Chlorine dioxide

Bioaccumulation: aquatic / sediment

Administrative data

Endpoint:

bioaccumulation in aquatic species: fish

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance has a low potential for bioaccumulation based on log Kow <=3

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING:
According to the REACH Annex IX (9.3.2) indicates that information on bioaccumulation in aquatic – preferably fish – species is required for substances manufactured or imported in quantities of 100 t/y or more. In general, this means the establishment of a fish bioconcentration factor, although a biomagnification factor may also be appropriate in some circumstances. Chlorine dioxide is very reactive and rapidly degrades to chloride ions, via the transient intermediate chlorite, on contact with oxidisable substances in the environment, such as organic and biological matter. In addition, the estimated log octanol – water partition coefficient for chlorine dioxide of -3.22 indicates that adsorption to sediment and hence accumulation in sediment would be very low. A sediment degradation study with chlorate demonstrates that chlorate undergoes quantitative conversion to chloride. This demonstrates that chlorite (as the intermediate in the degradation of chlorate to chloride) is rapidly degraded to chloride in water-sediment systems. The unstable nature of chlorine dioxide, the negative log Kow values for both chlorine dioxide and chlorite and the evidence from a degradation study in sediment leads to the conclusion that neither chlorine dioxide or chlorite will accumulate in the sediment and hence further studies are scientifically unjustified. According to the TGD on Risk Assessment, Part II Section 3.8.3.2, the BCF for fish can be predicted from the relationship between Kow and BCF. However, the standard equation used (Log BCFfish = 0.85 x log Kow – 0.70) is only valid in the range Log Kow 2-6. The Log Kow values for chlorine dioxide and chlorite are estimated to be -3.22 and <-2.7, respectively; hence use of the calculation method is not considered valid. Based on its rapid degradation in the environment, low Log Kow and high water solubility and the expected rapid metabolism of chlorine dioxide and chlorite, it is considered that the potential for bioaccumulation is low.