In March 2022, many people should have read a news article saying that microplastics were found in human blood. This may sound a little scary at first, but if you think about it carefully, it doesn’t seem strange. Human blood is not a place to be transformed, and it also circulates with the outside world, so why can’t there be microplastics? It has long been reported that microplastics can be detected in feces, and it has been surprising.
What many people worry about is, will the microplastics in the blood be harmful?
In this regard, I can only say now, I don’t know. Our research on microplastics is still in its infancy. In fact, even in the plastics field as a whole, our research on its hazards is not very mature. There are many reasons for the lag in research. One of the reasons is that there are too many types of plastics. Compared with traditional materials such as steel and ceramics, the speed of replacement is faster, and the research content cannot keep up. Of course, the more important reasons are social reasons, which will not be discussed in depth here.
The harm of plastic to human is mainly manifested in two aspects, one is the harm to human living environment, and the other is the harm to human health.
As the title says, we’ve now found traces of plastic in the blood, the atmosphere and the poles. The biggest confusion this question brings us is that plastic has become a part of the global material cycle, which may lead to a new pattern of the earth’s cycle.
It is not easy to understand so abstractly, we are talking about an event that once happened on earth.
Many people should have heard of the term “Carboniferous”. Geologically, it refers to the period of about 360 million to 290 million years ago, spanning tens of millions of years, and there are slight differences between different data. . However, there is no controversy about the characteristics of the Carboniferous period. As the name suggests, a large amount of coal was formed. Most of the coal we excavate today comes from this period.
Why not sooner or later, just at this time? Modern scientific inferences have a lot to do with lignin.
When tall trees just evolved, the earth encountered a very difficult problem. The trunks of tall trees are mainly composed of cellulose and lignin. Cellulose is an old face, but lignin is a new substance. The molecular weight of lignin is not too small or too small, and it cannot be called a polymer, but it is not a small molecule like glycerol. For the microorganisms at that time, this molecule had no way to metabolize, so it could only continue to accumulate.
As a result, the carbon cycle of the earth is disrupted, the carbon dioxide in the atmosphere is getting less and less, but more and more carbon is converted into lignin through trees, and finally buried deep in the ground and becomes coal. This cycle was not repaired until hundreds of millions of years later, because microbes that could break down lignin finally evolved on Earth. During this time, the atmosphere is much more abundant in oxygen due to the lack of carbon dioxide, many species have been eliminated, and the problem of climate change is far more severe than it is now.
It can be said that small lignin has changed the face of the entire earth.
This is of course an extreme case, but it can tell us how important the cycle of matter on Earth is, especially carbon.
Our ecosystems are as helpless when it comes to plastics today as they were for lignin back then.
Therefore, when talking about the topic of environmental protection, people often ask, if there is no degradable plastic, what is the best way to deal with the current plastic? Contrary to what many people think, incineration is the most environmentally friendly method because it forces plastics back into the earth’s cycle in the form of carbon dioxide and water.
On the contrary, when we find that more and more plastics are entering the earth’s circulation in their original form, we have to worry about a question, will those plastic bags floating on the poles be maintained forever? For now, that’s likely to be the case. On the scale of our human life span of just a few decades, it is actually difficult to give an accurate answer. We can only superficially study events with direct cause and effect, such as plastic rings in the ocean that suffocate sea turtles.
When I say “superficial”, I don’t mean to say that such research has no value. It is very valuable, but it is only for individuals, for human beings, we can’t even find the entrance to study big problems now, which is better than what to say. The harm is more serious.
We’ve all heard the popular expression “butterfly effect”: a butterfly in a South American forest flaps its wings and a storm blows in the Pacific Ocean. A butterfly is of course not that powerful, but its perturbations may have a significant impact on the results, because many perturbations will continue to amplify their effects in subsequent evolution. This phenomenon, we now use “symmetry breaking” to describe it. For example, all life on earth only digests D-glucose, and is not interested in its enantiomer L-glucose, which is nothing more than the initial “symmetry breaking”. Without the symmetry breaking, there should be as many organisms digesting D-glucose as L-glucose on Earth.
So, in the spirit of science, we cannot underestimate any cycle of plastic interference, not because of its immediate consequences. I can even speculate that the little bit of plastic found in the polar regions has almost no chance of causing penguins to choke to death, but we cannot rule out that the consequences of this disturbance will lead to the extinction of the species Homo sapiens.
After talking about the impact of the environment, let’s talk about the harm of plastic to human health.
The harm of plastic itself to human health is actually very limited.
The plastics we use now are all based on polymer materials, such as the seven common plastics, their components include: polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyethylene terephthalate (PET), etc. For non-professionals, memorizing these nouns doesn’t make much sense, and even acronyms don’t require much attention.
What we need to know is that these substances are actually harmless by themselves.
Many unknown substances can cause harm to the human body after ingestion, but we now know that the premise of harm is that the substance will undergo a chemical reaction in the body. For example, the so-called allergy is actually a reaction between the immune protein in our body and this allergic substance, which induces an excessive immune effect.
For plastics, think about it, even all kinds of microorganisms can’t metabolize them, which means that the substances in the living body that can react chemically with these things are very rare, so the possibility of them causing harm is extremely low. For example, when we eat a simple breakfast, we will inevitably use plastic bags to pack food. If we bite into the plastic bag and eat it, at most it will be excreted as it is. Unless you eat the whole bag and end up with a bowel obstruction, that’s another story.
However, when plastics are made into finished products, some additives are often required, and these additives may be problematic.
Here are a few common problems that can help us distinguish them in our daily life:
(1) Polyvinyl chloride (PVC, triangular identification number 3): Why is there generally no problem with polymers? This “general” is mainly to exclude Polyvinyl chloride and polycarbonate and epoxy resin to be said below. When PVC is used under improper conditions (such as high temperature or direct sunlight), it may decompose, and the product will be more complicated due to the presence of chlorine in the system. Therefore, PVC is now no longer allowed to be used in food packaging, including polyvinyl chloride cling film, and direct contact with cooked food is not allowed.
Of course, the hidden danger of PVC itself is actually very small. It is banned more because it is a plastic that needs to be added with plasticizers (plasticizers). More than 90% of plasticizers in the world are used in PVC. in plastic. Among the plasticizers, phthalates are commonly used, which may be harmful to the human body (the research results are not clear). Therefore, the abbreviation of PVC still needs to be remembered, and it is used when it is used, but do not use it in kitchen systems, such as hoses for extending faucets, tablecloths, coasters, etc., try to avoid it as much as possible.
(2) Polycarbonate (PC, triangular identification number 7): This plastic has been very popular in the past ten years, because it is restricted by the European Union, and China has also made some follow-ups. The problem is that it uses a substance called bisphenol A (BPA), which is an environmental estrogen. In other words, it is not a hormone itself, but it can act as a hormone in the body.
Research now shows that it is likely to be related to problems such as precocious puberty and teenage obesity. But it is also a very good transparent plastic, especially suitable for milk bottles. If you are still choosing a baby bottle, it is recommended to avoid it. Either choose the one with the word “BPA free”, or choose another plastic, such as PPSU.
(3) Epoxy resin (EP): This plastic is most commonly used in floor paint in life, and its problem is that bisphenol A is used in the raw material, and there may be residues. The opportunity for food to come into contact with EP is mainly the inner coating of the can, so can drinks may be the culprit of excessive BPA in some people. There is no need to pay too much attention to this plastic, and other diet scenes are too rare.
(4) Polystyrene (PS, triangular identification number 6): Polystyrene is divided into two categories, one is transparent polystyrene, which is commonly used in cups on planes; the other is expanded polystyrene, barrels It is commonly used in instant noodles. In the past, we were more worried about the harm of expanded polystyrene, mainly because the foaming agent may have residues. However, the technology at this stage has been able to overcome this problem very well.
(5) Polyethylene terephthalate (PET, triangular identification number 1): Mineral water bottles are commonly used, and there is basically no harm at all, but it is not recommended to drink highly acidic beverages. This is because some PET manufacturing processes still use traditional antimony catalysts. Antimony is a famous element because its element symbol is Sb. Too much intake is also harmful. Acidic beverages are more likely to extract antimony from beverage bottles. Therefore, acidic beverages in PET bottles should be avoided as much as possible.
Here, I recommend glass bottled soda. Generally, the grocery store also provides the service of recycling glass bottles. While ensuring good health, it also reuses resources within its power. By the way, PET recycling is still doing very well.
(6) Polytetrafluoroethylene (PTFE): The trade name is Teflon, which is the coating of the non-stick pan. There is no harm in itself, even if the temperature of cooking is more than 200 degrees, there is no harm. It also has a common name called the King of Plastics. General nitric acid, sulfuric acid, and even aqua regia cannot do anything, so its harm is basically non-existent.
However, if you have seen the movie “Black Water”, you may have a deep impression on this plastic, but in fact, “Black Water” investigates the production process, and a substance called perfluorooctanoic acid (PFOA) is used in the process. , this kind of thing is very harmful to living things. Seriously, because PFOA is used in the production process, no one dares to guarantee that PTFE is completely safe, but in terms of non-stick pan technology, there is no particularly ideal substitute, and PTFE is still the best solution for the time being.
(7) Polyethylene (PE, triangular identification number 2 and 4) and polypropylene (PP, triangular identification number 5): They are all very ideal plastics as food packaging. In the production process, they use some catalysts, involving aluminum and titanium, and the actual harm is really limited. No. 2 PE is HDPE, which is a rigid plastic. It is mainly used for packaging such as shampoo bottles. Generally, it does not come into contact with food, and the auxiliaries will be richer. And No. 4 PE is LDPE, mainly disposable plastic bags, not to mention No. 5 PP, many people know that it is a special plastic for microwave ovens, so the safety of these two types of plastics is very high. However, to be honest, PP and PE are the two most troublesome in the degradation of plastics.
Regarding the hazards of plastics, although the research progress is still in its infancy, there is still a lot that can be said. If we must simply draw conclusions, what I want to say is that, on the one hand, we should not panic because of the possible health problems caused by plastics, most of the hidden dangers advertised in the media are exaggerated; but on the other hand, we cannot underestimate The destructive effect of the plastic problem on the environment is not just the appearance we see now.
In a word, the real harm caused by plastic is measured in hundreds, thousands or even 10,000 years. The results that we can see or predict at present are very limited. I hope our generation can build reliable models. , to guide the production, application and recycling process of plastics more effectively.