and it's a very difficult problem to control, because they are so prevalent.

- [Michelle] The proof of how reliant we've all become on plastic can be found at the bottom of Narraganset Bay.

Researchers at the University of Rhode Island estimate the top two inches of the floor of the bay contain more than 1,000 tons of microplastics.

Plastic pieces less than five millimeters in diameter.

- That has been accumulating over the past 10 to 20 years.

And so, plastics are coming into the bay, they float through the water, and eventually, they land on the seabed.

And so over time, they're accumulating at these really high concentrations, because we just keep using plastics and the sources are not being mitigated.

- [Michelle] Doctoral student Victoria Fulfer said the levels were shocking.

She and JP Walsh, director of URI's Coastal Resources Center, published their study earlier this year.

Using a toad sled, they documented just how much debris lies in the water.

They found the upper parts of the bay near Providence contain higher concentrations of plastic waste than the lower bay.

- Plastics come from people.

And in Rhode Island, we have a really dense population, particularly surrounding the Northern Bay.

So, inherently there's going to be more plastic that can make its way into the bay - And before they end up at the bottom of the bay, many are littered throughout Rhode Island's beaches, including Rocky Point State Park in Warwick.

What did you find here?

- So, here we have a bottle cap and one of the rings that goes around a milk carton container.

I see some fragments of plastic and food wrapping, things like that.

Very common items to find.

- [Michelle] As debris makes its way into the water, Fulfer says it's slowly breaks down over time into microplastics then microscopic organisms like zooplankton confuse it for food.

- I've published a study looking at the impact on zooplankton, which form the base of the food web, and we're seeing that they are growing at much lower rates, they're reproducing less, and they're not living as long.

If there are less zooplankton, that's less food for fish.

And you know, that obviously, has far reaching implications.

- [Michelle] Fulfer says more research is needed to determine whether microplastics are causing the decline in the zooplankton population.

Still, she's concerned about how those small plastics are affecting marine life and humans.

- We eat seafood and unfortunately, marine organisms are eating microplastics and then we eat them.

And so, there's potential that we are ingesting microplastics when we eat our food.

- It's troubling to Jaime Ross as well, an assistant professor of neuroscience at URI.

She's been studying the health effects of microplastics in mammals.

- There's not really anything known about plastics on brain health and neurological disease, and also, the lifecycle of plastics in the body.

- [Michelle] Ross and her team exposed mice, young and old to microplastics in drinking water over the span of three weeks.

After observing them in an open field, researchers found ingesting microplastics cause the mice to have changes in their behavior akin to dementia in humans.

- The young adult animals and the older adult animals, they both did things that they shouldn't.

They spent a lot of time in the center of the arena.

Mice are not supposed to really do that.

- Did any of that surprise you?

- For three weeks of exposure it did.

I thought perhaps if you're chronically exposed for months and months, maybe you would see something like this, but only three weeks was really shocking to us.

- [Michelle] Ross's team also learned the plastic particles had begun to bioaccumulate in every organ in the mouse, including the brain.

- The fact that they are crossing the blood-brain barrier, which really is supposed to keep out bad things from the brain, including viruses and bacteria.

The fact that they were able to sneak in there was almost alarming to us.

- [Pamela] The mice that ingested microplastics had a decrease in glial fibrillary acidic protein, known as GFAP a protein that supports many cell processes in the brain.

- It suggests that the microplastics could be changing the environment in the brain, and the brain is reacting to them in a way that could point to changes in cognition down the road.

- Both Ross and Fulfer say there's an urgency to the work they're doing.

- I think we're going to see a wide range of ecosystem impacts, if we continue to create plastic and allow it to get into the environment.

I think eventually, you would see widespread collapse of shellfish and fisheries.

- [Michelle] Inside her lab, Fulfer has slides full of microplastics She's collected from Narraganset Bay ranging in size, shape, and color.

Many of the fragments are items we all use.

- So, three of the main types we found were polystyrene, which you might be familiar with as the white foam that we use in packaging, polypropylene and polyethylene.

And polypropylene and polyethylene are really common types of plastic used specifically in single-use plastics.

So, those are our takeout containers, our coffee cups, things like that.

- [Michelle] Littering is one way these plastics are getting into the water, but Fulfer says it's bigger than that.

- Microplastics take all kinds of forms, so we can have particles which are formed from the breakdown of larger items like bags or bottles, but we also have microfibers, which mostly come from your clothing.

And so, a lot of our clothing is unfortunately synthetic now that makes it last longer and have different qualities.

So, we like to use it, but unfortunately, when you wash your clothes, those microfibers are being released and going into the wastewater.

- [Michelle] That's why Ross says she tries to buy cotton fabrics when possible.

Among other changes she's made.

- I really try to always purchase a product that's not in plastic.

I try not to store our food in plastic.

I try not to drink out of plastic.

Sometimes these things are not avoidable.

- [Michelle] As Ross continues her research, there are several key questions she's eager to answer, including where do microplastics go once they enter the body, and how long do they stay there?

- Another question is, are they really contributing to this large uptick that we see in society of a lot of different inflammatory diseases and neurological disease?

Are they contributing to our health in a negative way?

- To be clear, it's not known, if microplastics can leave the body or how to get rid of them, right?

- Right, right.

- Ross hopes further analysis will shed light on the far reaching effects of these materials.

- And I think we need to really understand that black box of what are plastics doing to us and what plastics do we really need as a society for healthcare, for example, and what plastics can we part ways with and say, "We don't need this.

This is just to the benefit of packaging.

This is not really helping us."

And we need to find an alternative, either source or get rid of it.

(suspenseful music) - Finally, as we mentioned last week,