Check out some shower gel, and it might have lots of little bits in it. Most of the time, these are tiny spheres of plastic called “microbeads.” Designed to scrub your body and remove dead skin, they’re not just found in shower gel – cleaning products, facial scrub, and even toothpaste often contains them too. They might seem harmless and insignificant, but collectively trillions are being washed into our sewers and polluting our rivers and oceans every day.

“We're facing a plastic crisis and don't even know it,” says Stephanie Green, who co-authored the paper on microbeads published in Environmental Science and Technology. “Part of this problem can now start with brushing your teeth in the morning. Contaminants like these microbeads are not something our wastewater treatment plants were built to handle, and the overall amount of contamination is huge. The microbeads are very durable.”

The world’s oceans are being filled with microplastic, which is any piece of polymer less than 5 millimeters in size. Normally, these result from the break down by UV light of larger pieces that are floating in the oceans, but microbeads are a separate, distinct issue. No bigger than a grain of sand at around 1 millimeter, microbeads are not something our water treatment plants were designed to filter out from waste water.

As a result, the new study estimates that around 8 trillion microbeads a day in the United States alone make their way into lakes and rivers. But that is just a tiny fraction of the problem, as 99% of the tiny bits of plastic – around 800 trillion pieces – get caught up in the sewage treatment sludge, which is then spread on agricultural fields. Rain subsequently washes many of these back into the waterways.

But what effect does this have? Well, many aquatic animals such as fish can’t tell the difference between the tiny pieces of microbeads and their prey, meaning they often consume large quantities without even knowing it. On top of that, the plastic can act as a sponge, soaking up toxins from the water that then end up in the fish. And eventually, the fish end up on our plates.

This has led the authors of the new study, along with many conservationists and ecologists, to call for a ban on microbeads in cosmetic products. It is estimated that a single care product, like Neutrogena's Deep Clean, contains 360,000 of the things, which could be replaced with a biodegradable alternative, such as crushed nut shells or even salt. In fact, many states have already banned the sale of products containing microbeads, but more needs to be done to remove them all together.