Clioquinol

Endpoint summary

Additional information

Stability

Phototransformation in air

The atmospheric oxidation half-life of clioquinol was estimated using the level III multimedia model. It was estimated that the substance is not persistent in air medium as the half life period of clioquinol in air is only 1.9 days. This indicates that clioquinol is rapidly phototransformed in air.

OVERALL OH Rate Constant =0.0000000000086cm3/molecule-sec.

Media	Half life (days)	Percent in Medium
Air	1.9	0%

   

 

Hydrolysis:

The Hydrolysis rate constant of clioquinol is estimated to be 0.0000000000085559 cm3/molecule-sec. at half life of 15.002 hrs.The estimated half life of the substance indicates that the substance is moderately hydrolysable.

Phototransformation in water

No experimental data available. As this study is not a standard information requirement in REACH and there is no indication from the CSA on the need to investigate further the fate and behaviour of the substance (Annex X requirement), no further testing is considered necessary.

Phototransformation in soil

No experimental data available. As this study is not a standard information requirement in REACH and there is no indication from the CSA on the need to investigate further the fate and behaviour of the substance (Annex X requirement), no further testing is considered necessary.

Biodegradation

Biodegradation in water

The half life period ofclioquinolin water is 38 days and based on this value it can be concluded that the chemical is not persistent in water medium since the half life is less than the threshold of 60 days (to qualify the chemical as persistent). Also the diffusion percentage ofclioquinolin water medium is 11%. This coupled with the dilution of water shall result in ready biodegradabililty of the chemical.

The supporting study also shows the half life of clioquinol to be 900 hrs (37.5 days) indicating thet it is readily biodegradable

Media	Half-Life  (days)	Percent in Medium
Water	38	11%

 

Media	Half life (hrs)	Percent in Medium	Emission (kg/hr)
Water	900	10.8	1000

 

Biodegradation in water and sediment

Based on the Level III Fugacity Model, the half life period of theclioquinolwas estimated. The half period ofclioquinolin water is 38 days (912 hrs) therefore it is considered that the substance will qualify as not persistent as the half life does not exceed the threshold of 60 days. So, it can be confirmed that the substance is readily biodegradable in water medium where as in sediment the half life is 340 days (8160 hrs).

Based on this value, it can be inferred that the substance is persistent in sediment medium and is not readily biodegradable probably due to the anaerobic conditions existing in most sediments. However, it can be observed that clioquinol have very slightdiffusion in the sediment medium since it's percentage in the sediment medium is reported to be 3% and hence persistence in the sediment compartment is not likely to be critical.

Media	Half-Life  (days)	Percent in Each Medium
Water	38	11%
Sediment	340	3 %

Media	Half life (hrs)	Percent in Medium	Emission (kg/hr)
Water	900	10.8	1000
Sediment	8100	3.38	0

Biodegradation in soil

The PBT Profiler & EPI Suite has estimated thatclioquinolis expected to be found predominantly in soil and its persistence estimate is based on its transformation in this medium. Its half-life in soil, 75 days (1800 hrs). This exceeds the threshold of >= 2 months (and <= 6 months). Therefore,clioquinolis estimated to be persistent in the soil environment.

PBT profiler estimate

Media	Half-Life  (days)	Percent in Medium
Soil	75	86%

Fugacity Model by EPI Suite estimation database

	Mass Amount (percent)	Half-Life (hr)	Emissions (kg/hr)
soil	85.9	1.8e+003	1000

Bioaccumulation: aquatic/sediment

Bioaccumulation is the process by which the chemical concentration in an aquatic organism achieves a level that exceeds that in the water, as a result of chemical uptake through all possible routes of exposure.The relationship between bioaccumulation and bio-concentration is that, chemicals that have the potential to bioconcentrate also have the potential to bioaccumulate. Bioaccumulation is closely related to the Bioconcentration factor (BCF).

The estimated BCF of the key study was obtained to be 91.Supporting study also indicate the same BCF value. This low value of BCF of clioquinol indicates its non bioaccumulative nature as the BCF factor is less than the bio-concentration threshold of 2000.

Transport and distribution

Adsorption/Desorption

Soil Adsorption Coefficient i.e Koc value of clioquinol was estimated as 5425 L/kg (Log koc = 3.7343) at 25 deg C by means of MCI method. This indicates that clioquinol will have strong tendency of sorption to soil and sediment and therefore have negligible migration potential to groundwater.

This Koc value when converted at 20 degC is equivalent to 4340.

Henry's Law constant

Henry's Law states that at a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.Henry’s law constant of clioquinol was estimated to be 0.00000125 (1.25E-006) Pa m³/mol at 25 degC.