Those molecules, he believes, are either natural waste products or chemical weapons that are normally used against rival bacteria. (discovermagazine.com)
Free radicals, which are natural waste products produced by normal metabolic processes, are thought to contribute to aging and illness by damaging the cells they come into contact with. (petconsider.com)
The fairway is bordered with sand and natural waste areas, making accuracy off the tee important. (sbnation.com)