Occurrence and risk assessment of an azo dye – The case of Disperse Red 1

• Disperse Red 1 dye was found in river waters in concentrations above the PNEC.
• The PNEC was based on toxicity endpoints for a commercial dye and its purified form.
• The CRED method was used to evaluate the quality of endpoints used in PNEC derivation.

Water quality criteria to protect aquatic life are not available for most disperse dyes which are often used as commercial mixtures in textile coloration. In this study, the acute and chronic toxicity of the commercial dye Disperse Red 1 (DR1) to eight aquatic organisms from four trophic levels was evaluated. A safety threshold, i.e. Predicted No-Effect Concentration (PNEC), was derived based on the toxicity information of the commercial product and the purified dye. This approach was possible because the toxicity of DR1 was accounting for most of the toxicity of the commercial mixture. A long-term PNEC of 60 ng L−1 was proposed, based on the most sensitive chronic endpoint for Daphnia similis. A short-term PNEC of 1800 ng L−1 was proposed based on the most sensitive acute endpoint also for Daphnia similis. Both key studies have been evaluated with the new “Criteria for Reporting and Evaluating ecotoxicity Data” (CRED) methodology, applying more objective criteria to assess the quality of toxicity tests, resulting in two reliable and relevant endpoints with only minor restrictions. HPLC-MS/MS was used to quantify the occurrence of DR1 in river waters of three sites, influenced by textile industry discharges, resulting in a concentration range of 50–500 ng L−1. The risk quotients for DR1 obtained in this work suggest that this dye can pose a potential risk to freshwater biota. To reduce uncertainty of the derived PNEC, a fish partial or full lifecycle study should be performed.

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