Mixture Matters: Exploring the Overlooked Toxicity of Sulfamethoxazole and Trimethoprim in Aquatic Environments

• Type: Article in International Scientific Journal
• Date: 2025

Authors

Diogo B.S. (Author) Other; Rodrigues S. (Author) Other; Antunes, SC (Author) FCUP

Journal

Title: Environmental Toxicology

Vol. 40

Pages: 1277-1293

ISSN: 1520-4081

Publisher: Wiley-Blackwell

Indexing

Scopus - 2 Citations

Other information

Authenticus ID: P-018-X7A

DOI: 10.1002/tox.24528

Abstract (EN): Sulfamethoxazole (SMX) and trimethoprim (TRIM) are two antibiotics included in the third Watch list to be monitored in inland waters by the Water Framework Directive. However, their mixture (MIX) is overlooked and is especially concerning because it mirrors the real conditions in natural aquatic ecosystems. This study aimed to evaluate the toxic effects of environmentally relevant concentrations of SMX (150 ¿g/L), TRIM (30 ¿g/L), and MIX (150 ¿g/L SMX + 30 ¿g/L TRIM) in different standard species: Aliivibrio fischeri (bioluminescence inhibition), Escherichia coli ATCC 25922 (growth inhibition), Lemna minor (growth inhibition and biochemical biomarkers), Daphnia magna (immobilization/mortality, reproductive effects, and biochemical biomarkers), and Danio rerio (survival, hatchability, abnormalities, and biochemical biomarkers). Considering all the parameters evaluated, and using the Independent Action model and the antibiotics ecotoxicological assessment approach, the results reveal that: (i) all antibiotics affect the bacteria A. fischeri and E. coli differently, causing a pronounced E. coli inhibition growth; (ii) SMX and MIX were slightly toxic to D. magna (after 48 h) and D. rerio (after 96 h), and moderately toxic to L. minor (after 7 days) and D. magna (after 10 days); (iii) TRIM was slightly toxic to all organisms tested, except for L. minor, which exhibited moderate toxicity; (iv) the interaction of the antibiotics in mixture varied significantly depending on the parameter; however, it revealed similar toxicity to SMX. Significant ecotoxicological data were obtained, clarifying the ecological risks of these antibiotics in aquatic ecosystems. Remaining vigilant regarding environmental contamination linked to levels of SMX and TRIM in surface waters is crucial. Assessing the combined impacts of multiple stressors is essential for prioritizing environmental safety and ecotoxicity assessments for antibiotics amidst climate change, preserving the health and integrity of aquatic ecosystems.

Language: English

Type (Professor's evaluation): Scientific