Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

The primary source of possible environmental pollution of Direct Red 23 (DR23) is represented by industrial waste water, while secondary releases can occur during washing of dyed textile, thus the fate and pathways of DR23 in surface water are of primary concern.

For some of the data points a read-across is proposed with the structural analogue Direct Red 262 (DR262).

 

In the aquatic environment hydrolysis is not expected to be an important elimination process for DR23, based on read-across using DR262 data.

DR262 undergoes slow hydrolysis, with a calculated half-life greater than one year at 25 °C and pH values of 4, 7 and 9, based on measured hydrolysis rates at 50°C when after 2.4 hours only around 1% of the sample was hydrolysed at pH 4, 7 and 9 (BASF, 1992).

Phototransformation in air/water/soil has not been investigated because direct and indirect exposure to sunlight is unlikely based on release considerations reported above, the CSR and proposed risk management measures.

Furthermore, phototransformation is not considered a relevant process for the substance, although phototransformation can be enhanced using oxidants.

 

DR23 is expected to be a substance with a low potential for adsorption based on the partition coefficient Kow of 0.0019 (R&C, 2012).

However, literature on DR262 reports that adsorption to sediment of highly sulfonated bis(azo) dyes can be expected due to surface interaction of the sulphonated groups (Weber E. J., 1991, in National Industrial Chemicals Notification and Assessment Scheme, 1992). DR23 however has two sulphonate groups less than DR262 and therefore less adsorption to sediment is expected.

 

Under standard test conditions no ready biodegradation was observed. According to OECD guideline 302B, no biodegradation of DR23 based on CO2 evolution and calculated as % ThCO2 was observed in the Clariant key study of 2007 (Clariant, 2007): less than 20% degradation was attained after 28 days of contact time, data which were confirmed also by the Clariant key study of 2002 (Clariant, 2002).

BCF has not been tested because DR23 has a low estimated potential for bioaccumulation and/or a low potential to cross biological membranes; the estimated value of DR23 neutral form was 3.162 L/kg wet-wt, calculated using the software EpiSuite 4.1. The organic carbon partition coefficient of 0.0019 (R&C, 2012) reported in section 4.7 Partition Coefficient end point confirms this provisional consideration, leading to the conclusion that DR23 is not expected to be bioaccumulable.

 

Direct and indirect exposure of sediment and soil is unlikely, since environmental exposure only occurs through industrial waste water; based on the CSR and risk management measures reported there is no sediment and/or soil exposure expected.