Scientists have discovered tiny bits of plastic in mussels in oceans across the globe, from supposedly pristine Arctic waters near Norway to the coasts of China, Chile, Canada, Britain, and Belgium, Reuters reported. The findings from several recent surveys are the latest evidence that plastic pollution isn’t just ending up in marine environments, but also in the food we eat.

“Microplastics have been found in mussels everywhere scientists have looked,” said Amy Lusher, a scientist at the Norwegian Institute for Water Research (NIVA).

In a study released earlier this month, Lusher and her colleagues at NIVA reported finding plastics in more than 76 percent of blue mussels sampled at various points along the Norwegian coast. Each mollusk contained on average 1.8 pieces of microplastic — fragments measuring smaller than 5 millimeters long.

In September, scientists reported that sea salt, which is used by many consumers, also is contaminated with small quantities of microplastics.

Someone would have to consume a large amount of shellfish to put their health at risk, scientists said. But unlike fish and other marine life that move around constantly, mussels live on the seabed and stay in one place, which means they are useful indicators of exactly where microplastic pollution has spread.

“It’s a cause for concern at the moment rather than an alarm story for human consumption,” Richard Thompson, a professor at Plymouth University and an expert on microplastics, told Reuters. “It’s a warning signal that we need to do something about reducing the input of plastic to the ocean.”