John Metcalfe was CityLab’s Bay Area bureau chief, covering climate change and the science of cities.
People could be eating about 1,000 pieces of plastic annually, say Chinese researchers.
Humanity’s done a good job of trashing the ocean with trillions of microplastics—degraded material from packaging, beauty products, fishing gear, and other stuff—and now the seas are returning the favor, contaminating edible sea salt with bits of polyethylene terephthalate and cellophane.
This dismal discovery was made by researchers at East China Normal University and elsewhere, who write in a new, government-funded study about worrying plastic concentrations in salts at Chinese supermarkets. They filtered 15 brands of commercial salt, including lake and rock varieties for comparison, and found as many as 681 plastic particles per kilogram of sea salt. Using World Health Organization diet guidelines, they calculate sea-salt users could be unintentionally consuming roughly 1,000 pieces of plastic a year.
The most prolific foreign objects they found were fibers and fragments, with the majority measuring under 0.2 millimeters and shaded red, blue, white, and black. The rock and lake salts showed concentrations of plastic from 7 to 204 and 43 to 364 particles per kilogram, respectively. Polyethylene, PET, and cellophane were among the most common adulterants, though a wavelength analysis detected other fun stuff, like polyalkene, ethylene vinyl acetate, and polyester—the latter suggesting you could be eating the remnants of somebody’s ugly, 1970s-era pants.
These findings suggest China’s got a serious microplastics infestation, something researchers have known for a while; sediments in the southern island province of Hainan have shown up to 8,714 particles per kilogram, and Hong Kong’s beaches are teeming with as many as 5,595 pieces per square meter of seawater.
Of course, with plastic littering the world from the bottom of the ocean to the Arctic to the Great Lakes, it’s not just China’s problem. Microplastics have been found in honey from Europe and Mexico, and a study last year on contaminated mussels and oysters estimated Europeans ingest as much as 11,000 microplastics each year.
What are the health impacts from this inedible “seasoning”? That’s not clear, but they’re probably not good, the researchers write:
Microplastics are a particular threat to organisms due to their small size and their capacity to absorb persistent organic pollutants. The constituents of plastics, as well as the chemicals and metals they absorb, may ultimately be ingested by humans through the consumption of seafood. Due to the pollution of seawater, many contaminants have been found in sea salts, including plasticizers, such as di(2-ethylhexyl) adipate and benzyl butyl phthalate. Plastic might be the direct sources of these contaminants. However, plastics might absorb contaminants from the seawater and transfer them to the sea products. Therefore, the presence of marine microplastics in sea salts might pose a threat to food safety.