Registration Dossier

Administrative data

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:
PNEC aqua (freshwater)
PNEC value:
0.65 µg/L
Assessment factor:
1 000
Extrapolation method:
assessment factor
PNEC freshwater (intermittent releases):
0.006 mg/L

Marine water

Hazard assessment conclusion:
PNEC aqua (marine water)
PNEC value:
0.065 µg/L
Assessment factor:
10 000
Extrapolation method:
assessment factor

STP

Hazard assessment conclusion:
PNEC STP
PNEC value:
1 mg/L
Assessment factor:
100
Extrapolation method:
assessment factor

Sediment (freshwater)

Hazard assessment conclusion:
no exposure of sediment expected

Sediment (marine water)

Hazard assessment conclusion:
no exposure of sediment expected

Hazard for air

Air

Hazard assessment conclusion:
no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:
no exposure of soil expected

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:
no potential for bioaccumulation

Additional information

Sediment and soil exposure: Two routes of entry to the soil compartment are possible: via deposition of chlorite present in aerosols from cooling towers or via deposition of sewage sludge. Chlorine dioxide is fairly unstable and rapidly dissociates, predominantly into chlorite and chloride, and to a lesser extent, chlorate. There is a ready interconversion among these species in contact with water. The substance chlorine dioxide is highly reactive and it will readily react with organic matter and microorganisms present in sewage sludge or in soil and will be reduced to chloride via the transient intermediate chlorite. 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 exposure to soil via sewage sludge. Chlorite in aerosols deposited in soil would also be expected to degrade to chloride on contact with soil.

Conclusion on classification

Based on the available data on the three trophic levels:

96-h-LC50 fish = 105 mg/l

48-h EC50 Daphnia < 1 mg sodium chlorite/L (equivalent to 0.75 mg chlorite/L)

96-h LC50 Mysids = 0.65 mg/L of sodium chlorite (equivalent to 0.49 mg chlorite/L)

96-h EC50 algae = 1 mg/L (equivalent to 0.75 mg chlorite/L)

It is observed that for two trophic levels the EC50 values are lower or equal to 1 mg/l. Therefore, the substance is classified as Hazardous to the aquatic environment, Acute Category 1.

Based on the NOEC value in the algae study (NOEC < 1 mg/L) and since the substance is rapidly degradable (sodium chlorite is expected to be rapidly reduced to sodium chloride in the environment, especially in anaerobic conditions and sodium chlorite is unstable in water), the substance is classified as Chronic Category 3.