Story at-a-glance Negative ions are electrically charged molecules that concentrate naturally in areas like beaches, waterfalls, mountains, and forests, that help cleanse the air of unhealthy particles Scientists have found that high-density negative air ionization may help counter symptoms of seasonal affective disorder (SAD) The ocean's negative ions are created when water molecules gain electrons, while mountain air can be rich in negative ions due to mineral content like magnesium and calcium from limestone Taking a shower can generate negative ions at home through the "Lenard effect," where the shearing forces of fast-flowing water create friction that adds electrons to molecules Negative ions form when oxygen in the air (O2) takes on a negative electrical charge to become O2⎺, which then gets enveloped by microdroplets of moisture to create what we know as "fresh air"