Abstract <p>Ethidium bromide is extensively used as a fluorescent marker in biotechnology and molecular biology laboratories. Due to its mutagenic and carcinogenic properties, effluents containing ethidium bromide represent a significant environmental concern and require appropriate treatment prior to disposal. In the present study, the photocatalytic degradation of ethidium bromide using iron(III) oxide (Fe₂O₃) as a photocatalyst was investigated to assess its effectiveness and environmental safety. Photocatalytic experiments were conducted under controlled irradiation conditions, and the degradation process was monitored through spectroscopic analysis. The results indicate a noticeable reduction in the concentration of ethidium bromide during photocatalytic treatment. However, further examination of the treated effluent revealed the formation of degradation products that exhibit higher toxicity than the parent dye. This observation suggests that photocatalytic discoloration does not necessarily correspond to complete mineralization or detoxification of the compound. An environmental risk assessment was performed to evaluate the suitability of Fe₂O₃-assisted photocatalysis as a treatment strategy for laboratory waste containing ethidium bromide. The assessment demonstrates that although the photocatalytic process facilitates partial degradation of the dye, the persistence and potential harmful effects of the resulting intermediates limit its applicability as a standalone treatment method. The presence of toxic transformation products highlights the need for caution when relying solely on photocatalytic approaches for hazardous dye removal. Overall, the study concludes that Fe₂O₃-mediated photocatalytic treatment alone is insufficient to ensure the environmental safety of ethidium bromide–containing laboratory effluents. The process should be supplemented with appropriate tertiary treatment techniques to achieve effective detoxification prior to discharge into the environment.</p>