What Is Chlorine Dioxide?

ATSDR says chlorine dioxide is a yellow to reddish-yellow manufactured gas that does not occur naturally in the environment, and that when added to water it forms chlorite ion, which is also a very reactive chemical. It says chlorine dioxide is used as a bleaching agent at paper manufacturing plants and in public water treatment facilities to make water safe to drink.

EPA drinking water regulations at 40 CFR 141.65 set a maximum residual disinfectant level for chlorine dioxide of 0.8 mg/L, and 40 CFR 141.64 sets a maximum contaminant level for chlorite, a disinfection byproduct, of 1.0 mg/L.

The New Jersey Department of Health says breathing chlorine dioxide can irritate the lungs, causing coughing or shortness of breath, and that higher exposures can cause a build-up of fluid in the lungs, a medical emergency, with severe shortness of breath. It lists the OSHA permissible exposure limit as 0.1 ppm averaged over an 8-hour workshift, and the NIOSH recommended limit as 0.1 ppm averaged over a 10-hour workshift, with 0.3 ppm not to be exceeded during any 15-minute period.