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"In order to limit our exposure to microplastics, preventative measures are required, such as controlling the environmental discharge of mismanaged plastics and more importantly, reducing plastic waste," Seung-Kyu Kim, a marine science professor and author of the study, said in a statement.
The three brands that did not contain microplastics are a refined sea salt from Taiwan, a refined rock salt from China and an unrefined sea salt produced through solar evaporation from France, National Geographic reported.
The density of microplastics found varied by brand, with many of the salt samples from Asian countries testing higher, National Geographic reported.
The study, led by South Korea and Greenpeace, determined salt from Indonesia, which has some of the worst levels of plastic pollution in the world, tested highest for microplastic contamination, National Geographic reported.