Page 38 - FLI 2013 - 4th Quarter

FUELS & LUBES INTERNATIONAL Quarter Four 2013 38
F E A T U R E 专题报道
作者：Lorena Tonarelli
Diesel engine technol-
ogy is undergoing major improve-
ments to meet increasingly stringent
emission standards andminimize
health effects in humans. The impact
of diesel emissions on human health
has long been a cause of concern. All
vehicle emissions cause atmospheric
problems, but the unique nature of
diesel fuel adds pollutants not found in
gasoline-engine exhaust.
The gas and vapor components
of the fuel include air pollutants such
as nitrogen oxides (NOx), carbon
monoxide (CO) and sulfur dioxide
(SO2), which studies show can cause
potentially fatal respiratory problems
and birth defects, as well as variable
amounts of benzene, formaldehyde
and polycyclic aromatic hydrocarbons
(POM), which the International Agen-
cy for Research on Cancer (IARC)
classifies as carcinogenic.
In addition, diesel exhaust is a
significant contributor to atmospheric
particulate matter (PM), a mixture of
fine (≤ 2.5 μm) and ultrafine
(< 0.1 μm) particles composed of
solid spheres of elemental carbon
incorporating metals, sulfate, organic
compounds and other trace elements.
“In dense urban centers, diesel
exhaust contributes to 2 to 10% of
the particulate matter in the air, and
relatively strong evidence suggests that
long-term inhalation of these particles,
whether fromdiesel or other sources,
increases the risk of premature
mortality from respiratory and heart
diseases,” explains Dan Greenbaum,
president and chief executive of the
Health Effects Institute (HEI), an
independent, nonprofit research or-
ganization funded equally by the U.S.
Environmental Protection Agency
(EPA) and the Americanmotor
vehicle industry.
“Furthermore, human studies
conducted in the past three decades
have found a relatively consistent as-
sociation between long-term exposure
to diesel exhaust and lung cancer,
confirming previous evidence from
animal studies. This has led to the
decision by the IARC, the cancer arm
of theWorld Health Organization
(WHO), to classify diesel exhaust as
carcinogenic to humans.”
As carcinogenic as
smoking
The IARC issued a statement,
in June last year, warning that diesel
exhaust should be considered in the
same league as passive cigarette smok-
ing, ultraviolet radiation and asbestos.
In 1989, the agency labeled diesel
exhaust as probably carcinogenic.
It has now reclassified it as a certain
cause of cancer, increasing by about
40% the risk of lung tumors in people
working in at-risk industries, such as
truck drivers, railroad workers, min-
ers, toll booth operators, mechanics
and farmers.
The decision to reconsider the
status of diesel exhaust came after an
expert panel organized by the IARC
evaluated the available scientific
evidence on the topic. Its analysis
included a 50-year study conducted
by the U.S. National Cancer Institute,
which found a link between diesel
exhaust and lung cancer death in a
sample of 12,000+miners. Those who
were heavily exposed to diesel fumes
were three times more likely to die
from lung cancer than those with low
exposure. Among non-smoking min-
ers, those with greater diesel exposure
had seven times the risk of dying com-
pared with those with low exposure.
Limitations of
available evidence
So far, so simple, but Greenbaum
points out that there are two impor-
tant factors to consider.
“Many of the studies mentioned
above have significant limitations.
They found only small relative
risks, corresponding to a 20 to 50%
increased chance of developing lung
cancer. They did not adequately
control for other risk factors for the
disease, such as cigarette smoking.
And they did not use actual measure-
ments of diesel exhaust exposure lev-
Diesel exhaust:Howserious is
the threat?
柴油排放：威胁有多大？