Pollution is unwanted, harmful stuff contaminating an environment. The race to develop clean energy is motivated by high levels of pollution that people fear are permanently damaging the earth's environment.
When you hear about pollution, you’re most likely hearing about chemical emissions into air or water that come from industrial processing. But pollution isn’t just environmental. Anything we think of as pure can be contaminated by pollution polluted, whether that's a lake or an idea. If your mother finds you reading trashy magazines instead of doing your homework, she might worry about the pollution of your mind.