FROM BUSES AND TRUCKS
The purpose of this brochure is to answer the
most frequently asked questions about heavy-
duty diesel emissions and EPA's standards for
controlling them.
Control
In addition, NOx contributes to the formation
of ground-level ozone (smog). Ground-level
ozone is formed by complex photochemical
reactions involving hydrocarbons and NOx in
the presence of sunlight. Smog severely
irritates the mucous membranes of the nose
and throat, which can lead to coughing and
even choking. It also impairs normal function-
ing of the lungs and chronic exposure may
cause permanent damage. Smog also damages
paint and other building materials. (Ground-
level ozone should not be confused with
stratospheric ozone, a protective layer of the
upper atmosphere that filters the sun's harmful
ultraviolet rays.)
Hydrocarbons (HC) are gaseous organic
chemical compounds emitted by diesel engines
that also contribute to the formation of ground-
level ozone.
Carbon monoxide (CO) is a colorless, odorless,
poisonous gas composed of carbon and oxygen.
It is formed when carbon-based fuel is not
burned completely. When inhaled, CO enters
the bloodstream. It binds chemically to hemo-
globin, which normally carries oxygen to the
cells, and reduces oxygen delivery to all
tissues. Even at relatively low concentrations,
CO can adversely affect mental function, visual
acuity, and alertness.
For more information, write:
United States Environmental Protection Agency
National Vehicle and Fuel Emissions Laboratory
Engine and Vehicle Regulations Branch
2565 Plymouth Road
Ann Arbor, Michigan 48105
or call:
(313) 668-4278
EPA420-F-94-001 ®
Trucks
CONTROL OF EMISSIONS
Air pollution from diesel-fueled buses and
trucks is a problem that confronts many large
U.S. cities. To help alleviate this problem, the
U. S. Environmental Protection Agency (EPA)
now requires new heavy-duty diesel engines
to meet stringent exhaust emission standards.
Heavy-duty diesel engine pollutants include
diesel particulate matter (PM), oxides of
nitrogen (NOx), hydrocarbons (HC), and
carbon monoxide (CO).
Diesel particulate matter (PM) is a collection
of small particles emitted by a diesel engine.
Many different organic pollutants are
adsorbed on these particles. The size and
chemical composition of diesel particulate
matter are the main reasons for concern about
effects of PM on human health. Their small
size increases the likelihood that the particles
will reach and lodge in the deepest and most
sensitive areas of the human lungs. This can
lead to severe lung problems and increased
susceptibility to respiratory infection, such as
pneumonia, aggravation of acute and chronic
bronchitis, and asthma. Also, diesel particu-
late matter contributes to the formation of the
smoke that is widely associated with diesel
engines and that impairs visibility.
i
Oxides of Nitrogen (NOx) include several
gaseous compounds made of nitrogen and
oxygen. They are lung irritants and can
increase susceptibility to respiratory illness
and pulmonary infection.
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WHY TARGET EMISSIONS FROM HEAVY-DUTY
DIESEL ENGINES?
Engines, rather than entire vehicles, are
targeted by the regulations because heavy-
duty engine manufacturers often do not
assemble complete vehicles. Also/Jhejsame^
kind of^engmecan'bV^
manufacturers in many different kihds;of-; > 't'
, :., , ,-,,-,„ ,"~ - / ', ,- ,, '_,, ,
vehicles. ,, ; \ t = "; > ;
For many years,,heavy4iuty diesel engines
wereVnot substantially Regulated.; Th^wal]
The table shows that exhaust emission
standards for heavy-duty diesel engines have
been tightened substantially. The most
recent standards represent more than 60%
control for NOx and more than 90% control
for PM from
pollution.
However, thrie!develbpments prompted
to reexamine the issue. : -^ ?- *;
• As emissions wrere reduced from^other
sources (fOT-exam^le; new passenger ,car GC3,
and HC emission standards have been; reduced
by>nibfethan"9"percent in'the last 15
diesel engines becarnea proportionately larger
source of total emissions from all vehicles.
HOW CAN EMISSIONS BE REDUCED FROM
CORRHfTlY OPERATING FLEETS? r
' ' *' /? ' \
New emissions standards have no effect on
engines manufactured in previous'years.
'However, several technolpgies"can help
redrice emissions from^arJier model' h^avy-
duty diesel enginesf^For example, thefbrmu;,,X
latioh'of diesel fuel has been modified to -*
'• ? • ; '•',
lower its siJfur,,and,arprnatic content, which , ,
helpsrediice-emissions -firbnv-older engines.,;.
Other ways to reduce emissions from heavy-
duty diesel engines are being explored by
various groups in North America and West-
ern Europe. These include retrofitting buses
with trap oxidizers and modif^ing_engine
burrrclean'ruels; Buses are the main focus of
,,, ,these-programs. This is because they operate"
primarily,-in'urban areas," which* 'means that >
pollutibH^ reductions will have a beneficial
impact on urban air quality. Also, urban ,
buses are often refueled and maintained at „ ',
^centralffacilities;'which makes it easier for'' j,
them to use alternative fuels. Finally/these ,
>;/vehicleS;are publicly owned,^which^means <
that the fleets are large enouglvto justify I
,,,.,special'refueling,and maintenance prbgrams. f,
'f'lo-.
[PA Exhaust [mission Certifitation Standards for Heovy-Duty Diesel Engines
There
\ *>.,
.,„,,, ,, , , ,,.„,; / lft
ic health concern-'
about -PM/and'NOx/; Both of which,are;emitted
in relatively Jar ee^amouhts by diesel engines.!
»\ hf,/»,-,°j'S ',-, -,J~ , < v° -~,;\
'-*< k\: . <<",}-<, A: '••;•& . " *\\ (Vf:i
•: With new lechnolbgy/it hasfbecome/more
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