The average adult ingests about 2,000 microplastics each year through table salt, a study estimates. That’s because the same study found that microplastics were present in 90% of table salt brands sampled worldwide. It’s next to impossible to avoid adding plastic to your baked potato when you sprinkle it with salt. 
Researchers in South Korea and Greenpeace East Asia tested 39 salt brands and found microplastics in 36 of them. The team also used previous studies to help track the spread of microplastics in table salt around the globe and their correlation to the heaviest concentrations of plastic pollution in the environment.
Seung-Kyu Kim, a marine science professor at Incheon National University in South Korea, said:
“The findings suggest that human ingestion of microplastics via marine products is strongly related to emissions in a given region.”
Kim and colleagues gathered salt samples from 21 countries across Europe, North and South America, Africa, and Asia. The 3 brands that didn’t contain microplastics were sampled from Taiwan (refined sea salt), China (refined rock salt), and France (unrefined sea salt produced by solar evaporation).
Different brands of salt contained different densities of microplastics, the study shows. Asian brands were found to contain particularly high densities. Salt sold in Indonesia contained the highest quantities of minuscule plastic bits, and the finding makes sense as there are (literally and figuratively) tons of microplastics littering the waters around Asia. As of 2015, Indonesia’s 34,000 miles of coastline ranked 2nd-worst in the world for plastic pollution.
Sea salt was found to contain the most microplastics, followed by lake salt and rock salt, respectively.
An Unsavory Seasoning
So, the average person ingests about 2,000 pieces of microplastics from salt every year, but that’s just from salt. Humans likely wolf down far more plastic than that. 
Microplastics have been found in tap water, mollusks, and both indoor and outdoor air. Researchers believe those 4 pathways alone add up to about 32,000 pieces of microplastic per person, per year. About 80% of the microplastics people ingest come from inhaling them through the air.
That means that table salt only accounts for approximately 6% of the microplastics ingested by people every year.
A separate British study that sought to assess the risks of microplastics to the environment concluded that, well, more research is needed to determine if microplastics are harmful.
In August, a study published in the journal PLOS One showed that plastics emit methane and ethylene, both greenhouse gases, as they degrade. 
Then, a study published in September showed that birds and winged insects can carry microplastics through the air and contaminate a broader range of the environment. This also allows animals that would normally be untouched by plastic pollution to eat the tiny particles and pass them up the food chain.
But microplastics have been working their way up the food chain for decades, as aquatic life consumes the minuscule bits. If fish are ingesting microplastics, that certainly means that humans that eat the fish are ingesting them, too.
 The Scientist