Humans make plastic by using chemical reactions to turn petroleum into the compounds we call “plastic”. These compounds made from petroleum become plastic products we use in our everyday lives, like water bottles, car tires, and clothing. When plastic products are used, they undergo abrasion, weathering, exposure to UV radiation, and disintegration, creating microplastics (MP), and eventually nanoplastics (NP). Microplastics exist at a size of 0.1 microns to 5 millimeters. Nanoplastics are the result of further wear on microplastics and range in size from 0.001 microns to 0.1 microns. Because of their size and mobility through water and air, MP and NP can be found on every inch of the planet, including land untouched by human activity.
The three main sources of MP include plastic pellets, tires, and synthetic textiles. Plastic pellets are the initial products created in the transformation of petroleum to plastic; they are 2 to 5 millimeters in diameter or can be found in powder form. Once petroleum is converted into raw plastic material, the pellets are transported to factories to be turned into everyday items. They unintentionally enter the environment during transportation to factories, manufacturing, and are also emitted from factories through air and water as pollutants. Plastic is the primary component of tires. Tires undergo constant abrasion during use, causing them to slowly break down and leave small pieces of plastic, MP, and NP on roadways. These MP and NP are washed into the surrounding land during rainfall or become airborne. Lastly, synthetic textiles used in clothing, like nylon and polyester, create MP and NP through abrasion and shedding of fibers as the fabrics are run through washing machines. Wastewater and fibers from washing machines enter public water systems and oceans without undergoing filtration.
It was not until recently that the scientific community began to investigate the interactions between microplastics, the environment, and living organisms. In the past few years, scientists became aware of three ways MP and NP can enter the human body: ingestion, inhalation, and contact with skin or eyes. Humans ingest MP primarily through drinking water, but also through the consumption of animals and plants. Unfortunately, MP remain present in food no matter how they are cleaned or prepared. Scientists have proven that when crops are irrigated with water containing MP, plants are able to uptake MP and NP because of their small size. MP and NP pass through the plant cell wall, membrane barriers, and settle within the cells of plants.
Additionally, due to the presence of MP and NP in the oceans, organisms at the bottom of the food chain, like plankton, mistake MP for food, and ingest them. Small fish will then consume those plankton containing MP and also unknowingly consume other MP in the ocean, thinking they are food. A bigger fish will then consume the smaller fish that contains MP from the plankton it ate and from the MP it ate on its own. As the cycle continues and we move up the food chain, the concentration of MP in organisms increases due to both bioaccumulation happening on the individual organismal level and biomagnification taking place within the food chain. Lastly, humans consume the organisms from the top of the food chain and ingest all the MP and NP that have been passed up the food chain.
However, most MP that reside in humans, enter the body through ingestion of clean drinking water. Water treatment facilities do not have the technology to remove plastic particles that are smaller than approximately 50 to 150 microns, which is dependent on the filtration methods used. Water that comes from the tap, a water fountain, refrigerator, bottle of water, or any other source, all contain MP and NP; even an at home water filter is unable to remove MP and NP from water. Additionally, MP and NP can enter the human body through inhalation. MP that have a length of more than 5 microns and a diameter of less than 3 microns can remain airborne and penetrate the lungs when inhaled by a human. Lastly, many personal care products contain MP and NP. Hand lotions, soaps, face cleansers, and shampoos have MP in their core make up, and when applied, can enter the body through pores if they are less than 25 microns. MP have also been found in eye contact saline solution. When the solution meets the eye, the MP will penetrate it and be absorbed into the blood stream.
These 5 micron or less particles that can enter the human body through ingestion, inhalation, and contact, later enter the bloodstream, accumulating in cells and organs, leading to oxidative stress, DNA damage, and inflammation; it is speculated that MP attribute to or cause cancer, autism spectrum disorder, endocrine disruptions, and a handful of other diseases.