Detection and Characterization of Microplastics in Commercial Salts in India

Abstract

Plastic waste accumulation is an ever-growing menace affecting both aquatic and terrestrial environments. One of the primary concerns associated with plastic pollution is the accumulation of microplastics (MPs) in the ecosystem, particularly in the marine ecosystem. Microplastics pollution in marine environment is a matter of grave concern because marine resources are one of the primarily contributors to human food supply. In addition, the marine environment possesses a plethora of bioactive compounds that are used in a wide variety of products, intended for human use. One of the easiest routes of MPs ingestion from marine environment is through salt, an indispensable ingredient in cooking. This study aimed at analysing commercial brands of sea salt and rock salt for the presence of MPs by Nile red fluorescent staining (NR) and characterizing the plastic polymers by Fourier Transform Infrared Spectroscopy (FTIR). A total of thirty different brands of salts available in India were collected and analysed. The results indicate that presence of MPs is highly prevalent in sea salts with variable number, particles size and polymer types. In sea salt samples, the number of MPs ranged between 13- 27 particles/100g whereas in rock salt, it ranged between 8- 29 particles/100g. Both plastic microfibers and MPs were detected in the categories of samples analysed, ranging between 2- 14 particles/100 g for microfibers and 2- 27 particles/100g for microparticles. The size of MPs ranged between 19.45μm - 512.91μm in sea salts and between 29.69μm– 1432.85μm in rock salt. FTIR Spectroscopy identified polyethylene terephthalate as the most prevalent polymer (37%) in the salt samples, followed by polyvinyl chloride (25.9%) polypropylene (22.2%), polyethylene (11%), and polystyrene (3.7%). This study highlights yet another source of MPs ingestion by humans. Given the fact that salt is a preservative, a taste enhancer, and a source of an essential micronutrient, there is an imminent need for potential mitigation techniques to ensure MP-free salts for human consumption.