Scientists have discovered that various brands of table salt sold in China contain a range of plastic pollution, which might make food unsafe.
The highest proportion of plastic was found in sea salt, according to a paper from researchers at Shanghai’s East China Normal University. But even salt from salt mines, briny lakes, and wells contained significant amounts.
“Microplastics are a particular threat to organisms due to their small size and their capacity to absorb persistent organic pollutants,” said the report, led by Shi Huahong of the university’s Institute of Estuarine and Coastal Research and peer-reviewed in Environmental Science and Technology (pdf).
Shi and his colleagues discovered between 550 and 681 microplastic particles per kilogram of table salt that originated from the ocean, 43 to 364/kg in lake salts, and 7 to 204/kg in rock or well salts. Here is a rather gruesome photograph of their findings:
Although the oceans close to China appear to be a “hotspot” for microplastic pollutants, it is unlikely Chinese table salt is the only salt that is contaminated with plastics.
“Plastics have become such a ubiquitous contaminant, I doubt it matters whether you look for plastic in sea salt on Chinese or American supermarket shelves,” Sherri Mason, an environmental science researcher at the State University of New York Fredonia told Scientific American. “I’d like to see some ‘me-too’ studies,” she added.
People who follow World Health Organization guidelines on salt intake (most in the US consume much more) would consume around 1,000 microparticles of salt annually, Shi estimates. It’s not yet clear what kind of damage such consumption could mean for humans—if it causes any damage at all. Regarding the impact of microplastics on human health Richard Thompson, a professor of marine science and engineering at England’s Plymouth University, told the Environmental Health Perspectives journal that “there are more questions than answers.”
And indeed, other foods from the sea, such as shellfish, also contain microplastics, but people concerned about plastic intake can just stop eating those foods. The prevalence and necessity of salt in our diets makes cutting out those microplastics much harder.