Assessing the Ecotoxicological Effects of Emerging Drug and Dye Pollutants on Plant–Soil Systems Pre- and Post-Photocatalytic Wastewater Treatment

Emerging pollutants such as pharmaceuticals and synthetic dyes increasingly enter agricultural soils through irrigation with treated or untreated wastewater and via biosolid amendments, raising concerns for plant health, soil functionality, and food chain safety. Their environmental behavior is governed by complex interactions between compound physicochemistry, soil properties, and plant physiology, leading to variable persistence, mobility, and ecotoxicological outcomes. This review synthesizes current evidence on the fate, uptake, and phytotoxic effects of drug and dye contaminants in plant–soil systems, and provides a comparative assessment of ecological risks before and after photocatalytic wastewater treatment. The analysis integrates findings from soil- and hydroponic-based studies addressing pollutant sorption–desorption dynamics, leaching, microbial transformations, and plant responses ranging from germination impairment and biomass reduction to oxidative stress and genotoxicity. Special emphasis is given to the formation and behavior of transformation products generated during photocatalytic degradation, which may display altered mobility or toxicity relative to parent compounds. Comparative evaluation reveals that photocatalysis substantially reduces contaminant loads and toxicity in many cases, although incomplete mineralization or the formation of reactive intermediates can sustain or enhance adverse effects under certain conditions. By linking pollutant fate mechanisms with plant and soil responses, this review highlights both the potential and the limitations of photocatalysis as a sustainable strategy for safeguarding agroecosystems in the context of expanding wastewater reuse.