Microplastics from surgical masks: A piggy-back ride for sulfamethoxazole in the sea

Microplastics can act as carriers for several organic pollutants like poly aromatic hydrocarbons, pesticides, polychlorinated biphenyls, and other persistent pharmaceutical pollutants. It is important to be noted that pharmaceuticals are bio-active substances, structurally modified to induce pharmacological changes in living organisms. These pharmaceuticals pose a threat to the ecosystem and the organisms living in it when not treated effectively. Antibiotic residues may enter the aquatic environment through effluents from sewage treatment plants, application in aquaculture, and other riverine inputs. The transport of one such antibiotic, Sulfamethoxazole (SMX), with the aid of microplastics was investigated in this study.

Surgical masks are made up of polypropylene fibers and they tend to degrade faster in the air as compared to sea-water when exposed to sunlight. Surgical masks are used for medical and personal care purposes and are often disposed of irresponsibly. In this study, the sorption mechanism of SMX onto the mask fibers was observed. The optimum adsorption capacity was analyzed for the microplastics. The effects of pH, salinity, microplastic dose, and SMX concentration were observed. Kinetic models were used to identify the sorption behavior and mechanism. The sorption pattern was then fitted onto linear and Freundlich isotherms. The van Der Waal interactions were probably responsible for the interaction between SMX (hydrophilic) and microplastics (hydrophobic). The results indicate that the microplastics can adsorb up to 15 % of the SMX concentration, when in seawater. The adsorption and desorption of SMX aided by the microplastics from the surgical masks can be interpreted into a transport model for SMX. Thus, this study confirms that aged microplastics when left near the seashore, gradually enter the aquatic ecosystem and act as carriers for pharmaceuticals like SMX. The ability of microplastics to desorb a certain amount of adsorbed contaminant can lead to major health concerns, as the organisms may consume the same, causing complications to health.