Since our cars are some of the greatest sources of pollution in our daily lives, it makes sense to start there.
A short commute to work may not seem like a big polluter. Let's say you drive 10 miles (16 kilometers) each way. That means about a single gallon (3.7 liters) of gas round-trip -- maybe even less.
But that single gallon of gas sends 19 pounds (8.6 kilograms) of carbon dioxide into the air [source: Slate]. That's almost twice as much as running central air conditioning for a day, and central air is one of the biggest household polluters [source: WTOP]. So keeping those 19 pounds of greenhouse gas out of the air is a nice way to pitch in on Earth Day.
There are lots of ways to get to work without driving your car. You can carpool with someone from work, take the bus or train, arrange to work from home for the day, or, best yet, ride your bike. Then you'll be getting healthier right alongside the planet.
Up next: Be a little dirty.