Microplastics in Salt of Tuticorin, Southeast Coast of India

Microplastics (< 5 mm) are considered to be global environmental pollutants. This study investigates the occurrence, physical properties, polymer composition and surface morphology, and element composition of MPs present in food-grade salts produced from seawater and bore-well water in Tuticorin, Tamil Nadu, Southeast coast of India. Fourteen different brands of sea salts and bore-well salts were collected from the salt manufacturing units. The mean abundance of microplastics was 35 ± 15 to 72 ± 40 items/kg in sea salt and 2 ± 1 to 29 ± 11 items/kg in bore-well salt. Four types of polymers viz. polyethylene (51.6%), polypropylene (25%), polyester (21.8%), and polyamide (1.6%) were found in salt. Polyethylene fibers of size ranging from 100 to 500 µm were observed commonly. Being manufactured from seawater, sea salt had the highest quantities of different microplastic particles. The study reveals that people consume approximately 216 particles of MPs per year via sea salt and 48 items per year via bore-well salt if the average person has a daily salt intake of 5 g. The surface morphology of MPs as exhibited in the SEM-EDAX images obtained in the study revealed the different weathering features of MPs, such as pits, cracks, and particles adhering to the surface. The presence of the elements Fe, As, and Ni on the surfaces as identified by energy-dispersive x-ray spectroscopy indicates that these elements exist in the environment as contaminants and have become associated with the MPs. The trace metals adsorbed onto MPs increase the risks of human exposure and may cause some adverse effects in humans.