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U.S. Environmental Protection Agency
Office of Inspector General
At a Glance
2006-P-00039
September 27, 2006
Catalyst for Improving the Environment
Why We Did This Review
Emissions from nonroad
mobile sources can present
significant health and
environmental hazards. The
U.S. Environmental Protection
Agency (EPA) projects that
emissions from these sources
will decrease in some
categories but increase in
others. As such, we examined
EPA's efforts to reduce
nonroad mobile source
emissions, opportunities for
additional reductions, and
challenges to addressing
nonroad emissions problems.
Background
Nonroad mobile sources
include marine vessels,
locomotives, aircraft, farm and
construction machinery, lawn
and garden equipment,
recreational vehicles, and
outdoor power equipment.
Nonroad mobile sources
produce particulate matter and
ozone-forming nitrogen oxides
and volatile organic
compound emissions, as well
as toxic air pollutants, which
contribute to a host of health
and environmental hazards.
For further information,
contact our Office of
Congressional and Public
Liaison at (202) 566-2391.
To view the full report,
click on the following link:
www.epa.aov/oia/reports/2006/
20060927-2006-P-00039.pdf
Progress Report on EPA's Nonroad Mobile
Source Emissions Reduction Strategies
What We Found
EPA has issued nonroad mobile source emissions control regulations that, when
fully implemented, should result in significant reductions in such emissions.
However, more emission reduction efforts are needed and some challenges
remain.
Until the mid-1990s, emissions from nonroad mobile sources were largely
uncontrolled. In the 1990 Clean Air Act Amendments, Congress directed EPA to
study the contribution of nonroad sources to ozone and other air pollutants, and to
issue regulations if problems were found. EPA has since issued 14 regulations to
control pollutants from nonroad mobile sources, with a total of 20 standards for
various nonroad categories. The most recent regulation, the 2004 Nonroad Diesel
Engines rule, is based on a systems approach involving a combination of engine
modifications, reduced sulfur content in diesel fuel, and exhaust controls.
There are approximately 5 million nonroad diesel engines in the United States
today, many of which are not subject to EPA emissions standards. These engines
have the potential to continue to produce high levels of pollution over the next
20 years or more. Agency projections show that substantial emissions reductions
have already been made for some source categories. However, the full benefits of
EPA's regulations may not be realized until 2020-2030, when the standards are
expected to be fully implemented. Projected benefits assume engine turnover and
replacement - activities that may be influenced by cost, lead time, and overall
feasibility. EPA has encouraged emission reductions for existing engines through
voluntary efforts and incentive programs. Although a mandatory retrofit program
may achieve increased health protection sooner, such a requirement from the
Federal level can only come through a change in the Clean Air Act.
EPA faces significant challenges in addressing nonroad emissions, particularly
among the marine, aircraft, and small gasoline engine categories. The role that
other government entities and international communities play in regulating
emissions from these source categories hinders EPA's progress in achieving
reductions. Technical challenges, including the availability of low sulfur fuel, the
diversity of nonroad engines, and the wide range of applications, also must be
addressed to meet air quality standards and emission reduction goals.
This report provides information on the progress of EPA's efforts to address
nonroad emissions and makes no recommendations.

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