Antibiotic resistance occurrence and ecological impact in landfill leachate: A review on compound effect of antibiotics and non-antibiotics

Landfilling remains one of the primary methods for managing municipal solid waste (MSW), processing approximately 350 million tons of waste annually. Among the various components of landfill waste, pharmaceuticals and personal care products (PPCPs), including both antibiotics and non-antibiotic compounds, pose significant environmental challenges. Landfill leachate is a highly complex medium, consisting of diverse contaminants such as non-antibiotic pharmaceuticals (average concentration ∼1.74 μg/L), antibiotics (average concentration ∼527 ng/L), heavy metals, dissolved organic matter, and micro/nano-plastics (concentration range 0.64–2.16 mg/L). This unique mixture can alter the native microbial community structure, profoundly impacting antibiotic resistance, potentially disrupting soil and groundwater ecosystems, and threatening ecological balance. Existing research has extensively investigated the composition, physicochemical properties, environmental behavior, and microbial community structure of landfill leachate, leading to significant advancements in the field. However, due to the complexity and large volume of landfill leachate, current risk assessment approaches predominantly rely on conventional pollutant indicators, and most treatment strategies are designed for general contaminants. There is a lack of systematic descriptions that integrate pollutants with their direct impacts on microbial communities. This review focuses on the current pollution status, spatiotemporal trends, interactions, and migration risks of antibiotics and non-antibiotic pollutants in landfill leachate. In particular, we explore the in situ emergence of antibiotic resistance in landfill leachate (rather than the horizontal transfer of antibiotic resistance genes) and examine the influence of various leachate components on antibiotic resistance. By emphasizing the importance of understanding the combined effects of antibiotics and non-antibiotic pollutants in landfill environments, this review highlights the necessity of long-term ecological risk assessments for antibiotic-induced resistance as an emerging contaminant.