C. Particulate Matter The need to control the contribution of cars and light trucks to ambient concentrations of particulate matter ( PM) is the basis for our adoption of the new PM emission standards for vehicles. PM is also a supplemental consideration in our promulgation of VerDate 27< JAN> 2000 21: 29 Feb 09, 2000 Jkt 190000 PO 00000 Frm 00019 Fmt 4701 Sfmt 4700 E:\ FR\ FM\ 10FER2. SGM pfrm08 PsN: 10FER2 6716 Federal Register / Vol. 65, No. 28 / Thursday, February 10, 2000 / Rules and Regulations 27 U. S. EPA ( 1998) National Air Pollutant Emission Trends Update, 1970   1997. EPA   454/ E   98   007. There is evidence from ambient studies that emissions of these materials may be overestimated and/ or that once emitted they have less of an influence on monitored PM concentrations ( of both PM10 and PM2.5) than this inventory share would suggest. the vehicle emission standards for NOX and VOC, and for the limits on sulfur in gasoline, because SOx, NOX, and VOC are PM precursors. For cars and for light trucks under 3750 pounds loaded vehicle weight, we are establishing new emission standards under the provisions of CAA section 202( i), which ties our action to the need for additional emission reductions in order to attain and maintain the NAAQS. The NAAQS relevant to the PM emission standards is the PM10 NAAQS. The PM10 NAAQS also provides additional but not essential support to our promulgation of the NOX and VOC standards, since these standards are fully supportable on the basis of the 1 hour ozone NAAQS. For the vehicles not subject to CAA 202( i), and for the gasoline sulfur limits, our actions are tied to determinations regarding public health and welfare risks more broadly, under CAA sections 202( a), 202( b), and 211( c). The role of NOX, VOC, and PM emissions in contributing to atmospheric concentrations of PM10 is an important element of the risk that these emissions pose to public health and welfare. PM also poses risks to public health not fully reflected in the PM10 NAAQS. Though EPA has not relied on the adverse health impacts of fine PM to promulgate this rule, it is well established that such impacts exist. A summary of these effects is given in the next section. In addition, based on the available science, EPA's Office of Research and Development has recently submitted to a committee of our Science Advisory Board a draft assessment document which contains a proposed conclusion that diesel exhaust is a likely human cancer hazard and is a potential cause of other nonmalignant respiratory effects. The scientific advisory committee has met to discuss this document, and we are awaiting written review comments from the committee. We expect to submit a further revision of the document to the advisory committee before we make the document final.

1. Background on PM Particulate matter ( PM) represents a broad class of chemically and physically diverse substances that exist as discrete particles ( liquid droplets or solids) over a wide range of sizes. The NAAQS that regulates PM addresses only PM with a diameter less than or equal to 10 microns, or PM10. The coarse fraction of PM10 consists of those particles which have a diameter in the range between 2.5 and 10 microns, and the fine fraction consists of those particles which have a diameter less than or equal to 2.5 microns, or PM2.5. These particles and droplets are produced as a direct result of human activity and natural processes, and they are also formed as secondary particles from the atmospheric transformation of emissions of SOX, NOX, ammonia, and VOCs. Natural sources of particles in the coarse fraction of PM10 include windblown dust, salt from dried sea spray, fires, biogenic emanation ( e. g., pollen from plants, fungal spores), and volcanoes. Fugitive dust and crustal material ( geogenic materials) comprise approximately 80% of the coarse fraction of the PM10 inventory as estimated by methods in use today. 27 Manmade sources of these coarser particles arise predominantly from combustion of fossil fuel by large and small industrial sources ( including power generating plants, manufacturing plants, quarries, and kilns), wind erosion from crop land, roads, and construction, dust from industrial and agricultural grinding and handling operations, metals processing, and burning of firewood and solid waste. Coarse fraction PM10 remains suspended in the atmosphere a relatively short period of time. Most of the emission sources listed for coarse particles also have a substantial fine particle fraction. Their share of the PM2.5 inventory is somewhat smaller, however, because of the role of other sources that give rise primarily to PM2.5. The other sources of PM2.5 include carbon based particles emitted directly from gasoline and diesel internal combustion engines, sulfate based particles formed from SOX and ammonia, nitrate based particles formed from NOX and ammonia, and carbonaceous particles formed through transformation of VOC emissions. PM2.5 particles from fugitive dust and crustal sources comprise substantially less than their share of coarse PM emissions, approximately one half of the directly emitted PM2.5 inventory as estimated by methods in use today. The presence and magnitude of crustal PM2.5 in the ambient air is much lower even than suggested by this smaller inventory share, due to the additional presence of secondary PM from non crustal sources and the removal of a large portion of crustal emissions close to their source. This near source removal results from crustal PM's lack of inherent thermal buoyancy, low release height, and interaction with surrounding vegetation ( which acts to filter out some of these particles). Secondary PM is dominated by sulfate particles in the eastern U. S. and parts of the western U. S., with nitrate particles and carbonaceous particles dominant in some western areas. Mobile sources can reasonably be estimated to contribute to ambient secondary nitrate and sulfate PM in proportion to their contribution to total NOX and SOX emissions. The sources, ambient concentration, and chemical and physical properties of PM10 vary greatly with time, region, meteorology, and source category. A first step in developing a plan to attain the PM10 NAAQS is to disaggregate ambient PM10 into the basic categories of sulfate, nitrate, carbonaceous, and crustal PM, and then determine the major contributors to each category based on knowledge of local and upwind emission sources. Following this approach, SIP strategies to reduce ambient PM concentrations have generally focused on controlling fugitive dust from natural soil and soil disturbed by human activity, paving dirt roads and controlling soil on paved roads, reducing emissions from residential wood combustion, and controlling major stationary sources of PM10 where applicable. The control programs to reduce stationary, area, and mobile source emissions of sulfur dioxide, oxides of nitrogen, and volatile organic compounds in order to achieve attainment with the sulfur dioxide and ozone NAAQS also have contributed to reductions in the fine fraction of PM10 concentrations. In addition, the EPA standards for PM emissions from highway and nonroad engines are contributing to reducing PM10 concentrations. As a result of all these efforts, in the last ten years, there has been a downward trend in PM10 concentrations, with a leveling off in the later years. Particulate matter, like ozone, has been linked to a range of serious respiratory health problems. Scientific studies suggest a likely causal role of ambient particulate matter in contributing to a series of health effects. The key health effects categories associated with particulate matter include premature mortality, aggravation of respiratory and cardiovascular disease ( as indicated by increased hospital admissions and emergency room visits, school absences, work loss days, and restricted activity days), changes in lung function and increased respiratory symptoms, changes to lung tissues and structure, and altered respiratory defense VerDate 27< JAN> 2000 21: 29 Feb 09, 2000 Jkt 190000 PO 00000 Frm 00020 Fmt 4701 Sfmt 4700 E:\ FR\ FM\ 10FER2. SGM pfrm08 PsN: 10FER2 6717 Federal Register / Vol. 65, No. 28 / Thursday, February 10, 2000 / Rules and Regulations 28 U. S. EPA, 1996, Air Quality Criteria for Particulate Matter, EPA/ 600/ P   95/ 001aF. Review of the National Ambient Air Quality Standards for Particulate Matter: Policy Assessment of Scientific and Technical Information, OAQPS Staff Paper, EPA   452 R   96   013, July 1996. 29 The annual average PM10 NAAQS is based on a three year average, and the 24 hour NAAQS is based on expected exceedances over a three year period. 30 Health Assessment Document for Diesel Emissions, SAB Review Draft EPA/ 600/ 8   90/ 057D. November 1999. The document is available electronically at http:// www. epa. gov/ ncea/ diesel. htm. mechanisms. PM also causes damage to materials and soiling. It is a major cause of substantial visibility impairment in many parts of the U. S. Motor vehicle particle emissions and the particles formed by the transformation of motor vehicle gaseous emissions tend to be in the fine particle range. Fine particles are a special health concern because they easily reach the deepest recesses of the lungs. Scientific studies have linked fine particles ( alone or in combination with other air pollutants), with a series of significant health problems, including premature death; respiratory related hospital admissions and emergency room visits; aggravated asthma; acute respiratory symptoms, including aggravated coughing and difficult or painful breathing; chronic bronchitis; and decreased lung function that can be experienced as shortness of breath. These effects are discussed further in EPA's `` Staff Paper'' and `` Air Quality Criteria Document'' for particulate matter. 28 EPA first established primary ( healthbased and secondary ( welfare based) National Ambient Air Quality Standards for PM10 in 1987. The annual and 24 hour primary PM10 standards were set at 50 m g/ m33, and 150 m g/ m3, respectively. 29 In July 1997, the primary standards were revised to add two new PM2.5 standards. At the same time, we changed the statistical form of the primary PM10 standard and set all the secondary standards to be the same as the primary. On May 14, 1999, a panel of the U. S. Court of Appeals for the District of Columbia Circuit reviewed EPA's revisions to the ozone and PM NAAQS and found, by a 2   1 vote, that sections 108 and 109 of the Clean Air Act, as interpreted by EPA, represent unconstitutional delegations of Congressional power. American Trucking Ass'ns, Inc., et al., v. Environmental Protection Agency, 175 F. 3d 1027 ( D. C. Cir. 1999). Among other things the Court remanded the record for the 8 hour ozone NAAQS and the PM2.5 NAAQS to EPA. On October 29, 1999, EPA's petition for rehearing by the three judge panel was denied, with an exception regarding the revised ozone NAAQS. EPA's petition for rehearing en banc by the full Circuit was also denied, although five of the nine judges considering the petition agreed to rehear the case. The pre existing PM10 NAAQS remains in effect ( except for one area   Boise, ID   where prior to the court's decision we had determined it no longer to apply). We believe that given the uncertain status of the new PM2.5 NAAQS, it is most appropriate to rely primarily on the pre existing PM10 NAAQS in establishing the Tier 2/ Gasoline Sulfur program's vehicle emission standards and limits on sulfur in gasoline. However, because we believe, and the Court did not dispute, that there are very substantial public health risks from PM2.5 and substantial health and economic benefits from reducing PM2.5 concentrations, we have conducted analyses of the PM2.5 changes likely to occur from the Tier 2/ Gasoline Sulfur program. These analyses are summarized in the section of this preamble dealing with the economic benefits of the new standards, section IV. D. 5, and corresponding sections of the final RIA. There is additional concern regarding the health effects of PM from diesel vehicles, apart from the health effects which were considered in setting the NAAQS for PM10 and PM2.5. Diesel PM contains small quantities of chemical species that are known carcinogens, and diesel PM as a whole has been implicated in occupational epidemiology studies. EPA's Office of Research and Development has considered these studies, and has recently submitted to a committee of our Science Advisory Board a draft conclusion that diesel exhaust is a `` highly likely'' human cancer hazard. 30 Because we are awaiting a formal response from our advisory committee before revising and finalizing our assessment document, we are not relying on the conclusions in this document as formal support for our action today. More information about this aspect of PM air quality is given in section III. F of this preamble.

2. Need for Additional Reductions to Attain and Maintain the PM10 NAAQS The most recent PM10 monitoring data indicates that 15 designated PM10 nonattainment counties, with a population of almost 9 million in 1996, violated the PM10 NAAQS in the period 1996   1998. The areas that are violating do so because of exceedances of the 24 hour PM10 NAAQS. No areas had monitored violations of the annual standard in this period. Table III. C   1 lists the 15 counties. The table also indicates the classification for each area and the status of our review of the State Implementation Plan.

TABLE III. C   1.   FIFTEEN PM10 NONATTAINMENT AREAS VIOLATING THE PM10 NAAQS IN 1996   1998 a Area Classification SIP approved? 1996 Population ( millions)

Clark Co., NV ................................................................................................................. Serious .................... No ..................... 0.93 El Paso, TX .................................................................................................................... Moderate ................. Yes ................... 0.67 Gila, AZ ........................................................................................................................... Moderate ................. No ..................... 0.05 Imperial Co., CA ............................................................................................................. Moderate ................. No ..................... 0.14 Inyo Co., CA ................................................................................................................... Moderate ................. No ..................... 0.02 Kern Co., CA .................................................................................................................. Serious .................... No ..................... 0.62 Mono Co., CA ................................................................................................................. Moderate ................. No ..................... 0.01 Kings Co., CA ................................................................................................................. Serious .................... No ..................... 0.11 Maricopa Co., AZ ........................................................................................................... Serious .................... No ..................... 2.61 Power Co., ID ................................................................................................................. Moderate ................. No ..................... 0.01 Riverside Co., CA ........................................................................................................... Serious .................... No ..................... 1.41 San Bernardino Co., CA ................................................................................................. Serious .................... No ..................... 1.59 Santa Cruz Co., AZ ........................................................................................................ Moderate ................. No ..................... 0.04 Tulare Co., CA ................................................................................................................ Serious .................... No ..................... 0.35 VerDate 27< JAN> 2000 21: 29 Feb 09, 2000 Jkt 190000 PO 00000 Frm 00021 Fmt 4701 Sfmt 4700 E:\ FR\ FM\ 10FER2. SGM pfrm08 PsN: 10FER2 6718 Federal Register / Vol. 65, No. 28 / Thursday, February 10, 2000 / Rules and Regulations 31 Regulatory Impact Analyses for the Particulate Matter and Ozone National Ambient Air Quality Standards and Proposed Regional Haze Rule, Innovative Strategies and Economics Group, Office of Air Quality Planning and Standards, U. S. Environmental Protection Agency, Research Triangle Park, N. C., July 16, 1997. 32 We used the more recent modeling for 2030 rather than the earlier modeling for 2010, because the modeling the 2030 incorporates more recent estimates of emissions inventories. Our emission estimates in our final RIA indicate that PM10 emissions under the basline scenario increase steadily between 1996 and 2030, for 47 states combined and for four specific cities, suggesting that areas in nonattainment in both 1996   1998 and 2030 will be in nonatainment in the intermediate years as well assuming no further emission reductions. A factor tending to make Table III. C   2 shorter is that we have not relied on the sourcereceptor matrix model's prediction of 24 hour nonattainment, as those predictions on an individual areas basis are less reliable than the predictions of annual average nonattainment. TABLE III. C   1.   FIFTEEN PM10 NONATTAINMENT AREAS VIOLATING THE PM10 NAAQS IN 1996   1998 a   Continued Area Classification SIP approved? 1996 Population ( millions)

Walla Walla Co., WA ...................................................................................................... Moderate ................. Yes ................... 0.05 Total Population ................................................................................................... ............................. ...................... 8.61 a Although we do not believe that we are limited to considering only designated nonattainment areas in implementing CAA section 202( i), we have focused on the designated areas in the case of PM10. An official designation of PM10 nonattainment indicates the existence of a confirmed PM10 problem that is more than a result of a one time monitoring upset or a results of PM10 exceedances attributable to natural events. In addition to these designated nonattainment areas, there are 15 unclassified counties in 12 geographically spread out states, with a 1996 population of over 4 million, for which the state has reported PM10 monitoring data for this period indicating a PM10 NAAQS violation. We have not yet excluded the possibility that a one time monitoring upset or a natural event( s) is responsible for the monitored violations in 1996   1998 in the 15 unclassified counties. We adopted a policy in 1996 that allows areas whose PM10 exceedances are attributable to natural events to remain unclassified if the state is taking all reasonable measures to safeguard public health regardless of the source of PM10 emissions. Areas that remain unclassified areas are not required to submit attainment plans, but we work with each of these areas to understand the nature of the PM10 problem and to determine what best can be done to reduce it. The Tier 2/ Gasoline Sulfur program will reduce PM10 concentrations in these 15 unclassified counties, because all have car and light truck travel that contributes to PM10 and precursor emissions loadings. This reduction will assist these areas in reducing their PM10 nonattainment problem, if a problem is confirmed upon closer examination of each local situation. Boise, ID, had also been classified as a PM10 nonattainment area at one time and was monitored to have a PM10 NAAQS violation in 1996   1998. However the pre existing PM10 NAAQS does not presently apply in Boise, ID, because in the period between our revision of the old PM10 NAAQS and the Court's decision to vacate the revised PM10 NAAQS, we determined that Boise was in attainment with the old PM10 NAAQS and that it therefore no longer applied in that area.

Because the types and sources of PM10 are complex and vary from area to area, the best projections of future PM10 concentrations are the local emission inventory and air quality modeling analyses that states have developed or are still in the process of developing for their PM10 attainment plans. We do employ a modeling approach, known as the source receptor matrix approach, for relating emission reductions to PM10 reductions on a national scale. This approach is one of our established air quality models for purposes of quantifying the health and welfare related economic benefits of PM reductions from major regulatory actions. One application of this modeling approach was for the Regulatory Impact Analysis for the establishment of the new PM NAAQS 31. This model is also the basis for the estimates of PM10 ( and PM2.5) concentrations reductions we have used to estimate the economic benefits of the Tier 2/ Gasoline Sulfur program in 2030. Its use for this purpose is described in the final RIA. In both applications, we modeled an emissions scenario corresponding to controls currently in place or committed to by states. As such, this scenario is an appropriate baseline for determining if further reductions in emissions are needed in order to attain and maintain the PM10 NAAQS. In the RIA for the establishment of the PM NAAQS, we projected that in 2010 there will be 45 counties not in attainment with the original PM10 NAAQS . We cited these modeling results in our proposal for the Tier 2/ Gasoline Sulfur program and in our first supplemental notice. After reviewing public comments on our presentation of these modeling results, we have concluded that while the sourcereceptor matrix approach is a suitable model for estimating PM concentration reductions for economic benefits estimation, it is not a tool we can use with high confidence for predicting that individual areas that are now in attainment will become nonattainment in the future. However, we believe the source receptor matrix approach is appropriate for, and is a suitable tool for, determining that a current designated nonattainment area has a high risk of remaining in PM10 nonattainment at a future date. Therefore, we have cross matched the results for 2030 from our final RIA for Tier 2 and the list of current PM10 nonattainment areas with monitored violations in 1996 to 1998 shown in Table III. C   1.32 Based on this, we conclude that the 8 areas shown in Table III. C   2 have a high risk of failing to attain and maintain without further emission reductions. These areas have a population of nearly 8 million. Included in the group are the counties that are part of the Los Angeles, Phoenix, and Las Vegas metropolitan areas, where traffic from cars and light trucks is substantial. California areas will benefit from the Tier 2/ Gasoline Sulfur program because of travel within California by vehicles originally sold outside the state, and by reduced poisoning of catalysts from fuel purchased outside of California.

TABLE III. C   2.   EIGHT AREAS WITH A HIGH RISK OF FAILING TO ATTAIN AND MAINTAIN THE PM10 NAAQS WITHOUT FURTHER REDUCTIONS IN EMISSIONS Area 1996 population ( millions)

Clark Co., NV ........................... 0.93 Imperial Co., CA ....................... 0.14 Kern Co., CA ............................ 0.62 Kings Co., CA ........................... 0.11 Maricopa Co., AZ ..................... 2.61 Riverside Co., CA ..................... 1.41 San Bernardino Co., CA ........... 1.59 Tulare Co., CA .......................... 0.35 Total population ............. 7.76 Table III. C   2 is limited to designated PM10 nonattainment areas which both had monitored violations of the PM10 NAAQs in 1996   1998 and are predicted to be in nonattainment in 2030 in our PM10 air quality modeling. This gives us high confidence that these areas require further emission reductions to attain and maintain, but does not fully VerDate 27< JAN> 2000 21: 29 Feb 09, 2000 Jkt 190000 PO 00000 Frm 00022 Fmt 4701 Sfmt 4700 E:\ FR\ FM\ 10FER2. SGM pfrm08 PsN: 10FER2 6719 Federal Register / Vol. 65, No. 28 / Thursday, February 10, 2000 / Rules and Regulations 33 In fact, in two of these areas, New York Co., NY and Harris Co., TX, the average PM10 level in 1998 was above the 50 m g/ m3 value of the NAAQS. These two areas are not included in the Table III. C   2 list of areas with a high risk of failing to attain and maintain because lower PM10 levels in 1996 and 1997 caused their three year average PM10 level to be lower than the NAAQS. Official nonattainment determinations for the annual PM10 NAAQS are made based on the average of 12 quarterly PM10 averages. consider the possibility that there are other areas which are now meeting the PM10 NAAQS which have at least a significant probability of requiring further reductions to continue to maintain it. Our air quality modeling predicted 2030 violations of the annual average PM10 NAAQS in five additional counties that in either 1997 or 1998 had single year annual average monitored PM10 levels of at least 90 percent of the NAAQS, but did not exceed the formal definition of the NAAQS over the threeyear period ending in 1998 33. These areas are shown in Table III. C   3. They have a combined population of almost 17 million, and a broad geographic spread. Unlike the situation for ozone, for which precursor emissions are generally declining over the next 10 years or so before beginning to increase, we estimate that emissions of PM10 will rise steadily unless new controls are implemented. The small margin of attainment which these areas currently enjoy will likely erode; the PM air quality modeling suggests that it will be reversed. We therefore consider these areas to each individually have a significant risk of failing to maintain the NAAQS without further emission reductions. There is a substantial risk that at least some of them would fail to maintain without further emission reductions. The emission reductions from the Tier 2/ Gasoline Sulfur program will help to keep them in attainment.

TABLE III. C   3.   FIVE AREAS WITH A SIGNIFICANT RISK OF FAILING TO ATTAIN AND MAINTAIN THE PM10 NAAQS WITHOUT FURTHER REDUCTIONS IN EMISSIONS Area 1996 population ( millions)

New York Co., NY .................... 1.33 Cuyahoga Co., OH ................... 1.39 Harris, Co., TX .......................... 3.10 San Diego Co., CA ................... 2.67 Los Angeles Co., CA ................ 8.11 Total population ............. 16.6 Taken together and considering their number, size, and geographic distribution, these 13 areas are sufficient to establish the case that additional reductions are needed in order to attain and maintain the PM10 NAAQS. This determination provides additional support for the NOx and VOC standards and for the limits on gasoline sulfur, which are also fully supported on ozone attainment and health effects considerations. The sulfate particulate, sulfur dioxide, NOX, and VOC emission reductions from the Tier 2/ Gasoline Sulfur program will help the 8 areas in Table III. C   2 and the 5 areas in Table III. C.   3 to attain and maintain the PM10 NAAQS. The new PM standards for gasoline and diesel vehicles are also supported by this PM10 determination. We are also establishing the new PM emissions standard today to avoid the possibility that PM10 concentrations in these and other areas do get even worse due to an increase in sales of diesel vehicles, which could create a need for further reductions which would be larger and would affect more areas of the country. At the present time, virtually all cars and light trucks being sold are gasoline fueled. The ambient PM10 air quality data for 1996 to 1998 reflects that current situation, and this data was an important factor in what areas are listed in Tables III. C   2 and III. C   3. Also, the predictions of future PM10 air quality, used to develop the Tables III. C   2 and III. C   3 lists of areas with high or significant risk of being unable to attain and maintain, are based on an assumption that this will continue to be true. However, we are concerned over the possibility that diesels will become more prevalent in the car and light duty truck fleet, since automotive companies have announced their desire to increase their sales of diesel cars and light trucks. Because current diesel vehicles emit higher levels of PM10 than gasoline vehicles, a larger number of diesel vehicles could dramatically increase levels of exhaust PM10, especially if more stringent PM emissions standards are not in place. The new PM emissions standards will ensure that an increase in the sales of diesel cars and light trucks will not increase PM emissions from cars and light trucks so substantially as to endanger PM10 attainment and maintenance on a more widespread basis. Given this potential, it is appropriate to establish the new PM emissions standards now on the basis of the increase in sales of diesel vehicles being a reasonable possibility without such standards. Establishing the new PM emissions standards now avoids the public health impact and industry disruption that could result if we waited until an increase in sales of diesels with high PM emissions had already occurred. In order to assess the potential impact of increased diesel sales penetration on PM emissions, we analyzed the increase in PM10 emissions from cars and trucks under a scenario in which the use of diesel engines in cars and light trucks increases. We used projections developed by A. D. Little, Inc. as part of a study conducted for the American Petroleum Institute. The `` Most Likely'' case projected by A. D. Little forecasts that diesel engines'' share of the light truck market will grow to 24 percent by the 2015 model year. Diesel engines' share of the car market would grow somewhat more slowly, reaching 9 percent by 2015. The A. D. Little forecasts did not address the period after 2015; we have assumed that diesel sales stabilize at the level reached in 2015, with the fraction of in use vehicles with diesel engines continuing to increase through turnover. We believe these projections are more realistic than the scenario of even higher sales of diesels described in the notice for the proposed Tier 2/ Gasoline Sulfur program, though the A. D. Little forecasts still show much higher percentages of diesel vehicles in the light duty fleet than have ever existed historically in the U. S. The A. D. Little scenario of increased diesels, and even more so the scenario described in our proposal, would result in dramatic increases in direct PM10 emissions from cars and light trucks, if there were no change in these vehicles' PM standards. The increase in diesel exhaust PM10 emissions would more than overcome the reduction in direct PM10 attributable to the sulfur reduction in gasoline. With no change in the existing PM standards for cars and light trucks, our analysis of this scenario shows that direct PM10 emissions in 2020 would be approximately 98,000 tons per year, which is nearly two times the 50,000 tons projected if diesel sales do not increase. The portion of ambient PM10 concentrations attributable to cars and light trucks would climb steadily. The final RIA presents alternative estimates of the amount by which future PM10 concentrations could increase due to such an emissions increase, based on extrapolations from several studies' estimates of the contribution that heavyduty diesel vehicles have made to recent or PM10 concentrations. The increase is estimated to range from 0.6 to 20 m g/ m3. The added PM10 emissions from cars and trucks due to an increase in diesel sales without action to reduce PM10 from new diesel vehicles would exacerbate the PM10 nonattainment problems of the areas listed in Tables VerDate 27< JAN> 2000 21: 29 Feb 09, 2000 Jkt 190000 PO 00000 Frm 00023 Fmt 4701 Sfmt 4700 E:\ FR\ FM\ 10FER2. SGM pfrm08 PsN: 10FER2 6720 Federal Register / Vol. 65, No. 28 / Thursday, February 10, 2000 / Rules and Regulations III. C   2 and III. C   3, for which our air quality modeling predicted future nonattainment even without an increase in diesel sales. Moreover, it might cause PM10 nonattainment in additional areas. In addition to the counties already listed in Tables III. C   2 and III. C   3, there are other areas for which 1997 and 1998 data indicate that maintenance of the PM10 NAAQS is at risk if diesel sales of cars and light truck increase. Table III. C   4 lists additional counties for which either 1997 or 1998 monitoring data, or both, indicated a second high PM10 concentration for the single year within 10 percent of the PM10 24 hour NAAQS or an annual average PM10 concentration within 10 percent of the annual average PM10 NAAQS. Only counties which are part of metropolitan statistical areas are listed in Table III. C   4, in order to focus on those in which traffic densities are high. Considering both the annual and 24 hour NAAQS, there were 13 areas within 10 percent of the standard. Increases in PM10 emissions from more diesel vehicles would put these areas in greater risk of violating the PM10 NAAQS, especially if growth in other sources is high or meteorological conditions are more adverse than in the 1996 to 1998 period.

TABLE III. C   4.   THIRTEEN METROPOLITAN STATISTICAL AREA COUNTIES WITH 1997 AND/ OR 1998 AMBIENT PM10 Concentrations Within 10 Percent of the Annual or 24 Hour the PM10 NAAQSa 1996 population ( millions)

Areas within 10 percent of the annual PM10 NAAQS:

Lexington Co., SC ........................... 0.20 Union Co., TN ................................. 0.02 Washoe Co., NV ............................. 0.30 Madison Co., IL ............................... 0.26 Dona Ana Co., NM .......................... 0.16 El Paso Co., TX .............................. 0.68 Ellis Co., TX .................................... 0.97 Fresno Co., CA ............................... 0.74 Philadelphia Co., PA ....................... 1.47 Areas within 10 percent of the 24 hour PM10 NAAQS:

Lexington Co., SC ........................... 0.20 El Paso Co., TX .............................. 0.68 Union Co., TN ................................. 0.02 Mobile Co., AL ................................ 0.40 Dona Ana Co., NM .......................... 0.16 Lake Co., IN .................................... 0.48 Philadelphia Co., PA ....................... 1.47 Pennington Co., SD ........................ 0.09 Ventura Co., CA .............................. 0.71 Total Population of all 13 areas ................................. 6.48 Notes: a These areas are listed based on their second high 24 hour concentration and annual average concentration in 1997, 1998, or both. Official nonattainment determinations are made based on three years of data, and on estimates of expected exceedances of the 24 hour standard.

Fortunately, the standards included in today's actions will result in a steady decrease in total direct PM10 from cars and light trucks even if this increase in the use of diesel engines in these vehicles were to occur. If the A. D. Little `` Most Likely'' scenario for increased diesel engines in light trucks were to occur, today's actions would reduce diesel PM10 from cars and light trucks by over 75 percent in 2020. Stated differently, by 2030 today's actions would reduce 98,000 tons of the potential increase in PM10 emissions from passenger cars and light trucks. The result would be less direct PM10 than is emitted today, because the increase in diesel PM10 would be more than offset by the reduction in PM10 emissions from gasoline vehicles resulting from lower gasoline sulfur levels. We are establishing tighter PM standards for cars and light trucks to help avoid the adverse impact of greater diesel PM emissions on PM10 attainment and public health and welfare if diesel sales increased in the future without the protection of the tighter standards. Because diesel vehicles will essentially be performing the same functions as the gasoline vehicles they will replace, it is appropriate for the new PM standards to also apply equally to gasoline and diesel vehicles. We expect that gasoline vehicles will need little or no redesign to meet the new PM standards when free of defects and properly operating. However, the new vehicle and gasoline sulfur standards may achieve some reduction in real world PM emissions from gasoline vehicles by encouraging more durable designs and by ensuring that these vehicles are operated on lower sulfur fuel. The new standards for PM will also prevent any changes in gasoline engine design which would increase PM emissions. These changes would otherwise be possible because the current PM standard is so much higher than the current performance on the gasoline vehicles.

3. PM2.5 Discussion We are not basing our promulgation of the Tier 2 vehicle standards on a finding on the need for additional emission reductions in order to attain and maintain the NAAQS for PM2.5. We are providing this information to explain that this program will result in substantial benefit in reduction of PM2.5 concentrations, to an even broader set of geographic areas than will benefit in terms of PM10 attainment. The annual and 24 hour PM2.5 NAAQS set in 1997 are numerically much lower than the corresponding PM10 standards: 15 versus 50 m g/ m3 for the annual average standards and 65 versus 150 m g/ m3 for the 24 hour average standards. While geographically broad PM2.5 monitoring is just now reaching the end of the first of three years of operation needed to determine compliance, our best analysis from the more limited PM2.5 conducted in some areas indicates that many areas that are in compliance with the PM10 standards will be found to be in violation of the annual average PM2.5 standard. Violations of the 24 hour PM2.5 standard appear to be infrequent. Therefore, if we considered it appropriate to proceed with implementing the PM2.5 NAAQS, we are confident that there would be a larger set of areas for which we would determine that further reductions in emissions are needed in order to attain and maintain the NAAQS. Moreover, gasoline and diesel cars and light trucks have a more important contributing role for ambient PM2.5 concentrations, and other emission sources that play a major role in ambient PM10 concentrations will be relatively less important. Cars and light trucks contribute essentially the same absolute amount to ambient concentrations of PM10 and of PM2.5. However, most other sources contribute much more to PM10 than to PM2.5, so the relative contribution from cars and light trucks is larger. In addition, the absolute contribution from cars and light trucks is larger in relationship to the numerically lower PM2.5 standard, making them more important to attainment and maintenance. This is also true for the potential contribution that more diesel cars and light trucks would make to ambient PM2.5 concentrations.

4. Emission Reductions and Ambient PM Reductions The NOX and VOC emission reductions from the Tier 2/ Gasoline Sulfur program are presented in the ozone section above. The SOX and PM reductions are presented in our final RIA, and are essentially unchanged from those presented in our proposal, except for the revision of the diesel sales scenario discussed above. Because virtually all of the PM reduction from the Tier 2/ Gasoline VerDate 27< JAN> 2000 23: 03 Feb 09, 2000 Jkt 190000 PO 00000 Frm 00024 Fmt 4701 Sfmt 4700 E:\ FR\ FM\ 10FER2. SGM pfrm01 PsN: 10FER2 6721 Federal Register / Vol. 65, No. 28 / Thursday, February 10, 2000 / Rules and Regulations 34 `` National Parks and the American Public: A National Public Opinion Survey on the National Park System,'' Summary Report, National Parks and Conservation Association, June 1998. 35 `` Recommendations for Improving Western Vistas,'' Report of the Grand Canyon Visibility Transport Commission to the United States Environmental Protection Agency, June 10, 1996. Sulfur program is in the fine fraction of PM10, our estimates of the PM2.5 and PM10 reductions are essentially the same. Estimates of the ambient PM reductions in 2030 in different parts of the nation, after full phase in of the vehicle standards, are presented in the final RIA. The reductions in ambient PM are largest in the parts of the country with more vehicle travel, i. e, larger in the east than in the west and larger in urban areas than in rural areas. In the eastern half of the nation, the reductions in annual average PM concentrations range from 0.2 to over 1.2 micrograms per cubic meter.

D. Other Criteria Pollutants: Carbon Monoxide, Nitrogen Dioxide, Sulfur Dioxide The standards being promulgated today will help reduce levels of three other pollutants for which NAAQSs have been established: carbon monoxide ( CO), nitrogen dioxide ( NO2), and sulfur dioxide ( SO2). As of 1998, every area in the United States has been designated to be in attainment with the NO2 NAAQS. As of 1997, one area ( Buchanan County, Missouri) did not meet the primary SO2 short term standard, due to emissions from the local power plant. There are currently 20 designated CO nonattainment areas, with a combined population of 33 million. There are also 24 designated maintenance areas with a combined population of 22 million. However, the broad trends indicate that ambient levels of CO are declining. In 1997, 6 of 537 monitoring sites reported ambient CO levels in excess of the CO NAAQS. The reductions in SO2 precursor emissions from today's actions are essentially equal to the SOX reductions described in Section III. B. and III. C., respectively. The impact of today's actions on NO2 emissions depends on the specific emission control technologies used to meet the Tier 2 vehicle emission standards. However, essentially all of the NOX emitted by cars and light trucks converts to NO2 in the atmosphere; therefore, it is reasonable to assume that today's actions will substantially reduce ambient NO2 levels by the same proportion. Today's rule also will require light trucks to meet more stringent CO standards. These more stringent standards will help extend the trend towards lower CO emissions from motor vehicles and thereby help the remaining CO nonattainment areas reach attainment while helping other areas remain in attainment with the CO NAAQS. Our analysis of CO reductions from today's program is found in Chapter III of the RIA. The analysis of economic benefits and costs found in Section IV. D.   5. does not account for the economic benefits of the CO reductions expected to result from today's proposal.

E. Visibility Visibility impairment occurs as a result of the scattering and absorption of light by particles and gases in the atmosphere. It is most simply described as the haze that obscures the clarity, color, texture, and form of what we see. The principal cause of visibility reduction is fine particles between 0.1 and 1 m m in size. Of the pollutant gases, only NO2 absorbs significant amounts of light; it is partly responsible for the brownish cast of polluted skies. While the contribution of NO2 to visibility impairment varies from area to area, it is generally responsible for less than ten percent of visibility reduction. The CAA requires EPA to protect visibility, or visual air quality, through a number of programs. These programs include the national visibility program under Sections 169a and 169b of the Act, the Prevention of Significant Deterioration program for the review of potential impacts from new and modified sources, and the secondary NAAQS for PM10 and PM2.5. The national visibility program established in 1980 requires the protection of visibility in 156 mandatory federal Class I areas across the country ( primarily national parks and wilderness areas). More than 65 million visitors travel each year to these parks and wilderness areas. The CAA established as a national visibility goal, `` the prevention of any future, and the remedying of any existing, impairment of visibility in mandatory federal Class I areas in which impairment results from manmade air pollution.'' The Act also calls for state programs to make `` reasonable progress'' toward the national goal. In addition, a recent national opinion poll on the state of the national parks found that more than 80 percent of Americans believe air pollution affecting these parks should be cleaned up for the benefit of future generations. 34 There has been improvement in visibility in the western part of the country over the last ten years. However, visibility impairment remains a serious problem in Class I areas. Visibility in the East does not seem to have improved. As one part of addressing this national problem, EPA has required states to adopt and implement effective plans for protecting and improving visibility in Class I federal areas ( 64 FR 35714, July 1, 1999). Today's actions will result in visibility improvements due to the reduction in local and upwind PM and PM precursor emissions. Since mobile source emissions contribute to the formation of visibility reducing PM, control programs that reduce the mobile source emissions of direct and secondary PM would have the effect of improving visibility. The Grand Canyon Visibility Transport Commission's final recommendations report 35 found that reducing total mobile source emissions is an essential part of any program to protect visibility in the Western U. S. The Commission found that motor vehicle exhaust is responsible for about 14 percent of human caused visibility reduction ( excluding road dust). A substantial portion of motor vehicle exhaust comes from cars and light trucks. In light of that impact, the Commission's recommendations in 1996 supported federal Tier 2/ Gasoline Sulfur standards, as EPA is proposing today. More recently, a number of Western Governors noted the importance of controlling mobile sources as part of efforts to improve visibility in their comments on the Regional Haze Rule and on the need to protect the 16 Class I areas on the Colorado Plateau. In their joint letter dated June 29, 1998, they stated that, ``* * * the federal government must do its part in regulating emissions from mobile sources that contribute to regional haze in these areas. * * *'' and called on EPA to make a `` binding commitment * * * to fully consider the Commission's recommendations related to the * * * federal national mobile source emission control strategies.'' These recommendations included Tier 2 vehicle standards and reductions in gasoline sulfur levels. The recent Northern Front Range Air Quality Study provides another indication of how important car and light truck emissions can be to fine PM and visibility. This study reported findings that indicate that cars and light trucks are responsible for 39 percent of fine PM at a site within the metropolitan Denver area, and for 40 percent at a downwind rural site. This contribution includes both direct PM and indirect PM formed from sulfur dioxide and NOX from these vehicles.

VerDate 27< JAN> 2000 21: 29 Feb 09, 2000 Jkt 190000 PO 00000 Frm 00025 Fmt 4701 Sfmt 4700 E:\ FR\ FM\ 10FER2. SGM pfrm08 PsN: 10FER2 6722 Federal Register / Vol. 65, No. 28 / Thursday, February 10, 2000 / Rules and Regulations 36 EPA's diesel health assessment ( Health Assessment Document for Diesel Emissions, SAB Review Draft, U. S. Environmental Protection Agency, Washington, DC. EPA/ 600/ 8   90/ 057D, November 1999) can be found at the following EPA website: http:// www. epa. gov/ ncea/ diesel. htm. 37 National Institute for Occupational Safety and Health ( 1988) Carcinogenic effects of exposure to diesel exhaust. NIOSH Current Intelligence Bulletin 50. DHHS ( NIOSH) Publication No. 88   116. Centers for Disease Control, Atlanta, GA. International Agency for Research on Cancer ( 1989) Diesel and gasoline engine exhausts and some nitroarenes, Vol. 46. Monographs on the evaluation of carcinogenic risks to humans. World Health Organization, International Agency for Research on Cancer, Lyon, France. World Health Organization ( 1996) Diesel fuel and exhaust emissions: International program on chemical safety. World Health Organization, Geneva, Switzerland. California Environmental Protection Agency, Office of Environmental Health Hazard Assessment: Proposed Identification of Diesel Exhaust as a Toxic Air Contaminant, Part B Health Risk Assessment for Diesel Exhaust. April 22, 1998. 38 California Environmental Protection Agency, Office of Environmental Health Hazard Assessment: Proposed Identification of Diesel Exhaust as a Toxic Air Contaminant, Part B Health Risk Assessment for Diesel Exhaust. April 22, 1998. 39 `` U. S. Light Duty Dieselization Scenarios   Preliminary Study'', report to the American Petroleum Institute, July 2, 1999. Prepared by Arthur D. Little, Inc. The analysis of economic benefits and costs found in Section IV. D. 5. accounts for the economic benefits of the visibility improvements expected to result from today's actions.

F. Air Toxics Section 202( a) provides that EPA may promulgate standards regulating any air pollutants that in the Administrator's judgment, cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare. Section 202( l) provides specific provisions for regulation of hazardous air pollutants from motor vehicles and fuels, and states that at a minimum such regulations should apply to emissions of benzene and formaldehyde. Emissions from cars and light trucks include a number of air pollutants that are known or suspected human or animal carcinogens or that are known or suspected to have other, non cancer health impacts. These pollutants include benzene, formaldehyde, acetaldehyde, 1,3 butadiene, and diesel particulate matter. For several of these pollutants, motor vehicle emissions are believed to account for a significant proportion of total nation wide emissions. All of these compounds are present in exhaust emissions; benzene is also found in evaporative emissions from gasoline fueled vehicles. The health effects of diesel particulate matter are of particular relevance to today's actions, because of the possibility for increased diesel powered truck sales and the more stringent PM standard that will apply to these trucks as a result of today's actions. While we have not finalized our decision about the carcinogenicity of diesel exhaust, we are in the process of addressing this question. The Agency's recently released draft assessment 36 concludes that diesel exhaust is a highly likely human lung cancer hazard, but that the data are currently unsuitable to make a confident quantitative statement of risk. The draft report concludes, however, that this risk is applicable to ambient exposures and that the risk may be in the range of regulatory interest ( greater than one in a million over a lifetime). Several other agencies and governing bodies have designated diesel exhaust or diesel PM as a `` potential'' or `` probable'' human carcinogen. 37 The California Air Resources Board ( ARB), for example, found that diesel particulate matter constituted a toxic air contaminant and estimated a potency range of 1.3 ´   10 ¥ 4 to 2.4 ´   10 ¥ 3 per m g/ m3.38 The ARB's findings suggest that 130 to 2400 persons in one million exposed to 1 m g/ m3 of diesel exhaust particulate continuously for their lifetime ( 70 years) would develop cancer as a result of their exposure. Because our assessment for diesel exhaust is not complete, we are not presenting absolute estimates of how potential cancer risks from diesel particulate matter could be affected by today's rule. However, we can offer a qualitative or relative discussion of these risks. Diesel engines used in nonroad equipment and heavy duty highway vehicles currently constitute a far larger source of diesel PM than cars and light duty trucks, since diesel engines are used in a very small portion of the cars and light duty trucks in service today. However, engine and vehicle manufacturers have projected that diesel engines are likely to be used in an increasing share of cars and light trucks, and some manufacturers have announced capital investments to build such engines. If these projections are valid, then the proportion of cars and light trucks powered by diesel engines, and the associated potential health risks from diesel PM, could increase substantially. We modeled the most likely level of increase in light duty diesel engine sales developed for the American Petroleum Institute. 39 We found that the greater diesel engine usage in cars and light trucks resulted in an 80 percent increase in emissions from all diesel powered highway vehicles by 2020   emissions that have been implicated in potential cancer risks   assuming no change in the current light duty diesel PM standards. Today's rule would limit the increase in the potential cancer risks from cars and light trucks associated with any potential increase in light duty diesel engines. Using the same sales projections discussed above, we have estimated that today's rule would limit the increase in total highway diesel PM emissions in 2020 due to growth in light duty diesels to under 10 percent, in contrast to the 80 percent increase projected to occur without the Tier 2 PM standards. An analogous analysis that accounted for exposure patterns, but that assumed even more widespread use of diesels in the car and light truck fleet, found that today's rule would limit the increase in total highway diesel PM exposure to about 8 percent. This analysis is discussed more fully in Chapter III. F. 2 of the Regulatory Impact Analysis. In addition, the VOC emission reductions resulting from today's rule would reduce the potential cancer risk posed by air pollutants other than diesel PM emitted by cars and light trucks, since many of these pollutants are themselves VOCs. Furthermore, the rule would align the formaldehyde standards for all Tier 2 LDVs and LDTs with the formaldehyde standards for LDVs and LDT1s from the NLEV program, thereby helping to harmonize the Federal and California formaldehyde standards. The analysis of economic benefits and costs found in Section IV. D. 5. does not account for the economic benefits of the reduction in cancer risk from air toxics that could result from today's rule. Although we have completed a peer reviewed assessment of the impact of today's rule on exposure to toxic emissions, we have not engaged in a peer reviewed assessment of the baseline air toxics risks ( including a final quantitative risk assessment of the diesel particulate risks) or of the reductions that would be achieved by today's rule. We plan to complete our analysis of air toxics risks as part of our responsibilities under section 202( l)( 2) of the Clean Air Act, which requires EPA to establish regulations for the control of hazardous air pollutants from motor vehicles. The regulations may address vehicle emissions or fuel properties that influence emissions, or both. We plan to issue a proposal to address this requirement in April 2000, and a final rule in December 2000.

VerDate 27< JAN> 2000 21: 29 Feb 09, 2000 Jkt 190000 PO 00000 Frm 00026 Fmt 4701 Sfmt 4700 E:\ FR\ FM\ 10FER2. SGM pfrm08 PsN: 10FER2 6723 Federal Register / Vol. 65, No. 28 / Thursday, February 10, 2000 / Rules and Regulations 40 Much of the information in this section was excerpted from the EPA document, Human Health Benefits from Sulfate Reduction, written under Title IV of the 1990 Clean Air Act. Amendments, U. S. EPA, Office of Air and Radiation, Acid Rain Division, Washington, DC, November 1995. 41 Vitousek, Peter M., John Aber, Robert W. Howarth, Gene E. Likens, et al. 1997. Human Alteration of the Global Nitrogen Cycle: Causes and Consequences. Issues in Ecology. Published by Ecological Society of America, Number 1, Spring 1997. 42 Much of this information was taken from the following EPA documenta: Deposition of Air Pollutants to the Great Waters Second Report to Congress, Office of Air Quality Planning and Standards, June 1997, EPA   453/ R   97   011. 43 Terrestrial nitrogen deposition can act as a fertilizer. In some agricultural areas, this effect can be beneficial. G. Acid Deposition 40 Acid deposition, or acid rain as it is commonly known, occurs when SO2 and NOX react in the atmosphere with water, oxygen, and oxidants to form various acidic compounds that later fall to earth in the form of precipitation or dry deposition of acidic particles. It contributes to damage of trees at high elevations and in extreme cases may cause lakes and streams to become so acidic that they cannot support aquatic life. In addition, acid deposition accelerates the decay of building materials and paints, including irreplaceable buildings, statues, and sculptures that are part of our nation's cultural heritage. To reduce damage to automotive paint caused by acid rain and acidic dry deposition, some manufacturers use acid resistant paints, at an average cost of $ 5 per vehicle   a total of $ 61 million per year if applied to all new cars and trucks sold in the U. S. The general economic and environmental effects of acid rain are discussed at length in the RIA. Acid deposition primarily affects bodies of water that rest atop soil with a limited ability to neutralize acidic compounds. The National Surface Water Survey ( NSWS) investigated the effects of acidic deposition in over 1,000 lakes larger than 10 acres and in thousands of miles of streams. It found that acid deposition was the primary cause of acidity in 75 percent of the acidic lakes and about 50 percent of the acidic streams, and that the areas most sensitive to acid rain were the Adirondacks, the mid Appalachian highlands, the upper Midwest and the high elevation West. The NSWS found that approximately 580 streams in the Mid Atlantic Coastal Plain are acidic primarily due to acidic deposition. Hundreds of the lakes in the Adirondacks surveyed in the NSWS have acidity levels incompatible with the survival of sensitive fish species. Many of the over 1,350 acidic streams in the Mid Atlantic Highlands ( mid Appalachia) region have already experienced trout losses due to increased stream acidity. Emissions from U. S. sources contribute to acidic deposition in eastern Canada, where the Canadian government has estimated that 14,000 lakes are acidic. Acid deposition also has been implicated in contributing to degradation of high elevation spruce forests that populate the ridges of the Appalachian Mountains from Maine to Georgia. This area includes national parks such as the Shenandoah and Great Smoky Mountain National Parks. The SOX and NOX reductions from today's actions will help reduce acid rain and acid deposition, thereby helping to reduce acidity levels in lakes and streams throughout the U. S. These reductions will help accelerate the recovery of acidified lakes and streams and the revival of ecosystems adversely affected by acid deposition. Reduced acid deposition levels will also help reduce stress on forests, thereby accelerating reforestation efforts and improving timber production. Deterioration of our historic buildings and monuments, and of buildings, vehicles, and other structures exposed to acid rain and dry acid deposition, also will be reduced, and the costs borne to prevent acid related damage may also decline. While the reduction in sulfur and nitrogen acid deposition will be roughly proportional to the reduction in SOX and NOX emissions, respectively, the precise impact of today's vehicle and fuel standards will differ across different areas. Each area is affected by emissions from different source regions, and the mobile source contribution to the total SOX and NOX emission inventory will differ across different source regions. Nonetheless, the projected impact of today's actions on SOX and NOX emission inventories provides a rough indicator of the likely effect of the Tier 2/ Gasoline Sulfur standards on acid deposition. Our analysis indicates that today's actions will reduce SOX emissions by 1.8 percent and NOX emissions by 14.5 percent in 2030. The analysis of economic benefits and costs found in Section IV. D. 5. did not account for the economic benefits of the reduction in acid deposition expected to result from today's actions.

H. Eutrophication/ Nitrification Nitrogen deposition into bodies of water can cause problems beyond those associated with acid rain. The Ecological Society of America has included discussion of the contribution of air emissions to increasing nitrogen levels in surface waters in a recent major review of causes and consequences of human alteration of the global nitrogen cycle in its Issues in Ecology series 41. Long term monitoring in the United States, Europe, and other developed regions of the world shows a substantial rise of nitrogen levels in surface waters, which are highly correlated with human generated inputs of nitrogen to their watersheds. These nitrogen inputs are dominated by fertilizers and atmospheric deposition. Human activity can increase the flow of nutrients into those waters and result in excess algae and plant growth. This increased growth can cause numerous adverse ecological effects and economic impacts, including nuisance algal blooms, dieback of underwater plants due to reduced light penetration, and toxic plankton blooms. Algal and plankton blooms can also reduce the level of dissolved oxygen, which can also adversely affect fish and shellfish populations. This problem is of particular concern in coastal areas with poor or stratified circulation patterns, such as the Chesapeake Bay, Long Island Sound, or the Gulf of Mexico. In such areas, the `` overproduced'' algae tends to sink to the bottom and decay, using all or most of the available oxygen and thereby reducing or eliminating populations of bottom feeder fish and shellfish, distorting the normal population balance between different aquatic organisms, and in extreme cases causing dramatic fish kills. Collectively, these effects are referred to as eutrophication, which the National Research Council recently identified as the most serious pollution problem facing the estuarine waters of the United States ( NRC, 1993). Nitrogen is the primary cause of eutrophication in most coastal waters and estuaries 42. On the New England coast, for example, the number of red and brown tides and shellfish problems from nuisance and toxic plankton blooms have increased over the past two decades, a development thought to be linked to increased nitrogen loadings in coastal waters. Airborne NOX contributes from 12 to 44 percent of the total nitrogen loadings to United States coastal water bodies. For example, approximately one quarter of the nitrogen in the Chesapeake Bay comes from atmospheric deposition. Excessive fertilization with nitrogencontaining compounds can also affect terrestrial ecosystems 43. Research suggests that nitrogen fertilization can alter growth patterns and change the VerDate 27< JAN> 2000 21: 29 Feb 09, 2000 Jkt 190000 PO 00000 Frm 00027 Fmt 4701 Sfmt 4700 E:\ FR\ FM\ 10FER2. SGM pfrm08 PsN: 10FER2 6724 Federal Register / Vol. 65, No. 28 / Thursday, February 10, 2000 / Rules and Regulations balance of species in an ecosystem. In extreme cases, this process can result in nitrogen saturation when additions of nitrogen to soil over time exceed the capacity of the plants and microorganisms to utilize and retain the nitrogen. This phenomenon has already occurred in some areas of the U. S. Deposition of nitrogen from cars and light trucks contributes to these problems. As discussed in Section III. B. above, today's actions will reduce total NOX emissions by 4.5 percent in 2007 and by 14.5 percent in 2030. The NOX reductions should reduce the eutrophication problems associated with atmospheric deposition of nitrogen into watersheds and onto bodies of water, particularly in aquatic systems where atmospheric deposition of nitrogen represents a significant portion of total nitrogen loadings. Since air deposition accounts for 12   44 percent of total nitrogen loadings in coastal waters, the reduction in NOX from today's actions is projected to reduce nitrogen loadings by 0.5   2.0 percent in 2007 and 1.7   6.4 percent in 2030. To put these reductions in perspective, the reductions expected in the Chesapeake Bay area would amount to about 9 percent of the total reduction in nitrogen loading needed to maintain the reduction in nutrient loads agreed to by the signatory states in the Chesapeake Bay Agreement ( 40 percent of `` controllable nutrient loads'' by the year 2000). The analysis of economic benefits and costs found in Section IV. D. 5. does not account for the economic benefits of reduced eutrophication or reduced terrestrial nitrogen deposition expected to result from today's actions.

I. Cleaner Cars and Light Trucks Are Critically Important to Improving Air Quality Despite continued progress in reducing ozone and PM levels, tens of millions of Americans are still exposed to levels of these pollutants that exceed the National Ambient Air Quality Standards. Our projections show that without further action to reduce these pollutants, tens of millions of Americans will continue to breathe unhealthy air for decades to come. Our projections also show that emissions from cars and light trucks will continue to contribute a substantial share of the ozone and PM precursors in current and projected nonattainment areas, and in upwind areas whose emissions contribute to downwind nonattainment, unless additional measures are taken to reduce their emissions. Cars and light trucks also contribute substantially to ambient concentrations of CO. These vehicles will also continue to contribute to the ambient PM that affects visibility in Class I federal areas and some urban areas. Emissions from cars and light trucks also play a significant role in a wide range of health and environmental problems, including known and potential cancer risks from inhalation of air pollutants ( a problem that could become more significant if sales of diesel powered cars and light trucks were to increase), health risks from elevated drinking water nitrate levels, acidification of lakes and streams, and eutrophication of inland and coastal waters. Today's actions will reduce NOX, VOC, CO, PM, and SOX emissions from these vehicles substantially. These reductions will help reduce ozone levels nationwide and reduce the extent and severity of violations of the 1 hour ozone standard. These reductions will also help reduce PM levels, both by reducing direct PM emissions and by reducing emissions that give rise to secondary PM. The CO reductions will help extend the downward trend in carbon monoxide levels, thereby helping the remaining CO nonattainment areas attain the CO standard and helping other areas stay in attainment with the CO standard despite continued increases in vehicle miles traveled. The NOX and SOX reductions will help reduce acidification problems, and the NOX reductions will help reduce eutrophication problems and drinking water nitrate levels. The PM standards included in today's actions will help improve visibility and would help mitigate adverse health effects in the event of increases in light duty diesel engine sales.

IV. What Are the New Requirements for Vehicles and Gasoline?

A. Why Are We Proposing Vehicle and Fuel Standards Together?

1. Feasibility of Stringent Standards for Light Duty Vehicles and Light Duty Trucks.

a. Gasoline Fueled Vehicles We believe that the standards being promulgated today for gasoline fueled vehicles are well within the reach of existing control technology. Our determination of feasibility is based on the use of catalyst based strategies that are already in use and are well proven on the existing fleet of vehicles. In fact, as you will see below, many current engine families are already certified to levels at or below the new final Tier 2 requirements. All of the certification and research testing discussed below was performed on low sulfur test fuel ( nominally 30 ppm).

i. LDVs and LDT1s   LDT4s Certainly, larger vehicles and trucks, which are heavier and have larger frontal areas, will face the biggest challenges in meeting the final Tier 2 standards. However, conventional technology will be sufficient for even these vehicles, especially in light of the extra leadtime we have provided before LDT3s and LDT4s have to meet Tier 2 levels. We are also changing the test conditions for these trucks from `` adjusted loaded vehicle weight'' to `` loaded vehicle weight.'' Adjusted loaded vehicle weight, suitable for commercial truck operation, loads the truck to half of its full payload. Loaded vehicle weight, on the other hand, represents curb weight plus 300 pounds. This change more accurately reflects how these vehicles are used and makes heavy LDT testing consistent with passenger car and light LDT testing. This change is consistent with treating these vehicles as they were designed, i. e., for light load use. Emission control technology has evolved rapidly in recent years. Emission standards applicable to 1990 model year vehicles required roughly 90 percent reductions in exhaust HC and CO emissions and a 75 percent reduction in NOX emissions compared to uncontrolled emissions. Today, some vehicles currently in production are well below these levels, showing even greater overall emissions reductions of all three of these pollutants. These vehicles' emissions are well below those necessary to meet the current federal Tier 1 and even California Low Emission Vehicle ( LEV   I) standards. The reductions have been brought about by ongoing improvements in engine airfuel management hardware and software plus improvements in catalyst designs, all of which are described fully in the RIA. The types of changes being seen on current vehicles have not yet reached their technological limits, and continuing improvement will allow both LDVs and LDTs to meet the final standards. The RIA describes a range of specific techniques that we believe could be used. These range from improved computer software and engine air fuel controls to increases in precious metal loading and other exhaust system/ catalyst system improvements. All of these technologies are currently used on one or more production vehicle models. There is no need to invent new approaches or technologies. The focus of the effort is primarily development,

VerDate 27< JAN> 2000 21: 29 Feb 09, 2000 Jkt 190000 PO 00000 Frm 00028 Fmt 4701 Sfmt 4700 E:\ FR\ FM\ 10FER2. SGM pfrm08 PsN: 10FER2 6725 Federal Register / Vol. 65, No. 28 / Thursday, February 10, 2000 / Rules and Regulations 44 Powertrain control modules are computers used to control engine, transmission, and other vehicle functions on newer automobiles and trucks. The changes involved software changes in the case of the EPA NVFEL work, or the use of alternate means of engine control in the case of the SwRI work.

45 Although this testing was done on vehicles with catalysts aged to 50,000, we belive the overall experiments also strongly suggest that the Tier 2 full life standards would be achieved by highmileage vehicles. application, and optimization of these existing technologies. We can gain significant insight into the difficulty of meeting the final new standards by looking at current full life certification data. There are at least 48 engine family control systems combinations, out of approximately 400, certified in 1999 at levels below the Tier 2 NOX standard of 0.07 g/ mi. Of these, 35 also have hydrocarbon levels of 0.09 g/ mi or below. Looking at a somewhat higher threshold to identify vehicles certified near the final standard, there are an additional 113 car and light truck families certified at levels between 0.07 g/ mi and 0.10 g/ mi NOX. Although not yet complete at this time, we also examined the 2000 model year certification data and found that there are at least 60 engine family control systems combinations certified at levels below the Tier 2 NOX standard of 0.07 g/ mi and of those, 52 also have hydrocarbon levels of 0.09 g/ mi or below. All of the above vehicles are already able, or close to being able, to certify to our final standards. The further reductions needed are those to provide a compliance margin, or cushion, between the certified level and the emission standard. The degree of compliance margin required is a function of a variety of factors designed to provide the manufacturer a high confidence that production vehicles will meet the standards in use over their useful life. Historically, these determinations are manufacturer specific, with cushions generally growing smaller as standards decline ( reflecting more precision and repeatability in vehicle performance as more sophisticated controls are developed). The certification data reflects compliance cushions from as little as 20 percent below the standard to as high as 80 percent below the standard. The manufacturers commented that the most difficult vehicles to bring into compliance with the Tier 2 standards would be the larger light duty trucks, specifically those trucks currently certified under the LDT3 and LDT4 weight categories. Because of this, we undertook a technology demonstration program aimed at lowering the emissions of several large 1999 lightduty trucks. Two LDT3 Chevrolet Silverado pick up trucks were tested, one internally and one under contract. Two LDT4 Ford Expedition sport utility vehicles were also tested, also with one tested internally and one under contract. Both types of vehicles were tested with optional high horsepower engines ( 270 hp for the Silverado and 230 hp for the Expedition) and were equipped with four wheel drive. The vehicles had curb weights of 4,500 pounds ( GVWR of 6,100 lbs) for the Silverados and 5,800 pounds ( GVWR of 7,200 lbs) for the Expeditions. Figures IV. A.   1 and IV. A.   2 show the results to date of the emissions tests performed during this demonstration program at our National Vehicle and Fuel Emissions Laboratory ( NVFEL) and also for emissions tests conducted in parallel by and under contract at Southwest Research Institute ( SwRI) using similar Ford Expeditions and GM Chevrolet Silverados. During the evaluation, the trucks were equipped with a variety of catalysts that typically featured higher volume, higher precious metal loading, and higher cell densities than the original hardware used by the vehicles to meet California LEV   I standards. Details of the catalysts tested are included in the RIA. Different exhaust manifolds featuring an insulating air gap and low thermal mass were also evaluated. Finally, calibration changes were made to the powertrain control modules 44 to better match engine operating characteristics to the new catalyst systems, and to lower engine out NOx emissions. The Silverado and Expedition had very similar results. Similar results were also achieved by us and SwRI, but by fairly different methods. The SwRI work on both trucks relied primarily on engine calibration changes and secondary air injection. The advanced catalyst systems used by SwRI contained advanced washcoat formulations with only minor changes to catalyst volume and precious metal content compared to the manufacturer's original configuration. The work we conducted on the Expedition also relied primarily on engine calibration changes with no secondary air injection. The catalyst system also contained advanced washcoat formulations with modest changes to catalyst volume and precious metal content. The work we conducted on the Silverado relied primarily on an advanced catalyst system with volume and precious metal content changes, with only minor changes to engine calibration. As can be seen in the charts, the emissions of the vehicles tested clearly show the feasibility of the Tier 2 standards on the most difficult to certify vehicle categories. All vehicles reached emission levels well below the Tier 2 full life NOx and NMOG standards. At the same time, there were no significant impacts on either fuel economy or performance of the vehicles. Compared to the intermediate ( 50,000 mile) standards, the Ford Expedition tested at NVFEL consistently emitted NOx at less than one third of the intermediate useful life standard. 45 NMHC/ NMOG emissions were slightly below the intermediate standard level with no use of secondary air injection for cold start hydrocarbon control. The Silverado tested at NVFEL met the intermediate standards with primarily hardware ( catalyst) changes and only very minor calibration changes. The trucks tested at SwRI differed from those tested at NVFEL in their combination of emissions control hardware and calibration strategies, but achieved approximately the same emissions levels. The above results point out that not only are the Tier 2 standards feasible for larger trucks, but there are multiple means that can be taken in order to achieve the necessary emissions levels. All of those paths involve fairly simple enhancements to current technology systems. Furthermore, the testing was conducted with a very limited budget over a limited amount of time. With the interim program for heavy trucks under Tier 2, the manufacturers will have 9 years from the publishing of the Tier 2 rule to bring the largest trucks into compliance with the Tier 2 standards. Manufacturers will also have considerably more resources with respect to calibration changes and hardware design to bring trucks of this type within compliance than were available within this limited, but successful, demonstration.

BILLING CODE 6560   50   P VerDate 27< JAN> 2000 21: 29 Feb 09, 2000 Jkt 190000 PO 00000 Frm 00029 Fmt 4701 Sfmt 4700 E:\ FR\ FM\ 10FER2. SGM pfrm08 PsN: 10FER2 6726 Federal Register / Vol. 65, No. 28 / Thursday, February 10, 2000 / Rules and Regulations VerDate 27< JAN> 2000 21: 29 Feb 09, 2000 Jkt 190000 PO 00000 Frm 00030 Fmt 4701 Sfmt 4725 E:\ FR\ FM\ 10FER2. SGM pfrm08 PsN: 10FER2 6727 Federal Register / Vol. 65, No. 28 / Thursday, February 10, 2000 / Rules and Regulations BILLING CODE 6560   50   C The Manufacturers of Emission Controls Association ( MECA) sponsored a program that took two LDVs ( a Crown Victoria and a Buick LeSabre) and one LDT2 ( a Toyota T100) certified to the federal Tier 1 standards and replaced the original catalytic converter systems with more advanced catalytic converters, thermally aged to approximately 50,000 miles. With these systems and some related emission control modifications, the LeSabre and T100 emissions were well below our intermediate ( 50,000 mile) useful life standards, and the Crown Victoria was well below the NMOG standard and very close to the NOX standard. Finally, the California Air Resources Board ( ARB) tested five different production LEV light duty vehicle models. Three of the five models met the Tier 2 standards for NMOG and NOX prior to any modifications. After installing low mileage advanced catalytic converters and making some minor adjustments to fuel bias, air injection, and spark timing, all of the vehicles had emission levels well below the Tier 2 intermediate useful life NMOG and NOX standards. ARB also tested several Ford Expeditions ( LDT4) equipped with advanced catalytic converters. By adjusting several parameters, they were able to reduce NOX emissions to 0.06 g/ mi and NMOG to 0.07 g/ mi with a catalyst aged to 50,000 miles of use. A more expanded analysis of the feasibility of the Tier 2 standards for gasoline fueled vehicles can be found in the RIA, considering the types of changes that will allow manufacturers to extend effective new controls to the entire fleet of affected vehicles. That analysis includes discussion of gasoline direct injection engines, as well as the feasibility of the CO, formaldehyde and evaporative emission standards. The conclusion of all of our analyses is that the standards are feasible for gasolinefueled vehicles. As gasoline fueled vehicles represent the overwhelming majority of the LDV and LDT population ( i. e., over 99%), EPA concludes that the Tier 2 standards are feasible overall for LDVs and LDTs under 8500 lbs GVWR.

ii. Medium Duty Passenger Vehicles ( MDPVs)

The technologies and emission control strategies that will be used for LDT3 and LDT4 vehicles with a GVWR less than 8,500 pounds should apply directly to MDPV vehicles that have a GVWR greater than 8,500 pounds. In our LDT technology demonstration program discussed above, we found that a combination of calibration changes and improvements to the catalyst system resulted in emission levels for NOX well below and NMHC/ NMOG approximately at the Tier 2 intermediate useful life standards. The catalyst improvements consisted of increases in volume and precious metal loading, and higher cell densities than those found in the original hardware. We are confident that the use of secondary air injection will greatly help cold start hydrocarbon control, making the NMOG standards achievable. The most significant difference between LDT4s less than 8,500 pounds GVWR and MDPVs greater than 8,500 pounds GVWR is that MDPVs have a vehicle weight up to 800 pounds more than LDT4s. MDPVs will also be typically equipped with larger displacement engines. The potential impact of these differences is higher engine out emissions than LDT4s due to the larger engine displacement and VerDate 27< JAN> 2000 21: 29 Feb 09, 2000 Jkt 190000 PO 00000 Frm 00031 Fmt 4701 Sfmt 4700 E:\ FR\ FM\ 10FER2. SGM pfrm08 PsN: 10FER2 6728 Federal Register / Vol. 65, No. 28 / Thursday, February 10, 2000 / Rules and Regulations 46 `` Cummins Sees Diesel Feasible for Early Years of Tier 2''. Hart Diesel Fuel News, Sept. 20, 1999, p. 2. 47 Harts Diesel Fuel News, August 9, 1999, p4. greater load that the engine will be operated under due to the extra weight. However, neither of these preclude manufacturers from applying the same basic emission control technologies and strategies as used by LDVs and LDTs. The only difference will likely be the need for larger catalysts with higher precious metal loading than found in LDT4s. We are confident that MDPVs will be capable of meeting the final Tier 2 standards. We are currently testing a Ford Excursion as part of our LDT technology demonstration program. Preliminary baseline results with a ` green'' ( i. e., nearly new) catalyst indicate that emission levels are higher than baseline emissions for the Ford Expedition. These results, although with a green catalyst, are well below our interim Tier 2 upper bin standards. In fact, the majority of these vehicles certified on the chassis dynamometer in California have certification levels well below our interim upper bin standards. While this testing is ongoing, we feel that the preliminary results are encouraging since they suggest that the difference in emissions between the Excursion and Expedition suggest that the strategies used on the Expedition can be successful with the Excursion. Therefore, we believe that by using technologies and control strategies similar to what will be used by LDVs and LDTs, combined with larger catalysts, MDPVs will be able to meet our Tier 2 emission standards.

b. Diesel Vehicles As discussed above, the Tier 2 standards are intended to be `` fuel neutral.'' In today's document, we establish that the Tier 2 standards are technologically feasible and costeffective for LDVs and LDTs overall, based on the discussion in Section IV. A. 1. a. above. Under the principle of fuel neutrality, all cars and light trucks, including those using diesel engines, will be required to meet the Tier 2 standards. Contrary to some of the comments received on our proposal, given that the overwhelming majority of vehicles in these classes are gasolinefueled we do not believe it is appropriate to provide less stringent standards for diesel fueled vehicles. Manufacturers of LDVs and LDTs today provide consumers with a wide choice of vehicles that are overwhelmingly gasoline fueled. Less stringent standards for diesels would create provisions that could undermine the emission reductions expected from this program, especially given the expectation that some manufacturers may intend to greatly increase their diesel sales. As with gasoline engines, manufacturers of diesels have made abundant progress over the past 10 years in reducing engine out emissions from diesel engines. In heavy trucks and buses, PM emission standards, which were projected to require the use of exhaust aftertreatment devices, were actually met with only engine modifications. Indeed, emissions and performance of lighter diesel engine are rapidly approaching the characteristics of gasoline engines, while retaining the durability and fuel economy advantages that diesels enjoy. Against this background of continuing progress, we believe that the technological improvements that would be needed could be made in the time that would be available before diesels would have to meet the new Tier 2 standards. Manufacturers may take advantage of the flexibilities in today's rulemaking to delay the need for diesel LDVs and LDTs to meet the final Tier 2 levels until late in the phase in period ( as late as 2007 for LDVs/ LLDTs and 2009 for HLDTs), giving manufacturers a relatively large amount of leadtime. In a recent public statement, Cummins Engine Company has indicated that the interim Tier 2 standards in effect for vehicles and trucks in the early years of the Tier 2 program are feasible for diesel equipped models through further development of currently available engine and exhaust aftertreatment technology. 46 While reductions in `` engine out'' emissions, including incorporation of EGR strategies, may continue to be made, increasing emphasis is being placed on various aftertreatment devices for diesels. We believe that the use of aftertreatment devices will allow diesels to comply with the Tier 2 standards for NOX and PM. For NOX emissions, potential aftertreatment technologies include lean NOX catalysts, NOX adsorbers and selective catalytic reduction ( SCR). Lean NOX catalysts are still under development, but generally appear capable of reducing NOX emissions by about 15   30%. This efficiency is not likely to be sufficient to enable compliance with the final Tier 2 standards, but it could be used to meet the interim standards that would begin in 2004, with current diesel fuel. NOX adsorbers appear capable of reaching efficiency levels as high as 90%. Efficiency in this range is likely to be sufficient to enable compliance with the proposed Tier 2 standards. NOX adsorbers temporarily store the NOX and thus the engine must be run periodically for a brief time with excess fuel, so that the stored NOX can be released and converted to nitrogen and oxygen using a conventional three way catalyst, like that used on current gasoline vehicles. There is currently a substantial amount of development work being directed at NOX adsorber technology. While there are technical hurdles to be overcome, progress is continuing and it is our judgement that the technology should be available by the time it would be needed for the final Tier 2 standards. One serious concern with current NOX adsorbers is that they are quickly poisoned by sulfur in the fuel. Some manufacturers have strongly emphasized their belief that, in order to meet the final Tier 2 levels, low sulfur diesel fuel would also be required to mitigate or prevent this poisoning problem. In its comments on the NPRM, Navistar indicated that the Tier 2 standards may be achievable given low sulfur fuel and other programmatic changes such as those included in this Final Rule. Navistar has also been quoted publically as describing the Tier 2 standards as `` challenging but achievable'' given appropriate low sulfur fuel. 47 We intend to issue a Notice of Proposed Rulemaking early in the year 2000 intended to reduce sulfur in highway diesel fuel as a step to enable the technology most likely to be used to meet the Tier 2 standards. SCR has been demonstrated commercially on stationary diesel engines and can reduce NOX emissions by 80   90%. This efficiency would be sufficient to enable compliance with the proposed Tier 2 standards. However, SCR requires that the chemical urea be injected into the exhaust before the catalyst to assist in the destruction of NOX. The urea must be injected at very precise rates, which is difficult to achieve with an on highway engine, because of widely varying engine operating conditions. Otherwise, emissions of ammonia, which have a very objectionable odor, can occur. Substantial amounts of urea are required, meaning that vehicle owners would have to replenish their vehicles' supply of urea frequently, possibly as often as every fill up of fuel. As the engine and vehicle would operate satisfactorily without the urea ( only NOX emissions would be affected), some mechanism would be needed to ensure that vehicle owners maintained their supply of urea. Otherwise, little NOX emission reduction would be expected in use.

VerDate 27< JAN> 2000 21: 29 Feb 09, 2000 Jkt 190000 PO 00000 Frm 00032 Fmt 4701 Sfmt 4700 E:\ FR\ FM\ 10FER2. SGM pfrm08 PsN: 10FER2 6729 Federal Register / Vol. 65, No. 28 / Thursday, February 10, 2000 / Rules and Regulations 48 The air quality impacts discussed above under Section III above do not reflect these new estimates. Regarding PM, applicable aftertreatment devices tend to fall into two categories: Oxidation catalysts and traps. Diesel oxidation catalysts can reduce total PM emissions by roughly 15   30%. They would need to be used in conjunction with further reductions in PM engine out emissions in order to meet the proposed Tier 2 standards. Diesel particulate traps, on the other hand, can eliminate up to 90% of diesel PM emissions. However, some of the means of accomplishing the regeneration of particulate traps involve catalytic processes that also convert sulfur dioxide in the exhaust to sulfate. These techniques, if used, would also require a low sulfur fuel. In summary, we believe that the structure of our final program, including the available bins and phase in periods, will allow the orderly development of clean diesel engine technologies. We believe that the interim standards are feasible for diesel LDV/ LDTs, within the bin structure of this rule and without further reductions in diesel fuel sulfur levels. And, as indicated earlier, at least one major diesel engine manufacturer ( Cummins) has publicly agreed with this assessment. We further believe that in the long term, the final standards will be within reach for diesel fueled vehicles in combination with appropriate changes to diesel fuel to facilitate aftertreatment technologies. Manufacturers have argued that low sulfur diesel fuel will be required to permit diesels to meet the final Tier 2 standards, and we agree. At least one major manufacturer ( Navistar) has indicated its belief that the final Tier 2 standards may be achievable for diesel engines with low sulfur diesel fuel.

2. Gasoline Sulfur Control Is Needed to Support the Proposed Vehicle Standards As we discussed in the previous section, we believe that the stringent standards in this final rule are needed to meet air quality goals and are feasible for LDVs and LDTs. At the same time, we believe that for these standards to be feasible for gasoline LDVs and LDTs, low sulfur gasoline must be made available. The following paragraphs explain why we think gasoline sulfur control must accompany Tier 2 vehicle standards. Catalyst manufacturers generally use low sulfur gasoline in the development of their catalyst designs. Vehicle manufacturers then equip their vehicles with these catalysts and EPA certifies them to the exhaust emission standards, usually based on testing the manufacturer does using low sulfur gasoline. However, fundamental chemical and physical characteristics of exhaust catalytic converter technology generally result in a significant degradation of emission performance when these vehicles use gasoline with sulfur levels common in most of the country today. This sensitivity of catalytic converters to gasoline sulfur varies somewhat depending on a number of factors, some better understood than others. Clearly, however, as we discuss in the following paragraphs, gasoline sulfur's impact is large, especially in vehicles designed to meet very low emission standards. This is the reason EPA has decided to adopt a comprehensive approach to addressing emissions from cars and light trucks, including provisions to get low sulfur gasoline into the field in the same time frame needed for Tier 2 vehicles.

a. How Does Gasoline Sulfur Affect Vehicle Emission Performance? We know that gasoline sulfur has a negative impact on vehicle emission controls. Vehicles depend on the catalytic converter to reduce emissions of HC, CO, and NOX. Sulfur and sulfur compounds attach or `` adsorb'' to the precious metal catalysts that are required to convert these emissions. Sulfur also blocks sites on the catalyst designed to store oxygen that are necessary to optimize NOX emissions conversions. While the amount of sulfur contamination can vary depending on the metals used in the catalyst and other aspects of the design and operation of the vehicle, some level of sulfur contamination will occur in any catalyst. Sulfur sensitivity is impacted not only by the catalyst formulation ( the types and amounts of precious metals used in the catalyst) but also by factors including the following: · The materials used to provide oxygen storage capacity in the catalyst, as well as the general design of the catalyst, · The location of the catalyst relative to the engine, which impacts the temperatures inside the catalyst, · The mix of air and fuel entering the engine over the course of operation, which is varied by the engine's computer in response to the driving situation and affects the mix of gases entering the catalyst from the engine, and · The speeds the car is driven at and the load the vehicle is carrying, which also impact the temperatures experienced by the catalyst. Since these factors vary for every vehicle, the sulfur impact varies for every vehicle to some degree. There is no single factor that guarantees that a vehicle will be very sensitive or very insensitive to sulfur. We now believe that there are not ( and will not be in the foreseeable future) emission control devices available for gasoline powered vehicles that can meet the proposed Tier 2 emission standards that would not be significantly impaired by gasoline with sulfur levels common today.

b. How Large Is Gasoline Sulfur's Effect on Emissions? High sulfur levels have been shown to significantly impair the emission control systems of cleaner, later technology vehicles. The California LEV standards and Federal NLEV standards, as well as California's new LEV   II standards and our Tier 2 standards, require catalysts to be extremely efficient to adequately reduce emissions over the full useful life of the vehicle. In the NPRM we estimated that, based on data from test programs conducted by EPA and the automotive and oil industries, LEV and ULEV vehicles could experience, on average, a 40 percent increase in NMHC and 134 percent increase in NOX emissions when operated on 330 ppm sulfur fuel ( our estimate in the NPRM of the current national average sulfur level) compared to 30 ppm sulfur fuel. New data generated since the NPRM on similar LEVs and ULEVs show that when these vehicles were driven on high sulfur ( 330 ppm) fuel for a few thousand miles ( as opposed to less than 100 miles for the previous data), the NMHC and NOX emission increase due to high sulfur fuel increased by 149 percent and 47 percent, respectively. In other words, instead of the previous estimated 40 percent and 134 percent increases in NMHC and NOX emissions, respectively, more realistic estimates would be 100 percent and 197 percent, respectively. 48 Also, new data generated since the NPRM for late model LEV and ULEV vehicles that meet the federal and California supplemental federal test procedure ( SFTP) standards and also have very low FTP emission levels, indicate that, on average, a 51 percent increase in NMHC and a 242 percent increase in NOX emissions when operated for a short period of time on 330 ppm compared to 30 ppm could be realized. This level of emissions increase is significant enough on its own to cause a vehicle to exceed the full useful life emission standards when operated on sulfur levels that are substantially higher than the levels required by today's rule, even with the margin of VerDate 27< JAN> 2000 21: 29 Feb 09, 2000 Jkt 190000 PO 00000 Frm 00033 Fmt 4701 Sfmt 4700 E:\ FR\ FM\ 10FER2. SGM pfrm08 PsN: 10FER2 6730 Federal Register / Vol. 65, No. 28 / Thursday, February 10, 2000 / Rules and Regulations safety that auto manufacturers generally include. Average sulfur levels in the U. S. are currently high enough to significantly impair the emissions control systems in new technology vehicles, and to potentially cause these vehicles to fail emission standards required for vehicles up through 100,000 miles ( or more) of operation. For older vehicles designed to meet Tier 0 and Tier 1 emission standards, the effect of sulfur contamination is somewhat less. Still, testing shows that gasoline sulfur increases emissions of NMHC and NOX by almost 17% when one of these vehicles is operated on gasoline for less than 100 miles containing 330 ppm sulfur compared to operation on gasoline with 30 ppm sulfur. Thus, Tier 0 and Tier 1 vehicles can also have higher emissions when they are exposed to sulfur levels substantially higher than the proposed sulfur standard. This increase is generally not enough to cause a vehicle to exceed the full useful life emission standards in practice, but it can result in in use emissions increases since the vehicle could emit at levels higher than it would if it operated consistently on 30 ppm sulfur gasoline. As discussed in the RIA, NLEV and Tier 2 vehicles are significantly more sensitive to sulfur poisoning than Tier 1 and Tier 0 vehicles. Because of this, even in the absence of Tier 2 standards, gasoline sulfur control to 30 ppm would achieve about 700,000 tons of NOX reductions per year from LDVs and LDTs by 2020. This represents about a third of the national NOX emission reductions otherwise available from these vehicles. Without these potential emission reductions, many states would face the potentially unmeetable challenge of finding enough other costeffective sources of NOX emission reductions to address their ozone nonattainment and maintenance problems. Sulfur reductions will result in reductions of other pollutants as well. For example, the increase in CO emissions at 330 ppm compared to 30 ppm were very similar to the results above for NMHC. Thus, sulfur reductions would greatly reduce CO emissions. Another example is sulfur reductions will help reduce emissions of particulate matter, providing some benefit to PM nonattainment areas ( which may or may not coincide with ozone nonattainment areas) as well as with visibility problems. Sulfur reductions will also have benefits for areas across the country with acid deposition problems. Furthermore, sulfur reduction, by enabling tighter Tier 2 standards and by improving emissions performance of the vehicles already on the road, will lead to fewer NMOG emissions, since, as explained in the RIA, NMOG emissions are also impacted by gasoline sulfur ( although to a lesser extent than NOX emissions). Some of the NMOG emissions reduced are air toxics. As described in Section III above, air toxics, also known as hazardous air pollutants, or HAPs, contribute to a variety of human health problems.

c. Sulfur's Negative Impact on Tier 2 Catalysts As we discussed in the last section, sulfur contaminates the catalyst. In addition, essentially all vehicles that have been tested show that this effect is not reversible for one or more pollutants. The ability to reverse sulfur's negative effect on catalyst performance is dependent on a number of factors. The same factors that impact sulfur sensitivity also impact the irreversibility of the sulfur effect. For example, the location of the catalyst relative to the engine, the materials used to provide oxygen storage capacity in the catalyst, and the general design of the catalyst and the mix of air and fuel ( A/ F) entering the engine over the course of operation affect irreversibility, to name a few. Perhaps the most significant factors for reversibility are the mixture of air and fuel entering the engine and catalyst temperature. The results of numerous studies and test programs show that rich exhaust ( absence of oxygen) mixtures in addition to high catalyst temperatures ( in excess of 700 ° C) can remove sulfur from the catalyst. Rich exhaust mixtures can occur intentionally and unintentionally, depending on the level of sophistication of the fuel control system. An intentional rich exhaust mixture is known as fuel `` enrichment.'' There are different types of enrichment. For example, there is `` commanded'' enrichment, which is used to provide extra power when the engine is under a load ( e. g., accelerations), as well as a means to cool the catalyst. Also, there is enrichment which results from the normal fluctuations in A/ F that occur during typical `` closed loop'' FTP operating conditions. The amount of enrichment necessary for sulfur removal is a function of several factors: the `` magnitude'' of the enrichment event, the duration of the enrichment event, and the frequency of which the enrichment event occurs. While the amount of fuel enrichment is critical in the removal of sulfur from the catalyst, high catalyst temperature is equally as important. In order to meet strict Tier 2 standards, manufacturers are going to have to balance tight A/ F control with improved catalyst performance, with an eye towards better catalyst thermal management. Many manufacturers are going to have to depend more on the precious metal palladium for oxidation of NMOG and CO emissions, as well as the reduction of NOX, because palladium is more tolerant to high temperatures. Since the vast majority of emissions still occur immediately following a cold start when the catalyst is still cool, further reductions to cold start emissions can be achieved by locating the catalysts very close to the engine. The closer proximity to the engine helps to activate the catalyst sooner by taking advantage of the additional heat supplied to the catalyst by the exhaust manifolds. Palladium is very sensitive to sulfur and, consequentially, catalyst systems that rely heavily on this metal tend to be more sensitive to sulfur and less reversible. The precious metal platinum, although usually a little more effective at oxidizing NMOG and CO and slightly less sensitive to sulfur than palladium, is too sensitive to high temperature to survive the close proximity to the engine and is not anticipated to be used for close coupled applications. As discussed above, manufacturers will need to make modifications to their emission system calibrations by optimizing fuel control, spark timing, EGR and other parameters in conjunction with improvements to catalyst systems, in order to meet Tier 2 emission standards. This combination of emission control strategies can result in significant trade offs between NMOG and NOX control. There can be considerable uncertainty associated with balancing these trade offs at very low emissions levels if the vehicle is periodically operated on high sulfur fuels. Our federal supplemental federal test procedure ( SFTP) standards, as well as California's SFTP standards, both of which take effect in the 2001 model year, can further exacerbate this problem. The SFTP standards are intended to better address and control emissions under driving conditions not captured when compliance with our FTP based exhaust emissions standards is demonstrated, such as operation with the air conditioning turned on or driving at very high rates of acceleration and vehicle speeds ( hereafter referred to simply as aggressive driving). This is an important factor in assessing sulfur irreversibility, because Tier 2 vehicles will have to meet more stringent exhaust emission standards and will have to meet these standards over the wider variety of operating conditions VerDate 27< JAN> 2000 21: 29 Feb 09, 2000 Jkt 190000 PO 00000 Frm 00034 Fmt 4701 Sfmt 4700 E:\ FR\ FM\ 10FER2. SGM pfrm08 PsN: 10FER2 6731 Federal Register / Vol. 65, No. 28 / Thursday, February 10, 2000 / Rules and Regulations 49 The FTP ( Federal Test Procedure) is the basic driving cycle used for federal emissions testing; the LA4 cycle is a component of the FTP. The REP05 cycle developed by EPA is representative of all driving that occurs outside the LA4 or FTP cycle. All but one of the aggressive accelerations found in the US06 cycle were taken from the REP05. While each segment of the US06 cycle was taken from actual in use driving, the timing and combination of these segments is not representative of in use driving in the way REP05 is representative. included in the SFTP provisions. Hence, they will have to be designed to meet the emission standards under all such operating conditions; these design changes may influence how irreversible the sulfur effect will be, as explained below. Since wide variations in the A/ F ratio help to remove sulfur from the catalytic surface, there is concern that vehicles which meet the SFTP standards, when driven aggressively, will experience insufficient enrichment to purge sulfur from the catalyst. Currently, when driven aggressively, the A/ F ratio for most vehicles ( those not certified to SFTP standards) is quite variable. Meeting the SFTP standards will ensure that manufacturers carefully control the A/ F ratio over essentially all in use driving conditions. This absence of widely varying A/ F could therefore inhibit the removal of sulfur from the catalyst once operation on high sulfur fuel ceased. In order to quantify how irreversible the sulfur effect would be when catalysts exposed to high sulfur fuel are then exposed to lower sulfur fuel, several test programs were developed by EPA and industry. The vehicles in these test programs consisted of LDVs and LDTs that met either EPA Tier 1 or California LEV and ULEV emission standards. All of the vehicles were first tested at a low sulfur level ( e. g., 30 or 40 ppm) to establish a baseline. The vehicles were then re tested with high sulfur fuel ( e. g., 350 to 540 ppm). After emission results had stabilized, the vehicles were again re tested with low sulfur fuel. Prior to each of the second series of low sulfur tests, the vehicles were operated over a short driving cycle to help purge ( i. e., remove) sulfur from the catalyst. Two different cycles were used to purge sulfur, representing different types of driving: moderate urban conditions and aggressive conditions. The FTP cycle, which represents moderate urban driving, and the REP05 49 cycle, which represents very aggressive driving ( e. g., hard accelerations, high speed cruises), were the two cycles used. The vehicles tested exhibited a wide range of irreversibility, for reasons that are not fully understood. The data published in the NPRM, showed that the effect of operation on high sulfur fuel was irreversible on one or more pollutants after operation on low sulfur fuel. NOX emissions were 15 percent irreversible. None of the vehicles were designed or modified to meet either the California or federal SFTP emissions standards. The only data used in an attempt to quantify the effect of aggressive operation on sulfur reversibility was from a catalyst manufacturer that performed some vehicle testing with catalysts which were bench aged with low and high sulfur fuel that appeared to closely approximate the impact aggressive operation would have on sulfur irreversibility. It was this data on which we based our projection of sulfur irreversibility for Tier 2 vehicles at 50 percent for NMHC and NOX emissions. Subsequent comments on the validity of these estimates after the publishing of the NPRM prompted several additional test programs on sulfur irreversibility. The sulfur irreversibility test programs that followed the NPRM focused on vehicles that had emission levels that met or were close to Tier 2 emission standards and also met the US06 or aggressive driving portion of the SFTP emission standards. Although numerous vehicles were tested, only four met both of the above criteria. ( We had tried to supplement the data base, but we were only able to add a limited number of vehicles.) We also decided to quantify irreversibility for NMHC and NOX emissions together instead of independently, because per our discussion above, sensitivity and irreversibility of either pollutant appears to be very dependent on the particular strategy chosen to reduce these emissions ( particularly engine calibration and catalyst loading of precious metals and oxygen storage). The new data exhibited a range of variability among vehicles and pollutants, similar to the data presented in the NPRM. The most important distinction between the new FRM data and the old NPRM data was that the new data showed that, on average, NMHC+ NOX emissions in three out of four vehicles were not fully reversible after aggressive driving. Based on this data, we project that NMHC+ NOX emissions will be 20 to 65 percent irreversible for Tier 2 vehicles under typical in use driving, including aggressive driving. As discussed above, the combination of calibration changes and emission system hardware modifications needed to meet our stringent Tier 2 emissions standards, can result in significant trade offs between NMHC/ NMOG and NOX control. There can be considerable uncertainty associated with balancing these trade offs at very low emissions levels if the vehicle is periodically operated on high sulfur fuels, making the ability to remove sulfur from the catalyst highly uncertain. For example, a given catalyst today may be fully reversible for one pollutant and only partially reversible for another. However, because of the trade off in NMOG and NOX performance, the modifications necessary to get that vehicle to meet both emission standards may result in the opposite effect for reversibility; i. e., full reversibility for NMOG and partial reversibility for NOX. There is no technical certainty that both the NMOG and NOX emission standards can be met without compromising reversibility performance. Therefore, we continue to believe that sulfur's negative impact on Tier 2 catalysts is a substantial concern. The preceding discussion focused on the irreversibility of the sulfur impact on emissions from current gasoline engine technologies. There are new technologies under development, which could be sold in the U. S. in the middle of the next decade ( the same time that Tier 2 vehicles are being introduced), which also appear to be very sensitive to sulfur and largely unable to reverse this sulfur impact. One of these technologies is the direct injection gasoline ( GDI) engine. These engines utilize much more air than is needed to burn the fuel, unlike conventional gasoline engines that operate under conditions where only just enough air to completely burn the fuel is introduced into the engine. This GDI technology allows these engines to be up to 25% more fuel efficient than current gasoline engines and to emit up to 20% less carbon dioxide. GDI engines are currently being introduced in both Japan and Europe ( which have or will soon require low sulfur gasolines). Because of the significant operating differences with GDI engines, these vehicles will likely require emission control technology substantially different from that used on conventional gasoline engines. For example, a GDI engine may require a NOX adsorber to meet the proposed Tier 2 NOX standard. High fuel sulfur levels quickly and permanently degrade the performance of these NOX adsorbers. Thus, to enable the sale of advanced, high efficiency GDI engines in the U. S. under the Tier 2 standards, it appears that low sulfur gasoline would have to be available nationwide by the time this technology becomes available. The fuel cell is another promising propulsion system that is being developed for possible introduction to VerDate 27< JAN> 2000 21: 29 Feb 09, 2000 Jkt 190000 PO 00000 Frm 00035 Fmt 4701 Sfmt 4700 E:\ FR\ FM\ 10FER2. SGM pfrm08 PsN: 10FER2 6732 Federal Register / Vol. 65, No. 28 / Thursday, February 10, 2000 / Rules and Regulations 50 U. S. EPA, `` OBD & Sulfur Status Report: Sulfur's Effect on the OBD Catalyst Monitor on Low Emission Vehicles,'' March 1997, updated September 1997. 51 In this section and also in section V, we make various references to the Tier 2 program, the interim program ( or standards) and the final Tier 2 standards. The Tier 2 program includes the interim program ( or standards) and the final Tier 2 standards. Some discussion is applicable to the entire Tier 2 program, some to the interim program ( or standards) only and some is only applicable to the final Tier 2 standards. As the program is complex, we advise you to read carefully to discern the applicability of the text to the proper model years and categories of vehicles. consumers early in the next century. Fuel cells are being designed to operate on a variety of fuels, including gasoline and diesel fuel. The basic fuel cell technology is highly sensitive to sulfur. Almost any level of sulfur in the fuel will disable the fuel cell. One possible solution is to install a technology that essentially filters out the sulfur before it enters the fuel cell. However, such sulfur `` guards'' are costly and could not practically be used like a disposable filter ( requiring the vehicle owner to change the sulfur guard frequently, much like changing an oil filter) in situations where constant exposure to high sulfur levels occurs. ( Even exposure to relatively low sulfur levels will likely require periodic replacement of the sulfur guard to ensure adequate protection for the fuel cell.) Therefore, the amount of sulfur in the fuel must be limited to that which can be removed by one or at most two sulfur guards over the life of the vehicle. Thus, in order for fuel cells operating on gasoline to be feasible in the U. S., low sulfur fuels would have to be available nationwide by the time this technology becomes available.

d. Sulfur Has Negative Impacts on OBD Systems As discussed in more detail in the RIA, EPA believes that sulfur in gasoline can adversely impact the onboard diagnostic ( OBD) systems of current vehicles as well as vehicles meeting the Tier 2 standards. This is an important factor supporting the need for a national sulfur control program. EPA's onboard diagnostics ( OBD) regulations require that all vehicles be equipped with a system that monitors, among other things, the performance of the catalyst and warns the owner if the catalyst is not functioning properly. The OBD catalyst monitor is designed to identify those catalysts with pollutant conversion efficiencies that have been reduced to the extent that tailpipe emissions would exceed a specified multiple of the applicable hydrocarbon emissions standard. For California LEV and federal NLEV vehicles, that multiple is 1.75 times the applicable hydrocarbon emissions standard; for federal Tier 1 vehicles, that multiple is 1.5 times the applicable hydrocarbon standard added to the 4,000 mile emission level. We want to ensure that OBD systems operate correctly, and thus the possibility that gasoline sulfur may interfere with these systems was another consideration when evaluating the need for a national sulfur program. Our evaluation of sulfur's effect on OBD systems was summarized in a staff paper in 1997.50 We concluded that sulfur can affect the decisions made by the OBD systems. Sulfur appears to affect the oxygen sensor downstream of the catalyst, which is used in the OBD systems, and it is not clear that the conditions that seem to reverse sulfur's effect on the catalyst will also reverse any sulfur impact on the downstream oxygen sensors. Indirectly, sulfur impacts OBD systems because it can impair a catalyst that would otherwise be operating satisfactorily, thereby triggering the OBD warning lights. While this would indicate a properly operating OBD system, auto manufacturers have expressed the concern that consumers using high sulfur fuel may experience OBD warnings much more frequently than they would if operating on low sulfur gasoline, and that this could lead to a loss of consumer confidence in or support for OBD systems. Consumers may then ignore the OBD warning system and drive a potentially high emitting vehicle ( which may have nothing to do with exposure to sulfur), contributing even more to air quality problems. Another possible scenario is that the OBD system may be impaired by sulfur in such a way that it does not register an improperly functioning catalyst, even if the catalyst is impaired for reasons unrelated to exposure to sulfur. This would defeat the purpose of OBD systems. The reduction of sulfur levels for gasoline should resolve any concerns over the ability of the OBD system to make proper decisions. The use of low sulfur fuel should ensure that the OBD warning light goes on when it is supposed to and is not influenced by sulfur contamination of the catalyst and/ or OBD system.

B. Our Program for Vehicles The program we are establishing today for cars, light trucks, and large passenger vehicles will achieve the same large NOX reductions that we projected for the proposed program. The program is very similar to our proposed program in all major respects. We have been able to retain the general structure, stringency, and emissions benefits of the proposal in this final rule. Where we have made adjustments to the proposed program, we have done so in ways that improve the implementation of the program without changing the overall environmental benefits that the program will achieve. And by creating a new category of vehicles subject to the Tier 2 standards, medium duty passenger vehicles, the final rule will ensure that all passenger vehicles expected to be on the road in the foreseeable future will be very clean. We have seriously considered the input of all stakeholders in developing our final rule and believe the program finalized below balances the concerns of all stakeholders while achieving the needed air quality benefits. In general, the adjustments we have made are aimed at improving the implementation efficiency of the program by better aligning the federal Tier 2 program with the NLEV program and with California's program especially during the interim program. 51 Extensive comments from manufacturers led us to conclude that better harmony between the two programs would reduce the engineering, testing and certification workload related to our interim program. Where we could make changes to increase the overlap of the two programs while maintaining the NOX reductions of the proposal, we have done so. These changes are discussed in detail in this section IV. B. and in sections V. A. and V. B. Our final rule also includes provisions to regulate complete heavyduty passenger vehicles ( primarily SUVs and passenger vans) of less than 10,000 pounds GVWR within the Tier 2 program. Standards for these vehicles were not included in the Tier 2 NPRM, but were proposed in a subsequent NPRM on October 29, 1999 ( 64 FR 58472). The final provisions for these vehicles are addressed in section IV. B. 4. g. These heavier vehicles have been recategorized as medium duty passenger vehicles ( MDPVs). They are included in the Tier 2 program starting with model year 2004 and will be treated similarly to HLDTs, unless otherwise noted. The next sections of the preamble describe our final program in detail and include changes and adjustments from the NPRM that we believe address many concerns raised by the Alliance and others. While these changes ease the burden on manufacturers, they have little or no impact on the air quality benefits of the Tier 2 program.

VerDate 27< JAN> 2000 21: 29 Feb 09, 2000 Jkt 190000 PO 00000 Frm 00036 Fmt 4701 Sfmt 4700 E:\ FR\ FM\ 10FER2. SGM pfrm08 PsN: 10FER2 6733 Federal Register / Vol. 65, No. 28 / Thursday, February 10, 2000 / Rules and Regulations 52 The NLEV program is a voluntary program, adopted by all major LDV and LDT manufacturers. It applies only to LDVs, LDT1s and LDT2s. It does not apply to HLDTs. 53 Throughout this text, the term `` full life'' is used in reference to vehicle standards to mean `` full useful life'' which is currently 10 years/ 100,000 miles for LDVs and LLDTs, but 11 years/ 120,000 miles for HLDTs. Similarly, `` intermediate life'' refers to intermediate useful life standards which apply for the period of 5 years/ 50,000 miles. In this rulemaking we are retaining the current full useful life period for interim LDVs and LLDTs, but raising it for Tier 2 vehicles to 10 years/ 120,000 miles. In a number of places in the following text, we mention that changes are being made `` in response to comments''. For a full summary of the comments and for our responses to those comments, we refer you to the Response to Comments document contained in the docket for this rulemaking or available from the Office of Mobile Sources web site ( see web address at the beginning of this document).

1. Overview of the Vehicle Program The vehicle related part of today's final rule covers a wide range of standards, concepts, and provisions that affect how vehicle manufacturers will develop, certify, produce, and market Tier 2 vehicles. This Overview subsection provides readers with a broad summary of the major vehiclerelated aspects of the rule. Readers for whom this Overview is sufficient may want to move on to the discussion of the key gasoline sulfur control provisions ( Section IV. C.). Readers wishing a more detailed understanding of the vehicle provisions can continue beyond the Overview to deeper discussions of key issues and provisions ( Sections IV. B.   2, 3, and 4) as well as discussions of additional provisions ( Section V. A.). Readers should refer to the regulatory language found at the end of this preamble for a complete compilation of the requirements. To understand how the program will work, it is useful to review EPA's classification system for light duty vehicles and trucks. The light duty category of motor vehicles includes all vehicles and trucks at or below 8500 pounds gross vehicle weight rating, or GVWR ( i. e., vehicle weight plus rated cargo capacity). Table IV. B.   1 shows the various light duty categories and also shows our new medium duty passenger vehicle ( MDPV) category, discussed in section IV. B. 4. g.. In the discussion below, we make frequent reference to two separate groups of light vehicles: ( 1) LDV/ LLDTs, which include all LDVs and all LDT1s and LDT2s; and ( 2) HLDTs, which include LDT3s and LDT4s. We also make mention of MDPVs although the details of our program for those vehicles are deferred to IV. B. 4. g. at the end of section IV. B. TABLE IV. B.   1 LIGHT DUTY VEHICLES AND TRUCKS AND MEDIUM DUTY PASSENGER VEHICLES; CATEGORY CHARACTERISTICS Characteristics LDV .................... A passenger car or passenger car derivative seating 12 passengers or less. Light LDT ( LLDT) Any LDT rated at up through 6,000 lbs GVWR. Includes LDT1 and LDT2. Heavy LDT ( HLDT). Any LDT rated at greater than 6,000 lbs GVWR. Includes LDT3 and LDT4s. MDPV ................. A heavy duty passenger vehicle rated at less than 10,000 lbs GVWR. ( The inclusion of MDPVs is discussed primarily in Section IV. B. 4. g.)

a. Introduction Today's final rule incorporates concepts from the federal NLEV program which began phase in in the 1999 model year for LDV/ LLDTs. 52 The program in today's rule takes the corporate averaging concept and other provisions from NLEV but changes the focus from NMOG to NOX and applies them to all LDVs and LDTs. The final rule is compatible with the California LEV II ( CalLEV II) program scheduled to take effect in 2004. The emission standard `` bins'' used for this average calculation are different in several respects from those of the CalLEV II program, yet still allow harmonization of federal and California vehicle technology. The Tier 2 corporate average NOX level to be met through these requirements ultimately applies to all of a manufacturer's LDVs and LDTs ( subject to two different phase in schedules) regardless of the fuel used. Meanwhile, until the final Tier 2 standards are completely phased in, separate interim standards apply to LDV/ LLDTs and HLDTs. As proposed in the NPRM and finalized in today's document, the Tier 2 program will take effect in 2004, with full phase in occurring by 2007 for LDV/ LLDTs and 2009 for HLDTs. During the phase in years of 2004   2008, vehicles not certified to Tier 2 requirements will meet interim requirements also using a bins system, but with less stringent corporate average NOX standards. In the discussions below, we set forth different Tier 2 phase in schedules for the two different groups of vehicles ( LDV/ LLDTs and HLDTs) as well as two different interim fleet average NOX standards for 2004 and later model year vehicles awaiting phase in to the Tier 2 standards. In the NPRM, we set forth separate tables of full life standard bins for the interim programs and the final Tier 2 program, but we proposed that manufacturers could use all bins for interim or Tier 2 vehicles during the phase in years. 53 We also proposed similar sets of tables for intermediate life standards. In this final rule, for simplicity and to accommodate additional bins, including some suggested by the Alliance, we have combined all of the full life bins into one table and all of the intermediate life bins into one table. The bins system and the choice of the individual bins is discussed in detail below.