# Risk Reduction Plan to Reduce

Particulate Matter Emissions from Diesel-Fueled Engines and Vehicles

Stationary Source Division Mobile Source Control Division

October 2000i Prepared by
Stationary Source Division Mobile Source Control Division

Contributors
Compliance Division Mobile Source Operations Division Planning and Technical Support Division

Research Division Office of Environmental Health Hazard Assessment

Acknowledgements:

In a ppreciation of their participation, the Air Resources Board staff extends its appreciation to the members of the Advisory Committee, Risk Management Subcommittee, Stationary Source Subcommittee, Mobile Source Subcommittee, and Fuels Subcommittee.ii 

## T ABLE OF 

## C ONTENTS

Contents Page

I. Executive Summary

................................ ................................ .............................. 1

II. Background

................................ ................................ ................................ ........... 3 A. How is this report structured?

................................ ................................ ..... 4 B. What does this report contain and how was it developed?

........................ 5

III. Diesel-Fueled Engines: Definition and Uses

................................ ........................ 6 A. How is “diesel-fueled engine” def ined?

................................ ...................... 6 B. What categories of diesel-fueled engines and vehicles were evaluated in this report?

................................ ................................ .... 6 C. What are mobile engines?

................................ ................................ ......... 8 D. What are stationary engines?

................................ ................................ ..... 8

IV. Summary of Existing and Proposed Regulations

................................ .................. 9 A. What current federal, state, or local r egulations address diesel PM emissions from mobile diesel-fueled engines?

................................ ........... 9 B. What current federal, state, or local regulations address diesel PM emissions from stationary and portable diesel-fueled engines?

............... 10 C. What current federal, state or local regu lations address diesel fuel formulation?

................................ ................................ ............................. 10

V. Emission Inventory and Risk

................................ ................................ ............... 11 A. What are the estimated diesel PM emissions for 1990, 2000, 2010, and 2020?

................................ ................................ .. 11 B. What are the estimated statewide potential cancer risks associated with diesel PM emissions?

................................ ..................... 13 C. How much of the estimated statewide potential cancer risk level from air toxics is due to diesel PM emissions?

................................ 15 D. What are the potential cancer risks associated with some typical activities where diesel-fueled engines are used?

.......................... 16

VI. Control Technology and Fuel Options

................................ ................................ . 19 A. Has ARB identified control technology options that can further reduce diesel PM emissions from diesel-fueled engines and vehicles?

... 19 B. What are the costs associated with the control technology options?

....... 20

VII. Alternative Tec hnologies

................................ ................................ ..................... 22 A. What alternatives to diesel-fueled engines and vehicles exist today that would result in lower diesel PM emissions?

............................ 22iii 

## T ABLE OF 

## C ONTENTS 

## ( cont. )

Contents Page

VIII. Staff’s Recommendation

................................ ................................ ..................... 23 A. What measures does ARB recommend be developed to further reduce diesel PM emissions from mobile diesel-fueled engines and vehicles?

................................ ................................ ........................... 24 B. What measures does ARB recommend be developed to further reduce diesel PM emissions from stationary and off-road portable diesel-fueled engines?

................................ ................................ ............. 27 C. What measures does ARB recommended regarding diesel fuel reformulation?

................................ ................................ .......................... 30 D. What impact will the recommended measures have on diesel PM emissions and risk?

................................ ................................ .................. 31 E. What other expected benefits are associated with implementing the recommended measures ?

................................ ................................ . 33 F. What possible adverse impacts may be associated with the recommended measures?

................................ ................................ ........ 33 G. What actions should the U.S. EPA pursue to support the ARB staff’s recommended measures?

................................ ..................... 33

Appendix I: Glossary of Terms and Acronyms Appendix II: Stationary and Portable Die sel-Fueled Engines: Appendix to the Diesel

Risk Reduction Plan, September 2000 Appendix III: Mobile Diesel-Fueled Engines: Appendix to the Diesel Risk Reduction

Plan, September 2000 Appendix IV: Fuels Report: Appendix to the Diesel Risk Reduction Plan,

September 2000 Appendix V: Summary of Existing Regulations Appendix VI: Methodology for Estimating the Ambient Concentrations of Particulate

Matter from Diesel-Fueled Engines and Vehicles Appendix VII: Risk Characterization Scenarios Appendix VIII: Hea lth and Safety Code Section 39665 Appendix IX: Diesel PM Control Technologies1

I. EXECUTIVE SUMMARY
Particulate matter emissions from diesel-fueled vehicles and engines are about 28,000 tons per year in California. These emissions come from a wide variety of sources including over one million on-road and off-road vehicles, about 16,000 stationary engines, and close to 50,000 portable engines. On-road engines account for about 27 percent of the emissions, off-road engines about 66 percent, with the remaining 7 percent from stationary and portable engines. With full implementation of the current vehicle standards on the books and vehicle turnover, diesel particulate matter (diesel PM) will still be about 22,000 tons per year in 2010 and about 19,000 tons per year in 2020.
In 1998, following an exhaustive 10-year scientific assessment process, the Air Resources Board (ARB or Board) identified particulate matter from diesel-fueled engines as a toxic air contaminant (TAC). On a statewide basis, the average potential cancer risk associated with these emissions is over 500 potential cases per million. In the South Coast Air Basin, the potential risk associated with diesel PM emissions is estimated to be 1,000 per million people. Compared to other air toxics the Board has identified and controlled, diesel PM emissions are estimated to be responsible for about 70 percent of the total ambient air toxics risk. In addition to these general risks, diesel PM can also present elevated localized or near-source exposures. Depending on the activity and nearness to receptors, these potential risks can range from small to 1,500 per million or more. As a result of this significant potential risk, when the Board identified diesel PM as a TAC, it directed staff to convene an advisory committee of interested parties to engage in a dialogue on the steps that can be taken to reduce these emissions.
This plan, the Diesel Risk Reduction Plan or Diesel RRP, represents the staff’s proposal for a comprehensive plan to significantly reduce diesel PM emissions. The basic premise behind the staff proposal is simple : to require all new diesel -fueled vehicles and engines to use state-of-the-art catalyzed diesel particulate filters (DPFs) and very low-sulfur diesel fuel. Further, all existing vehicles and engines should be evaluated, and wherever technically feasible and cost-effective, retrofitted with DPFs. As with new engines, very low-sulfur diesel fuel should be used by retrofitted vehicles and engines. In short, the staff’s proposed plan contains the following three components:

1. New regulatory standards for all new on-road, off-road, and stationary diesel-fueled engines and vehicles to reduce diesel PM emissions by about 90 percent overall from current levels;

2. New retrofit requirements for existing on-road, off-road, and stationary diesel-fueled engines and vehicles where determined to be technically feasible and cost-effective; and2

3. New Phase 2 diesel fuel regulations to reduce the sulfur content levels of diesel fuel to no more than 15 ppm to provide the quality of diesel fuel needed by the advanced diesel PM emission controls.
Diesel PM filter control technology is now available and has been demonstrated in over 40,000 applications worldwide. It is staff’s vision that well before the end of this decade these filters will become as commonplace on diesel-fueled engines as catalysts are now on gasoline-fueled vehicles.
Upon the Board’s approval of this comprehensive plan with its various control measures, staff will begin the full regulatory process to develop the actual regulations envisioned by this plan. During the regulatory development process, the details associated with each specific regulation will be fully developed. Over the next several years, staff will be developing these regulations and bringing them to the Board for consideration of adoption. To assist staff in evaluating retrofit applications and provide technical advice to staff, the Board created an Advisory Committee on Toxic Air Contaminant Emissions from Diesel-Fueled Engines and Vehicles.
While the principal focus of this plan is the reduction in emissions of diesel PM, staff are well aware that there are a number of viable alternative technologies, such as compressed natural gas and electrification that in many cases could be used to accomplish the same results. It is staff’s full intent, as it develops the regulations proposed in this plan, to fully explore and engage in dialogue with interested parties concerning opportunities for using these alternatives to reduce diesel PM emissions.
The projected emission benefits associated with the full implementation of this plan, including proposed federal measures, are reductions in diesel PM emissions and associated cancer risks of 75 percent by 2010 and 85 percent by 2020. The measures recommended in this plan will have a great impact on reducing the localized risks associated with activities that expose nearby individuals to diesel PM emissions. Further, there are other benefits associated with reducing diesel PM emissions. These include reduced ambient fine particulate matter levels, increased visibility, less material damage due to soiling of surfaces, and reduced incidences of noncancer health effects, such as bronchitis and asthma. Staff expects that the costs associated with carrying out this plan will be significant and will be on the order of the costs associated with other major ARB programs.3

II. BACKGROUND
The public’s exposure to TACs is a significant public health issue in California. In 1983, the California Legislature enacted a program to identify the health effects of TACs and to reduce exposure to these contaminants to protect the public health (Assembly Bill (AB) 1807 : Health and Safety Code sections 39650 -39674). The Legislature established a two-step process to address the potential health effects from TACs. The first step is the risk assessment (or identification) phase. The second step is the risk management (or control) phase of the process.
In August 1998, the ARB identified diesel PM as a TAC, following a 10-year review process. This marked the completion of the identification phase of the process to address the potential for adverse health effects associated with diesel PM emissions.
This Diesel RRP is the first formal product of the risk management phase of the AB 1807 process. This report presents information that identifies the available options to reduce diesel PM, and identifies recommended control measures to achieve further reductions. The recommended control measures would be developed as mobile source regulations or stationary source airborne toxic control measures (ATCMs).
The next step in the AB 1807 process, following approval of this plan by the Board, is the development of the specific ATCMs and fuel or vehicular emissions regulations designed to reduce diesel PM emissions. The goal of each regulation is to reduce diesel PM to the greatest extent feasible. These regulations must be technically feasible and be cost-effective, and they will provide an opportunity to address issues associated with the application of controls on a specific source categories. In developing rules to implement the Diesel RRP, the staff will consider the availability and cost of engine modifications, add-on control technology, changes in fuel parameters, alternative fuels, and alternative methods of performing the function of the diesel engine application. Thus, although most of the Board’s regulatory activities are expected to be focused on emission controls that can be added to or built into diesel-fueled engines, staff will also fully integrate alternative “non -diesel” technologies (e.g., electrification and compressed natural gas (CNG)) as possible control options for reducing diesel PM emissions.
ARB staff will develop the ATCMs and regulations with full public involvement and dialogue through public workshops and meetings with groups and individuals. Draft versions of the ATCMs and regulations will be presented to the public for review and comment, and final draft versions will be presented to the Board for approval. Public outreach is an essential element in the development of any ATCM or regulation to ensure that all affected and interested parties have full opportunity to provide input and shape rules that are both effective and workable.
As part of the identification process, the Office of Environmental Health Hazard Assessment (OEHHA) evaluated the potential for diesel exhaust to affect human health. The OEHHA found that exposures to diesel PM resulted in an increased risk of cancer and an increase in chronic noncancer health effects including a greater incidence of4

cough, labored breathing, chest tightness, wheezing, and bronchitis. The OEHHA estimated that based upon available studies, the potential cancer risk from exposure to diesel PM in concentrations of one microgram per cubic meter ranged from 130 to 2400 excess cancers per million. The Scientific Review Panel (SRP) approved the OEHHA’s determinations concerning health effects and approved the range of risk for particulate matter from diesel-fueled engines. The SRP concluded that a value of 300 excess cancers per million people, per microgram per cubic meter of diesel PM, was appropriate as a point estimate of unit risk for diesel PM.
The OEHHA also concluded that exposure to diesel PM in concentrations exceeding 5 micrograms per cubic meter can result in a number of long-term (chronic) noncancer health effects including greater incidence of cough, phlegm, and bronchitis. The 5 microgram per cubic meter value is referred to as the Chronic Reference Exposure Value (REL) for diesel PM. The SRP supported the OEHHA’s conclusion and noted that the REL may need to be lowered further as more data emerge on potential adverse noncancer effects of diesel PM.
As part of its formal identification of diesel PM as a TAC, the Board accepted the OEHHA and SRP’s conclusions and directed the ARB staff to begin the risk management process. The staff was directed to develop control measures to reduce both diesel PM and other potentially harmful pollutants. The staff was also directed to form a diesel risk management working group to advise the staff during its risk management efforts. This working group, the Advisory Committee and subcommittees, are discussed in Section B., below.

A. How is this report structured?
This report consists of a main report and appendices that summarize and discuss the proposed Diesel RRP to reduce emissions, exposure, and potential cancer risk associated with particulate matter from diesel-fueled engines.
The main report provides the following information:

♦ defines the term “diesel-fueled engine” and identifies the categories of diesel -fueled engines and vehicles evaluated in this report;
♦ summarizes current regulations that address diesel PM emissions from diesel-fueled engines and vehicles;
♦ presents diesel PM emission inventory estimates, estimated ambient concentrations, and associated potential cancer risk information for the years 1990, 2000, 2010, and 2020;
♦ presents current near-source diesel PM emissions exposure and potential cancer risk estimates;
♦ discusses available diesel PM emissions control technology options;
♦ present’s ARB staff’s recommendation, based upon the above information, to further control particulate matter emissions from diesel-fueled engines and vehicles;5

♦ estimates the reduction in diesel PM emissions, exposure, and risk by 2010 and 2020 that could be achieved if all recommended measures were implemented; and
♦ recommends specific measures to be developed to further reduce diesel PM emissions from diesel-fueled engines and vehicles.
Appendix I is a list of terms, definitions and acronyms used in both the main report and appendices. Appendix II is a report on the need for further regulation of stationary and portable diesel-fueled engines. Appendix III is a report on the need for further regulation of mobile on-and off-road diesel-fueled engines (excluding portable equipment, which is addressed in Appendix II). Appendix IV is a report on the need for further regulation of diesel fuel. Appendix V is a summary of existing regulations addressing diesel-fueled engines, vehicles, and diesel fuel. Appendix VI is a discussion of the methodology for estimating the ambient concentrations of diesel PM emissions from diesel-fueled engines and vehicles. Appendix VII is a discussion of the potential risks associated with typical activities where diesel-fueled engines and vehicles are used (risk characterization scenarios). Appendix VIII is Health and Safety Code Section 39665, which identifies the requirements this report must meet. Appendix IX is a discussion of diesel PM control technologies.

B. What does this report contain and how was it developed?
In accordance with California Health and Safety Code Section 39665 (see Appendix VIII), this report includes the following information:

♦ number (population) and categories of diesel-fueled engines and vehicles;
♦ consideration of all past and current measures for reducing diesel PM;
♦ emissions and associated ambient and near-source potential risk levels for diesel PM;
♦ available technologies for reducing diesel PM;
♦ initial estimates for the costs of reducing diesel PM;
♦ alternative methods of emission reductions;
♦ recommended measures to be developed to reduce emissions and potential risk;
♦ potential adverse health, safety, or environmental impacts from implementation of the recommended measures; and
♦ impact of the recommended measures on diesel PM emissions and potential risk.
While the above items are addressed in this plan, staff will further refine and update this information as it develops the various control measures identified in this plan.
To ensure full opportunity for public consultation and input in developing this report, an Advisory Committee was created to serve as a forum for on-going communication, cooperation, and coordination in identifying opportunities to reduce6

diesel PM emissions. The Advisory Committee consists of the Stationary Source, Fuels, Mobile Source/Alternative Strategies, and Risk Management subcommittees. The Advisory Committee and each of the four subcommittees include representatives from industry, local districts, environmental organizations, ARB, the United States Environmental Protection Agency (U.S. EPA), and the public.
ARB staff presented a draft of this document to each of the four subcommittees and the Advisory Committee for review and comment. All comments were considered and the draft report was revised in a number of ways to reflect these comments.

III. DIESEL-FUELED ENGINES : DEFINITION AND USES

A. How is “diesel-fueled engine” defined?
For purposes of this report, a diesel-fueled engine is defined as any internal combustion, compression-ignition (diesel-cycle) engine. It is generally assumed that the engine will be using diesel fuel. However, diesel-cycle engines using alternative fuels or fuel reformulation (e.g., jet fuel, biodiesel, CNG, and diesel/water mixtures) will also be addressed during the development of each specific ATCM or regulation.

B. What categories of diesel-fueled engines and vehicles were evaluated in this report?
Staff’s goal in this plan was to address all diesel-fueled engines in California. Figure 1 identifies the specific categories of diesel-fueled engines and vehicles evaluated in this report. The following paragraphs provide a brief description of each category. Detailed descriptions can be found in Appendix II for Stationary Engines and in Appendix III for Mobile Engines.7 Cars

Trucks

Buses On-Road

Off-Road Vehicles & Equipment

Portable

Prime Engines

Emergency/ Standby Mobile

Stationary 

### Figure 1: Diesel-Fueled Engines and Vehicle Categories

Diesel Engines8

C. What are mobile engines?
Mobile engines can be divided into two categories : on-road vehicles and off-road engines and vehicles.

On-Road Vehicles : Diesel-fueled engines are used in every category of on-road vehicles except motorcycles, and include light to heavy-duty trucks, school buses, urban buses, and passengers vehicles. In California, the majority of on-road diesel-fueled engines are found in the heavy-duty vehicles with a gross vehicle weight rating (GVWR) greater than 14,000 pounds. There are approximately 700,000 on -road diesel-fueled vehicles currently in use in California.
Off-Road Engines and vehicles : Diesel-fueled off-road engines comprise over 100 individual off-road vehicle and equipment types classified into 17 equipment categories. Engine sizes range from under 15 horsepower to over 10,000 horsepower. These equipment categories include agriculture, airport ground support, construction and mining, commercial, industrial, logging, transportation refrigeration units, lawn and garden, commercial marine vessels, pleasure craft, and locomotives. Many of the off -road categories contain equipment types that are classified as portable (equipment of 25 horsepower or greater that is designed and capable of being carried or moved from one location to another). There are approximately 550,000 off-road diesel-fueled engines and vehicles currently in use in California. A more detailed breakdown is presented in Appendix III.

D. What are stationary engines?
Stationary engines can be divided into two categories : emergency/standby engines and prime engines.
Emergency/standby engine : Emergency/standby engines are typically used for emergency back-up electric power generation or the emergency pumping of water. Sizes range from 50 to 6,000 horsepower, depending on the needs of the user. There are over 11,000 diesel -fueled emergency/standby engines in use in California. Emergency/standby engines make up about 70 percent of the total number of stationary engines throughout the State. Several local air pollution control and air quality management districts (districts) have rules that regulate NOx and CO emissions, but not PM from internal combustion engines. However, some districts currently exempt emergency/standby engines from complying with these requirements.
Prime Engines : Prime engines are stationary engines that are not used in an emergency back-up or standby mode. There are approximately 5,000 diesel-fueled prime engines currently in use in California. Examples include diesel-fueled engines that are used to power compressors, cranes, generators, pumps, and grinders. Prime engines make up about 30 percent of the total stationary engine inventory throughout the State.9

Of the prime engines operating throughout the State, about 70 percent are agricultural irrigation pump engines.

IV. SUMMARY OF EXISTING AND PROPOSED REGULATIONS
The ARB has the responsibility for control of emissions from mobile sources. The local air districts have the primary responsibility for control of air pollution for all sources, other than emissions for mobile sources. State law, however, provides the South Coast AQMD with the authority to require fleets of 15 or more vehicles to purchase clean vehicles when adding or replacing vehicles, authority which they have recently exercised.
There are certain categories of mobile sources, however, for which ARB lacks direct authority to regulate. The federal Clean Air Act Amendments of 1990 (CAA) preempt state and local authorities from the control of emissions from new farm and construction equipment under 175 horsepower and from new locomotives or locomotive engines (CAA Section 209(e)(1)(A)); only the U.S. EPA has the authority to establish emission standards for those engines. In addition, heavy-duty diesel vehicles that travel in California but are registered in other states are subject only to federal emission certification standards; these vehicles contribute approximately 25 percent of the heavy heavy-duty vehicle-miles-traveled in California.
The CAA also requires California to receive authorization from the U.S. EPA for controls over on-road (CAA Section 209(b)(1)) and the non-preempted off-road sources (CAA section 209(e)(2)(A)). Overall these provisions make the U.S. EPA an important partner in control of emissions from diesel engines.
The following sections briefly describe the existing federal, state, and local programs that currently apply to diesel-fueled engines and vehicles operating in California. A more detailed summary of the statutes and regulations may be found in the tables in Appendix V.

A. What current federal, state, or local regulations address diesel PM emissions from mobile diesel-fueled engines?
Virtually all new diesel-fueled on-road and off-road motor engines and vehicles sold in California are required to meet both federal and state emission certification requirements. Preempted engines, as noted above, must meet only the federal requirements. In most cases, California’s motor vehicle and diesel-fueled engine programs are designed to be consistent with the federal programs. To ensure the
on -road engi nes continue to have functional controls and proper maintenance, California has implemented Heavy-Duty Vehicle Inspection and Periodic Smoke Inspection Programs to reduce excessive smoke emissions and tampering with on-road diesel-fueled vehicles over 6,000 pounds gross vehicular weight for both in-state and out-of-state registered heavy-duty diesel vehicles. Non -regulatory strategies, which10

include incentives and voluntary agreements with vehicle and engine manufacturers, have also been implemented in California to accelerate reductions in certain criteria pollutants.

B. What current federal, state, or local regulations address diesel PM emissions from stationary and portable diesel-fueled engines?
In California, the local air pollution control and air quality management districts (Districts) establish rules and regulations for controlling emissions from new and existing stationary sources of air contaminants. These rules and regulations address both criteria and toxic air contaminant emissions.
District preconstruction and operating permit programs implement the local, State, and federal air pollution control requirements applicable to new or modified sources of air pollution. Larger new or modified sources located in a nonattainment area must apply the Lowest Achievable Emission Rate control technology to minimize emissions, and they must “offset” the remaining emissions with reductions from other sources when appropriate. A new or modifying source located in an attainment or unclassified area must apply the Best Available Control Technology and meet additional requirements aimed at maintaining the region’s clean air. In addition, “major sources” of air pollution must obtain federal Title V operating permits that govern continuing operation.
Many Districts have also adopted, pursuant to the California Health and Safety Code, Reasonably Available Control Technology/Best Available Retrofit Control Technology requirements that apply to existing sources located in nonattainment, attainment, and unclassified areas. These requirements are also implemented through the district’s permit program.
Pursuant to State law, the ARB has established the Portable Equipment Registration Program (PERP) which is a voluntary program for the registration and regulation of portable engines and associated equipment. Several Districts have implemented similar registration programs. Portable equipment not registered through the ARB or a local district may be subject to District stationary source permit requirements, depending on the size of the engine. In addition, the U.S. EPA and ARB have established engine certification standards for new off-road engines (of which portable engines are a subset). These engines are available for use in portable equipment.

C. What current federal, state or local regulations address diesel fuel formulation?
Current federal U.S. EPA regulations establish fuel registration and formulation requirements. All diesel fuels and all additives for on-road motor vehicles are required to be registered with the U.S. EPA. The ARB has established California fuel formulation requirements, applicable to all motor vehicles, that either meet or exceed existing11

federal formulation requirements. In addition, ASTM D 975 specifies standards which diesel fuels should meet to ensure safety, reliability, and performance. Generally, alternative diesel fuels do not meet all of the ASTM specifications.
Since 1993, the sulfur content limit of California diesel (as well as diesel fuel sold to on-road vehicles nationwide) has been set at a maximum 500 parts per million by weight ( ppmw). However, the average sulfur content of complying fuel formulations currently being sold in California is about 140 ppmw. 1 Further, California’s diesel fuel specifications include an aromatics limit and the fuel specifications apply to both
on -road and off-road vehicles (EPA’s fuel sulfur requirements only apply to on-road vehicles). Although stationary engines are not required to use fuel that meets California Air Resources Board diesel (CARB diesel) formulation requirements, virtually all use complying fuel because of California’s single fuel distribution network. Also, under state law, districts have the authority to establish formulation requirements for fuels to be used in stationary engines. To date, several districts have established diesel-fueled engine best available control technology requirements specifying the use of CARB diesel. Portable engines registered under ARB’s Statewide Portable Equipment Registration program are required to use CARB diesel. Beginning July 1, 2002, medium and larger transit agencies must use diesel fuel with a sulfur content no greater than 15 ppmw in all diesel buses.

V. EMISSION INVENTORY AND RISK
This section summarizes the statewide diesel PM emissions inventory from diesel-fueled engines and provides ambient and near-source potential cancer risk estimates for those emissions. A detailed description of how the inventory, ambient concentration, and ambient risk values listed in Tables 1 through 5 of this chapter were determined is presented in Appendix VI.

A. What are the estimated diesel particulate matter emissions for 1990, 2000, 2010, and 2020?
Table 1 lists the estimates for the statewide diesel PM emissions inventory from diesel-fueled engines and vehicles for 1990. Tables 2, 3, and 4 provide similar estimates for 2000, 2010, and 2020. The relative contribution of the major subcategories of engines and vehicles that comprise the stationary and mobile categories are also shown. All tables take into account growth in engines due to population and economic growth and emission reductions due to both federal and state regulations in effect at the time of the inventory estimate. These estimates do not include proposed recommended measures discussed in Chapter VIII, including the recently proposed 2007 federal on-road and diesel fuel standards.

1 141 ppmw is the volume-weighted average determined by the California Energy Commission’s 1997 California refiner survey. (See Appendix IV.)12

Table 1: Estimated Statewide Diesel PM Emissions Inventory –

Diesel-Fueled Engines and Vehicles (1990)

Category Engine Population Diesel PM

(tons per year) % of Total

Diesel PM Emissions STATIONARY Prime 4,600 400 0.9 Emergency Stand-by 10,200 124 0.3 MOBILE On-road 606,700 18,400 39.7 Off-road (Excluding Portable Equipment) 476,300 25,300 54.5 Portable 47,600 2,200 4.7 TOTAL 1,145,300 46,400 100.0

Table 2: Estimated Statewide Diesel PM Emissions Inventory –

Diesel-Fueled Engines and Vehicles (2000)

Category Engine Population Diesel PM

(tons per year) % of Total

Diesel PM Emissions STATIONARY Prime 4,800 420 1.5 Emergency Stand-by 11,300 138 0.5 MOBILE On-road 687,200 7,500 26.8 Off-road (Excluding Portable Equipment) 498,200 18,500 66.1 Portable 49,200 1,400 5.0 TOTAL 1,250,700 28,000 100.0

Table 3: Estimated Statewide Diesel PM Emissions Invento ry –

Diesel-Fueled Engines and Vehicles (2010)

Category Engine Population Diesel PM

(tons per year) % of Total

Diesel PM Emissions STATIONARY Prime 4,400 360 1.6 Emergency/Standby 12,300 143 0.6 MOBILE On-road 643,900 5,200 22.9 Off-road (Excluding Portable Equipment) 521,300 15,900 70.0 Portable 53,600 1,100 4.9 TOTAL 1,235,500 22,700 100.013

Table 4: Estimated Statewide Diesel PM Emissions Inventory –

Diesel-Fueled Engines and Vehicles (2020)

Category Engine Population Diesel PM

(tons per year) % of Total

Diesel PM Emissions STATIONARY Prime 4,400 350 1.9 Emergency/Standby 13,200 149 0.8 MOBILE On-road 610,200 4,900 26.0 Off-road (Excluding Portable Equipment) 527,800 12,800 67.9 Portable 55,200 660 3.5 TOTAL 1,210,800 18,900 100.0
The current inventory of diesel PM emissions in Table 2 shows that there are about 28,000 tons per year of diesel PM that can potentially be reduced from a variety of sources. The inventory also shows that the sources are numerous, with over 1.25 million diesel-fueled engines operating statewide. Comparing the statewide diesel PM emissions in Table 1 (1990) and Table 2 (2000), shows that significant progress has been made to reduce diesel PM emissions in California.
The bulk of the 30 percent decrease in diesel PM emissions from 2000 to 2020 is due to currently adopted on-road standards and fleet turn-over as new vehicles with controls replace older vehicles with little or far less effective controls. Proposed federal standards for diesel-fueled engines are not considered in this inventory, but would reduce total diesel PM in California by approximately 3,500 tons per year (or an additional 15 percent when compared to year 2000 emissions) in 2020. Some reduction in diesel PM emissions is due to a slight decrease in the on-road engine population.

B. What are the estimated statewide potential cancer risks associated with diesel PM emissions?
Table 5 lists the estimates for the statewide population-weighted annual outdoor average diesel PM concentrations and corresponding percent change in the concentration for the years 1990, 2000, 2010, and 2020 resulting from diesel PM emissions. These estimates are based on the emission inventory estimates presented in Tables 1 through 4.

The Proposed Identification of Diesel Exhaust as a Toxic Air Contaminant, Appendix III, Part A, Exposure Assessment 2 (ID Report) reported the statewide population–weighted annual outdoor average diesel PM concentration as 3.0 μ g/m 3 for 1990. The ARB staff reviewed studies conducted in the San Joaquin Valley, the South

2 As approved by the Scientific Review Panel on April 22, 1998.14

Coast Air Basin, and the city of San Jose to obtain more complete PM 10 ambient data. These data, along with routinely collected ambient PM 10 monitoring network data and the 1990 PM 10 emissions inventory, were used in a receptor model to estimate the statewide outdoor concentration of diesel PM in 1990.

We estimated the statewide outdoor concentration of diesel PM for 1990, 2000, 2010, and 2020 by assuming that the ambient concentration is proportional (linearly) to the statewide emissions. The ratio of the ambient concentration to statewide emissions was assumed to remain constant for the years 1990, 2000, 2010, and 2020. For 1990, this ratio was determined by using the ambient concentration from the ID report (3.0 μ g/m 3 ) and the statewide emission estimate for 1990 from Table 1 (46,400 TPY). Using the 1990 ratio and the statewide emissions estimates for 2000, 2010, and 2020 from Tables 2, 3, and 4, the ambient concentration estimates for 2000, 2010, and 2020 were estimated. These are presented in Table 5.
Table 5: Statewide Population-Weighted Annual Outdoor

Average Diesel PM Concentration for 1990, 2000, 2010, and 2020
1990 2000 2010 2020

Concentration ( μ g/m 3 ) 3.0 1.8 1.5 1.2
Percent Reduction in Diesel PM from 1990 Concentration N/A 40% 50% 60%

The ID Report provided estimates of indoor and total exposure to diesel PM. Applying the 1990 ratio to the estimated population-weighted annual outdoor average diesel PM concentrations for 2000, 2010, and 2020 results in the following indoor exposure estimates, respectively: 1.2 μ /m 3 , 1.0 μ

/m 3 , and 0.8 μ

/m 3 . Total exposure estimates for 2000, 2010, and 2020 are 1.3 μ /m 3 , 1.1 μ

/m 3 , and 0.84 μ

/m 3 . The potential risk was estimated by multiplying the statewide ambient concentration by the unit risk factor of 300 excess cancers per million people per microgram per cubic meter of diesel PM. 3 This information, along with the estimated potential cancer risk values, is summarized in Table 6.

3 The full range of unit risk factors i dentified by the SRP is 130 to 2400 excess cancers per million per microgram per cubic meter of diesel particulate matter. The 300 value was recommended by the SRP for use as a point estimate of the unit risk.15

Table 6: Estimated Exposure of Californians to Diesel PM for 2000, 2010

and 2020 Estimated Average Air Exposure Concentration ( μ g/m 3 ) and Potential Risk (excess cancers/million) 2000 2010 2020 Estimated Average Air Exposure Concentration – 1990 μ g/m 3 1990

Ratio

Conc. Risk Conc. Risk Conc. Risk Outdoor Ambient Estimate 3.0 1.8 540 1.5 450 1.2 360

Total Indoor Exposure Estimate 2.0 2.0/3.0 1.2 360 1.0 300 0.8 240

Total Exposure Estimate 2.1 2.1/3.0 1.26 380 1.05 315 0.84 252

C. How much of the estimated statewide potential cancer risk level from air toxics is due to diesel PM emissions?
To provide a perspective on the contribution that diesel PM has on the overall statewide average ambient air toxics potential cancer risk, ARB staff evaluated risks from other compounds using data from ARB’s ambient monitoring network. ARB maintains a 21 site air toxics monitoring network which measures outdoor ambient concentration levels for approximately 60 air toxics.
Table 7 shows the potential cancer risk from the top ten inhalation risk contributors that the State of California has identified as TACs and routinely monitors. The diesel PM values are calculated based on the procedure discussed in the previous section. The risk values for the other compounds are based on the annual average concentration (determined from ambient monitoring) multiplied by the unit risk factor for each compound. Table 7 also shows that for the top ten risk contributors, diesel PM contributes over 70 percent of the state estimated potential cancer risk levels.16

Table 7: Estimated Statewide Average Potential Cancer Risk from

Outdoor Ambient Levels of Air Toxics for the year 2000

Compound Potential Cancer Risk 1,2 Excess Cancers/Million Percent Contribution to Total Risk Diesel Exhaust PM 10 540 71.2 1,3-Butadiene 74 9.8 Benzene 57 7.5 Carbon Tetrachloride 30 4.0 Formaldehyde 19 2.5 Hexavalent Chromium 17 2.2 para-Dichlorobenzene 9 1.2 Acetaldehyde 5 0.7 Perchloroethylene 5 0.7 Methylene Chloride 2 0.3 TOTAL 758 100
1. Diesel exhaust PM 10 potential cancer risk based on 2000 emission inventory estimates presented in Table 5. All other potential cancer risks based on air toxics network data. Used 1997 data for para-Dichlorobenzene. Used 1998 monitoring data for all others. 2. Assumes measured concentrations are equivalent to annual average concentrations and duration of exposure is 70 years, inhalation pathway only. The South Coast Air Quality Management District also conducted a study of air toxics in the South Coast Air Basin (Multiple Air Toxics Exposure Study II (MATES-II)) in 1998 and 1999. The MATES-II study estimated that the average basin wide potential cancer risk from diesel PM was about 1,000 excess cancers per million, or 71 percent of the average cancer risk from all air toxics in the South Coast Air Basin.
ARB staff’s findings are consistent with the MATES-II study in that diesel PM is a major contributor to potential ambient risk levels and accounts for approximately 70 percent of the ambient air toxics cancer risk. Our analysis also indicates that average ambient concentrations of air toxics are higher in the South Coast Air Basin than elsewhere in the state, resulting in higher estimates of risk for residents of that air basin. Staff concludes that reducing the risk from diesel PM is an essential element in reducing the public’s overall ambient exposure to air toxics.

D. What are the potential cancer risks associated with some typical activities where diesel-fueled engines are used?
ARB staff estimated the range of potential cancer risks from seven common activities or situations to determine if the concentrated operation of diesel -fueled engines could expose nearby individuals to locally elevated diesel PM concentrations higher than average regional concentrations. The specific situations investigated included idling school buses, truck stops, freeways, emergency and standby diesel engine operations, prime engine operations, and warehouse distribution center operations. Figure 2 shows the range of potential cancer risk, above background levels, estimated for each type of activity. The risk estimate for each activity does not account for the risk from any other diesel -fueled engines or vehicles and assumes a 70-year, or lifetime, exposure. For more detailed information regarding each activity and the methodology used to derive the estimates, see Appendix VII.17 0 100 200 300 400 500 600 700 800 900

Potential Excess Cancers (Chances per million based on 70-years exposure) Truck Stop Idling School Buses

High Volume Freeway Prime Engine Emergency/Standby Engine

1,700 Distribution Center The ranges within each activity result from variations of operating times and durations, stack parameters, facility sizes, numbers and sizes of equipment, and meteorological conditions. The estimated 70-year cancer risks occur at the point of maximum off-site impact (PMI). PMI is the off-site location closest to the emission source that shows the highest modeled concentration of diesel PM. PMI can be located as close as 20 meters from the emission source.

Low Volume Freeway 

### Figure 2: Potential Cancer Risk Range of Activities

Using Diesel-Fueled Engines18

Risk is a function of the lifetime average daily dose and the carcinogenic potency of the compound. The potential risks reported here were estimated by multiplying the modeled concentration of a toxic compound by the carcinogenic potency value, also known as the unit risk factor. The unit risk factor is defined as the estimated probability of a person contracting cancer as a result of constant exposure to an ambient concentration of 1 μ g/m 3 over a 70-year lifetime. This approach and the use of a 70 -year lifetime is consistent with the OEHHA/ARB methodology for evaluating the potential risk from exposure to air toxics.
We expect the estimated 70-year potential cancer risk range for each of these activities will fall within the ranges in Figure 2. Each range assumes a 70-year exposure to diesel PM emissions at current levels, and uses SRP’s diesel PM unit risk factor point estimate of 300 excess cancers per million people per microgram per cubic meter of diesel PM. The ranges within each activity result from variations in assumptions of operating times and durations, stack parameters, facility sizes, numbers and sizes of equipment, and meteorological conditions. For example, in the Idling School Buses scenario the activity ranged from five buses idling two minutes each twice per day to 20 buses idling 15 minutes each twice per day for 180 days per year.

The estimated 70 -year potential cancer risks in Figure 2 are based on the modeled diesel PM concentrations at the point of maximum impact (PMI). PMI is the off-site location closest to the emission source that shows the highest modeled concentration of diesel PM. The PMI can be located as close as 20 meters from the emission point. The diesel PM concentrations and associated potential risk decreases as one moves away from the point of maximum impact. For example, the potential cancer risk at the point of maximum impact for the Low -Volume Freeway scenario is estimated to be 200 excess cancers per million if a residence were located 20 meters away. For a residence located 500 meters away, the estimated potential cancer risk drops to 30 excess cancers per million.
The estimated risks presented in Figure 2, and the assumptions used to determine these risks, are not based on a specific source of diesel PM. Instead, general assumptions bracketing a fairly broad range of possible operating scenarios were used. The estimated risks are based on the diesel PM concentration at the point of maximum impact as determined using air dispersion modeling. The estimated risk ranges are used to provide a “qualitative” assessment of potential risk levels near sources of diesel PM. These estimates are based on the risk assessment methodology and assumptions identified in Appendix VII. Actual risk levels from these types of sources at any individual site will vary due to site specific parameters, including equipment technologies and emission rates, fuel properties, operating schedules, meteorology, and the actual location of off-site receptors.
Figure 2 shows that each of the investigated activities has the potential of significant increases in potential cancer risk under certain circumstances. The potential cancer risk associated with these activities, combined with the high statewide ambient19

risk levels reported earlier, provide additional evidence that all categories of diesel -fueled engines should be subject to further co ntrol requirements.

VI. CONTROL TECHNOLOGY AND FUEL OPTIONS

A. Has ARB identified control technology options that can further reduce diesel PM emissions from diesel-fueled engines and vehicles?
Yes. The ARB has evaluated various types of control options identifying the control efficiency, description of technology, cost, and source test data. Technical evaluations of the control technologies, including summaries of the available emission test information, are included in Appendix IX. Because emission test information was deemed essential for a thorough evaluation of diesel PM control technologies, detailed technical evaluations were not performed where the technology proponent did not provide adequate emission test information. The most effective control technologies evaluated by ARB staff are catalyst-based diesel particulate filters (catalyst-based DPFs).
Catalyst-based DPFs use catalyst materials to reduce the temperature at which collected diesel PM oxidizes. The catalyst material can either be directly incorporated into the filter system, or can be added to the fuel as a fuel-borne catalyst (FBC-DPF). Although catalyst-based DPFs can be used with diesel fuels of varying sulfur content, the greatest reductions come from using very low-sulfur fuels. Used with very low-sulfur (<15 ppmw sulfur) diesel fuel, catalyst-based DPFs have been reported to reduce diesel PM emissions by over 85 percent.
Table 8 provides a description and range of control efficiencies of catalyst-based DPFs and new diesel-fueled engines. The control efficiency information is based on available test information summarized in Appendix IX. As shown, the range of control efficiencies for catalyst-based DPFs is 85 to 97 percent.

Table 8: Control Technology Efficiencies

Control Technology Diesel PM Control Efficiency Description

Catalyst-Based DPFs / Very low-sulfur Fuel 85% - 97% Particulate filter system where the catalyst material is either incorporated into the filter or added to the fuel; Diesel fuel with a sulfur content < 15 ppmw.

New Engine Up to 85% Replaces existing engines with engines certified to meet ARB/U.S. EPA off -road engine emission standards.20

For existing diesel engine applications, catalyst-based DPFs have been shown to be effective in reducing diesel PM emissions. Worldwide, DPFs have been used in over 20,000 applications. In several European countries, catalyst -based DPFs have been installed on more than 6,500 buses, heavy-duty trucks, and municipal vehicles. In the United States, the application of catalyst-based DPF’s is less prevalent, but several demonstration projects have been initiated. In California, diesel-fueled school buses and tanker trucks have been retrofitted with catalyzed DPFs as part of a program to evaluate the effectiveness of a refiner’s low-sulfur diesel formulation. In New York, the New York City Transit Authority’s fleet demonstration program will test the effectiveness of catalyzed DPF’s on 50 diesel-fueled buses.
For new diesel engine applications, catalyst-based DPF technology is playing a key role in both establishing and complying with new more stringent diesel PM standards. The U.S. EPA recently announced its proposed regulation for heavy-duty engine and vehicle standards and highway diesel fuel sulfur control requirements. A diesel PM emission standard of 0.01 g/bhp/hr is proposed. This proposed standard is based on the anticipated emission reductions from low-sulfur diesel fuel and the use of a catalyst-based diesel particulate filter. To comply with a 2005 European Union (EU) emission standard for diesel fueled vehicles, the French automaker, Peugeot Citroen, recently unveiled a diesel PM catalyst-based DPF system which is expected to go into production in the year 2000.

B. What are the costs associated with these control technology options?
Tables 9a through 9d present information on the costs associated with applying catalyst-based DPFs 4 to stationary, off-road, and on-road diesel engines, including both retrofit and new engine applications. Table 9a provides information on the capital costs associated with retrofitting stationary diesel engines with catalyst-based DPFs. This information was obtained from representative catalyst-based DPF manufacturers and is intended to represent the range in the retail costs at this time. These cost estimates are mostly consistent with the $30 to $50 per horsepower range reported by the Manufacturers of Emission Controls Association (MECA) in “Emission Control Technology for Stationary Internal Combustion Engines” dated July 1997.
Table 9a: Stationary Engines - Current Catalyst-Based DPF Retrofit

Costs Technology 40 hp 100 hp 275 hp 400 hp 1,400 hp
Capital Cost $1,300 -

$5,000 $2,000 -

$7,500 $3,500 -

$9,000 $7,000 –

$10,500 $30,000 -

$44,000

4 Some Catalyst-Based DPFs require, and all Catalyst-Based DPF’s will benefit from, the use of very low-sulfur fuel. The incremental cost of this fuel is projected to be less than $ 0.05 per gallon and is discussed further in Appendix IV.21

The costs associated with retrofitting off-road engines with catalyst-based DPFs are presented in Table 9b. This information also assumes a cost of $30 to $50 per horsepower, as reported by MECA representatives in “Exhaust Controls Available to Reduce Emissions from Non-road Heavy-Duty Engines. ”
Table 9b: Off-Road Engines - Current Catalyst-Based DPF Retrofit

Costs Technology 190 hp 5 275 hp 475 hp
Catalyst-Based DPF $5,700-9,500 $8,250-13,750 $13,500- 23,750

Table 9c provides an estimate of the current cost to retrofit on-road engines and vehicles with catalyst-based DPFs. This information assumes a cost of $10 to $20 per horsepower, as reported by MECA in “Emission Control Retrofit of Diesel-Fueled Vehicles” dated March 2000.
Table 9c: On-Road Engines - Current Catalyst-Based DPF Retrofit

Costs
Vehicle Class LHD MHD HHD Average Horsepower 6 190 hp 250 hp 475 hp
Capital Cost $1,900 - $3,800 $2,500 - $5,000 $4,750 -

$9,500
In contrast to the retrofit costs presented in Tables 9a – 9c, Table 9d presents the U.S. EPA’s estimate of the future (2007) costs of applying catalyst-based DPFs to new on-road engines and vehicles. The U.S. EPA estimates are based on higher production volumes, and they are similar to the future cost projections presented by MECA in “Emission Control Retrofit of Diesel-Fueled Vehicles (March 2000).”

Table 9d: On-Road Engines - Future (2007) Catalyst-Based DPF Costs

Vehicle Class LHD MHD HHD Average Horsepower 7 190 hp 250 hp 475 hp Catalyst-Based DPF Costs 8 $670 $890 $1,100

5 The power range noted has been selected to facilitate com parison with on-road costs. 6 The average horsepower was derived from the U.S. EPA’s engine certification database for LHDD, MHDD, and HHDD engines for model years 1999 and 2000. 7 The engine horsepower ranges were derived from the U.S. EPA’s engine cert ification database for LHDD, MHDD, and HHDD engines for model years 1999 and 2000. 8 The U.S. EPA Catalyst Based-DPF cost estimates include both fixed costs (e.g., tooling, research and development, and certification) and variable costs (e.g., hardware, assembly and markup).22

There is a stark difference between the current costs associated with retrofitting existing engines and the future costs associated with applying catalyst-based DPFs to new engines and vehicles. However, we expect these costs to decline as production volumes and experience increase. ARB staff expects that, over the next few years, the retrofit costs presented in Tables 9a- 9c will approach the new engine costs presented in Table 9d.
Detailed cost and cost-effectiveness analyses will be completed during the preparation of each control measure. However, staff expects that the costs associated with carrying out this plan will be significant and will be on the order of the costs associated with other major ARB programs. In addition, ARB staff recognize that there may be unique situations that require a special evaluation of the feasibility and/or cost -effectiveness of applying catalyst-based DPF technology. These issues will be fully investigated and considered during the development of the specific control
measures.

VII. ALTERNATIVE TECHNOLOGIES

A. What alternatives to diesel-fueled engines and vehicles exist today that would result in lower diesel PM emissions?
Diesel-fueled engines are extensively used throughout California in equipment and vehicles that provide for the transportation of goods, construction of homes, and emergency power generation. (See Chapter III for more information on the uses of diesel-fueled engines.) Diesels are the engines of choice for most “heavy -duty” applications. However, for a significant number of applications, lower PM emitting alternatives to existing diesel-fueled engines exist. As ARB staff develop the control measures recommended in this report, the feasibility and cost of these alternatives will be evaluated and considered. In most cases, it is expected that well controlled diesel engines using very low-sulfur fuel will have equivalent PM emissions as benchmark gasoline or CNG fueled engines. Where this is true, it is envisioned that regulations would be structured to provide a choice of fuels. In cases where alternatively-fueled engines offer emission performance that cannot be matched by diesel-fueled engines, the feasibility and costs of setting standards based on the capability of alternatively fueled engines will be assessed.
Current alternatives to diesel-fueled vehicles and equipment include:
♦ natural gas fueled vehicles and equipment;
♦ gasoline-fueled vehicles and equipment;
♦ dual-fueled vehicles and equipment;
♦ electrically-powered vehicles and equipment;
♦ fuel cell technology; and
♦ other alternatively fueled (e.g., Bio-diesel) vehicles and equipment.23

The next step in the AB 1807 process, following approval of this report, is the development of the specific ATCMs and regulations designed to reduce diesel PM emissions from diesel-fueled engines and vehicles. Chapter VIII identifies the specific control measures we currently recommend be developed. As part of the process in developing these recommended measures, where appropriate, the ARB staff will thoroughly evaluate available alternatives to diesel-fueled engines and diesel fuel. Criteria evaluated by the ARB staff when considering the recommendation of alternative technologies include:

♦ reduction in emissions of air toxics;
♦ the availability and quality of source test information;
♦ cost and cost-effectiveness of the alternative technology; and
♦ operation or design constraints associated with the alternative.
In summary, diesel-fueled engines have established themselves for a variety of reasons as the preferred power source for many functions in our industrial society. However, cleaner alternatives do exist which ARB staff will consider when developing the measures recommended in this report.
ARB staff will develop the ATCMs and regulations in an open and public process. Draft versions of ATCMs and regulations will be presented to the public for review and comment, and a final draft version will be presented to the Board for approval. Public outreach is an essential element in the development of any ATCM or regulation to ensure that all affected and interested parties have full opportunity to provide input and shape rules that are both effective and workable.

VIII. STAFF’S RECOMMENDATION
In August 1998, the ARB identified particulate matter emissions from diesel fueled engines as a TAC, and staff was directed to begin the risk management process. A working group was convened to advise the staff with its risk management efforts. Since October 1998, staff has been working with the advisory committee to develop this report on the need for further control of particulate emissions from diesel engines. Staff finds that:

1. The current inventory of diesel PM emissions, as presented in Chapter V of this report, demonstrates that stationary and mobile diesel engines currently emit over 28,000 tons per year of diesel PM in California; 2. The current statewide population-weighted annual outdoor and indoor risk from exposure to diesel PM emissions, as presented in Chapter V of this report, is estimated at over 500 and 350 potential excess cancers per million people, respectively; and 3. The evaluation of available diesel PM control technologies and strategies, as presented in Appendix II, Appendix III, and Appendix IX to this report,24 demonstrates that technically feasible and commercially available diesel PM control measures are available for diesel-fueled engines and vehicles.
Therefore, we recommend that the Board direct staff to develop measures to reduce diesel PM emissions from all diesel-fueled engines and vehicles. Measures that we recommend to be developed are presented below. None of the recommended measures will result in an increase in NOx emissions above applicable NOx emission certification levels.
The recommended measures for regulation development are discussed in sections A, B, and C below. Section D discusses the actions we believe the U.S. EPA needs to pursue to support our recommendations and to reduce diesel PM emissions in California. Section E discusses possible adverse impacts associated with the recommended measures. A more detailed description of each recommended measure and the associated emission reduction, risk reduction, cost analysis, and proposed implementation date for each measure can be found in Appendices II, III, and IV.

A. What measures does ARB recommend be developed to further reduce diesel PM emissions from mobile diesel-fueled engines and vehicles?
Table 10 summarizes the recommended measures for all mobile sources except for retrofit of off-road portable equipment, which is discussed in the next section. Together, these measures comprise a comprehensive program to be implemented in California to control and reduce potential cancer risk from exposure to diesel particulate matter from mobile sources. These measures are further subcategorized for on-road and off -road applications. Alternative strategy applications, which are non-regulatory, are also part of the comprehensive program. They are discussed later in this section.
As discussed in Chapter II, the recommended measures will be developed in accordance with the requirements of AB 1807. The specific control requirements of each measure will be developed in an open and public process. Details concerning each specific recommended measure, which include the cost and cost-effectiveness of controls and the availability of alternative technologies, will be explored as each recommended measure is developed.25

Table 10: Recommended Measures to Reduce Diesel PM from Mobile Sources

Measures Proposed

Board Adoption Date Proposed

Implementation Date Est. PM

Reduction, tons per year Est. PM

Reduction, tons per year Est. Cost

per Unit, $

On-Road Measures 2010 2020
Supplemental test procedures HDV certification 2000 2005 n/a n/a to be determined
Lower emission standards for new HDV engines 2001 2007 1,600 3,500 670-1,100

Control of emissions from existing engines (retrofit) 2002 2002-2008 1,870 280 1,900-9,500

Solid waste collection vehicles 2002 Other public HDV fleets 2002 Other public & private HDV fleets 2003-2008

Control of HDV in -use emissions 2003 2005 n/a n/a 130-150

Off-Road Measures

Lower emission standards for new engines 2002 2006-2008 910 3,600 1,300-1,800

Control of emissions from existing engines (retrofit) 2002 2002-2008 6,000 1,500 5,700-23,800

Public fleets 2002-2003 Other off-road fleets 2006-2008
Control of in-use emissions 2003 2006-2008 n/a n/a to be determined PM standards for new diesel pleasure craft engines 2002 2005 9 24 to be determined

Federal Measures

Locomotive retrofit 860 760 to be determined Commercial marine vessels retrofit 3900 4500 to be determined26

On-Road

The recommended measures for diesel-fueled on-road mobile vehicles listed in Table 10 address both new and existing vehicles. The proposed implementation dates listed in Table 10 are tentative. The actual implementation dates may vary based on engine type or service and on the availability of very low-sulfur fuel. For new vehicles, ARB staff is proposing new engine diesel PM standards that will reduce diesel PM emission by at least 90 percent from the current on-road standards. This proposal is based upon the U.S. EPA’s proposed heavy-duty engine and vehicle standards and highway diesel fuel sulfur control requirements rule, and the expected engine, fuel, and control technology development needed to meet the proposed standards. For existing vehicles, ARB staff is proposing diesel PM emissions be reduced, for almost all (90 percent) engines, by at least 85 percent. This equates to an overall diesel PM emission reduction of 75 percent from existing vehicles. This reduction can be achieved through the addition of after-treatment technology, or replacement of existing engines with new technology or alternatively fueled engines. The details of each of the recommended measures will be addressed during the actual regulation development process. In-use compliance programs will be implemented or enhanced to maintain the diesel PM emission reductions achieved through cleaner new engine standards and retrofits.

Off-Road
The recommended measures for diesel-fueled off-road engines are similar to those for on-road vehicles : more stringent diesel PM standards, after-treatment control retrofit requirements, and in-use compliance programs. In contrast, to on-road vehicles, most off-road engines are not registered by the State, with the exception of portable engines, boats, and off-highway motorcycles that are permitted and/or registered by local districts or the State. Therefore, to ensure the application of recommended measures such as inspection and maintenance programs, in-use compliance testing, or mandatory retrofitting of older equipment, the ARB and district staff may rely on mechanisms such as warranty registration, local operating permits, and contract requirements.
Non-Regulatory Strategies
Non-regulatory strategies for mobile sources include guideline development, voluntary memoranda of understanding, and non-regulatory incentive programs. A variety of voluntary and incentive programs are being proposed to achieve reductions beyond those California can achieve through regulatory action. These are activities the ARB does not currently have the authority to regulate and for which regulations may not be the most effective action. While pursuing these non-regulatory strategies, ARB staff will work with the appropriate stakeholders to achieve voluntary reductions in diesel PM. The non-regulatory strategies being considered by the ARB staff include:27

♦ the voluntary application of diesel particulate filters for locomotives;
♦ the voluntary application of diesel particulate filters for commercial marine vessels;
♦ developing a memorandum of understanding (MOU) for the retrofit of airport ground support equipment;
♦ the voluntary retrofit of emergency vehicles; and
♦ implementing transportation control measures – idling restrictions;

B. What measures does ARB recommend be developed to further reduce diesel PM emissions from stationary and off-road portable diesel-fueled engines?
Table 11 summarizes the recommended measures designed to reduce diesel PM emissions from stationary and off-road portable diesel-fueled engines. The proposed implementation dates listed in Table 11 are tentative. The actual implementation dates may vary based on engine type or service and on the availability of very low-sulfur fuel. The measures identified in this section are discussed in more detail in Appendix II. For new engines, the recommended control measures presented in Table 11 require the application of catalyst-based DPFs or a similar technology that will reduce diesel PM emissions by at least 90 percent from uncontrolled levels. For existing vehicles, ARB staff is proposing diesel PM emissions be reduced, for almost all (90 percent) engines, by at least 85 percent. This equates to an overall diesel PM emission reduction of 75 percent from existing vehicles. This reduction will be achieved through the addition of after-treatment technology, replacement of older technology engines with new technology or alternatively fueled engines, or restrictions placed on the operation of existing equipment. The details of each of the recommended measures will be addressed during the development of each of the air toxic control measures and regulations. Because of the variety of existing engines, as well as the multitude of applications, staff expects that no single control technology will be universally applicable to all retrofit applications.
Tables 9a and 9b presented information on the costs associated with applying catalyst-based DPFs on both new and retrofit stationary and portable engines. The preliminary cost-effectiveness for the control measures identified in Table 11 ranges from 5 to 200 dollars per pound of diesel PM reduced. The cost per pound of diesel PM reduced reflects the predicted costs associated with purchasing, installing, and maintaining a catalyst-based DPF on each of the diesel-fueled engines addressed by the recommended measures. We believe these cost-effectiveness estimates similar to the cost-effectiveness estimates for regulations developed to reduce other particulate compounds that have been identified as toxic air contaminants (e.g., hexavalent chromium and lead).28

Table 11: Recommended Measures to Reduce Diesel PM from Stationary and

Off-Road Portable Sources

Control Measure Proposed Board Adoption Date Proposed

Implementation Date Estimated PM

Reduction 2010 (TPY) Estimated PM

Reduction 2020 (TPY) Stationary Engine New Engines 2002 2002 33 21 Prime Engine Retrofit 2002 2003 70 66 Emergency Standby Retrofit 2002 2003 105 105 Off-Road Portable Engine Retrofit 2002 2003-2005 712 252 Agricultural Engine Retrofit 2002 2003-2005 297 197

Stationary
The recommended measures for stationary diesel-fueled engines listed in Table 11 address both new and existing engines. For new engines, the ARB staff recommends an ATCM be developed based on the requirements of the ARB’s permitting guidance document, Risk Management Guidance for the Permitting of New Stationary Diesel-fueled Engines, (September 2000). (See Appendix II for a more detailed description of Guidance requirements.) Diesel PM emission reductions from new stationary diesel-fueled engines will be accomplished by requiring these engines to meet either specific technology requirements (i.e., stringent diesel PM engine certification levels, usage of low-sulfur diesel fuel, and application of catalyst -based DPFs); or an equally stringent performance standard.
For existing prime (non-emergency) engines and emergency standby engines, ARB staff recommends the development of ATCMs that define retrofit control requirements. As shown in Table 11, ARB staff predicts the implementation of the prime engine and emergency standby engine ATCMs by 2003 will result in diesel PM reductions of up to 70 tons and 105 tons in 2010, respectively. To achieve this reduction, ARB staff is proposing diesel PM emissions be reduced, for almost all (90 percent) engines, by at least 85 percent. This represents a 75 percent reduction in diesel PM emissions from engines in these categories. The details of each of the recommended measures will be addressed during the development of the regulations. Although catalyst-based DPFs are available, for these sources, this technology may not prove to be cost-effective for all engines especially smaller engines with limited hours of operation. During the ATCM development process, the ARB staff will conduct a more detailed cost-effectiveness analysis to help in determining the appropriateness of these controls. It is anticipated that both of these ATCMs would be fully implemented prior to 2010.29

There are over 6,000 agricultural irrigation pump engines in California, representing about 11 percent of the total stationary and portable engine inventory. Because of the high use of these engines, they are a significant source of diesel PM and contribute about half of the diesel PM emissions from the entire stationary engine category. In addition, agricultural irrigation pumps tend to be concentrated in specific regions of the State, contributing proportionally higher emissions within these regions.
H&SC section 42310(e) prohibits districts from requiring a permit for most equipment used in agricultural operations. However, the State and districts may establish emission control requirements for stationary agricultural equipment. Therefore, ARB staff recommends working with the agricultural community to develop a comprehensive program to reduce emissions from engines used in agricultural operations. This program should evaluate both the substitution of diesel engines with electrically driven equipment and a comprehensive retrofit element.
ARB staff predicts a reduction of diesel PM from agricultural irrigation pumps of up to 297 tons per year by 2010 and 197 tons per year by 2020. To achieve this reduction, ARB staff is proposing diesel PM emissions be reduced, for almost all (90 percent) engines, by at least 85 percent. This represents a 75 percent reduction in diesel PM emissions from the engines in this category. This reduction will be achieved through the addition of after-treatment technology, replacement of older technology engines with new technology engines, use of alternative-fueled engines, or electrification. The details of each of the recommended measures will be addressed during the development of each of the regulations.

Off-Road Portable
Staff recommends that the ARB develop regulations to reduce diesel PM emissions from existing off-road portable diesel engines. New engines for off-road portable equipment will be regulated by the off-road rules discussed above. The ARB currently administers the Statewide Portable Equipment Registration Program (Statewide Registration Program) Regulation (Title 13 California Code of Regulation §2450

- 2466), which is a voluntary program for the statewide registration and regulation of off-road portable engines. To date, approximately 12,000 off-road portable engines have been registered. The staff recommends that the Statewide Registration Program Regulation be amended to include requirements for reducing diesel PM emissions from portable diesel engines through the application of catalyst-based DPFs, electrification where feasible, and consideration of alternate fuels. In addition, staff recommends the development of an ATCM, for implementation by local districts, consistent with amendments to the PERP regulation. Staff predicts compliance with the ATCM would reduce diesel PM emissions up to 712 tons per year in 2010 and up to 252 tons per year by 2020. To achieve this reduction, ARB staff is proposing diesel PM emissions be reduced, for almost all (90 percent) engines, by at least 85 percent. This represent s a 75 percent reduction in diesel PM emissions the engines in this category. This reduction will be achieved through the addition of after-treatment technology, replacement of existing engines with new technology or alternatively fueled engines, or30

restrictions placed on the operation of existing equipment. The details of each of the recommended measures will be addressed during the development of the regulations.

C. What measures does ARB recommend regarding diesel fuel reformulation?
Table 12 summarizes the recommended measures regarding diesel fuel reformulation. The measures identified in this section are discussed in more detail in Appendix IV.
Table 12: Summary of Recommendations

Emission Reduction (%) Recommendation Diesel PM Incremental Cost ($/gal) Implementation

or Issue Date Very low-sulfur CARB diesel ( < 15 ppmw S) > 90 * < 0.05 2005-2006
Guidance on alternative “diesel” fuels 20 ** < 0.18 ** 2001

* Emission reductions with after-treatment

. ** Estimated for emulsions of water in CARB diesel.
ARB staff recommends that a regulation be adopted in 2001 that requires very low-sulfur CARB diesel for all diesel-fueled engines statewide, effective in 2006. ARB also recommends that programs be developed to ensure the adequate supply of very low-sulfur diesel fuel for vehicle fleets and stationary engines that are required through state or local rules to install catalytic add-on controls prior to 2006. The U.S. EPA has published proposed regulations which would require that all diesel fuel sold for use in on-road vehicles have a sulfur content no greater than 15 ppmw, beginning June 1, 2006. It is envisioned that the ARB regulation would apply to on-road and off-road sources but would otherwise be consistent with the U.S. EPA’s efforts an d enable the retrofit of off-road and stationary diesel engines with catalyst -based after-treatment control technologies.
ARB staff is also proposing to develop guidance on synthetic or alternative diesel fuel options. Synthetic or alternative diesel fuels may cost more than reformulated very low -sulfur CARB diesel, but should be considered if shown to be cost-effective for reducing diesel PM. These alternatives may result in significant benefits for higher -emitting categories, such as off-road engines. Synthetic or alternative diesel fuels may also prove to be part of the preferred control strategy for diesel-fueled engines or vehicles that result in relatively high risk, or where control retrofit options are very expensive or difficult to implement.
The guidance will identify alternative diesel fuels and provide information on associated emission reductions and cost. The guidance would assist local districts in their permitting of fleets and equipment, and may be especially useful in cases where control equipment retrofits are impractical.31

D. What impact will the recommended measures have on diesel PM emissions and risk?
As illustrated in Figures 3 and 4, ARB staff estimates the full implementation of the recommended measures, including retrofit of locomotives and commercial marine vessels, will result in an overall 75 percent reduction in the diesel PM inventory and the associated potential cancer risk for 2010, and an 85 percent reduction for 2020, when compared to today’s diesel PM inventory and risk. These reductions will occur through the combined actions of both California and the U.S. EPA to adopt and implement rules that reduce diesel PM.
From 2000 to 2010, ARB staff predicts diesel PM emissions and risk would decrease by only about 20 percent if the recommended measures are not implemented. This reduction would result from the implementation of existing federal and state regulations and the attrition of older diesel-fueled passenger cars and light-duty trucks from the on-road fleet. The U.S. EPA has proposed new, lower emission standards for heavy-duty trucks for 2007 and lower sulfur limits for diesel fuel (on-road vehicles only) in 2006. The benefits of these proposed rules are not included as existing measures because they have not been adopted as of the date of this Plan.
The recommended measures can be grouped as follows : measures addressing on-road vehicles; measures addressing off-road equipment and vehicles, and measures addressing stationary and portable engines. These measures include the U.S. EPA proposed 2007 new heavy-duty truck standards and the proposed 2006 low-sulfur fuel limits. Figure 4 illustrates the impact of each of these groups of measures on projected diesel PM emission levels for 2010 and 2020. As shown, off-road recommended measures have the largest impact. Of the off-road recommended measures, the retrofit measures (see Table 10) result in over 90 percent of the diesel PM reductions associated with all of the off-road measures.32 Figure 3: Projected Percent Reduction in Diesel PM Cancer Risk from year 2000 Levels With and Without ARB Risk Reduction Plan (RRP) Implemented

0 10 20 30 40 50 60 70 80 90 100

2000 2010(w/o RRP) 2010(w RRP) 2020(w RRP) YearPercent of Year 2000 Cancer Risk

Figure 4: Projected Diesel PM Emission Levels With and Without ARB Risk Reduction Plan (RRP) Implemented

0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 18,000 20,000

2000 2010 (w/o RRP) 2010 (w/ RRP) 2020 (w/o RRP) 2020 (w/ RRP) YearDiesel PM Emissions (Tons/Year)

Off-Road On-Road Stationary & Portable33

E. What other expected benefits are associated with implementing the recommended measures?
As discussed in the previous two sections, full implementation of the measures in this plan will result in significant reductions in diesel PM emissions and the associated risk. There are additional benefits associated with reducing diesel PM emissions. These include:

♦ Increased visibility;
♦ Less material damage due to “soiling” of surfaces with diesel PM;
♦ Decreased noncancer health effects associated with diesel PM; and
♦ Decreased deposits of diesel PM and toxic chemicals on to surface water.

F. What possible adverse impacts may be associated with the recommended measures?
Most recommended measures require the use of add-on control devices, engine modifications, catalysts, low-sulfur diesel fuel and/or alternative fuel formulations. ARB staff has identified possible adverse environmental and safety impacts associated with the recommended measures. Each of these impacts will be fully investigated and addressed during the rulemaking process. Possible adverse impacts are identified below.

♦ Potential for decrease in fuel economy;
♦ Potential for increases in emissions of hydrocarbons (HC), oxides of nitrogen (NOx), and carbon monoxide (CO);
♦ Potential for changes in composition of diesel exhaust that could result in an increase in emissions of other toxic air pollutants.
♦ Potential for contamination of ground and surface waters;
♦ Potential safety issues due to use and handling of gaseous-fuels; and
♦ Potential increase in hazardous waste from the disposal of spent catalyst material.

G. What actions should the U.S. EPA pursue to support the ARB staff’s recommended measures?
ARB staff recommends that the U.S. EPA adopt standards and regulations applicable to all 50 states that are similar in both scope and stringency to the measures in this plan. Further, ARB staff recommends the U.S. EPA take the following actions to support the measures in this plan and to reduce diesel PM emissions nationwide.

♦ The U.S. EPA should implement more stringent emission standards for diesel PM in the Tier 3 rulemaking than are currently envisioned in the Off-Road Statement of Principles.34 Currently, the federal Clean Air Act preempts California from regulating new construction and farm equipment below 175 horsepower, new locomotives and locomotive engines, and commercial marine engines. Preempted off -road vehicles and equipment generate approximately 60 percent of the diesel PM emissions from off -road sources, thus limiting California’s ability to achieve significant emission reductions on its own. Recent developments suggest that off-road engine control can move directly to after-treatment technology-based standards with higher emission reductions, on a cost -effective per engine basis. The U.S. EPA should, therefo re, consider accelerating the implementation of emission standards based on after -treatment technologies with the goal of reducing diesel PM emissions by 90 percent from engines in these categories.

♦ Require all diesel-fueled on-road and off-road engines and vehicles to use very low-sulfur diesel fuel ( < 15 ppm). The U.S. EPA has proposed regulations that would require all very low-sulfur diesel fuel to be sold for use in on-road vehicles beginning June 1, 2006, but has not proposed to extend this requirement to off-road sources. ARB staff’s recommended measures for off-road engines are based on the use of very low-sulfur diesel fuel and the use of exhaust after-treatment devices which would require low-sulfur fuel. It is critical that very low-sulfur diesel fuel be required to be sold nationwide for use in both on-road and off-road engines and vehicles. If not, California -only off-road regulations should be developed, but issues concerning the cost-effectiveness of developing California-only engine/after treatment systems and the compatibility of those systems with a higher sulfur national off-road diesel fuel need to be explored.

♦ The U.S. EPA should require more stringent control of PM emissions from commercial marine vessels through retrofit of existing engines. Emissions from commercial marine vessels, which include ocean-going vessels, tugboats, fishing boats, cruise ships, and other large ships, are a major source of diesel PM which is expected to grow from 2000 to 2010. A program to retrofit existing engines could provide significant benefits over the adopted controls for new engines recently adopted by the U.S. EPA. The U.S. EPA should, therefore, develop standards to reduce diesel PM emissions from these engines.

♦ The U.S. EPA should require the implementation of a retrofit program to reduce diesel PM from locomotives. The current national rule only affects particulate matter emissions from model year 2005 and later locomotives and does not significantly reduce PM emissions from older locomotives. Recent developments in diesel particulate filter technology suggest that a locomotive retrofit program may be feasible and cost-effective. The U.S. EPA should, therefore, develop retrofit standards to reduce diesel PM emissions from engines in these categories.