Microplastics (MPs) are small particles less than 5mm, resulting from the degradation of various large plastic items, manufacturing pellets, tyre wear, and synthetic textiles.
Microbeads are tiny pieces of plastic added to some health and beauty products as exfoliants. In 2015, the U.S. banned the use of microbeads, but microplastics still remain a huge problem.
Microplastics can be
- present in various places like air, water, soil, animals, food and beverages.
- part of tyres that can end up on roads and in the purification systems
- found in synthetic fibres from clothing that can find their way to water bodies and the ocean.
- harmful to the environment, threatening aquatic/marine life and other ecosystems, and to human health as well.
- ingested through food and drink, and inhaled, or absorbed through skin contact.
- the cause of a range of health issues, including cancer, autoimmune diseases, endocrine disorders, reproductive problems, and metabolic disorders.
Types
MPs include different thermoplastic polymer plastic types, such as:
- polyvinyl chloride (PVC)
- polyethylene terephthalate (PET)
- polyethylene (PE)
- polypropylene (PP)
- polystyrene (PS).
Microplastics (MPs) is an umbrella term for microplastic (MP=<5mm) and nanoplastic (NP= 1nm-1micron) particles, so sometimes the term macro-nano plastics (MNPs) is used.
A study showed that people consume an average of 39,000–52,000 MP particles per year from different foods, and if inhaled, microplastic particles are added to this, the number can rise to around 74,000 particles.
For drinking tap water, another 4000 particles are added, while for drinking water bottled in plastic, the number increases by 9000 particles. This is likely to be an underestimation, and in reality, the values could be much higher.
The pandemic caused by COVID-19 has affected not only human health and national economies, but the environment as well, due to the large volume of waste in the form of discarded personal protective equipment. The remarkable increase in global use of face masks, which mainly contain polypropylene, and poor waste management have led to worsening of microplastics pollution.
Role in Cancer
MPs can play a role in the pathogenesis of cancer. Microplastics cause inflammation, oxidative stress, and DNA damage at the cellular level. Data from animal studies have shown that once absorbed, plastic micro-nanoparticles from MPs can distribute to the liver, gut, heart, lungs, thymus, reproductive organs, kidneys, and even the brain (crossing the blood–brain barrier).
In addition, MPs are transport operators of persistent organic pollutants or heavy metals from invertebrate organisms to other higher trophic levels. After ingestion, the additives and monomers in their composition can interfere with important biological processes in the human body and can cause disruption of the endocrine and immune system, which can have a negative impact on mobility, reproduction, and development, and thereby possibly cause of cancer.
In humans, due to long-term microplastic exposure most common cancers that can develop are colorectal, lung, breast, ovary, and skin cancer.
Summarized evidence supports the idea that oral macro-nano plastic exposure causes intestinal epithelial damage, chronic intestinal inflammation, and colonic mucus layer disruption that facilitates its passage into the bloodstream, thus contributing to the toxic effects on different organs, and platelet activation, which may, in turn, contribute to the chronic development of inflammation and colorectal cancer development.
In human lung primary alveolar macrophages, 0.2–2 µm PVC particles consistently reduced the cell viability and were found to be cytotoxic and pro-inflammatory. It is therefore likely that prolonged exposure of the epithelial barrier to MNPs can contribute to the development of lung disease and cancer.
Experiments showed that MPs were internalized into the skin squamous cell carcinoma cell line in a time- and dose-dependent manner and promoted the proliferation of skin cancer cells.
Precautions and Protective Measures
MP pollution should be dealt with a combination of remediation and preventive measures. While remediation helps to clean up the environmental damage caused by the pollution, preventive measures attempt to curtail further pollution. Bioremediation, the use of microorganisms to break down MPs via hydrolysis, has been proposed to reduce microplastic-contaminated environments, particularly soil.
Bioretention cells, which are depressions in the ground where stormwater runoff is collected and treated, have been proposed as an effective method of removing MPs from urban stormwater and have been shown to achieve a median 84% decrease in MPs. Eliminating the overuse of compost and fertilizer could help reduce soil contamination with MPs.
In order to achieve a reduction in plastic usage, countries are currently introducing regulations and bans on the most commonly used single-use plastic items and replacing them with alternatives like ceramic and glass wherever possible. There is also a possibility of cancer risk in using tea/coffee paper cups, as they have a coating of thin film made of PFA, which again is a carcinogen. Such regulations are also needed for the use of plastics in packaging materials.
A few countries have banned microbeads (the United States Congress introduced the Microbead-Free Waters Act in 2015 to prohibit the manufacturing, packaging, and distribution of rinse-off cosmetics that contain plastic microbeads, while Australia phased out microbeads in 2020). In its fifth assembly, convened in 2022, the United Nations Environment Assembly (UNEA) unanimously agreed on developing a legally binding treaty to combat plastic pollution, undoubtedly the most important development related to MP pollution in its entire history.
The 3R slogan (reduce, reuse, recycle), with proper disposal of the rest of the waste, is an excellent effort. Daily vacuuming, recycling clothes, and choosing sustainably sourced natural materials while buying new clothes, switching to glass/ceramics, etc., are some useful individual measures. However, the challenge is that MPs are not responsive to, and escape from, most of the waste management methods currently in use, mainly due to their size and origin. Although enhanced recycling can help to address the larger issue of plastic pollution, it is of limited value to stop microplastic pollution.
Therefore, novel concepts and innovative methods need to be developed and added to policies. Enhancement of plastic waste management activities cannot guarantee results until all MP escape routes within waste management processes are shut. For this, the escape pathways and relative proportions of MP flows through these routes need to be researched and evaluated. Other important measures include obtaining additional data needed for prevention planning, closing the MP loop between landfills and wastewater treatment plants, enforcing quality control measures on recovery and cycling associated with plastics, and proper disposal of unattended plastic items.
Dr Ankit Jain is a Senior Consultant Medical Oncologist, Indraprastha Apollo Hospital, Delhi and Ex-Senior Consultant Medical Oncologist, NHS UK.
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