Even though plastics have existed for only about a century, its products have spread around the globe. Latest findings estimate that every year about 13 million ton plastic waste is discarded in the oceans. This marine plastic wastes have not only created global environmental problems but are also found to have adverse effect on economy, health and culture.
It takes hundreds of years for these plastic wastes to decompose; however, during this time, they get disintegrated into smaller sizes creating micro-particles which have a diameter of less than 5 millimeter. These microplastic particles have a damaging effect on marine organisms and products, and are considered as global environmental pollutant. Numerous scholars have stated the presence of microplastics in various marine and freshwater products such as clams, fulmars, mussels, marine and freshwater fish. Several products consumed by humans are obtained from the sea. Microplastics can contaminate these products and enter our body. For example, European shellfish consumers are seen to ingest up to 11,000 plastic particles every year. Moreover, these microplastics have recently been discovered in deep-sea creatures, indicating the exposure of deep sea to human plastic waste.
Some of the important products obtained from the sea are:
- Precious stones, gems and pretty collectibles such as seashells and sea glass
- Materials used in household products such as kelp and sea sponges
- Ingredients of skin care products for example red and brown algae, and seaweed
- Products with medicinal properties like corals
- Sea sand used in construction industry
- Edible salt, a very important food ingredient
- Oil and gas for household, industrial and transportation usage
- Copper, nickel, silver, platinum and gold from deep sea mining
One of the most important products obtained from the sea is salt, in which the primary constituent is sodium chloride, but also has around 0.5 to 10% (concentration may vary in commercially available salts) of other salts like calcium, potassium, and magnesium salts of chloride and sulfate. Salt is the principle source of sodium ions which is essential for maintaining nerve and muscle function and is also involved in the regulation of body fluids, blood pressure and blood volume, and thus plays significant role in maintaining good human health.
Manufacturing process of salt consists of pumping saltwater into evaporation ponds, and concentrating it by the action of sun and wind. This leads to formation of salt crystal bed which is cut and subjected to various physical processes before its packing.
Several types of salts according to their origin are:
- Sea salt
- Lake salt
- Rock salt
- River or well salt
The occurrence of microplastics in saltwater bodies, sea creatures and even in human bodies is relatively well studied, but its presence in edible commercial salts has been reported only recently. Some of the works published are:
- Iniguez et al. analyzed 21 commercial table salts from Spain comprising sea salts and also well salts, before and after packing. They determined about 50–280 microplastic particles per kg salt, which were predominantly polyethylene-terephthalate, polypropylene and polyethylene.
- Karami et al. extracted microplastic particles larger than 149 μm size from 17 different salt brands obtained from 8 countries followed its identification using micro-Raman spectroscopy. They discovered 1 to 10microplastic particles per kg of salt, which were mostly common polymers such as polypropylene and polyethylene having mean particle size of about 515 μm.
- Gundogdu tested 16 brands of table salts, for microplastics, obtained from the Turkish market using microscopic and Raman spectroscopic examination techniques, and determined 16-84 microplastic particles per kg in sea salt, 8-102 microplastic particles per kg in lake salt and 9-16 microplastic particles per kg in rock salt; wherein, most common polymers were polyethylene and polypropylene.
- Kim et al. hypothesized that the presence of microplastics in commercial sea salts can act as indicators of its pollution in the surrounding environment unless these are filtered out during production. They investigated 39 commercial salt brands from geospatially different sites – 16 countries/regions on six continents, and determined 1674 microplastic particles per kg in sea salts, 148 microplastic particles per kg in rock salt, and 28–462 microplastic particles per kg in lake salt; wherein, highest content was identified in sea salts produced in Asian countries/regions.
- Yang et al. collected 15 different types of salts such as sea salts, lake salts, and rock/well salts from supermarkets throughout China, and found 550−681 particles/kg in sea salts, 43−364 particles/kg in lake salts, and 7−204 particles/kg in rock/well salts; which were predominantly fragments and fibers.
- Seth et al. collected samples from eight brands sea salts in India, and determined concentrations of microplastics ranging from 100 to 50 particles kg−1 of salt, which were mostly polyesters, polyethylene terephthalate (PET), polyamide, polyethylene, and polystyrene having fragments size smaller than 500 μm.
- Lee et al. utilized fourier transform infrared spectroscopy to determine concentration of microplastics in Taiwanese commercial table salt and found about 9.77 microplastic particles/kg of the same, and were identified as polypropylene, polyethylene, polystyrene, polyester, polyetherimide, polyethylene terephthalate, and polyoxymethylene.
- Tahir et al. examined 7 Indonesian sea salts and discovered them to be contaminated with 54 particles/kg of the salt which were majorly polyvinyl acetate (41.7%), polyethylene (33.3%) and polystyrene (25%).
Thus, it can be confirmed from above studies that even the salt we eat is contaminated with microplastics, hence we can say that those who don’t eat seafood have also consumed microplastics in all probability. This is really alarming!
Some of the points to be discussed further could be:
- How can the salt production technique be improved to eliminate microplastics in salts?
- Can a study be performed to find microplastics in final packed salt product sold at the retail stores?
- Can a study be performed to find microplastics in final consumed food product, which has this salts added in them?
- At what rate this microplastic particles are increasing or decreasing every year?
Dear Readers, do go through the above literature and let me know your viewpoints in the Comments section.
Thanks for reading!
I put up a new post whenever I come across an interesting topic, so follow my blog and stay updated about the developments in the polymer industry.
- Iñiguez, Maria E., Juan A. Conesa, and Andres Fullana. “Microplastics in Spanish table salt.” Scientific reports 7.1 (2017): 1-7. https://doi.org/10.1038/s41598-017-09128-x
- Karami, Ali, et al. “The presence of microplastics in commercial salts from different countries.” Scientific Reports 7 (2017): 46173. https://doi.org/10.1038/srep46173
- Gündoğdu, Sedat. “Contamination of table salts from Turkey with microplastics.” Food Additives & Contaminants: Part A 35.5 (2018): 1006-1014. https://doi.org/10.1080/19440049.2018.1447694
- Kim, Ji-Su, et al. “Global pattern of microplastics (MPs) in commercial food-grade salts: sea salt as an indicator of seawater MP pollution.” Environmental science & technology 52.21 (2018): 12819-12828. https://doi.org/10.1021/acs.est.8b04180
- Yang, Dongqi, et al. “Microplastic pollution in table salts from China.” Environmental science & technology 49.22 (2015): 13622-13627. https://doi.org/10.1021/acs.est.5b03163
- Seth, Chandan Krishna, and Amritanshu Shriwastav. “Contamination of Indian sea salts with microplastics and a potential prevention strategy.” Environmental Science and Pollution Research 25.30 (2018): 30122-30131. https://doi.org/10.1007/s11356-018-3028-5
- Renzi, Monia, and Andrea Blašković. “Litter & microplastics features in table salts from marine origin: Italian versus Croatian brands.” Marine pollution bulletin 135 (2018): 62-68. https://doi.org/10.1016/j.marpolbul.2018.06.065
- Sivagami, M., et al. “Extraction of microplastics from commonly used sea salts in India and their toxicological evaluation.” Chemosphere 263 (2020): 128181. https://doi.org/10.1016/j.chemosphere.2020.128181
- Zhang, Jixiong, et al. “Identification and quantification of microplastics in table sea salts using micro-NIR imaging methods.” Analytical Methods 10.24 (2018): 2881-2887. https://doi.org/10.1039/C8AY00125A
- Tahir, A., et al. “Microplastics in water, sediment and salts from traditional salt producing ponds.” Global Journal of Environmental Science and Management 5.4 (2019): 431-440. https://dx.doi.org/10.22034/GJESM.2019.04.03
- Sathish, M. Narmatha, Immaculate Jeyasanta, and Jamila Patterson. “Microplastics in Salt of Tuticorin, Southeast Coast of India.” Archives of Environmental Contamination and Toxicology (2020): 1-11. https://doi.org/10.1007/s00244-020-00731-0
- Lee, Hyemi, et al. “Microplastic contamination of table salts from Taiwan, including a global review.” Scientific reports 9.1 (2019): 1-9. https://doi.org/10.1038/s41598-019-46417-z