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Ethanol vehicles pose health risk, study finds

April 18, 2007
Courtesy Stanford University
and World Science staff

Eth­a­nol is wide­ly touted as an eco-friendly, clean-burning fu­el; its pro­duc­tion has soared in re­cent years. But if eve­ry ve­hi­cle in the Unit­ed States ran on fu­el made main­ly from eth­a­nol in­stead of gas­o­line, it would like­ly lead to more respiratory-related deaths and hos­pi­tal­iza­tions, a new study in­di­cates.

An eth­a­nol plant con­verts corn to eth­a­nol, form of al­co­hol that has been pro­posed as a clean al­ter­na­tive to gas­o­line. (Im­age cour­te­sy U.S. Nat'l Re­new­able En­er­gy Lab­o­ra­to­ry)


The work, by at­mos­pher­ic sci­ent­ist Mark Z. Ja­cob­son of Stan­ford Uni­ver­si­ty in Stan­ford, Calif., ap­pears in the April 18 on­line edi­tion of the re­search jour­nal En­vi­ron­men­tal Sci­ence & Tech­nol­o­gy.

“Eth­a­nol is be­ing pro­mot­ed as a clean and re­new­able fu­el that will re­duce glob­al warm­ing and air pol­lu­tion,” said Ja­cob­son. “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 com­put­er mod­el to sim­u­late air qual­i­ty in the year 2020, when eth­a­nol-fu­eled ve­hi­cles are ex­pected to be wide­ly avail­a­ble in the Unit­ed States. He sim­u­lated at­mos­pher­ic con­di­tions na­tion­wide, but fo­cused on Los An­ge­les be­cause it “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,” he wrote.

He com­pared the ef­fects of gas­o­line-fueled ve­hi­cles to those fu­eled by E85, a pop­u­lar blend of 85 pe­r­cent eth­a­nol and 15 pe­r­cent gas­o­line. 

“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 can de­crease lung ca­pac­i­ty, in­flame the lungs, wors­en asth­ma and impa­ir the im­mune sys­tem, ac­cord­ing to the U.S. En­vi­ron­men­tal Pro­tec­tion Agen­cy. The World Health Or­ga­ni­za­tion es­ti­mates that 800,000 peo­ple die year­ly 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.”

Ozone in­creases in Los An­ge­les and the north­east­ern Unit­ed States will be par­tially off­set by de­creases in the south­east, the study found. But “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.”

“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.”


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Ethanol is widely touted as an eco-friendly, clean-burning fuel; its production has soared in recent years. But if every vehicle in the United States ran on fuel made mainly from ethanol instead of gasoline, it would likely lead to more respiratory-related deaths and hospitalizations, a new study indicates. The work, by atmospheric scientist Mark Z. Jacobson of Stanford University in Stanford, Calif., appears in the April 18 online edition of the research journal Environ mental Science & Technology. “Ethanol is being promoted as a clean and renewable fuel that will reduce global warming and air pollution,’’ said Jacobson. “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 computer model to simulate air quality in the year 2020, when ethanol-fueled vehicles are expected to be widely available in the United States. He simulated atmospheric conditions nationwide, focusing especially on Los Angeles because it “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,” he wrote. He compared the effects of vehicles fueled by gasoline versus those fueled by E85, a popular blend of 85 percent ethanol and 15 percent gasoline. “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 can decrease lung capacity, inflame the lungs, worsen asthma and impair the immune system, according to the U.S. Environ mental Protection Agency. The World Health Organ ization estimates that 800,000 people die yearly 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.” Ozone increases in Los Angeles and the northeastern United States will be partially offset by decreases in the southeast, the study found. But “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.” “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.”