According to National Geographic, more than half the air pollution in the United States is caused by mobile devices, primarily by automobiles. These greenhouse gases that vehicles emit, such as carbon dioxide, are wreaking havoc on the ozone layer as well as polluting the soil and surface water in many cases.

Bottom line— while cars are an everyday necessity and convenience, they’re not doing the environment any favors. That’s part of the reason why the federal government is offering tax incentives to those who purchase hybrid or electric vehicles, as well as challenging automakers to develop vehicles by 2025 that are able to achieve 55 mpg on the highway. It’s a bold goal but, as you can see from how much cars are responsible for pollution, it’s a necessary one that’s becoming more important.