Sulfamethoxazole in the environment: Occurrence, fate, risks, and remediation strategies

The extensive use of antibiotics in human and veterinary medicine has led to their widespread occurrence in the environment, raising concerns about pseudo-persistence, ecological effects, and their contribution to antimicrobial resistance. Sulfamethoxazole (SMX) is one of the most common sulfonamides and is an environmentally relevant contaminant. This review provides a comprehensive assessment of the environmental behavior and management of SMX, integrating its occurrence, fate, transformation, associated risks, regulatory frameworks, and remediation strategies, while identifying remaining knowledge gaps. The reported concentrations of SMX in aqueous matrices range from ng/L to µg/L and in solid matrices with levels reaching up to 0.18, 12.7, and 0.63 mg/kg in soils, manure, and sewage sludge, respectively. SMX exhibits a low solid-liquid distribution coefficient, suggesting high mobility and the potential for environmental transport, leaching, and plant uptake, with concentrations in plant roots reaching up to 13.8 mg/kg under highly contaminated conditions. Despite the relatively low potential of SMX for bioaccumulation, continuous input may lead to chronic exposure and thus ecotoxicological effects and the development of antimicrobial resistance. Transformation products, recent regulatory advances, and remediation strategies are also reviewed, focusing on the limitations of treatment approaches, including incomplete mineralization and by-product formation. Hybrid treatment systems are proposed as a promising solution to overcome these limitations, but further validation is required to assess their scalability, sustainability, and efficiency under realistic conditions. The review concludes by highlighting the need for integrated monitoring, risk-based regulation, and sustainable remediation strategies to mitigate environmental and health concerns associated with SMX pollution.