We breathe in and absorb chunks of microplastics all the time, so the suggestion to get rid of their large source looks like a good one. Alas, in reality everything is not so simple: let's try to show why.
Plastic bags are most often made of polyethylene, a harmless and fairly chemically resistant plastic. Packages from it come out light and cheap, so they make a lot - a trillion pieces a year. The main part is thrown into the trash, and only 13% of them are recycled. The rest goes to landfills and on the way there (and even from there) can be blown anywhere. As a result, some of the packages end up in the seas - only in the Atlantic Ocean at 300 million pieces per year. It seems to be a little (not a trillion!).
But the problem lies in the durability of the plastic: under normal conditions it decomposes very little. Therefore, it can accumulate without decomposition in the environment for very many years. In theory, ultraviolet light can decompose it, but if something obscures the bag, its scraps in nature can exist for hundreds of years in a row. It's no coincidence that we said "scraps": plastic bags can lose their integrity under the influence of a number of factors, and scientists have only recently begun to realize the possible scale of the problem.
From 70 thousand pieces of plastic inside each of us
In 2018, researchers in Austria asked eight people from different countries, including Russia, to donate samples of their stool while recording what they ate. As a result, it turned out that every 10 grams of stool contains 20 pieces of microplastics. On average, 800-1000 pieces of plastic with sizes ranging from 50 to 500 micrometers are removed from the human gastrointestinal tract every day - or about three hundred thousand per year. The work was the first of its kind, generally interested in how much microplastics goes through a person. Therefore, she did not have normal funding, and it turned out to attract very few participants. But in the near future, similar studies are expected to be performed on a larger number of people.
On average, 800-1000 pieces of plastic are removed from the human gastrointestinal tract every day - or about three hundred thousand a year.
Note that indirect studies - whose authors preferred not to dig into people's stools, but to calculate the absorption of microplastics by a person based on its content in a typical food - call much smaller numbers. North American scientists have calculated that people eat only 39-52 thousand particles of microplastics a year and inhale 32-69 thousand micro-particles with air a year. In total, one American absorbs one hundred thousand of these microparticles a year. Those who drink water from plastic bottles receive an additional 90,000 particles of plastic per year. Of course, this does not mean that if you drink tap water, there will be no microplastics in it: according to the latest data, in 83% of cases, tap water also contains pieces of microplastics, however, usually a person can swallow no more than four thousand with them. microparticles of plastic per year.
Where does the plastic come from
Microplastic tends to have jagged edges, which indicates its formation by tearing large pieces of plastic - and among the sources, of course, are plastic packaging. A person often cannot see objects made of transparent plastic 500 micrometers in food. Therefore, it fearlessly absorbs it, after which such microplastic is excreted from the body.
While this may not sound particularly pleasant, there is little reason to worry. The stomach and intestines usually keep microparticles out of the rest of the body. If something overcomes this barrier, then there is no data on this yet. However, it is too early to calm down completely: the fact that a person daily excretes a thousand pieces of microplastic from somewhere in him, also became known recently, only a year ago.
Scientists ask questions: "Does plastic enter our bloodstream, the lymphatic system, or even the liver?"
It should be clearly understood: we are at the very beginning of the study of this topic. Scientists who first discovered plastic in human stool are asking troubling questions: "Does plastic enter our bloodstream, lymphatic system, or even liver?" There are no answers to them yet, because no one has yet had time to study the issue. Maybe they do, or maybe they don't.
One researcher notes that in animals, microplastics can interfere with the functioning of the gastrointestinal tract (found in mice) and damage the liver (in fish). However, only polystyrene was evaluated there, while most of the microplastics particles have a different composition. It is not yet known whether pieces of bags consisting of polyethylene are harmful: the necessary experiments on animals have simply not been carried out yet.
That is, while we can confidently say only that plastic bags are harmful to wildlife. A significant portion of the eight million tons of plastic that ends up in the sea each year is in bag pieces. In marine conditions, polyethylene rather quickly receives dimethyl sulfide molecules, which, as a food target, are guided by zooplankton and many more complex animals. Therefore, they actively eat it, accumulating it in their tissues. Most organisms do not decompose plastic, so it simply serves as ballast in them. Occasionally, large fragments of plastic bags can strangle wildlife, including pelicans, other birds, and even individual cetaceans.
Plastic bags are really ubiquitous. But the point is not even that their fragments were found at the bottom of the Mariana Trench. It is not so much pollution that is dangerous, but the fact that sometimes it inhibits the vital activity of the inhabitants of the sea. Among other things, they reduce the activity of marine cyanobacteria of the genus Prochlorococcus - the most numerous photosynthetic organisms on Earth.
What will replace ordinary plastic bags
So, with the harm of plastic inside us, there is no clarity yet, since no one has normally investigated this issue. But the fact that plastic bags harm the inhabitants of the sea seems to be enough to ban them. The question remains: what instead of them?
Most often, two alternatives are offered: the so-called biodegradable and paper bags. The former consist of modified plastic, in theory, biodegradable by a number of bacteria. One problem: experiments have shown that in real conditions, biodegradable bags thrown on the ground decompose very poorly, much like ordinary plastic ones. In general, we have a story with sugar and sugar substitutes: they wanted to replace the greater evil with the lesser, but in the end it is difficult to say what actually became the greater evil.
Paper bags decompose on their own, but this is where their advantages end. The disadvantages are more noticeable: a lot of water is spent on paper production (20 times more than on a plastic bag), energy (almost four times more than on a plastic analogue), and trees have to be cut down. Obtaining plastic bags is low energy, requires little water and does not threaten trees.
In theory, the best solution is to use reusable cloth bags rather than disposable bags that we take at the checkout. Yes, they are much more expensive, but if you use them at least 20 times, then the costs will pay off. If the bag is made of cotton rather than synthetic fibers, then it is also completely biodegradable. Even when you tear it, it cannot harm marine or land animals in the same way as a plastic bag.
One problem: the consumer does not like to strain. To use the cloth bag 20 times, you need to remember it at home. As long as people have an alternative between a disposable bag and a cloth bag, many more disposable bags will be produced.
We are looking for keys not where we lost them, but under the lantern - after all, it is lighter there
One of the main problems with the package ban initiative is that it is far from the most pressing problem of plastic pollution. Plastic PET bottles release phthalates - compounds that interfere with the hormonal system of a wide variety of organisms. As we noted above, a person who drinks water from such bottles swallows up to 90 thousand particles of plastic a year - more than from all other sources of food and water. Why did we focus on bags, the harm from which to humans has not yet been even proven, but ignore bottles?
The most likely answer is that the topic of packages has long been promoted with high quality by environmental organizations. Fortunately, plastic bags entered the life of earthlings a dozen years earlier than plastic PET bottles. But how justified is it to fight this or that problem only on the basis of its hype in the media? Doesn't it turn out that we do not respond to the most pressing issues, but only to those that are best covered in the media?