THE NATIONAL
CLEAN BUS NETWORK
home || about ||
news || the
problem || solutions ||
clean bus fleets || links ||
comments
THE PROBLEM WITH
CONVENTIONAL DIESEL ENGINES
What is a
Conventional Diesel Engine?
Rudolf
Diesel is responsible for designing and building the compression
ignition engine or "diesel" engine in the 1890s. The basic
design has changed little over time. By compressing fuel oil in a
chamber, the pressure and temperature of the oil rise to such a
degree that it combusts spontaneously, driving the engine pistons
and moving the vehicle forward. These engines were originally used
only in submarines and large ships due to their size. Now diesel
engines power a variety of medium- and heavy-duty vehicle
applications, including trucks, buses, farm equipment, boats and
locomotives.
Diesel
engines have been favored for use in buses because they provide the
power and fuel efficiency to carry heavy loads of passengers over
long distances. Though diesel engines have provided enormous
benefits to the nation's transportation needs for a long time, the
vast majority of buses using diesel engines, referred to here as
conventional diesel engines, produce emissions that threaten public
health, compromise national energy security for their demand of
petroleum imports and harm the natural environment. Some of these
problems are due to incomplete combustion occurring within the
engine, use of fuel with high sulfur content and absence of an
after-treatment device on the vehicle. Diesel engines using one or
several of these mitigation measures are not categorized as
conventional.
Problems with
Conventional Diesel Engines
Increases
Risk of Contracting Lung Cancer
The
National Institute of Occupational Safety and Health, the
International Agency for Research on Cancer, the U.S. Environmental
Protection Agency (EPA) and the California EPA have agreed that a
relationship exists between diesel exhaust exposure and lung cancer.
The South Coast Air Quality Management District has found that
particulate emissions from conventional diesel are responsible for
71 percent of airborne cancer risk
Linked
to Asthma and Other Respiratory Diseases
The
EPA has shown that fine particulate matter and oxides of nitrogen
within diesel exhaust can impair lung function, contribute to
asthma, decrease the body’s respiratory defense mechanisms, and
lead to acute respiratory illness. Ninety-eight percent of diesel
emissions are composed of fine particulates capable of lodging deep
into the lungs and inflicting respiratory damage. Poor community
health as a result of particulate pollution has been linked to
greater numbers of hospital stays for respiratory disease, pulmonary
diseases, pneumonia, heart disease and death. In 2000 the EPA
indicates that diesel vehicles like trucks and buses were
significant contributors among highway vehicles of nitrogen oxide
and fine particulate matter. While they produced 40.5 percent of
highway vehicle emissions of nitrogen oxide, they emitted 69.4
percent of highway emissions of fine particulate matter. According
to the new American Lung Association report, over 137 million
Americans are exposed to unhealthy levels of ozone. Control of
nitrogen oxide emissions is important since these are precursors to
ozone formation.
Children
More at Risk
Children
are among the most susceptible to the health effects of diesel
exhaust exposure because of their higher breathing rates; greater
time spent outdoors, and increased level of activity.
The Union of Concerned Scientists has shown that children
riding a school bus are exposed to diesel exhaust concentrations
four times higher than if they were walking or riding beside it. A
study led by the
University
of
Southern California
has shown that the inhalation of nitrogen oxides, a significant
component of diesel exhaust, is related to decreased lung function
growth in children.
Threats
to the Natural Environment
Incomplete
combustion of petroleum diesel produces exhaust laden with
particulates and chemical compounds, contributing to regional haze,
acid rain and global warming. The
U.S.
transportation sector emits
approximately one-third of all
U.S.
heat trapping gases. A 2001 study published in the journal Nature
estimates that black carbon soot like that from diesel exhaust could
be responsible for 15 to 30 percent of global warming.
Geopolitical
Vulnerability
The
U.S.
transportation sector
relies almost entirely on petroleum fuel. Nearly 98 percent of all
transit operations use petroleum, while imports satisfied 54 percent
of net petroleum consumption in 2001. The Energy Information
Administration (EIA) in its 2003 Energy Outlook projects net
petroleum imports to account for 68 percent of
U.S.
demand in 2025
Environmental
Injustice
Pollution
from diesel buses impacts a disproportionate number of low-income
communities. Citizens in these communities rely upon diesel-powered
buses to commute to school and to work. They are exposed more
frequently and more directly to harmful diesel emissions both
through travel and through proximity to bus refueling and
maintenance stations.
1.
Air
Quality Management District, Multiple Air Toxics Exposure Study
II, draft report, Nov 1999
2.
State
and Territorial Air Pollution Program Administrators and the
Association of Local Air Pollution Control Officials (STAAPA/ALAPCO).
Cancer Risk from Diesel Particulate: National and Metropolitan
Area Estimates for the
United States
,
Mar 15, 2000
. http://www.4cleanair.com
|
