Unseen in the air around us are tiny molecules that drive the chemical cocktail of our atmosphere. As plants, animals, volcanoes, wildfires and human activities spew particles into the atmosphere, some of these molecules act as cleanup crews that remove that pollution. The main molecules responsible for breaking down all these emissions are called oxidants. The oxygen-containing molecules, mainly ozone and hydrogen-based detergents, react with pollutants and reactive greenhouse gases, such as methane.