Plastic Pollution-Microplastic Pollution

Microplastics found in the body? Not only invade blood, liver and so on, but also what harm does it have?

At last, it's human's turn to micro-plastic pollution.

At a recent meeting of the European Society of Gastroenterology, researchers reported that for the first time, up to nine microplastics were detected in human faeces, ranging in diameter from 50 to 500 microns. This study shows that plastic eventually reaches the human intestine and stomach. This may not be good news for us.

More worrying is that microplastics are ubiquitous. These 5mm or rice-sized plastics come from degraded plastic debris, synthetic fibers and plastic rubber balls. Some studies have found that marine organisms such as tuna and lobster have a large amount of micro-plastics in their bodies, and 83% of the world's tap water samples also have their presence.

Therefore, it is possible for humans to ingest microplastics through the food chain or other means. According to the diaries of eight participants from different countries who participated in the study, they all ate food packaged in plastic and drank bottled water. Six of them also ate seafood. There are 20 particles in every 10 grams of fecal samples. The most common particles are polypropylene (PP) and polyethylene terephthalate (PET), which are the main components of plastic bottles and caps.

Experts say it's not clear where these microplastics come from, and whether they can remain in the body needs further research. However, it is worth noting that the smallest microplastics can enter the blood, lymphatic system and even liver, and the intestinal microplastics may also affect the immune response of the digestive system.

Green turtles swallow plastic. People thought plastic waste would cause marine life to eat it by mistake. Now they have further discovered the problem of microplastics | Troy Mayne / WWF

Microplastics can cause physical damage to organs. The filtered toxic chemicals, such as endocrine interferon BPA and pesticides, can also damage immune function and endanger the growth and reproduction of organisms. Microplastics and toxic substances may also accumulate in the food chain, potentially affecting the ecosystem as a whole, such as the health of planted soils. In addition, micro-plastics in air and water can also directly affect human beings.

More and more scientists are trying to figure out how this extensive and complex microplastic pollution affects animals and ecosystems. From the decline in fish production to changes in soil microbial environment, some compelling evidence is emerging. As researchers accumulate more data, they begin to realize that these findings are just the tip of the iceberg.

Threatening organs and blood

Before 2008, many researchers believed that animals could excrete any microplastics they consumed, such as what he called "unnatural fibers". However, Ecotoxicologist Mark Browne is not entirely convinced. He did an experiment: first put the mussels into the tank, then put in the tiny plastic coated with light-emitting materials, smaller than human blood cells. After the mussels ingested the tiny plastic, they were put into clean water.

Mark Anthony Browne

Microplastics in fish, earthworms and other animals are disturbing enough. But if these particles remain in the body, especially from the viscera to the blood circulation system and other organs, they can cause real damage. Scientists have observed signs of physical injury, such as inflammation caused by particles hitting and rubbing organ walls.

Polymers added in plastic production process will be transferred from micro-plastic particles to the environment. These environmental pollutants (and pesticides adsorbed on the surface of plastic) will be intercepted by micro-plastics. Researchers have found that they can damage organs such as the liver. Ecotoxicologist Marco Vighi and others are testing which pollutants different polymers will absorb and whether they will be ingested by freshwater and terrestrial animals. The total amount of microplastics in lake water and soil is comparable to the amount of microplastics floating on the surface of the ocean - they may exceed 15 trillion tons.

The most important question is whether these physical and chemical effects will ultimately affect the growth, reproduction or susceptibility of organisms. A study published in March showed that fish exposed to microplastics reduced reproduction, as did their offspring when they were not directly exposed to microplastics. This suggests that microplastics can affect the offspring of species.

Researchers have pointed out that some animals are not negatively affected by microplastics, such as freshwater crustaceans of amphipods, which may be able to cope with indigestible natural substances such as stones. For some organisms, some microplastics may be toxic, while others may not.

Most of the studies on the effect of microplastics are carried out in the laboratory, and the experimental time is very short. Researchers usually study only one kind of plastic, which has larger particles than those ingested by organisms and higher concentration than those found in natural environments. However, Martin Wagner, an ecotoxicologist, says that we cannot know the long-term ecological consequences of low-concentration microplastics.

In order to remedy the shortcomings of laboratory research, Wagner and others have carried out outdoor research. They try to match animals with the polymers and pollutants they most likely encounter, and integrate other complex factors in the real world into their research, because microplastics are "not the only source of stress". Microplastics may be the last straw to crush species under pressure from chemical pollutants, overfishing and climate change.

What about microplastics in real scenes?

On the green lawn of a Frankfurt botanical garden, researchers tried to create a chaotic reality scene. They put rows of the same small pools on the lawn and exposed them to the natural environment. Wagner put different micro-plastics into each pool, some of which were primitive polymers, some of which were mixed with pollutants. He wanted to know how freshwater insects and zooplankton lived in the pool.

德国法兰克福歌德大学的户外实验水池 | Martin Wagner

Wagner has not yet observed any significant impact, but he is studying whether there are subtle signs of damage to certain organisms, which can produce a ripple effect in the ecological food web.

This effect can occur even if some organisms seem to be unaffected. Brown's mussels were not harmed in the short term, but he feared that the accumulated microplastics in the mussels would be transferred to their predators. "These particles may not be so friendly to other organisms." He said.

Like Wagner, Brown extends his research to the real world. He and his team collected fish and other organisms from Sydney Harbour and then studied whether they were related to the route of microplastics entering Sydney Harbour. They also tried to find some signs of ecological damage, such as changes in population size. This approach means that organisms can behave normally and expose themselves to typical environmental conditions, such as tides, storms, changes in ocean temperature and industrial pollutants. Wagner said that if microplastics can influence beyond other stressors, we need to really worry about them.

Matthias Rillig, a plant ecologist, has shown how microplastics affect organisms by changing the environment. In a recent co-author paper, he wrote that soil containing polyester microplastics is more fluffy and humid, which seems to affect the activities of certain microorganisms, which are important in the nutrient cycle of the soil. This research is still at an early stage, but it is worth noting because farmers around the world are using microfibre-rich, treated sewage sludge as fertilizer. Lillig and others wanted to figure out how microfibers in the soil affected crop growth.

近距离观看户外实验水池。实验昆虫和其他生物生活在植物和沉积物之中 | Martin Wagner

Inhalation, blood accumulation, microplastics everywhere

Microplastics may pose a more direct threat to humans. A study published in April showed that researchers found microplastics and microfibers in packaged sea salt, beer, bottled water and tap water. Therefore, it is almost certain that humans have been ingesting microplastics. In the process of filling the beverage, micro-plastics will seep into the beverage, and micro-fibers in the atmosphere will also fall into the tap water reservoir. The researchers were shocked: "This shows that we are once again exposing the problem of poor waste management."

Because deliberately allowing humans to ingest microplastics violates ethics, researchers such as Brown have turned their attention to medical research, using microplastics to deliver precise doses of drugs to specific areas of the human body. Through these studies, they can better observe the transfer of microplastics in human body. If the particles are small enough, they may leave the organs and accumulate in the blood. Studies of mice injected with microplastics have shown that these particles can cause thrombosis.

Humans can also inhale microfibers that fall from the air. It is known that air particles can reside deep in the lungs, leading to various diseases, including cancer. Evidence has shown that workers dealing with nylon and polyester fibers are much more exposed to harmful fibers than the general population, their lungs are stimulated and their lung capacity is reduced (although not cancer).

Some scientists believe that focusing on micro-plastics in the human body may lead researchers to miss a more important issue: at least for chemicals added to plastics, such as endocrine interferon BPA, plastic dietary packaging, which humans frequently come into contact with, is a major source of these substances. In other words, microplastics from packaging should also be vigilant.

Other researchers point out that, like many pollutants, the hazards of microplastics are likely to depend on thresholds. Only when they exceed a certain value can they really affect organisms.

Nevertheless, experts say that harmful micro-plastic pollutants are ubiquitous, and that alone is enough for environmental action.