Pollution is easy to spot: a soda can on the side of the road, an old tire in someone's yard, or flyers that have been blown into the park by the wind. But litter is just a part of it. Air pollution and light pollution are problems too! Citizen scientists are sometimes the perfect people to observe and measure it. In this volume, readers are introduced to many kinds of pollution, how they harm Earth, and ways they can get involved in cleaning it up. Five activities show readers basic research and project strategies.