Pharmaceutical-microplastic interactions in soil environments: a critical review of emerging co-contamination dynamics

The simultaneous presence of pharmaceutical compounds (PCs) and microplastics (MPs) in soil environments poses a significant yet understudied environmental challenge with critical implications for soil health, agricultural sustainability, and human exposure pathways. Despite widespread co-contamination through overlapping input pathways, current risk assessment frameworks treat these contaminants independently, potentially underestimating combined environmental risks. This review was conducted to map research trends and to synthesize current knowledge on PC-MP interactions specifically in soil environments, examining their individual behaviors, interaction mechanisms, and combined effects on soil processes and biological activities. Agricultural soils serve as major reservoirs where PCs exhibit variable persistence ranging from days to years, while MPs alter key soil properties, including water retention and aggregation patterns. While aquatic studies demonstrate that MPs transport PCs via adsorption and co-transport processes, terrestrial research remains limited, with complex and sometimes conflicting results regarding MP influence on PC dissipation rates. Bibliometric analysis revealed that soil-specific studies represent only 19% of PC-MP interaction research, with significant geographic disparities in scientific attention, particularly in arid and semi-arid regions facing acute contamination risks. Critical methodological limitations, including over-reliance on simplified experimental systems, short exposure durations, and single-PC focus, hinder understanding of real-world behavior. Key research priorities include standardized analytical protocols, environmentally relevant exposure scenarios, long-term field studies, and mechanistic exploration across diverse soil types and climatic conditions. Addressing this escalating co-contamination issue requires interdisciplinary efforts to develop integrated risk assessment frameworks and evidence-based policies that protect soil health and ensure agricultural sustainability globally.