Hospital wastewater as a significant source of microplastics in Northern Iran: Abundance, polymer composition, and environmental risk assessment.

BACKGROUND

Microplastics (MPs) are ubiquitous contaminants increasingly detected in aquatic environments and wastewater systems, raising concerns regarding ecosystem and human health. Hospital wastewater has been identified as a source of MPs entering municipal systems; however, data on their occurrence, characteristics, and associated risks remain limited. This study aimed to characterize MP contamination in hospital wastewater and assess the associated environmental and health risks.

METHODS

Wastewater samples were collected from the influent and effluent of a hospital wastewater treatment plant in northern Iran. MPs were isolated using stainless-steel sieving followed by hydrogen peroxide (H2O2) digestion. Abundance, morphology, and size distribution were determined through microscopic examination, and chemical composition was analyzed using Scanning Electron Microscopy coupled with Energy Dispersive X-ray (SEM-EDX) and micro-Raman spectroscopy. The Pollution Load Index (PLI) and Hazard Index (HI) were calculated to evaluate contamination levels and associated risks.

RESULTS

The analysis showed mean MP concentrations of 21.13 ± 12.8 particles L-1 in the influent and 1.45 ± 0.89 particles L-1 in the effluent, reflecting a removal efficiency of 93.13%. Morphologically, fibrous particles predominated (92-96%), with black as the most common color and sizes below 250 µm being the most prevalent. Identified polymer compositions included polyamide (PA), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and polyurethane (PU). Based on the calculated indices, the hospital wastewater reached a PLI of 1.86 and an HI of 1416.45, which corresponds to hazard level IV, primarily attributed to the high hazard score of PVC (5001) due to its carcinogenic monomer and additive leaching.

CONCLUSIONS

Hospital wastewater is a significant source of MPs, particularly hazardous polymers such as PVC and PU. These findings highlight the need for targeted mitigation strategies, including advanced treatment processes and reduced use of toxic polymers in healthcare settings, to minimize MP discharge and protect environmental and public health.