Chlorine dioxide is a gas that does not occur naturally in the environment. In agriculture, it is an antimicrobial pesticide recognized for its disinfectant properties since the early 1900s. It kills microorganisms by disrupting transport of nutrients across the cell wall. For water treatment, it is used to disinfect drinking water and make it safe to drink. Approximately 700 to 900 public water systems use chlorine dioxide to treat potable water. In Italy, over 30 percent of the water works utilize chlorine dioxide and in Germany, over 10%. Acceptance of chlorine dioxide as an oxidant and disinfectant for drinking water in the United States has grown dramaticlly over the past 20 years. As it were, if chemical compounds can be thought of as actors in the theater of public health, chlorine dioxide (ClO2) is one of the busiest performers, playing supporting roles in various productions.