Eco(geno)toxicological effects of the dye Direct Red 09 on plants and soil invertebrates: a preliminary terrestrial risk assessment based on species sensitivity distributions

This study aimed to determine the eco(geno)toxicological effects of the widely used textile dye Direct Red 09 on multiple terrestrial species as bioindicator models of exposure and integrating the newly obtained results with previously published data. Bioassays with Cenchrus americanus, Allium cepa, Panagrellus redivivus, and Enchytraeus crypticus were conducted at concentrations ranging from 0.437 to 14 g/L, assessing germination, seedling growth, mitotic index, micronucleus frequency, and organism immobilization. The dye markedly induced cytogenotoxicity in A. cepa, moderate phytotoxicity in C. americanus, higher sensitivity in P. redivivus, and limited effects on E. crypticus. By integrating these findings with previous data for Lactuca sativa, a species sensitivity distribution (SSD) was established, noting the following the sensitivity gradient A. cepa > L. sativa > C. americanus > P. redivivus > E. crypticus. The hazardous concentration for 5% of species (HC5) was determined to be 1.79 g/L Direct Red 09 textile dye and the predicted no-effect concentration (PNEC) was 0.089 g/L. The relatively high HC5 indicated a low potential for acute ecological risk under typical exposure conditions. However, the cytogenotoxic responses observed in sensitive species indicate that potential chronic effects need to be considered, reinforcing the necessity for environmentally realistic and long-term studies to refine protective thresholds.