Plastics have become an inseparable part of human life. Offering many benefits, plastics have over time made our lives so much easier. Contributing to some of the greatest advancements in modern technology, plastics are low cost, durable, and rapidly produced in a wide variety of products and have largely replaced wood, glass, and metal.
Being used worldwide, the global annual output of plastic products reached a staggering 400,3 million metric tons in 2022. China has emerged as the leading producer of plastics, accounting for 32% of global plastic materials, with the rest of Asia accounting for an additional 19%. North America accounted for another 17% of global plastic production, about the same as Europe.
The booming plastic production has also led to a significant increase in pollution, with an estimated up to 70% of plastics ending up in landfills or being mismanaged in the environment. Plastic pollution has become one of the most serious environmental challenges in the 21st century. Of particular concern in the real environment, from extremely complex sources and with many hidden hazards to the environment and even human life, is plastic pollution from microplastics.
What are microplastics?
Microplastics are extremely small pieces of plastic debris in the environment, which results from the disposal and breakdown of consumer products and industrial waste. These synthetic compounds have been micronized into plastic particles smaller than 5 mm in size. Such materials have a low biodegradation rate and mostly remain in the environment.
Primary microplastics enter the environment directly and are plastic products that are manufactured smaller than 5 mm in size. They include products such as tiny microbeads found in personal care products, plastic pellets (also known as nurdles) that are used in industrial manufacturing, and plastic fibers that are used in synthetic textiles, such as nylon.
Secondary microplastics enter the environment as breakdown products of larger plastics, such as the weathering of larger plastics through exposure to the elements.
Nanoplastics: While microplastics refer to plastic particles and fragments with a diameter of less then 5 mm, with particle sizes ranging from a few microns to a few millimeters, miniscule fragments are referred to as nanoplastics when the diameter of microplastics become less than 1 micron. While microplastics are on the scale of micrometers, nanoplastics are mere nanometers in size. (A single nanometer is 0, 000001 millimeters.) Due to their small size, nanoplastics are probably much more dangerous for living organisms than microplastics, as they are more abundant and with their more penetrative physical characteristics, can potentially reach more remote locations and penetrate in living cells. Very little is known about the behaviour of nanoplastics in humans and the environment.
Microplastics consists of carbon and hydrogen atoms bound together in polymer chains. Many other chemicals (such as phthalates, polybrominated diphenyl ethers, and tetrabromobisphenol A) are present in microplastics and many of these chemicals leach out when plastics decompose after entering the environment.
Where are microplastics found?
As microplastics are not biodegradable, they accumulate and persist once in the environment. They have been found in environments such as the oceans, freshwater ecosystems, air pollution, and have even been detected in drinking water, beer, and in food products.
Plastics form the largest part of marine garbage and as recent as 2017 an estimated more than eight million tons of plastic ended up in the oceans. By 2018 microplastics had been found in more than 114 aquatic species, which can cause them to consume less food and may result in neurological and reproductive toxicity. Fish and birds are likely to ingest floating microplastics, by mistaking the plastic bits for food, and microplastics are suspected of working its way up the food chain to large marine predators. Microplastics have been detected in marine species from tiny plankton to huge whales.
Microplastics are found in animals, including in the feces of pets such as cats and dogs. It also exists in plants and a Chinese study has shown that microplastics can transfer from roots to the aboveground parts of rice seedlings.
Humans are exposed to microplastics through the consumption of water, seafood, consumer products (such as salt, sugar, toothpaste, clothing and other fabrics, beer, products stored in plastic bottles, plastic food containers including Styrofoam) and via inhalation from textiles, plastic covers, and synthetic rubber tyres. Microplastics have been detected not only in the lungs and intestinal tract, but also in the blood circulation system and in biological components such as the colon, liver, spleen, and feces. Of particular concern is the presence of microplastics found in the placenta and breastmilk, and even in the feces of infants, which worryingly was found at ten times higher levels than in adults. This means the exposure level of microplastics in infants may be much higher than in adults.
At this point in time no accurate statistics are available regarding all the sources of microplastics, or the total amount of microplastics found on land and sea.
Health effects of microplastics.
Very little is known about the health effects of microplastics on humans and scientists are still unsure whether consumed microplastics are hamful to our health, and if so, what specific dangers they may pose.
Experiments on the toxicology of exposure to microplastics have shown a variety of toxic effects, such as neurotoxicity, oxidative stress, metabolic disorder, reproductive toxicity, and developmental toxicity. Limitations posed by existing technical methods means there is very little systematic research on the potential toxic effects and other health hazards.
In vivo laboratory experiments with human cells and animal experiments have shown that microplastics may affect various systems in the human body:
- The digestive system may be affected when microplastics are ingested and the resulting physical irritation may lead to inflammation in the gastrointestinal tract. It may also cause an imbalance between beneficial and harmful bacteria in the gut, resulting in symptoms such as abdominal pain, changes in bowel habits, and bloating. Toxic substances may enter the body with microplastics and cause chemical toxicity in the digestive system.
- The respiratory system may also be affected when microplastics are inhaled, which may lead to symptoms such as coughing, sneezing, and shortness of breath due to inflammation and low blood oxygen concentration. Airborne microplastics may also act as carriers of toxins, increasing the risk of chronic obstructive pulmonary disease.
- The endocrine system may also be vulnerable to the potential negative effects of microplastics, which may interfere with the production and distribution of hormones in the body and lead to endocrine disorders, such as metabolic disorders, developmental disorders, and reproductive disorders. There are an estimated 1 000 endocrine disrupting chemicals that can interfere with any aspect of hormone action, for example industrial chemicals and plasticizers used in the manufacturing of plastic products.
Recent research (2023) on the impact of microplastics on mice found that microplastics could be as widespread in the body as in the environment. Researchers exposed mice to different levels of microplastics (in the form of pristine polystyrene microplastics) through drinking water, while studying the impact on organs and behaviour.
Of concern is that they found that microplastics accumulate in every tissue they examined, including the heart, lungs, and even deep in the brain tissue, indicating distribution via the blood circulation system. Behaviour changes similar to dementia in humans were also observed, with older mice worse affected than younger mice.
Nobody really understands the life cycle of microplastics in the body and this begs the question – what happens as you get older?
These findings highlight the need for further research to better understand the mechanisms by which microplastics may induce physiological and cognitive changes, concludes the researchers.
Much more research is needed to gain an understanding of the cellular and molecular mechanisms which may be affected by our exposure to microplastics.
Conclusions:
Humans are exposed to microplastics in various ways, but research on the adverse effects of microplastics remain limited and little is known of the impact on human health, which may vary depending on the type, size, shape, concentration, toxic effects, and exposure levels of microplastics.
Microplastics are deemed to be a health hazard, the full extent of which will hopefully be revealed soon through further research.
References:
What are microplastics? Published online and updated 14 December 2023. National Ocean Service. National Oceanic and Atmospheric Administration. USA. (www.oceanservice.noaa.gov)
Microplastics. Published online and updated 10 March 2024. Britannica. (www.britannica.com)
Microplastics. Published online. National Geographic. (www.nationalgeographic.org)
Potential health impact of microplastics: A review of environmental distribution, human exposure, and toxic effects. Published 10 August 2023. ACS Publications. American Chemical Society. (www.pubs.acs.org)
Microplastics ingested in humans can be found in every organ including the brain, new study found. Published 30 August 2023. Euronews. Health. (www.euronews.com)
Acute exposure to microplastics induced changes in behavior and inflammation in young and old mice. Published 1 August 2023. International Journal of Molecular Sciences. MDPI. (Open access publishing, based in Basel, Switzerland.) (www.mdpi.com)
Health effects of microplastic exposures: Current issues and perspectives in South Corea. Published May 2023 in Yonsei Medical Journal (South Korea). PubMed Central. National Centre for Biotechnology Information. US National Library for Medicine. National Institutes of Health. USA. (www.ncbi.nlm.nih.gov)
Annual production of plastics worldwide from 1950 to 2022. Published online with release date October 2023. Statista. (ww.statista.com)
Nanoplastics are potentially more dangerous than microplastics. Published 9 November 2022. Environmental Chemistry Letters, Vol 21, pages 1933 – 1936, (2023). Springer Link. (www.link.springer.com)
Endocrine disrupting chemicals: Exposure, effects on human health, mechanism of action, models for testing and strategies for prevention. Published 3 December 2019. Reviews in Endocrine and Metabolic Disorders. Springer Link. (www.link.springer.com)
HEALTH INSIGHT
