Another benefit, though controversial, is that using ethanol might decrease emissions of certain emissions. Toxic, ozone-forming compounds are emitted during the combustion of gasoline, such as aromatics, olefins, and hydrocarbons, would be eliminated with the use of ethanol. The concentration of particulates, produced in especially large amounts by diesel engines, would also decrease. However, emissions of carbon monoxide and nitrogen oxides are expected to be similar to those associated with newer, reformulated gasolines. Carbon dioxide emissions might be improved (-100%) or worsened (+100%), depending the choice of material for the ethanol production and the energy source used in its production.