Chlorine dioxide

Toxicity to birds

Description of key information

Chlorine dioxide reacts rapidly in aqueous solution degrading to chlorite and chlorate as dominant species under environmental conditions. In the absence of oxidisable substances, and in the presence of pH > 9, chlorine dioxide dissolves in water and decomposes with the slow formation of chlorite and chlorate ions.

Additional information

According to the TNsG on Data Requirements for Active Substances and Biocidal Products, and REACH Guidance: an acute oral toxicity test, a short term toxicity test, and a study on the effects on reproduction in birds might be required. The direct exposure of birds to chlorine dioxide is highly unlikely. Three routes or release to the soil compartment are possible: via deposition of manure, via deposition of aerosols cooling towers, or via deposition of sewage sludge. As described in the data waiver for anaerobic degradation, the active substance, chlorine dioxide is highly reactive and it will readily react with organic matter and microorganisms present in manure, in aerosols or sewage sludge and will be reduced to chloride via the transient intermediate chlorite. The ESD for disinfection of animal houses assumes that up to six disinfection treatments are performed during a year, with the manure itself being stored for a total of one year prior to use. On this basis there will be sufficient contact time between the chlorine dioxide and the manure to ensure that complete degradation to chloride ion occurs. Hence there will be no release to soil via manure. With regards to exposure via sewage sludge, the vast quantity of organic matter and metal ions dissolved in the aqueous phase in the STP would ensure the complete conversion of chlorine dioxide to chloride via the transient intermediate chlorite. Hence there will be no release to soil via sewage sludge. Chlorite in aerosols deposited in soil would also be expected to degrade to chloride on contact with soil. In addition, the rapid degradation of chlorine dioxide in the environment, its low Log Kow and high water solubility indicate that the potential for bioaccumulation is low. There is therefore little concern for exposure to birds from secondary poisoning. Therefore, an acute oral toxicity test, a short term toxicity test, and a study on the effects on reproduction in birds are not required.

Chlorine dioxide react easily and rapidly generating chlorite and chlorate as dominant species. In the absence of oxidisable substances, and in the presence of pH > 9, chlorine dioxide dissolves in water and decomposes with the slow formation of chlorite and chlorate ions.

No key study valid was found in chlorite for birds but two key studies valid were found in Sodium chlorate for evaluated toxicity to birds bobwhite quail Colinus virginianus or mallard duck Anas platyrhynchos (Arch 2004, according to OECD Guideline 206 and Fink 1990, according to EPA OPP 71 -1). These studies demonstrated a NOEC (154 days) = 300 ppm of sodium chlorate in bobwhite quail (Arch 2004) and a LD50 (14 days) > 2510 mg/kg of sodium chlorate in mallard duck (Fink 1990).