The amount of plastic in our oceans—and thus in our seafood—is rising. The authors of a forthcoming study say Europeans alone ingest about 11,000 microscopic pieces of plastic apiece every year. And unless we make some very big changes, that number could reach 780,000 pieces per person within a few decades.

Microplastics, also known as microbeads, are popular additives to a wide range of personal care products, from face wash to toothpaste. We rinse them off and send them down the drain, where they head out into the water supply. And there they’ll stay, absorbing chemicals, until something or somebody comes along and eats them.

Studies have found that fish that consume microbeads are smaller than others. They reject real food in favor of more plastic. Their eggs are less likely to hatch, and hatchlings are less likely to escape predators.

Researchers at the University of Ghent in Belgium have been studying the effects of microplastics on shellfish like mussels, oysters, and clams, all of which are filter feeders. The average mussel sucks in and spits out about 20 liters of water per day. Most of the plastic particles in that water will be filtered and sent back out into the ocean. Most, but not all; lead researcher Colin Janssen says the mussels they examined had an average of one tiny plastic fragment apiece.

Janssen and his colleagues say the same process occurs in humans who consume shellfish. About 99 percent of the microplastic will pass through your system. That still leaves 1 percent to stay in the body, and we don’t yet know what that means for our health.

“We do need to know the fate of the plastics,” Janssen told Sky News. “Where do they go? Are they encapsulated by tissue and forgotten about by the body, or are they causing inflammation or doing other things? Are chemicals leaching out of these plastics and then causing toxicity? We don't know."

Experts estimate we’re currently dumping one garbage truck’s worth of microplastic into the ocean every minute. By 2050, there could be more plastic than fish in the sea [PDF]. We’ve started to take some steps—in 2016, Congress voted to ban microbeads altogether—but we’ve still got a lot of work to do.

"We have to do something about it,” Janssen said. “We have to act now."