SubscribeDirect Particulates. Recent data indicates thatNote that this does include direct injection diesels, the same engine technology as in the vehicle that sparked the discussion.
diesels emit at least 10 and perhaps as much as 300
times more PM mass than properly operating modern
gasoline vehicles (Table 5). Many factors—such as
vehicle age, condition, temperature, and driving cycle
—can impact these vehicle-to-vehicle comparisons.
For example, gasoline cars that are malfunctioning
can increase PM emissions by a factor of 100.
But even emissions from malfunctioning gasoline
cars appear to be several times lower than from diesel
vehicles.
*********
Carcinogenesis. In addition to its contribution to
mainstream air pollution problems, major public
health agencies also consider diesel exhaust a potential
human carcinogen (Table 3). While diesel exhaust
contains over 40 compounds thought to cause
cancer (CalEPA 1998a), most public health studies of
diesel exhaust have focused on the aggregate emissions
rather than on specific compounds. In its recent
ruling, however, the California Air Resources Board
voted to list only diesel exhaust particulates as a
toxic, rather than whole diesel exhaust, which contains
both particulates and vapor-phase emissions
(CARB 1998b).
Studies of humans routinely exposed to diesel
exhaust indicate a greater risk of lung cancer. For example,
occupational health studies of railroad, dock,
trucking, and bus garage workers exposed to high
levels of diesel exhaust over many years consistently
demonstrate a 20–50 percent increase in the risk of
lung cancer or mortality (HEI 1995; Bhatia et al.
1998).
Even at the average rates of exposure experienced
by most people, diesel exhaust poses a potential cancer
risk. Extrapolating from epidemiological studies,
at current exposure levels it is estimated that up to
450 of every million Californians are at risk of contracting
lung cancer as a result of lifetime exposure to
diesel exhaust, or over 14,000 residents.
*********
Emissions modeling suggests that lifetime average
NOx emissions from diesel vehicles are roughly
twice that of gasoline cars being sold in some states
by 1999 and the rest of the country by 2001 (Table 4).
These results must be viewed with caution, however,
because the EPA model used to construct these estimates
is based on relatively little diesel vehicle emissions
data.
*********
Toxics. Comprehensive and detailed comparisons
of the carcinogenic properties of diesel exhaust
versus gasoline exhaust have not been made, but early
evaluations suggest that important differences may
exist. For example, the International Agency for Research
on Cancer has classified diesel engine exhaust
as “probably carcinogenic” but assigned gasoline exhaust
a lower risk of “possibly carcinogenic” (IARC
1989).
More detailed and recent research into gasoline
has focused on specific toxic compounds, such as
benzene or 1,3 butadiene, rather than whole gasoline
exhaust.17 Current evidence suggests that diesel exhaust
is more potent than these individual toxic constituents
(as measured by its unit risk); however, a
complete risk assessment would need to compare
public exposure to these compounds as well as their
potency relative to diesel (Table 6).
*********
Emission Regulations. Today’s diesel passenger
vehicles are allowed to emit more of two key pollutants,
nitrogen oxides (NOx) and particulate matter
(PM), than their gasoline counterparts under existing
regulations, the Federal “Tier 1” standards (Table 7).
This loophole is largest for diesel automobiles and
some small pickups and sport-utility vehicles, for
which NOx standards are over two times higher than
for gasoline cars. Although gasoline vehicles are not
required to meet a PM standard, their emissions are
typically 16 times lower than the PM standards for
diesel cars.
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"My two great-grandfathers, Henry Ford and Harvey Firestone, used to take these camping trips every year with Thomas Edison (and whoever the president at the time was)."
I love the way the president is almost an afterthought. It wasn't even a permanent position. As soon as you're out of office no more rich-industrialist-camping for you!
Screw mileage. I was much more impressed by this new VW.
posted by pjdoland at 6:36 AM on April 17, 2002