High levels of negative ions neutralize the effect that tobacco smoke has on the cilia. Cilia are the microscopic hairs located in the trachea that move rapidly back and forth to prevent pollutants and toxins from traveling into the vulnerable areas of the respiratory tract. The faster the cilia move, the more effective they are. However, tobacco smoke slows down the ciliary beat, diminishing the body’s ability to keep cancer-causing pollutants from entering the depths of the respiratory tract. Tests have shown though, that adding high levels of negative ions to the air accelerates the ciliary beat to normal levels (Soyka, 1991).