Plastic Bags in the Ocean

Vijayalaxmi Kinhal
Plastic Grocery Bag

The hazard of plastic bags in the ocean is greater than ever before. Studies show new effects and are revealing the extent of the problem it poses.

Plastic, Plastic Everywhere!

Plastic has become an integral part of people's lives. It is single-use plastic packages, especially bags, that are a matter of grave concern as they are used for a few minutes and then thrown away rather than being recycled. Their use can be reduced or avoided completely. The bags' buoyancy carries them from landfills and dumps. They reach streams and rivers and finally enter oceans explains a 2017 National Geographic report.

Global Reach of Floating Plastic

Ocean currents do the rest, transporting them as part of the trash that is accumulating in oceans. Plastic has even reached remote parts of the world with little or no populations, so that no part of the world is free of them anymore. The British Antarctic Survey has reported the presence of plastic wastes, including bags and wraps that stem from floating plastic debris on and around this remote continent.

Plastic bags are the largest component of the marine plastic debris according to Clean Water.

Number of Single-Use Plastic Bags

Plastics Europe estimates that 40% of all plastic produced is used for packaging which are single-use containers and bags (pg.15). While plastic wraps and bags, single and thicker grocery bags account for 17.5% of plastic produce (pg. 16). Demand for all kind of plastic is growing.

It is however not easy to peg the number of plastic bags used and discarded, as there are different estimates of its annual use.

  • Waste in the sea
    A 2003 National Geographic release reported that 500 billion to one trillion plastic bags were consumed every year. During the same time period World Watch estimated 4-5 trillion plastic bags were used every year worldwide, with USA and Europe together using 80% of bags.
  • There seem to be no recent reliable estimates, with these two figures still circulating in the media after ten years. The Earth Institute Policy pegged the number of bags used every year in 2014, still at 1 trillion, and the Ocean Watch Australia estimate in 2017 for number of plastic bags used annually stands at 5 trillion plastic bags.
  • The U.S. was estimated to consume 100 billion bags in 2014, more recent estimates stand at 360 billion bags per year, according to an EPA blog. EPA-Plastic (pg. 3) reports that only 10 % of thick or HDPE bags and 5% of thin bags are recovered, so the rest goes waste.
  • Extrapolating with the help of estimates from the 2017 National Geographic report that 79% of plastic in landfills ends as free floating waste worldwide (6.3 billion tons), it can be estimated that the U.S. is responsible for 327 billion bags that goes into the seas. And the global contribution to ocean debris is 3.95 trillion bags each year.

It is likely that the number of plastic bags used and that end up in the ocean are in fact higher.

Decomposition Time of Plastic Bags

The length of time needed for bags to decompose completely depends on their composition, and the conditions they are exposed to.


As Mercer explains, thicker bags are made from PET or type 1 plastic, and high-density polyethylene (HDPE) also called type 2 plastic, while the thin produce bags are made from low-density polyethylene LDPE or type 4 plastic. LDPE are more difficult to recycle and so their collection rate is also less.

The New Hampshire Department of Environmental Services writes that "Once in the water, plastic never fully biodegrades" and includes an estimated decomposition time for plastic bags at 10 to 20 years. However, depending on the bag's composition, it could take upwards of 1,000 years.


All plastic types break down faster if they are exposed to sunlight, than if they get buried underground or under sand points out ABC News. Water, rain, and other environmental conditions also hasten this process adds

As part of the process, the plastic breaks into smaller pieces, and finally into polymers that it is made of and all these phases make it a danger to marine life.

Effect on Marine Life

Plastic bags affect marine life in different ways, and have already led to the death of hundreds of thousands of marine animals according to Ocean Plastic. Being buoyant bags float on water or accumulate along coasts.

  • Jelly-fish look-alike: Sea turtles mistake floating plastics for their prey the jellyfish, and are most likely to consume them. It has been proved that turtles actually seek plastic bags out mistaking them for food . This causes the animals to choke to death, or die of hunger when the bags clog their stomachs, reports Center for Biological Diversity. Once these animals die, the undecomposed plastic bag can be re-eaten by another animal. So a single bag can kill more than once according to Ocean Crusader. It is not just turtles, but also dolphins and whales that are choked or starved to death due to plastic bags.
  • Route to the sea-bed: Though intact bags stay on the ocean surface, once the plastic bags break down to small pieces they are eaten by fish and other animals that travel to deeper waters where they themselves get eaten by larger marine animals. Another way plastics bag reaches the ocean floor is through faecal matter that sink down explains a 2017 scientific review. So plastic bags and their deleterious effects are not confined to the ocean surface alone.
  • Food-flavored plastic pieces: Smaller pieces of plastic because they do not decompose soon, act as a place where microbes and algae grow, which are used as food by small marine animals. Once plastic gets coated with microbes and start to smell like food are sought out by small fish and other marine animals according to Guardian. These plastics ultimately reach people's table inside seafood.
  • Seagull Holding Plastic Bag On Beach
    Plastic ingestion is one effect of ocean pollution on marine life and this includes eating plastic bags. Small pieces of plastic can come from different plastic articles, so it is also difficult to separate effects for just plastic bags. The ABC News reports that 90% of birds have eaten plastic at some time in their lives.
  • Ecosystem affects: Plastic bags - both the non-degradable and the bio-degradable ones - deposited on coasts are affecting whole ecosystems finds a 2015 study. The place under them has little oxygen, nutrients and also sunlight. This affects growth of algae and there are only one-sixth of animals like worms and crabs in these areas compared to open areas.

Gyres in the Ocean

Many of the plastic bags are also driven by ocean currents as part of the debris that is accumulating in many oceans of the world. Because of the ocean currents, shape and sizes of these gyres can be dynamic explains the National Oceanic and Atmospheric Administration. Nevertheless, gyres have been found to stretch for millions of kilometers. There are five massive sub-tropical gyres in the oceans. Besides them there are many smaller gyres that are also formed. The Pacific Ocean has many such garbage patches in it.

A Matter of Individual Choice

Of all the type of plastics, single-use shopping bags are used primarily by individuals and the consumption is direct. Since single use bags are a matter of individual choice, people can tackle this problem alone without help and involvement from the government, industry or supermarkets, by simply saying no to plastic bags.

Plastic Bags in the Ocean