Toxicological Evaluation of Acetylsalicylic Acid (Aspirin) on the Freshwater Alga Chlorella vulgaris

The pervasive presence of pharmaceutical residues in aquatic ecosystems raises critical concerns regarding their potential ecological impacts. This study investigated the toxicological effects of one of commonly used non- steroidal anti-inflammatory drugs (NSAIDs) Aspirin (acetylsalicylic acid) on the unicellular green alga Chlorella vulgaris. Algal cultures were exposed to a gradient of concentrations to determine sub-lethal doses (LC10, LC25, LC50) over 24, 48, and 96-hour intervals. The impacts on algal growth, pigment composition (chlorophyll a, b), biochemical constituents (proteins, lipids, carbohydrates). assessed. Results indicated a concentration- and time- dependent inhibition of algal growth and a significant decline in pigment and macromolecule content, particularly at LC50 levels after 96 hours. Chlorophyll a decreased by about 57%, Chlorophyll b by 80%, Protein levels fell by roughly 33%, Total carbohydrates showed a decrease of around 22% and Lipid content declined by nearly 28% LC50 levels after 96 hours compared with the control. Overall, the findings demonstrate that aspirin at ecotoxicologically relevant levels exerts pronounced physiological stress on C. vulgaris, primarily through suppression of photosynthesis and depletion of cellular macromolecules, highlighting the potential ecological risk of pharmaceutical contamination in aquatic systems, which makes it necessary to take this into consideration during wastewater treatment processes.