Sunday, November 18, 2007


Ethanol is produced biologically by fermenting sugar with Saccharomyces yeasts. Under anaerobic (meaning in the absence of oxygen) conditions, when yeast metabolize sugar, they produce ethanol and carbon dioxide. Bioethanol (meaning ethanol production derived from crops) is the most common renewable fuel today and is derived from corn grain (starch) and sugar cane (sucrose) [1]. Thus, ethanol is an inherently renewable eco-friendly resource, contributing nothing in itself to greenhouse gases. However, a study published in the journal Environmental Science & Technology (ES&T) concludes that if every vehicle in the U.S. ran on ethanol-based fuel, the number of respiratory-related deaths and hospitalizations would likely increase.

You read that right, widespread use of E85 would likely result in an increase in respiratory-related deaths and hospitalizations.

Stanford University atmospheric chemist Mark Z. Jacobson, author of the study said:

“Ethanol is being promoted as a clean and renewable fuel that will reduce global warming and air pollution, 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.”

Jacobson used a sophisticated 3-D atmospheric computer model that accounted for the transport of tailpipe emissions across the U.S. along with chemical and radiative transformations in the atmosphere - key components that have been neglected in previous studies. He combined the ambient concentrations with health effects and population data to simulate air quality in the year 2020, when ethanol-powered vehicles are expected to be widely available in the U.S. He then determined the health risks due to gasoline and ethanol, and analyzed the results at high resolution in Los Angeles and at lower resolution in the entire U.S.

Jacobson explained that:

“… chemicals that come out of a tailpipe are affected by a variety of factors, including chemical reactions, temperatures, sunlight, clouds, wind and precipitation. 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.”

The results

The study results show that converting to E85 (85% ethanol, 15% gasoline) could result in higher ozone-related asthma, hospitalization and mortality. The death rate increases about 9% in Los Angeles and 4% in the U.S. over projected death rates with gasoline vehicles.

E85 vehicles reduced atmospheric levels of two carcinogens, benzene and butadiene, but increased two others, acetaldehyde and formaldehyde. As a result, cancer rates for E85 are likely to be similar to those for gasoline. In some parts of the country (Los Angeles and the Northeast), E85 use was projected in increase ozone levels. The oxidant ozone is a well-known air pollutant. According to the Environmental Protection Agency (EPA), ozone inhalation is associated with respiratory tract inflammation and functional alterations of the lung [3]. The increased levels of ozone were partially offset by decreased levels in the Southeast. Nonetheless, future E85 use may be a greater overall public health risk than gasoline. Jacobson concludes that E85 is unlikely to improve air quality over future gasoline vehicles and that unburned ethanol emissions from E85 may result in a global-scale source of acetaldehyde larger than that of direct emissions.


Brazil is the only country in the world where a large-scale ethanol fuel program, introduced in 1979, has been implemented. By 1997, approximately 4 million Brazilian automobiles ran on neat ethanol (100% ethanol) and another 9 million ran on an ethanol-gasoline blend (22% ethanol) [4]. Since the introduction of ethanol fuel in Brazil, several studies on air quality have been conducted that confirm Jacobson’s recent projections.

In 1990, the concentration of ambient acetaldehyde was determined to be the most abundant carbonyl in three major cities of Brazil [5]. Indeed, acetaldehyde concentrations in urban areas of Brazil were substantially higher than concentrations measured elsewhere in the world, and was thought to be the result of large-scale ethanol fuel use. A more recent study measuring the ambient concentrations of up to 61 carbonyls in Rio de Janeiro found that the most abundant were formaldehyde and acetaldehyde [6]. The authors ranked measured carbonyls with respect to ozone formation potential and reaction with OH and found that ozone formation is dominated by formaldehyde (43% of total) followed by acetaldehyde (32%).

Health effects

In children, repeated short-term exposure to ozone may damage developing lungs and may lead to permanent reductions in lung function [7]. Indeed, time spent outside in areas of high ozone is associated with a higher incidence of asthma than areas of low ozone. Adults exposed to ozone exhibit impaired lung function and irritative lower airway symptoms. Ozone exposure has been associated with an increased number of hospital admissions.

Alternative alternatives

E85 clearly has it’s advantages: in addition to the potential carbon savings and reduced impact on global warming, E85 can be distributed and dispensed like conventional liquid fuel and can be used in vehicles that cost automakers very little in terms of additional cost. However, although I am all for decreased dependence on fossil energy, it shouldn’t come at the expense of our health.

There are alternatives, including hybrid technology and biodiesel.

In a recent interview with NPR, former Chrysler chairman Lee Iacocca said that the Big Three American automakers (General Motors Corporation, Ford Motor Company and Chrysler) lost their dominance because they failed to “follow-the-market”.

At the end of the interview, he said:

” … I’ve become real fan in the past year of plug-in hybrids. That’s the wave of the future.”

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