Seven tons. That’s how much plastic a study from The Citadel estimates is breaking down in Charleston Harbor right now.

It’s bad enough that so much trash is littering a body of water so important to local commerce, recreation and ecology.

But according to The Citadel researchers, natural processes may be turning those tons of plastic into a serious health risk to marine animals — and potentially humans too.

Sun, waves and other processes break down larger pieces of plastic into smaller bits, some of which are too small to be seen by the naked eye. Those tiny pieces, which are broadly referred to as microplastics, can be eaten by animals like shrimp or periwinkles and make their way up the food chain.

Aside from the obvious dangers to marine animals that ingest microplastics, their presence in shrimp, fish and other sources of food poses an unknown risk to human health.

Tackling one source of the problem, the federal government banned plastic microbeads earlier this month. The tiny beads had been used as abrasives in face washes, toothpastes and other cosmetic and hygiene products, but trillions of them end up in rivers, lakes and coastal waters each year.

Banning microbeads was unquestionably the right move, but it’s not likely to make a big dent in the larger problem of plastics clogging the planet’s waters.

And the problem is very large.

A recent, widely-publicized study from the Ellen MacArthur Foundation, a non-profit promoting sustainable economic practice, and the World Economic Forum estimates that at least 8 million metric tons of plastics are dumped into earth’s oceans every year.

That’s the equivalent of a garbage truck full of plastic emptying into the ocean every minute around the clock.

And as the world’s population continues to grow and more people move out of extreme poverty, the amount of plastic being improperly disposed each year is expected to increase dramatically over the next few decades.

To compound those alarming statistics, other recent studies have found microscopic particles of plastic in drinking water, juices and even beer.

Scientists aren’t yet sure exactly how drinking or eating microplastics affects human health in the short or long term, but there is plenty of cause for concern.

“Microplastics have the potential to both sorb and desorb chemicals in the marine environment; these chemicals may be persistent, bioaccumulative and toxic,” states a recent report generated from an expert discussion hosted by the federal Environmental Protection Agency (EPA).

Indeed, some plastics contain toxic or carcinogenic chemicals like bisphenol A, phthalates and dioxin that can be released when they are heated or broken down. And small pieces of plastic have been shown to absorb other toxic chemicals, including by-products of coal-fired power plants and industrial flame retardants, from water.

In other words, the seven tons of plastic in Charleston harbor and the 8 million tons per year that enter waters around the world are a potentially serious public health threat.

Fortunately, there are ways all of us can help tackle the problem.

Communities and individuals can make an extra effort to recycle more plastic, for example. And people can reduce unnecessary plastic consumption by choosing products with minimal packaging and using reusable bags and other items instead of disposable alternatives.

Charleston’s waters are critical to the region’s economic prosperity and quality of life. Plastic trash has no place in such an invaluable natural resource.