Salt in foods: a definitive source of microplastics to humans

Abstract

The pervasive contamination of the environment with microplastics (MPs) poses a significant threat to food safety as MPs enter and move up the food chain. Understanding the exposure route via foodstuffs is essential. In this study, we analyzed MP contamination in commonly available brands of crystal and iodized powder salts from India and Sri Lanka. MPs were isolated and identified using digestion, filtration, microscopy, and Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy. MPs were more abundant in Indian salt (17.16 ± 8.81 MPs/kg) than in Sri Lankan salt (7.9 ± 6.2 MPs/kg), with crystal salt showing higher MP levels than iodized salt in both countries. Fiber-shaped black and white MPs (< 1 mm) were the most common. ATR-FTIR analysis confirmed the polymer composition, predominantly polypropylene and polyethylene, in both Indian (56%, 24%) and Sri Lankan (42%, 28%) samples. Based on polymer hazard scores, the chemical risk of salts was categorized as level II (Sri Lanka) and IV (India). If a person consumes 5 g of salt per day (World Health Organization), Indians would ingest 0.085 MPs/day (31.025 MPs/year), and Sri Lankans would consume 0.0395 MPs/day (14.4175 MPs/year). The presence of MPs in salts is likely due to the use of contaminated water in production and specific manufacturing processes. Ingesting MPs through daily salt consumption poses a risk to human health, highlighting the need for measures to protect salt sources and improve production processes.