The Basics

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… 

Sources 

https://doi.org/10.1371/journal.pone.0240792 

https://doi.org/10.5620/eaht.e2020004

https://doi.org/10.1016/j.coesh.2017.10.003 

https://doi.org/10.1016/j.scitotenv.2021.145758 

https://doi.org/10.2305/IUCN.CH.2017.01.en 

Guiding Points 

• Microplastics are any plastic smaller than 5 mm 
• They are created by disintegrating plastics  
• Microplastics end up in reservoirs and bioaccumulate in aquatic organisms(fish), attach to organic  compounds, and float in the water until reaching a wastewater treatment facility or water  treatment facility  
• Here, water is run through filters, exposed to bacteria, and allowed to sit in order to filter out  many of the harmful water pollutants we all know of like viruses, bacteria, metals, etc • However, there is no water treatment technology to filter microplastics from the water • The potable water with microplastics leaves water treatment facilities and enters the pipes that  supply our houses with tap water, shower water, etc. 
• 2/3 of the releases are from the erosion of synthetic textiles  
• washing synthetic textiles in industrial laundries and households creates primary microplastics  through abrasion and shedding of fibers. Fibers are discharged in sewage water and end up in the  ocean  
• Tires erode when they are used and particles form on the outer parts of the tire and consist of a  matrix of synthetic polymers mixed with natural rubber plus many other additives • Tire dust will then either be spread by the wind or washed off the road by rain 
• As of now, scientists know microplastics can enter the human body in 3 ways: ingestion,  inhalation, and contact 
• MP are ingested through drinking water (bottled, tap, and Britta-filtered) because there is  currently no technology on the market to filter them from water sources
• MP bioaccumulate in many organisms that are consumed by humans, acting as another source for  MP to enter the human body  
• MP can be found in food packaged in plastic 
• MP can also enter plants when MP in water penetrates the outer-most membrane of plants,  entering the organism  
• MP can enter the human body through inhalation because they are able be airborne when they are  of an appropriate mass  
• The largest source for airborne microplastics is from tire disintegration on roadways • MP can take a home in soil and dust, taking an airborne form when disturbed  • In order for MP to enter the human body through inhalation and penetrate the lungs, they have to  have a length of more than 5 microns and a diameter of less than 3 microns  
• MP can enter the human body through contact with personal care products that contain plastics • In order to enter the body through pores, these MP have to be less than 25 microns