Detection and Characterisation of Microplastics in Food Grade Salts in India

Objectives Plastic waste accumulation is a 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 marine ecosystem, which is a matter of grave concern because marine resources are one of the primary contributors to the 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 the marine environment is through salt, an indispensable ingredient in cooking. This study aimed to analyse commercial brands of sea salt and rock salt for the presence of MPs. Material and Methods A total of thirty different brands of salts available in India were collected and analysed by Nile red fluorescent staining (NR) and characterizing the plastic polymers by Fourier transform infrared spectroscopy (FTIR). Results The results indicate a high prevalence of Microplastics (MPs) in sea salt samples, ranging from 13 to 27 particles/100g, and in rock salt, ranging from 8 to 29 particles/100g. Both plastic microfibers and microparticles were detected, ranging between 2-14 particles/100g and 2-27 particles/100g, respectively. Microplastic sizes varied from 19.45 μm to 512.91 μm in sea salt and 29.69 μm to 1432.85 μm in rock salt. Fourier transform infrared spectroscopy (FTIR) identified polyethylene terephthalate (PET) as the most prevalent polymer (37%) in salt samples, followed by polyvinyl chloride (PVC-25.9%), polypropylene (PP-22.2%), polyethylene (PE -11%), and polystyrene (PS -3.7%). Conclusion 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.