The use of ethanol as a transportation fuel in the U.S. increased significantly from 2000–2009, and in 2010 nearly all gasoline contained 10% ethanol. In accordance with this increased use, atmospheric measurements of volatile organic compounds in Los Angeles in 2010 were significantly enriched in ethanol compared to measurements in urban outflow in the Northeast U.S. in 2002 and 2004. Mixing ratios of acetaldehyde, an atmospheric oxidation product of ethanol, decreased between 2002 and 2010 in Los Angeles. Previous work has suggested that large‐scale use of ethanol may have detrimental effects on air quality. While we see no evidence for this in the U.S., our study indicates that ethanol has become a ubiquitous compound in urban air and that better measurements are required to monitor its increase and effects. Key Points The use of fuel ethanol has increased by a factor of ten in the last decade Measurements show that ethanol in urban air has increased strongly Acetaldehyde, a hazardous air pollutant produced from ethanol, has decreased