Acyclovir contamination in environment: Occurrence, transformation, toxicity, risk, and evaluation as a pharmaceutical indicator.

Acyclovir (ACV), a widely used antiviral medication effective against herpes simplex viruses (HSV), is raising concern due to its pervasive presence in global water and the associated potential risks. ACV can undergo transformation under varying conditions, leading to the generation of diverse transformation products that may exhibit heightened toxicity. This review aims to present a comprehensive overview of the environmental impact of ACV. We compile data on ACV concentrations in different water sources worldwide to shed light on its global prevalence. The levels of ACV detected in both wastewater and natural water sources generally remain at low concentrations, typically in the range of ng L level. ACV poses minimal threats to aquatic organisms and humans in comparison to its transformation products, and conventional wastewater treatment methods utilizing biological processes can reduce ACV concentrations, yet only achieve transformation rather than complete elimination of risks, as the intermediates often demonstrate elevated toxicity levels and increased persistence. Additionally, perspectives are proposed to inspire future research on risk assessment of ACV, its intermediates and other pharmaceuticals. Given the challenges in keeping pace with the proliferation of chemical varieties, prioritizing and optimizing risk assessment methodologies is imperative. To this end, the suitability of ACV indicators is evaluated by summarizing data across diverse water bodies.