Hidden pathways: Detection and quantification of microplastics across treatment stages of pharmaceutical WWTPs

Recently, it has been recognised that the pharmaceutical industry has emerged as a new source of microplastic contamination, particularly when treated wastewater is discharged into aquatic systems. Microplastics have been widely reported in aquatic animals, the terrestrial environment, and food systems, but the prevalence and characteristics of microplastics associated with the pharmaceutical industry remain poorly understood. This study investigates the degree of microplastic contamination, along with its loading and retention capacity, in samples collected from various treatment processes at five pharmaceutical industrial plants. Microplastics found in influent and effluent samples ranged from 720 to 920 particles/L and 170-490 particles/L, respectively. Similarly, the loading and retention capacities between the influent and effluent range from 0.99 to 1.90 × 10⁸ and 54.76-67.07%, respectively. Microplastics were categorised by size, shape, and color using an optical microscope, with white (3290 ± 765.44 particles), fragment (4270 ± 522.2 particles), and size (100-500 µm) being predominantly identified in all samples of the treatment process. Polymer compositional analysis revealed that polyethylene was the most abundant. Further, the effluent samples were evaluated using a conditional fragmentational model and SEM analysis, which indicates that microplastics may likely be produced by the breakdown of larger plastic material under stressor environmental conditions of EC and pH, which play a role in MPs distribution, polymer characterisation and morphology. Additionally, the environmental risk assessment indicates varying ecological risks posed by effluent microplastics and emphasises the need to mitigate microplastic pollution to maintain ecosystem and human health.