On April 7, a research paper published in the Journal of Environmental Science, the top journal in the field of environmental science, showed that a team of researchers led by the University of Hull in the United Kingdom had found microplastics deep in the human lungs for the first time.
What is microplastic? How does it differ from the plastics we know? How is it produced? How does it enter the human body? What is the impact on human health and the ecological environment? How should we deal with microplastics? Science and Technology Weekly interviewed relevant experts to solve the problem.
The "invisible" microplastics are everywhere
Microplastics, first proposed by British scientists in 2004, usually refer to pieces of plastic less than 5 mm in diameter. "Microplastics are actually polymeric materials that are usually not observable with the naked eye, and these tiny particles can float in the air, in tap or bottled water, and in the ocean or soil. People are easily exposed to higher concentrations of microplastics in their homes or in outdoor areas where they are active."
On April 7, a team of researchers from the University of Hull in the United Kingdom released the news that microplastics have been found deep in the human lungs, attracting worldwide attention. "In fact, this is not the first time that microplastics have been found in the bodies of living people." Back in March this year, a research paper published in World Environment, another top journal in the field of environmental science, showed that a team of researchers led by the Free University of Amsterdam from the Netherlands also found microplastics in the blood of human volunteers.
The commonly adopted definition of microplastics is less than 5 millimeters in diameter, however, the microplastic particles that enter the human body and into crops are often at the micron level and nanometer level." The significant difference between microplastic particles and common plastics is that they are tiny and difficult to observe directly with the naked eye, generally with the help of microscopes and other optoelectronic instruments to "find out".
Common types of plastics include polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyethylene terephthalate (PET), nylon (PA), etc. These materials are all very stable chemically. There are many sources of microplastics that we are exposed to in our daily production life, some of them are secondary microplastic pellets that are turned into secondary microplastics after breaking and degradation of large plastics that are more stable in nature. Everyday personal care products such as scrubs, toothpaste, and cosmetics may also contain microplastic particles less than 2 mm in diameter.
In addition, mineral water bottles, household appliances shells may involve PET, while food packaging, take-out containers, plastic bags will involve PS, PE, PP, etc., the use of these products will also be exposed to microplastics. "If these items are discarded into the natural environment, they are degraded and broken over time, creating 'ubiquitous' microplastics."
"Microplastics in the external environment should not be ignored either." For example, washing clothes made of microplastic fibers such as polyester and nylon can also cause microplastic particles to enter the sewage and thus the water cycle; the decomposition of randomly discarded plastic waste in the wind and sun, and car tires rubbing against the road can release microplastic particles into the atmosphere.
Microplastic particles may have an impact on human health
A paper in the journal Science reported that microplastics can enter the human body through inhalation and ingestion. "There are three usual ways for microplastics to enter the body, and the synthetic fiber clothing people wear is actually the most significant intake channel." Synthetic fiber clothes shed microplastic particles when rubbed and enter the body through the respiratory tract. In addition, car tires on the road will likewise shed a large number of microplastic particles, these particles will enter the rivers, lakes and seas with the rainwater and then to the human water supply; chemical coatings used for decoration are likewise not negligible, they will volatilize into the human body. "But bags, plastic film produced by the microplastic particles negligible."
A lightly active male can inhale close to 300 microplastic particles per day, according to an article from the School of Public Health at China Medical University. Cellulose and plastic microfibers can also be seen by pathological examination in cancerous and adjacent lung tissue specimens from lung cancer patients. In addition, microplastics are also found in foods such as salt. in 2015, researchers from some Chinese universities collected 15 brands of three types of edible salt and found that the samples all contained a rich variety of microplastics.
"Microplastics can enter the human body both through food and drinking water, for example, and through the respiratory and food chain." Microplastics have been involved in various cycles of nature. Eating crops or animals containing microplastic particles, encountering microplastic particles in the external environment such as air, water, dust, etc., and coming into contact with scattered microplastic particles when using plastic products can lead to microplastic particles entering the human body.
From finding microplastics in intestinal cells to finding them in placenta, blood and lungs, what exactly are the effects of microplastics on the human body? The professor believes that many microplastic particles are hard and may cause physical wear and tear on the intestinal tract, impacting the immune system and possibly creating aggregates that can cause blockages. In addition, microplastic particles can carry other pollutants or microbial pathogens, etc., which may cause biological toxicity and damage. However, as new pollutants, the specific hazards of microplastics to human beings still need further observational studies and continuous attention.
"Although there is not enough evidence to confirm the toxicity of microplastics to humans, plastic products are sometimes adulterated with various toxic additives to enhance performance during the manufacturing process." The hydrophobicity and high surface area of microplastics allow them to adsorb and accumulate persistent contaminants, forming toxic aggregates. As the release of microplastics into the human body occurs, further verification of whether they cause harm to humans is still needed.
Biodegradable plastics may be able to find a "way out" of the problem
"More than 70 countries and regions around the world, including China, have enacted and implemented 'plastic bans', and in such a context, boosting biodegradable plastics as one of the emerging industries with great development prospects." Microplastic particles "invade" life, become the "sword of Damocles" hanging over the human head, the development of biodegradable plastics may be able to find a "way out", he suggested that the promotion of bio-based biodegradable plastic industry development to deal with the pollution brought by microplastics.
The raw material of biodegradable mulch is mainly starch compound biodegradable polymer material. Under the specific environment of field soil, the mulch can be degraded in a short period of time by microbial action, eventually forming carbon dioxide and water to be returned to nature. "Biodegradable mulch can effectively reduce environmental stress and simultaneously improve crop yield and quality, but its high cost is one of the major limitations to its current large-scale use."
After a series of raw material analyses and comparisons, experts zeroed in on agricultural waste - straw. "The straw was crushed in situ and straw powder was used instead of the commonly used starch and mixed with degraded resin to make the 'foundation' for the new agricultural film." Experts, straw powder and degradation of resin compatibility is poor, like cold water brewing milk powder, the surface floating large and small "milk lumps", can not reach the film conditions. After several technical studies, they found a modification method to solve the compatibility problem, and in the future, the final pricing of this new biodegradable film product will be much lower than the existing fully degradable film.
In addition to this, biodegradable plastics have certain limitations. " Still, clothing made of synthetic fibers, for example, does not meet the needs of people wearing them if they degrade easily. There are also tires and paints that need to have durability, and materials that degrade easily will make the product not last long enough." The development of a biodegradable plastics industry also needs to be combined with durability. In addition, the use of water bottles with filter devices for drinking water, "Filters are able to filter out microscopic substances including microplastic particles and are the most practical tool to deal with new contaminants."
