Issue Summary
Nonroad Diesel Emission Reduction Rule
Description of Issue
EPA has announced that it intends to propose rules aimed at reducing pollution from dieselpowered nonroad vehicles and equipment.
Background
Controlling emissions from nonroad engines and equipment, in conjunction with fuel
controls, has an important public health and welfare benefit. Diesel engines used in nonroad
equipment are significant sources of emissions of particulate matter (PM), nitrogen oxides
(NOx), and other pollutants such as air toxics and carcinogens.
One estimate indicates that by the year 2007, 50% of mobile source NOx emissions and 70%
of mobile source PM emissions will be attributable to nonroad diesel engines. Reducing PM
and nitrogen oxides will assist states in meeting health-based air quality standards as well as
make reasonable progress toward improving visibility in the nation’s Class I areas
States will also benefit from reducing diesel emission by reducing adverse impacts on public
health. An analysis completed by State and Territorial Air Pollution Program Administrators
(STAPPA) and the Association of Local Air Pollution Control Officials (ALAPCO),
indicated that if EPA were to adopt nonroad diesel engine and fuel regulations, up to 8500
premature deaths per year could be avoided.
EPA is currently drafting a nonroad diesel emission reduction rule projected to be published
in the Federal Register some time in April 2003. The rule will control nonroad diesel
emissions by establishing new requirements on newly manufactured diesel engines as well as
lowering sulfur content in diesel fuel.
The proposed rule will likely:

Require refiners to cut the sulfur content of diesel fuel for bulldozers, tractors and other
off-road vehicles to 15 parts per million, down from current levels of as much as 3,400
parts.

Require makers of diesel engines to reduce sharply the amount of particulate, nitrogen
oxide and other pollutants produced by the engines they sell. Administration officials
indicate the cuts for most vehicles would eventually come to more than 95 percent.
Officials are currently debating two approaches on the plan's timing. The first would require
refiners to reduce the sulfur content to 15 parts per million (ppm) by 2007. The second is a
"two step" approach that would call for a reduction to 500 ppm by 2007, then a further
reduction to 15 ppm by 2010.
WESTAR Mobile Sources Committee
February 2003
Approach or Resolution
With the advent of more stringent controls on highway vehicles and their fuels, emissions
from nonroad sources will contribute significantly more harmful pollution than on-road
sources. The Mobile Sources committee recommends supporting efforts to reduce emissions
from nonroad diesel equipment.
Actions to support nonroad diesel emission reductions could include:
1. A letter to EPA from WESTAR indicating support of a proposed rule.
2. Organize a regional effort among Western states to develop strategies like buyouts,
specifications for public projects promoting “clean nonroad diesel”, and/or
retrofitting.
3. Organize efforts to address special concerns of Western industries, such as
agriculture, mining, and petroleum refiners in order to facilitate implementation of
nonroad diesel emission reduction programs and rules.
4. Address fuel supply/demand concerns as discussed in the WESTAR Mobile Sources
Committee Issue Summary, “Ultra Low Sulfur Gasoline and Diesel Fuels”.
Contact Information:
WESTAR Mobile Sources Committee
Trista Glazier
tglazier@state.mt.us
(406) 444-3403
February 2003