Environmental Implications of Caffeine Exposure on Terrestrial Plant Establishment.

Background: The ecotoxicological assessment of caffeine is essential to understand its potential impacts on non-target organisms and to support environmental risk assessment. Caffeine is an emerging contaminant widely detected in aquatic and terrestrial environments due to human consumption and its continuous release via domestic and industrial effluents. Its persistence may affect non-target organisms, including terrestrial plants, by altering physiological and developmental processes. Objective: To evaluate the phytotoxic effects of caffeine on four terrestrial plant species (C. americanus, Triticum aestivum, Lactuca sativa, and Raphanus sativus) using germination, development, and growth endpoints. Methods: Bioassays were conducted following OECD 208 and ISO 18763 guidelines under controlled dark conditions for 72 h. Ten caffeine concentrations (0.0028–97.42 mg/L, ≥99% purity) were tested per species, with six replicates per treatment and ten seeds per replicate. Germination and early seedling development parameters were evaluated after exposure. Effect percentages were calculated and doses classified as non-toxic, moderately toxic, or toxic based on EC₁₀ and EC₅₀ thresholds. A final toxicity index was derived from the integrated response of all endpoints for each species. Results: The strongest effects were observed in root and shoot growth. Root inhibition exceeded 50% in C. americanus and T. aestivum (53.96% and 64.89%), classifying caffeine as toxic for this endpoint. Shoot growth inhibition remained below 50% but showed moderate effects, particularly in T. aestivum (27.09%) and R. sativus (19.29%). In the GSI endpoint, caffeine showed moderate toxicity for C. americanus. Integrated analysis indicated higher sensitivity in C. americanus, followed by R. sativus, T. aestivum, and L. sativa. Conclusions: Caffeine can impair early plant development, mainly growth-related parameters, potentially affecting establishment and regeneration. These findings support further ecotoxicological studies and its consideration in environmental regulations to protect soil quality and ecosystem functioning.