United States Air and Radiation EPA420-F-01-030
Environmental Protection September 2001
Agency
Office of Transportation and Air Quality
vvEPA Environmental
Fact Sheet
Frequently Asked Questions:
Environmental Impacts of
Recreational Vehicles and
Other Nonroad Engines
In September 2001, the U.S. Environmental Protection Agency (EPA)
published a Notice of Proposed Rulemaking (NPRM) seeking public
comment on our plan to set emission control standards for recreational
and other nonroad vehicles. This information sheet addresses common
questions about the environmental impacts of this proposal.
What vehicles and engines are covered in this
proposal?
We are proposing new emission control standards for three groups of
previously unregulated nonroad engines and vehicles that cause or
contribute to air pollution:
• Large Industrial SI Engines: Spark-ignition nonroad engines rated
over 25 horsepower (19 kW) used in commercial and industrial
applications, including forklifts, electric generators, airport baggage
transport vehicles, and a variety of other construction, farm, and
industrial equipment.
• Recreational Vehicles: Spark-ignition nonroad engines used in off-
highway motorcycles, all-terrain-vehicles (ATVs), and snowmo-
biles.
• Diesel Marine Engines: Diesel engines rated at or above 50 horse-
power (37 kW) used in recreational boats.
I Printed on Recycled Paper
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How do these engines and vehicles affect air quality?
Nationwide, these engines and vehicles are a significant source of mo-
bile-source air pollution. In 2000, they accounted for about 13 percent of
national mobile-source hydrocarbon (HC) emissions, 6 percent of mo-
bile-source carbon monoxide (CO) emissions, 3 percent of mobile-source
oxides of nitrogen (NOx) emissions, and 1 percent of mobile-source
particulate matter (PM) emissions. Recreational vehicles by themselves
account for nearly 10 percent of national mobile-source HC emissions
and about 3 percent of national mobile-source CO emissions. If left
uncontrolled, these engines will contribute 33 percent of national mobile
source HC emissions, 9 percent of CO emissions, 9 percent of NOx
emissions, and 2 percent of PM emissions in 2020.
On an individual basis, these vehicles can have very high emission rates.
This is illustrated in the figure below, which shows that a two-stroke
ATV or motorcycle can emit as much pollution in one hour as over 30
automobiles operating for one hour. Similarly, a snowmobile can emit as
much as nearly 100 automobiles.
Comparison of HC+CO+NOx Emissions
From Recreational Vehicles and Automobiles
4-STR OHMC
20
40
60
80
100
120
The number of automobiles it would take to emit as much pollution as
one of these vehicles in the same amount of time
What are the human health and welfare effects of
these pollutants?
The engines that are covered by this proposal contribute to ozone forma-
tion and ambient PM and CO levels. These pollutants are subject to our
National Ambient Air Quality Standards (NAAQS), and states that
exceed NAAQS levels are required to take measures to reduce emissions.
In addition, these engines also emit Mobile Source Air Toxics.
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Ozone. Ground-level ozone, the main ingredient in smog, is
formed by complex chemical reactions of volatile organic com-
pounds (VOC) and NOx in the presence of heat and sunlight.
Ozone forms readily in the lower atmosphere, usually during hot
summer weather. Volatile organic compounds are emitted from a
variety of sources, including motor vehicles, chemical plants,
refineries, factories, consumer and commercial products, and
other industrial sources. Volatile organic compounds also are
emitted by natural sources such as vegetation. Oxides of nitrogen
are emitted largely from motor vehicles, off-highway equipment,
power plants, and other sources of combustion. Hydrocarbons
(HC) are a large subset of VOC, and to reduce mobile source
VOC levels we set maximum emissions limits for hydrocarbon as
well as paniculate matter emissions.
Elevated ozone concentrations remain a serious public health
concern throughout the nation. In 1999, 90.8 million people lived
in 31 areas designated nonattainment under the 1-hour ozone
NAAQS. Increases in ozone concentrations in the air have been
associated with increases in hospitalization for respiratory causes
for individuals with asthma, worsening of symptoms, decrements
in lung function, and increased medication use, and chronic
exposure may cause permanent lung damage. The risk of suffer-
ing these effects is particularly high for children and for people
with compromised respiratory systems. There is strong and
convincing evidence that exposure to ozone is associated with
exacerbation of asthma-related symptoms.
Carbon Monoxide. Carbon monoxide (CO) is a colorless, odor-
less gas produced through the incomplete combustion of carbon-
based fuels. Carbon monoxide enters the bloodstream through the
lungs and reduces the delivery of oxygen to the body's organs and
tissues. The health threat from CO is most serious for those who
suffer from cardiovascular disease, particularly those with angina
or peripheral vascular disease. Healthy individuals also are
affected, but only at higher CO levels. Exposure to elevated CO
levels is associated with impairment of visual perception, work
capacity, manual dexterity, learning ability and performance of
complex tasks.
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In 1999, 30.5 million people lived in 17 areas designated nonat-
tainment under the CO NAAQS. High concentrations of CO
generally occur in areas with elevated mobile-source emissions.
Peak concentrations typically occur during the colder months of
the year when mobile-source CO emissions are greater and
nighttime inversion conditions are more frequent. Snowmobiles,
which have relatively high per engine CO emissions, contribute
to ambient CO levels in CO nonattainment areas.
Particulate Matter. Particulate matter represents a broad class of
chemically and physically diverse substances. It can be princi-
pally characterized as discrete particles that exist in the con-
densed (liquid or solid) phase spanning several orders of magni-
tude in size. All particles equal to and less than 10 microns are
called PM10. Fine particles can be generally defined as those
particles with an aerodynamic diameter of 2.5 microns or less
(also known as PM25), and coarse fraction particles are those
particles with an aerodynamic diameter greater than 2.5 microns,
but equal to or less than a nominal 10 microns.
Particulate matter, like ozone, has been linked to a range of
serious respiratory health problems, including premature mortal-
ity, aggravation of respiratory and cardiovascular disease (as
indicated by increased hospital admissions and emergency room
visits, school absences, work loss days, and restricted activity
days), aggravated asthma, acute respiratory symptoms, including
aggravated coughing and difficult or painful breathing, chronic
bronchitis, and decreased lung function that can be experienced
as shortness of breath.
The most recent PM10 monitoring data indicate that 14 designated
PM10 nonattainment areas with a population of 23 million vio-
lated the PM10 NAAQS in the period 1997-99. In addition, there
are 25 unclassifiable areas that have recently recorded ambient
concentrations of PM10 above the PM10 NAAQS. According to
our national modeled predictions, there were a total of 76 million
people (1996 population) living in areas with modeled annual
average PM25 concentrations at or above 16 |ig/m3 (29 percent of
the population), a level that is associated with harmful human
health effects, including premature mortality.
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Sources contribute to ambient PM levels directly, through PM in
their emissions, and indirectly, through their emissions of organic
carbon, especially NOx and SOx. Organic carbon accounts for
between 27 and 36 percent of fine particle mass depending on the
area of the country. Secondary PM is dominated by sulfate in the
eastern U.S. and nitrate in the western U.S. The vast majority
(>90 percent) of the direct mobile source PM emissions are in the
fine PM size range.
Air Toxics. Emissions from the engines covered by this proposal
also contain several Mobile Source Air Toxics, including ben-
zene, 1,3-butadiene, formaldehyde, acetaldehyde, and acrolein.
Users of these engines and vehicles can experience high levels of
personal exposure to these substances. For example, snowmobile
riders and those directly exposed to snowmobile exhaust emis-
sions can be exposed to benzene levels two to three orders of
magnitude greater than the 1996 national average benzene
concentrations. These elevated levels are also known as air toxic
"hot spots," which are of particular concern to EPA.
Visibility. Fine PM is the major cause of reduced visibility in
parts of the United States, including many of our national parks.
In particular, HC emissions from snowmobiles in the winter
months can contribute significantly to the organic carbon fraction
of fine particles which are largely responsible for visibility
impairment. In Yellowstone National Park, a park with high
snowmobile usage during the winter months, snowmobile HC
emissions can exceed 500 tons per year, as much as several large
stationary sources, and account for nearly 65 percent of annual
HC emissions in the park.
How would the proposed standards affect emissions
and air quality?
When the proposed emission standards for Large SI, recreational en-
gines, and marine diesel engines are fully implemented in 2020, we
expect a 70 percent reduction in HC emissions from these engines, a 75
percent reduction in NOx emissions, and a 56 percent reduction in CO
emissions. These emission reductions will help reduce ambient concen-
trations of ozone, CO, and fine PM. In addition, they will reduce per-
sonal exposure for people who operate or who work with or are other-
wise in close proximity to these engines and vehicles. They will also
improve visibility in national parks.
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For More Information:
See Chapter 1, Health and Welfare Concerns, of the Draft Regulatory
Support Document for this proposal. That document can be found on our
website: http://www.epa.gov/otaq/nonroad. You can also obtain addi-
tional information by contacting Margaret Borushko at:
U.S. Environmental Protection Agency
Office of Transportation and Air Quality
2000 Traverwood Drive
Ann Arbor, MI 48105
borushko.margaret@epa.gov
734-214-4334
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