too—being swept up to great heights, traveling  with the wind, and raining back down on Earth. 

And now an international team  of scientists have figured out  

where they're coming from—and the places are  probably not what you'd expect. But how does  

all this plastic in the air affect our health?

Let's start with the basics. Microplastics  

are tiny specks of plastic less than 5  millimeters long—think anything shorter than the  

width of a pencil eraser. They come in two main  categories. The first type is known as primary,  

which are already small plastics, like glitter,  and are directly released into the environment.  

The other type is secondary microplastics,  which form when larger plastics degrade. 

Most plastics are broken down through  weathering, like when they're exposed to waves,  

wind abrasion, and UV radiation. And depending on  the type of plastic, it can take up to hundreds  

of years to break down, if at all. And because  microplastics are so tiny and lightweight, they  

can be transported over long distances globally.

-We were really interested  

in first understanding how much plastic is  being deposited. But then we wanted to ask,  

Where is it coming from? How long can  it stay in the atmosphere? And how is  

it getting into the atmosphere to begin with?

So, Dr. Brahney and her colleagues tackled  

those questions using atmospheric  transport modeling and data from  

sampling sites in the western United States.

-We estimated that somewhere between 1000 and  

4000 tons of microplastics are being  deposited into Western protected areas. 

And this is the equivalent to about 100 million  to 400 million plastic bottles every single year. 

The team found that 84 percent of those  microplastics likely originated from roads. With  

the rest coming from oceans and agricultural dust.

So, why are we seeing so much microplastic  

coming from roads? Well, roads and  the cars that drive on them provide  

the mechanical energy needed to make plastic  airborne. As you're racing down the highway,  

tiny bits of tire and other microplastics  stuck to your tire fling off and fly away. 

-I think of it much like the way  people move sand away from a beach,  

cars can move plastic away  from cities, and then also  

move those plastics high into the atmosphere.

-We're already seeing the negative effects  

of microplastic pollution. Limited research  has also revealed that microplastics affect the  

health of plants and animals, which has impacts  on the entire food chain. And as microplastics  

clutter our land, waterways, and atmosphere in  higher concentrations, we'll have to monitor  

if and how they might change atmospheric  processes too. There's also the unsettling  

potential of how they could be affecting us.  Some of these microplastics are small enough  

to be inhaled into the human pulmonary system.

Once these tiny plastics get into the body,  

they can have quite a big number of effects.  Some larger microplastics can be filtered out of  

our respiratory system when we cough, sneeze, or  blow our nose. But limited research suggests that  

smaller microplastics can reach and remain  in the respiratory system, and continued  

exposure to plastic, like when you're working in a  synthetic fiber factory, can lead to inflammation,  

lesions, and respiratory conditions.  

Unfortunately though, we don't have 

enough info on how everyday exposure to plastics  affects us. I.E. not in a plastic factory. So,  

some scientists are trying to find out more.

In 2019, an international team of  

scientists used dummies to mimic the  inhalation of microplastics indoors.  

The study found microplastics in every sample  of air. A more recently published study from  

Florida State University focused on the impacts  of microplastic exposure on the cellular level.  

After exposing human lung cells to  polystyrene microplastic spheres,  

the team saw their metabolic processes slow down  and rings of microplastics form around the nuclei. 

But none of the cells died. These studies are still  

very limited, but they are getting us closer  to understanding how the accumulation of  

plastic in our environment, particularly  our atmosphere, is affecting human health. 

What we know for sure is that if our plastic  production and consumption continues to grow in  

the coming decades as expected, plastic pollution  will increase too. And we're just starting  

to understand what those impacts will be. -Well, I think we can't ever begin to start  

mitigating an issue until we really understand it.  So understanding not only how plastics are  

being deposited and moving through the atmosphere,  but how they're getting into the atmosphere is, is  

really critical for us mitigating the  amount of plastics that are emitted. 

-If you want to learn more about the creative ways  scientists are combating COVID's plastic problem,  

check out that video here. Let us know in  the comments what else you want to know  

about microplastics. Make sure to subscribe to  Seeker for more groundbreaking science news.  

Thanks so much for watching and  I'll see you next time on Seeker.