How Many Plastic Bags are in the Ocean?

Globally, we use (a shocking) 5 trillion plastic bags each year. That is more than 700 yearly for each individual on earth and 160,000 every second! We use around 100 billion plastic bags each year in the US alone.

Of course, all those bags, usually made from polyethylene, required fossil fuels for production. Petroleum derived, they require these finite and polluting materials to make them. And the energy used in manufacturing usually involves burning more fossil fuels too. Use around 14 plastic bags, and you will have used the same amount of fuel required to drive one mile5.

Yet, we simply throw most of those single-use plastic bags away. Every ton of plastic bags recycled saves the energy equivalent of 11 barrels of oil. But we recycle less than 1% of them.

The plastic bags we throw away often end up in landfills or blow away into the surrounding environments. They join all the other plastics we throw away each year. Ultimately, around 10% of all this plastic waste will end up in our oceans.

An estimated 300 million plastic bags each year end up in the Atlantic Ocean– a proportion of the millions of tonnes of plastic produced that pollutes the oceans globally each year. But exactly how many plastic bags are in the ocean right now is a far more difficult question to answer.

How Plastic Bags End Up in The Ocean

80% of the plastic bags floating in the ocean originated from land, not ships. So it is important to recognize ordinary households' role in creating this problem.

Easily air-borne and buoyant, it is very easy for plastic bags to end up in streams and rivers, blow off shorelines, and make their way into the seas and oceans. Individuals litter them, or the wind blows away from garbage trucks and landfills.

Various types of plastic waste, including plastic bags and food containers, and packaging, account for around 31.7% of the municipal solid waste stream. They are also the most significant component of floating marine debris1 (excepting items less than 5mm, such as pre-production plastic pellets, fragments, and polystyrene pieces).

Related: Environmental impact of plastic water bottles

What Happens Once They End Up in The Ocean

Plastic Bag in the Ocean
Photo by Cristian Palmer on Unsplash

Once plastic bags are floating in our seas and oceans, the current transport them, often into massive ocean gyres of marine debris like the Great Pacific Garbage Patch and the North Atlantic Garbage Patch. Or they are washed up on shorelines around the globe.

It is important to remember that each one of those plastic bags, like all of our plastic trash, can take 1,000 years to break down – a long time, especially considering we use each one, on average, for just 12 minutes.

Though traditional plastic bags won't biodegrade, they will break down into ever smaller and smaller pieces. In the ocean, the sun breaks down these plastics into tinier and tinier pieces, a process known as photodegradation. Over time, they fragment into tiny micro-plastic particles, which are an even more dangerous and insidious problem.

Biodegradable plastic bags aren't the answer either, as they often require certain land-based conditions to break down.

We can no longer recognize, nor even see with the naked eye, many of the plastic bags in the ocean. But they are still there, nonetheless, as tiny micro-plastic particles that have infiltrated every single ecosystem on earth.

Plastic is the most prevalent type of marine debris found in our ocean. Data collected by scientists suggests a minimum of 5.25tn plastic particles in the oceans, most of them "micro plastics" measuring less than 5mm. But more recent work has revealed that this is a major underestimate2. And photodegraded plastic bags make up a proportion of that plastic.

We can find ocean microplastics at every depth within the submarine environment. Some plastics float, some drift underwater, and others make their way down to the ocean floor. It is relatively difficult to keep track of pieces of plastic smaller than 5mm in size. But recent research reveals that ocean current moves these micro-plastics, along with weather patterns and animals – through their digestive tracts.

Researchers have documented microplastics everywhere, from the seafloor to the surface waters of the remote Arctic.

Related: More plastic pollutions facts

The Impact of Plastic Bags in the Ocean

Explorers and researchers have documented the negative impact of plastic bags and other plastic pollution in the ocean. Both in larger pieces and when they degrade to microplastics, plastic bags pose a significant and lasting threat to marine ecosystems, marine wildlife, and human health.

  • Wildlife, such as sea turtles, get entangled in larger pieces of plastic, and these bags can kill or injure them.
  • Diverse marine animals are impacted by plastic waste – from birds to fish, to turtles, to whales – and more – ingest plastic – mistaking the debris for prey. Plastic injures marine animals internally, and frequently, they die of starvation as plastic builds up in their digestive systems.
  • Ingesting plastic also leads to infections and mobility problems for a range of marine mammals and other creatures.
  • We can also implicate floating plastics in the spread of invasive marine species, pathogens, and bacteria, which disrupt ocean ecosystems as plastics break down.
  • Manufacturers use several chemicals in producing plastic materials that we know to be carcinogenic and interfere with the body's endocrine system. This causes developmental, reproductive, neurological, and immune disorders in both wildlife and humans. Yet micro-plastics are in the food chain.
  • Further toxic contaminants also build up on the surface of plastic in the ocean. These enter the food web and also pose a risk to wildlife and (when they eat seafood) people too.

We are all familiar with the ugly sight of plastic washed up on beaches, despoiling local beauty spots, and impacting local tourism. But it is important to understand that the adverse effects of plastic go much deeper and much further.

But Plastic That Reaches the Ocean Doesn't Always Remain There

It is very difficult to track precisely how many micro-plastic particles there are in the ocean (and, therefore, how many plastic bags there are at any one time). These microplastics are everywhere and often on the move, complicating things in other ways.

Scientists have long noticed a discrepancy in the amount of plastic making its way into the ocean and the amounts of plastic they found there.

Now, there is new evidence that the oceans don't hang onto all the plastic that enters them. Collected evidence accounts for some of that 'missing plastic.' We know plastic sticks around. So, where does it go?

A recent study has shown that thousands of tonnes of ocean plastic pollution could be blowing back onto land each year, carried up on land with sea breezes and salt spray3.

Experts estimate that up to 136,000 tons of micro-plastics could be expelled from the sea annually around the world, likely through bubble burst ejection. This is when waves bring air pockets up to the surface and burst, ejecting tiny particles into the atmosphere4. So that 'fresh sea air' might not be as healthy and fresh as you think.

Plastic Bags on Our Plates

Plastic bags on our plates
Photo by Austin Neill on Unsplash

Plastic also leaves the oceans, of course, by entering the food chain, affecting coastal ecosystems and wildlife too. Fish eat plastics; therefore, when we choose to eat them, some of the plastic bags we've used in our lifetimes could end up on our plates.

There is no question that when we eat seafood, we ingest plastic. The only question that remains is what plastic ingestion does to us. The transfer of contaminants between marine species and humans through seafood consumption has been identified as a health hazard. But researchers have not properly studied this concern. However, there is evidence to at least suggest that the plastic bags we throw away could ultimately become a health problem in our very own bodies.

The UN's Food and Agriculture Organisation pointed out in 2014 just how reliant we have become on seafood as a protein source globally. Seafood production is annually increasing at a rate of 3.2%, growing twice as fast as the world population.

This is rather worrying when we consider its viability as a healthy food source is at risk from plastic pollution. Something has to change – and it is increasingly evident that it is our reliance on disposable plastics like plastic bags.

Conclusion

The question of how many plastic bags are in the ocean right now is a difficult and complex one to answer. But it is undoubtedly clear that we should stop using them or even ban them and other disposable plastics immediately.

We should all aim for no more plastic bags. Change is essential for the sake of our oceans, for the sake of wildlife, and for humanity and its future on this planet. And a lot of the power to generate a change in the impact of ocean pollution is in our hands.

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1An Implementation Strategy for the California Ocean Protection Council Resolution to Reduce and Prevent Ocean Litter, California Ocean Protection Council, 2008
2Hurley, R., Woodward, J. & Rothwell, J.J. Microplastic contamination of river beds significantly reduced by catchment-wide flooding. Nature Geosci 11, 251–257 (2018). https://doi.org/10.1038/s41561-018-0080-1
3Allen S, Allen D, Moss K, Le Roux G, Phoenix VR, Sonke JE (2020) Examination of the ocean as a source for atmospheric microplastics. PLoS ONE 15(5): e0232746. https://doi.org/10.1371/journal.pone.0232746
4Allen S, Allen D, Moss K, Le Roux G, Phoenix VR, Sonke JE (2020) Examination of the ocean as a source for atmospheric microplastics. PLoS ONE 15(5): e0232746. https://doi.org/10.1371/journal.pone.0232746
5Secretariat of the Pacific Regional Environment Programme Factsheet: Plastic Bags

Jen’s a passionate environmentalist and sustainability expert. With a science degree from Babcock University Jen loves applying her research skills to craft editorial that connects with our global changemaker and readership audiences centered around topics including zero waste, sustainability, climate change, and biodiversity.

Elsewhere Jen’s interests include the role that future technology and data have in helping us solve some of the planet’s biggest challenges.

Main Photo by Brian Yurasits on Unsplash
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