Microplastics have been a significant environmental concern in recent years. As they emerge as a global environmental pollutant, they have gained the interest of researchers worldwide. In the past ten years, many efforts have been made to understand what are microplastics. This term has been used previously across different research areas. These tiny particles are often invisible to the naked eye. They have been detected in oceans, rivers, and the atmosphere. But what are microplastics, and where do they come from?
What Are Microplastics?
Small plastic particles that measure less than 5 mm in size are called microplastics. In oceans and lakes, plastic is the most common form of debris. Some microplastics come from the breakdown of large plastics. Microplastics are found in many products such as synthetic clothing, cosmetics, plastic bags, detergents, paints, diapers, pesticides, and bottles.
Microbeads are tiny polyethylene particles, a type of microplastic that is intentionally added to cosmetic products like cleansers and toothpaste for exfoliation. These particles enter the water filtration system and flood oceans and lakes, potentially harming aquatic life. [sources]
Properties of Microplastics:
The following are the properties of microplastics. Microplastics are polymer chains of hydrogen and carbon atoms. Most plastics are synthesized from polypropylene, polystyrene, low/high-density polyethylene, sodium polyacrylate, polyvinyl acetate, polyvinyl chloride, polyethylene terephthalate, etc.
Some chemicals, such as tetrabromobisphenol A and polybrominated diphenyl ethers, are also present in microplastics. Many of these chemicals enter the environment by leaching out from the plastics. Due to the small size of 5 mm, microplastics easily spread into air, water, and soil.
Microplastics break down slowly and persist in the environment for decades. They are hydrophobic and allow the absorption of harmful substances such as pesticides and pollutants from the surroundings. Microplastics are lightweight and float on water, so they travel long distances and spread globally. They have diverse shapes, including beads, fragments, and fibers, which depend on how they degrade.
Classification of Microplastics:
There are two types of microplastics:
- Primary Microplastics
- Secondary Microplastics
What are Primary Microplastics?
Microscopic synthetic polymers or tiny plastic particles are manufactured for different purposes and used as exfoliants in many processes. Primary microplastics are used as scrubbers and have replaced natural ingredients like almonds, oatmeal, pumice, brown sugar, and coffee in exfoliating cleansers and facial scrubs. They are found in personal care products such as cosmetics.
Primary microplastics are used in synthetic textiles as fiber plastics. They are used in air-blasting technologies. In air-blasting techniques, small plastic particles like melamine and polyester are used to remove rust and paint from machinery and engines. As these scrubbers break down over time, they become contaminated with heavy metals like cadmium, lead, and chromium. Moreover, some microplastics are used in medicine for drug delivery.
What are Secondary Microplastics?
Secondary microplastics are particles that form from the breakdown of larger plastic items. The physical breakdown, mechanical and biological degradation, and photo-oxidation damage the structure of large plastic debris into smaller particles undetectable to the naked eye. This process is called fragmentation.
The different shapes of particles prove that fragmentation plays an important role in their formation. Due to fragmentation, the particles can become even smaller, with sizes of 1.6 micrometers. A recent study proves that biodegradable plastics create more microplastics than non-biodegradable ones. Microplastics enter the ecosystem by washing synthetic clothes. Tires are also made of synthetic rubber, and when used, tiny particles enter the environment.
Nanoplastics:
Tiny plastic particles smaller than 1 micrometer or 100 nanometers are defined as nanoplastics. It is still unclear whether nanoplastics are byproducts of the breakdown of larger plastics or another invisible environmental concern. These particles have been detected in the North Atlantic Subtropical Gyre. New techniques are being developed to measure the amount of nanoplastics in the environment.
These techniques include nano-FTIR and atomic force infrared. Fluorescence technology is the best and quickest way to identify and measure nanoplastics. Nanoplastics pose potential risks to both the environment and human health. These tiny plastic particles are lipophilic, so they embed in cell membranes and affect cellular function.
Some studies prove that nanoplastics cross cell membranes and accumulate in different fish organs, like the pancreas, brain, and gallbladder. Moreover, it has been proven that polystyrene nanoplastics trigger stress responses in zebrafish and change cortisol and glucose levels. Nanoplastics have the ability to absorb harmful substances like antibiotics, which can cause the spread of antibiotic-resistant bacteria.
Are Microplastics Bad for You?
Primary and secondary microparticles are persistent and difficult to remove from the environment. Different studies show that microplastics are harmful to organisms because they cause poisoning, reduced feeding, and increased mortality. They also contaminate the food chain, which has serious consequences for human health. Microplastics have been found in oceans, rivers, air, and even in human bodies.
Once microplastics enter the environment, they accumulate because they do not break down. Microplastics have been discovered in over 114 species in marine and freshwater ecosystems. These tiny plastics cause reproductive and neurological problems in humans. They enter the food chain and travel from small marine creatures to larger predators. They have also been found in drinking water and human tissues. The situation is alarming, and scientists are unsure about the exact impact of microplastics on human health.
Reducing Microplastic Pollution:
Policymakers in many countries are taking steps to reduce microplastic pollution in the environment. The UK banned all products containing microbeads in 2018. The goal of the European Chemical Agency was to reduce microplastic pollution by 400,000 tons in 20 years. So, in 2019, they also took steps to ban a variety of intentionally added microplastics.
To address the problem of increasing plastic waste ending up in landfills and the environment, the United Nations Environment Programme started raising awareness of plastic pollution in over 100 countries. This awareness includes recycling and reducing plastic use.
International programs have been established to tackle marine waste, including microplastics. The United States passed the Microbead-Free Waters Act in 2015, which banned plastic microbeads in rinse-off cosmetics.
Where Do Microplastics Come From?
Cleaning Up Microplastics Already Present in the Environment:
How can we reduce existing microplastics already present in the environment? This is the key part of addressing microplastic pollution. The use of certain bacteria and fungi that break down synthetic microplastics like polystyrene, polyester, and polyethylene is a promising strategy. Some species of bacteria, such as Pseudomonas and Ideonella sakaiensis, and fungi like Aspergillus and Penicillium, can degrade synthetic plastic polymers.
These microorganisms produce enzymes that break down the chemical structure of plastics and reduce the amount of microplastic pollution. These organisms are potentially useful for reducing contaminants in the environment. This biodegradation approach is natural and more effective for reducing microplastic pollution.
