Ecotoxicological effects of pharmaceuticals, personal care products, and endocrine disruptors on microalgae: a comprehensive review

Pharmaceuticals, personal care products (PCPs), and endocrine-disrupting compounds (EDCs) have been widely identified as emerging contaminants in aquatic systems and likely pose risks to microalgae, which serve as primary producers and early indicators of water contamination. Current information is compiled and synthesized concerning the physiological, biochemical, metabolic, and ecotoxicological effects of pharmaceuticals, PCPs, and EDCs on microalgae, focusing on growth inhibition and biomass productivity, interference with photosynthesis, cellular damage, oxidative stress, metabolic changes, adaptive response, and biotechnological applications. Based on this evidence, it is clear that the severity of contaminant toxicity varies with contaminant class, concentration, and duration of exposure and microalgal species sensitivity, with growth inhibition and decreased productivity being reported more often than other parameters, while the photosynthetic pigments, system II, and electron flow and carbon fixation are among those sensitive biological targets affected by contaminant- induced physiological damage. Oxidative stress is likely a central toxic pathway in which overproduction of ROS leads to cellular damage through lipid peroxidation, pigment damage, cellular injury, altered metabolic functions, and other adverse effects. Microalgae can defend against contaminant stress through the activation of antioxidants, adjustment of pigments, nonphotochemical quenching, production of extracellular polymeric substances, and other protective adaptations, although long-term exposure or overload of the protective system leads to severe damage. It is clear that differences among microalgal species are notable; current limitations stem from studies based on short-term acute toxicity assays and single-contaminant studies. Specifically, chronic exposure studies, studies on contaminant mixtures, quantitative toxicity values, and the effects of contaminants accumulated on biomass quality were addressed. In the final section, some future applications of microalgae for contaminant removal from waters, wastewater treatment, resource recovery, value-added products, and circular bioeconomy applications were discussed, focusing future research on ecological realities, omics-guided strain design, and a green algal biorefinery.