of the Standards and Regulated Entities

B. VOC Regulated Under This Rule

C. Regulatory Limits

D. Compliance Dates

E. Labeling Requirements

F. Recordkeeping and Reporting

G. Variance

H. Test Methods
III. Response to Significant Comments

A. Format of Regulation

B. Downwind Effects and Robustness of Relative Reactivity Scale

C. Consideration of Other Factors in the Consideration of Best Available Control

D. Variance, Small Quantity Manufacturers and Extended Compliance Date

E. Additional Reporting Requirements
IV. Summary of Impacts

A. Environmental Impacts

B. Energy Impacts

C. Cost and Economic Impacts

V. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review

B. Paperwork Reduction Act

C. Regulatory Flexibility Act

D. Unfunded Mandates Reform Act

E. Executive Order 13132: Federalism

F. Executive Order 13175: Consultation and Coordination With Indian Tribal Governments

G. Executive Order 13045: Protection of Children From Environmental Health and Safety Risks

H. Executive Order 13211: Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution or Use

I. National Technology Transfer and Advancement Act

J. Executive Order 12898: Federal Actions to Address Environmental Justice in Minority Populations and LowIncome Populations

K. Congressional Review Act
I. Background

A. The Ozone Problem

Groundlevel ozone, a major component of smog, is formed in the atmosphere by reactions of VOC and oxides of nitrogen in the presence of sunlight. The formation of groundlevel ozone is a complex process that is affected by many variables.

Exposure to groundlevel ozone is associated with a wide variety of human health effects, as well as agricultural crop loss, and damage to forests and ecosystems. Controlled human exposure studies show that acute health effects are induced by shortterm (1 to 2 hour) exposures (observed at concentrations as low as 0.12 parts per million (ppm)), generally while individuals are engaged in moderate or heavy exertion, and by prolonged (6 to 8 hour) exposures to ozone (observed at concentrations as low as 0.08 ppm and possibly lower), typically while individuals are engaged in moderate exertion. Transient effects from acute exposures include pulmonary inflammation, respiratory symptoms, effects on exercise performance, and increased airway responsiveness. Epidemiological studies have shown associations between ambient ozone levels and increased susceptibility to respiratory infection, increased hospital admissions and emergency room visits. Groups at increased risk of experiencing elevated exposures include active children, outdoor workers, and others who regularly engage in outdoor activities. Those most susceptible to the effects of ozone include those with pre existing respiratory disease, children, and older adults. The literature suggests the possibility that longterm exposures to ozone may cause chronic health effects (e.g., structural damage to lung tissue and accelerated decline in baseline lung function).

B. Statutory and Regulatory Background

Under section 183(e) of the CAA, EPA conducted a study of VOC emissions from the use of consumer and commercial products to assess their potential to contribute to levels of ozone that violate the National Ambient Air Quality Standards (NAAQS) for ozone, and to establish criteria for regulating VOC emissions from these products. Section 183(e) of the CAA directed EPA to list for regulation those categories of products that account for at least 80 percent of the VOC emissions, on a reactivityadjusted basis, from consumer and commercial products in areas that violate the NAAQS for ozone (i.e., ozone nonattainment areas), and to divide the list of categories to be regulated into four groups.

EPA published the initial list in the Federal Register on March 23, 1995 (60 FR 15264). In that notice, EPA stated that it may amend the list of products for regulation, and the groups of product categories listed for regulation, in order to achieve an effective regulatory program in accordance with EPA's discretion under CAA section 183(e). EPA has revised the list several times. Most recently, in May 2006, EPA revised the list to add one product category, portable fuel containers, and to remove one product category, petroleum dry cleaning solvents. See 71 FR 28320 (May 16, 2006). The aerosol spray paints (aerosol coatings) category currently is listed for regulation as part of Group III of the CAA section 183(e) list.

CAA section 183(e) directs EPA to regulate consumer and commercial products using ``best available controls'' (BAC). CAA section 183(e)(1)(A) defines BAC as ``the degree of emissions reduction that the Administrator
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determines, on the basis of technological and economic feasibility, health, environmental, and energy impacts, is achievable through the application of the most effective equipment, measures, processes, methods, systems or techniques, including chemical reformulation, product or feedstock substitution, repackaging, and directions for use, consumption, storage, or disposal.'' CAA section 183(e) also provides EPA with authority to use any system or systems of regulation that EPA determines is the most appropriate for the product category. Under CAA section 183(e)(4), EPA can impose ``any system or systems of regulation as the Administrator deems appropriate, including requirements for registration and labeling, selfmonitoring and reporting, prohibitions, limitations, or economic incentives (including marketable permits and auctions of emissions rights) concerning the manufacture, processing, distribution, use, consumption or disposal of the product.'' Under these provisions, EPA has previously issued national regulations for architectural coatings, autobody refinishing coatings, consumer products, and portable fuel containers.\1\ \2\ \3\ \4\ \5\
\1\ ``National Volatile Organic Compound Emission Standards for Architectural Coatings'' 63 FR 48848, (September 11, 1998). \2\ ``National Volatile Organic Compound Emission Standards for Automobile Refinish Coatings'' 63 FR 48806, (September 11, 1998). \3\ ``Consumer and Commercial Products: Schedule for
Regulation'' 63 FR 48792, (September 11, 1998)
\4\ National Volatile Organic Compound Emission Standards for Consumer Products'' 63 FR 48819, (September 11, 1998).
\5\ ``National Volatile Organic Compound Emission Standards for Portable Fuel Containers'' 72 FR 8428, (February 26, 2007).

For any category of consumer or commercial products, the Administrator may issue control techniques guidelines (CTG) in lieu of national regulations if the Administrator determines that such guidance will be substantially as effective as a national regulation in reducing emissions of VOC which contribute to ozone levels in areas which violate the NAAQS for ozone. In many cases, a CTG can be an effective regulatory approach to reduce emissions of VOC in nonattainment areas because of the nature of the specific product and the uses of such product. A critical distinction between a national rule and a CTG is that a CTG may include provisions that affect the users of the products. For other product categories, such as wood furniture coatings and shipbuilding coatings, EPA has previously determined that, under CAA section 183(e)(3)(C), a CTG would be substantially as effective as a national rule and, therefore, issued CTGs to provide guidance to States for development of appropriate State regulations. Most recently, EPA determined that a CTG would be substantially as effective as a national rule for three other Group III categories: Paper, Film and Foil Coating; Metal Furniture Coating; and Large Appliance Coating.\6\ \6\ ``Consumer and Commercial Products: Control Techniques Guidelines in Lieu of Regulations for Paper, Film, and Foil Coatings; Metal Furniture Coatings; and Large Appliance Coatings'' 72 FR 57215, (October 9, 2007).

For the category of aerosol coatings, EPA has determined that a national rule applicable nationwide is the best system of regulation to achieve necessary VOC emission reductions from this type of product. Aerosol coatings are typically used in relatively small amounts by consumers and others on an occasional basis and at varying times and locations. Under such circumstances, reformulation of the VOC content of the products is a more feasible way to achieve VOC emission reductions, rather than through a CTG approach that would only affect a smaller number of relatively large users.

Aerosol coatings regulations are already in place in three States (California, Oregon, and Washington), and other States are considering developing regulations for these products. For the companies that market aerosol coatings in different States, trying to fulfill the differing requirements of State rules may create administrative, technical, and marketing problems. Although Section 183(e) does not preempt States from having more stringent State standards, EPA's national rule is expected to provide some degree of consistency, predictability, and administrative ease for the industry. A national rule also helps States reduce potential compliance problems associated with noncompliant coatings being transported into nonattainment areas from neighboring areas and neighboring States. A national rule will also enable States to obtain needed VOC emission reductions from this sector in the near term, without having to expend their limited resources to develop similar rules in each State.\7\
\7\ Courts have already approved EPA's creation of national rules under section 183(e). See, ALARM Caucus v. EPA, 215 F.3d 61,76 (D.C. Cir. 2000), cert. denied, 532 U.S. 1018 (2001).

C. Photochemical Reactivity

There are thousands of individual species of VOC that can participate in a series of reactions involving nitrogen oxides (NOX) and the energy from sunlight, resulting in the formation of ozone. The impact of a given species of VOC on formation of groundlevel ozone is sometimes referred to as its ``reactivity.'' It is generally understood that not all VOC are equal in their effects on groundlevel ozone formation. Some VOC react extremely slowly and changes in their emissions have limited effects on ozone pollution episodes. Some VOC form ozone more quickly than other VOC, or they may form more ozone than other VOC. Other VOC not only form ozone themselves, but also act as catalysts and enhance ozone formation from other VOC. By distinguishing between more reactive and less reactive VOC, however, EPA concludes that it may be possible to develop regulations that will decrease ozone concentrations further or more efficiently than by controlling all VOC equally.

Assigning a value to the reactivity of a specific VOC species is a complex undertaking. 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. Therefore, the reactivity of a specific VOC varies with VOC:NOX ratios, meteorological conditions, the mix of other VOC in the atmosphere, and the time interval of interest. Designing an effective regulation that takes account of these interactions is difficult. Implementing and enforcing such a regulation requires an extra burden for both industry and regulators, as those impacted by the rule must characterize and track the full chemical composition of VOC emissions rather than only having to track total VOC content as is required by traditional massbased rules. EPA's September 13, 2005, final rule approving a comparable reactivitybased aerosol coating rule as part of the California State Implementation Plan for ozone contains additional background information on photochemical reactivity.\8\ Recently, EPA issued interim guidance to States regarding the use of VOC reactivity information in the development of ozone control measures.\9\ \8\ ``Revisions to the California State Implementation Plan and Revision to the Definition of Volatile Organic Compounds (VOC) Removal of VOC Exemptions for California's Aerosol Coating Products Reactivitybased Regulation'' 70 FR 53930, (September 13, 2005). \9\ ``Interim Guidance on Control of Volatile Organic Compounds in Ozone State Implementation Plans'') 70 FR 54046, (September 13, 2005).

1. What Research Has Been Conducted on VOC Reactivity?

Much of the initial work on reactivity scales was funded by the California Air
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Resources Board (CARB), which was interested in comparing the reactivity of emissions from different alternative fuel vehicles. In the late 1980s, CARB provided funding to William P. L. Carter at the University of California to develop a reactivity scale. Carter investigated 18 different methods of ranking the reactivity of individual VOC in the atmosphere using a singlecell trajectory model with a stateoftheart chemical reaction mechanism.\10\ Carter suggested three scales for further consideration:
\10\ Carter, W. P. L. (1994) ``Development of ozone reactivity scales for organic gases,'' J. Air Waste Manage. Assoc., 44: 881 899.

i. Maximum Incremental Reactivity (MIR) scalean ozone yield scale derived by adjusting the NOX emissions in a base case to yield the highest incremental reactivity of the base reactive organic gas mixture.

ii. Maximum Ozone Incremental Reactivity (MOIR) scalean ozone yield scale derived by adjusting the NOX emission in a base case to yield the highest peak ozone concentration.

iii. Equal Benefit Incremental Reactivity (EBIR) scalean ozone yield scale derived by adjusting the NOX emissions in a base case scenario so VOC and NOX reductions are equally effective in reducing ozone.

Carter concluded that, if only one scale is used for regulatory purposes, the MIR scale is the most appropriate.\11\ The MIR scale is defined in terms of environmental conditions where ozone production is most sensitive to changes in hydrocarbon emissions and, therefore, represents conditions where hydrocarbon controls would be the most effective. CARB used the MIR scale to establish fuelneutral VOC emissions limits in its lowemitting vehicle and alternative fuels regulation.\12\ \13\ Subsequently, Carter has updated the MIR scale several times as the chemical mechanisms in the model used to derive the scale have evolved with new scientific information. CARB incorporated a 1999 version of the MIR scale in its own aerosol coatings rule. The latest revision to the MIR scale was issued in 2003. \11\ ``Initial Statement of Reasons for the California Aerosol Coatings Regulation, California Air Resources Board,'' 2000. \12\ California Air Resources Board ``Proposed Regulations for LowEmission Vehicles and Clean FuelsStaff Report and Technical Support Document,'' State of California, Air Resources Board, P.O. Box 2815, Sacramento, CA 95812, August 13, 1990.
\13\ California Air Resources Board ``Proposed Regulations for LowEmission Vehicles and Clean FuelsFinal Statement of Reasons,'' State of California, Air Resources Board, July 1991.

In addition to Carter's work, there have been other attempts to create reactivity scales. One such effort is the work of R.G. Derwent and coworkers, who have published articles on a scale called the photochemical ozone creation potential (POCP) scale.\14\ \15\ This scale was designed for the emissions and meteorological conditions prevalent in Europe. The POCP scale is generally consistent with that of Carter, although there are some differences because it uses a different model, chemical mechanism, and emission and meteorological scenarios. Despite these differences, there is a good correlation of r\2\=0.9 between the results of the POCP and the MIR scales.\16\ \14\ Derwent, R.G., M.E. Jenkin, S.M. Saunders and M.J. Pilling (2001) ``Characterization of the Reactivities of Volatile Organic Compounds Using a Master Chemical Mechanism,'' J. Air Waste Management Assoc., 51: 699707.
\15\ Derwent, R.G., M.E. Jenkin, S.M. Saunders and M.J. Pilling (1998) ``Photochemical Ozone Creation Potentials for Organic Compounds in Northwest Europe Calculated with a Master Chemical Mechanism,'' Atmos. Env., 32(14/15):24292441.
\16\ See http://www.narsto.org/section.src?SID=10.

As CARB worked to develop reactivitybased regulations in California, EPA began to explore the implications of applying reactivity scales in other parts of the country. In developing its regulations, CARB has maintained that the MIR scale is the most appropriate metric for application in California, but cautioned that its research has focused on California atmospheric conditions and that the suitability of the MIR scale for regulatory purposes in other areas has not been demonstrated. In particular, specific concerns have been raised about the suitability of using the MIR scale in relation to multiday stagnation or transport scenarios or over geographic regions with very different VOC:NOX ratios than those of California.

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 reactivityrelated regulatory policies.\16\ 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 efforts to explore:

i. The sensitivity of ozone to VOC mass reductions and changes in VOC composition under a variety of environmental conditions;

ii. The derivation and evaluation of reactivity scales using photochemical airshed models under a variety of environmental conditions;

iii. The development of emissions inventory processing tools for exploring reactivitybased strategies; and

iv. The fate of VOC emissions and their availability for atmospheric reactions.

This research has led to a number of findings that increase EPA's confidence in the ability to develop regulatory approaches that differentiate between specific VOC on the basis of relative reactivity. The first two research objectives listed above were explored in a series of three parallel modeling studies that resulted in four reports and one journal article.\17\ \18\ \19\ \20\ \21\ EPA commissioned a review of these reports to address a series of policyrelevant science questions.\22\ In 2007, an additional peer review was commissioned by EPA to assess the appropriateness of basing a national aerosol coatings regulation on reactivity. Generally, the peer reviews support the appropriateness of the use of the boxmodel based MIR metric nationwide for the aerosol coatings category. The results are available in the rulemaking docket.
\17\ Carter, W.P.L., G. Tonnesen, and G. Yarwood (2003) Investigation of VOC Reactivity Effects Using Existing Regional Air Quality Models, Report to American Chemistry Council, Contract SC 20.0UCRVOCRRWG, April 17, 2003.
\18\ Hakami, A., M.S. Bergin, and A.G. Russell (2003) Assessment of the Ozone and Aerosol Formation Potentials (Reactivities) of Organic Compounds over the Eastern United States, Final Report, Prepared for California Air Resources Board, Contract No. 00339, January 2003.
\19\ Hakami, A., M.S. Bergin, and A.G. Russell (2004a) Ozone Formation Potential of Organic Compounds in the Eastern United States: A Comparison of Episodes, Inventories, and Domains, Environ. Sci. Technol. 2004, 38, 67486759.
\20\ Hakami, A., M. Arhami, and A.G. Russell (2004b) Further Analysis of VOC Reactivity Metrics and Scales, Final Report to the U.S. EPA, Contract 4D5751NAEX, July 2004.
\21\ Arunachalam S., R. Mathur, A. Holland, M.R. Lee, D. Olerud, Jr., and H. Jeffries (2003) Investigation of VOC Reactivity Assessment with Comprehensive Air Quality Modeling, Prepared for U.S. EPA, GSA Contract GS35F0067K, Task Order ID: 4TCG68022755, June 2003.
\22\ Derwent, R.G. (2004) Evaluation and Characterization of Reactivity Metrics, Final Draft, Report to the U.S. EPA, Order No. 4D5844NATX, November 2004.

The results of the RRWGorganized study and the subsequent reviews suggest that there is good correlation between different relative reactivity metrics calculated with photochemical airshed models, regardless of the choice of model, model domain, scenario, or averaging times. Moreover, the scales calculated with photochemical airshed models correlate relatively well with the MIR metric derived with a single cell, onedimensional box model. Prior to the
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RRWGorganized studies, little analysis of the robustness of the box model derived MIR metric and its applicability to environmental conditions outside California had been conducted. Although these studies were not specifically designed to test the robustness of the boxmodel derived MIR metrics, the results suggest that the MIR metric is relatively robust.

D. Role of Reactivity in VOC/Ozone Regulations

Historically, EPA's general approach to regulation of VOC emissions has been based upon control of total VOC by mass, without
distinguishing between individual species of VOC. EPA considered the regulation of VOC by mass to be the most effective and practical approach based upon the scientific and technical information available when EPA developed its VOC control policy.

EPA issued the first version of its VOC control policy in 1971, as part of EPA's State Implementation Plan (SIP) preparation guidance.\23\ In that guidance, EPA emphasized the need to reduce the total mass of VOC emissions, but also suggested that substitution of one compound for another might be useful when it would result in a clearly evident decrease in reactivity and thus tend to reduce photochemical oxidant formation. This latter statement encouraged States to promulgate SIPs with VOC emission substitution provisions similar to the Los Angeles County Air Pollution Control District's (LACAPCD) Rule 66, which allowed some VOC that were believed to have low to moderate reactivity to be exempted from control. The exempt status of many of those VOC was questioned a few years later, when research results indicated that, although some of those compounds do not produce much ozone close to the source, they may produce significant amounts of ozone after they are transported downwind from urban areas.
\23\ ``Requirements for Preparation, Adoption and Submittal of Implementation Plans'', Appendix B, 36 FR 15495, (August 14, 1971).

In 1977, further research led EPA to issue a revised VOC policy under the title ``Recommended Policy on Control of Volatile Organic Compounds,'' (42 FR 35314, July 8, 1977), offering its own, more limited, list of exempt organic compounds. The 1977 policy identified four compounds that have very low photochemical reactivity and determined that their contribution to ozone formation and accumulation could be considered negligible. The policy exempted these ``negligibly reactive'' compounds from VOC emissions limitations in programs designed to meet the ozone NAAQS. Since 1977, EPA has added other compounds to the list of negligibly reactive compounds based on new information as it has been developed. In 1992, EPA adopted a formal regulatory definition of VOC for use in SIPs, which explicitly excludes compounds that have been identified as negligibly reactive [40 CFR 51.100(s)].

To date, EPA has exempted 54 compounds or classes of compounds in this manner. In effect, EPA's current VOC exemption policy has generally resulted in a two bin system in which most compounds are treated equally as VOC, and are controlled. A separate smaller group of compounds are treated as negligibly reactive, and are exempt from VOC controls.\24\ This approach was intended to encourage the reduction of emissions of all VOC that participate in ozone formation. From one perspective, it appears that this approach has been relatively successful. EPA estimates that, between 1970 and 2003, VOC emissions from manmade sources nationwide declined by 54 percent. This decline in VOC emissions has helped to decrease average ozone concentration by 29 percent (based on 1hour averages) and 21 percent (based on 8hour averages) between 1980 and 2003. These reductions occurred even though, between 1970 and 2003, population, vehicle miles traveled, and gross domestic product rose 39 percent, 155 percent and 176 percent, respectively.\25\
\24\ For some analytical purposes, EPA has distinguished between VOC and ``highly reactive'' VOC, such as in the EPA's initial evaluation of consumer products for regulation. See, ``Final Listing,'' 63 FR 48792, 487956 (Sept. 11, 1998) (explaining EPA's approach); see also, ALARM Caucus v. EPA, 215 F. 3d 61, 6973 (D. C. Cir. 2000), cert. denied, 532 U.S. 1018 (2001) (approving EPA's approach as meeting the requirements of CAA section 183(e)). \25\ ``Latest Findings on National Air Quality: 2002 Status and Trends,'' EPA 454/K03001, (August 2003); and ``The Ozone Report Measuring Progress through 2003,'' EPA 454/K04001, (April 2004); Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, North Carolina.

On the other hand, some have argued that a reactivitybased approach for reducing VOC emissions would be more effective than the current massbased approach. One group of researchers conducted a detailed modeling study of the Los Angeles area and concluded that, compared to the current approach, a reactivitybased approach could achieve the same reductions in ozone concentrations at significantly less cost or, for a given cost, could achieve a significantly greater reduction in ozone concentrations.\26\ The traditional approach to VOC control that focused on reducing the overall mass of emissions may be adequate in some areas of the country. However, EPA's recent SIP guidance recognizes that approaches to VOC control that differentiate between VOC based on relative reactivity are likely to be more effective and efficient under certain circumstances.\27\ In particular, reactivitybased approaches are likely to be important in areas for which aggressive VOC control is a key strategy for reducing ozone concentrations. Such areas include:
\26\ A. Russell, J. Milford, M. S. Bergin, S. McBride, L. McNair, Y. Yang, W. R. Stockwell, B. Croes, ``Urban Ozone Control and Atmospheric Reactivity of Organic Gases,'' Science, 269: 491 495, (1995).
\27\ ``Interim Guidance on Control of Volatile Organic Compounds in Ozone State Implementation Plans,'' 70 FR 54046, September 13, 2005).