|
Mark Z. Jacobson, associate
professor of civil and environmental engineering, Stanford
University
Photo by L.A. Cicero, Stanford
University |
''Ethanol is being promoted as a clean and
renewable fuel that will reduce global warming and air pollution,''
said Jacobson, associate professor of civil and environmental
engineering. ''But our results show that a high blend of ethanol poses
an equal or greater risk to public health than gasoline, which already
causes significant health damage.''
Gasoline vs. ethanol
For the study, Jacobson used a sophisticated
computer model to simulate air quality in the year 2020, when
ethanol-fueled vehicles are expected to be widely available in the
United States.
''The chemicals that come out of a tailpipe are
affected by a variety of factors, including chemical reactions,
temperatures, sunlight, clouds, wind and precipitation,'' he explained.
''In addition, overall health effects depend on exposure to these
airborne chemicals, which varies from region to region. Ours is the
first ethanol study that takes into account population distribution
and the complex environmental interactions.''
In the experiment, Jacobson ran a series of
computer tests simulating atmospheric conditions throughout the United
States in 2020, with a special focus on Los Angeles. ''Since Los
Angeles has historically been the most polluted airshed in the U.S.,
the testbed for nearly all U.S. air pollution regulation and home to
about 6 percent of the U.S. population, it is also ideal for a more
detailed study,'' he wrote.
Jacobson programmed the computer to run air quality
simulations comparing two future scenarios:
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A vehicle fleet (that is, all cars, trucks,
motorcycles, etc., in the United States) fueled by gasoline, versus
-
A fleet powered by E85, a popular blend of 85
percent ethanol and 15 percent gasoline.
Deaths and hospitalizations
The results of the computer simulations were
striking.
''We found that E85 vehicles reduce atmospheric
levels of two carcinogens, benzene and butadiene, but increase two
others-formaldehyde and acetaldehyde,'' Jacobson said. ''As a result,
cancer rates for E85 are likely to be similar to those for gasoline.
However, in some parts of the country, E85 significantly increased
ozone, a prime ingredient of smog.''
Inhaling ozone-even at low levels-can decrease lung
capacity, inflame lung tissue, worsen asthma and impair the body's
immune system, according to the Environmental Protection Agency. The
World Health Organization estimates that 800,000 people die each year
from ozone and other chemicals in smog.
''In our study, E85 increased ozone-related
mortalities in the United States by about 200 deaths per year compared
to gasoline, with about 120 of those deaths occurring in Los
Angeles,'' Jacobson said. ''These mortality rates represent an
increase of about 4 percent in the U.S. and 9 percent in Los Angeles
above the projected ozone-related death rates for gasoline-fueled
vehicles in 2020.''
The study showed that ozone increases in Los
Angeles and the northeastern United States will be partially offset by
decreases in the southeast. ''However, we found that nationwide, E85
is likely to increase the annual number of asthma-related emergency
room visits by 770 and the number of respiratory-related
hospitalizations by 990,'' Jacobson said. ''Los Angeles can expect 650
more hospitalizations in 2020, along with 1,200 additional
asthma-related emergency visits.''
The deleterious health effects of E85 will be the
same, whether the ethanol is made from corn, switchgrass or other
plant products, Jacobson noted. ''Today, there is a lot of investment
in ethanol,'' he said. ''But we found that using E85 will cause at
least as much health damage as gasoline, which already causes about
10,000 U.S. premature deaths annually from ozone and particulate
matter. The question is, if we're not getting any health benefits,
then why continue to promote ethanol and other biofuels?
''There are alternatives, such as battery-electric,
plug-in-hybrid and hydrogen-fuel cell vehicles, whose energy can be
derived from wind or solar power,'' he added. ''These vehicles produce
virtually no toxic emissions or greenhouse gases and cause very little
disruption to the land-unlike ethanol made from corn or switchgrass,
which will require millions of acres of farmland to mass-produce. It
would seem prudent, therefore, to address climate, health and energy
with technologies that have known benefits. '' |
