What are Microplastics?

In this Article (Index)

Plastics pose a health risk.

• What are Microplastics?
• Ubiquitous plastics: They are everywhere
• The effect of Microplastics on the body
• Nanoplastics
• MPs and gut microbiome
• Effect on Lungs
• Effect on the Skin
• Closing Comments

What are Microplastics?

Microplastics (MPs) is a term that was coined in 2004 and is used to describe small fragments of plastic up to a size of 5 millimeters (mm) or 1⁄5 of an inch, and as small as one micrometer.
1 micrometer or 1 μm (1,000 μm = 1 mm) as a reference, one human hair is about 100 μm diameter.

They are tiny particles of plastic formed from the degradation of plastic objects.
Bottles, spoons, plastic wrappers, flipflops, straws, cups, glasses, toothpaste tubes, caps, tires, paint, clothes, most of our daily articles are made from man-made polymers known as plastics, and they suffer the wear and tear of use and when they are discarded, they can be broken down into small particles: microplastics.

Some are produced intentionally, and used as ingredients in cosmetics, called exfoliants to remove dead skin, or in makeup to add sparkle and texture. These are called Primary microplastics.

Others, called Secondary microplastics, are produced when tires wear away abraded against roadways, when paint chips off walls, is sanded, or when clothes lose tiny fibers when they are washed.
Some plastics are recycled, not many; most of the plastic objects are trashed, and a lot is discarded as litter. Garbage ends up in landfills, and litter ends in waterways and finally is washed into the oceans.

The plastic objects tear, break and crumble as they go through this process. Sunlight, ultraviolet radiation, waves, friction, heat, thawing, salt in the sea, are factors that combine to break the plastic into tiny pieces, microplastics, and even tinier, ultrafine particles smaller than one micrometer (1 μm) These small particles are called nanoplastics (NPs).

Not only the polymer but also the additives

Plastics contain the polymer (Polystyrene, polyethylene, PET, acrylic, etc) and also many other ingredients used to process it. All of these chemicals form part of the MPs and NPs, and are released into the environment.

Plastics leach plasticizers and additives used to make them such as antioxidants, antidegradants, dyes, lubricants, processing promoters. These chemicals are contaminants and are also ingested by animals and humans. (1), (2)

An example are tires; one tire can release between 1 and 7 kg (2-14 lbs) of rubber particles as they wear against the road surface over its full life cycle. They are tiny particles that are washed into rivers or blown away by the wind. They don't only include plastic, but also heavy metals, additives, oils and other chemicals that leach into water and soil.

An antioxidant commonly used in tires and other rubber artifacts knwon as 6PPD reacts with ozone in the air to produce a chemical called 6PPD-Q that was found in 2020 to be highly toxic to different species of salmon. (5)

Ubiquitous plastics: They are everywhere

Once they enter nature, these plastics spread, they are carried by the wind, ingested by sea animals, deposited in the soil, and eaten by herbivores. They enter the food chain and are ingested by humans when we eat.
Microplastics and nanoplastics are all over the place: in foods, salt, honey, fish, shellfish. They are found in drinking water tap and bottled water, and in the air, so they are inhaled.
Plastics from cosmetics and clothing may also be absorbed by the skin.

The effect of Microplastics on the body

Once the MPs are absorbed the bloodstream transports them across the body, and end up in different organs: lungs, heart, liver, spleen, thymus, kidneys, reproductive organs, and also, as shown by recent research, they can cross the blood-brain barrier and accumulate in the brain.

They have been found in many samples taken from human beings, including blood, saliva, urine, semen, feces, and saliva. (4)

Once they are ingested, the components of these plastics (monomers) and the additives they contain, such as catalysts, dyes, lubricants, as well as some heavy metals and persistent organic pollutants interfere with biological processes in the human body.

Their shape, polarity and composition interacts with biomolecules in the body, altering proteins, lipids and sugars they can possibly change the properties of serum and plasma.

They can cause disruption in the normal working of hormones, alter the immune system, and even cause cancer. (3)
In marine organisms they causes abnormalities in their internal organs, malnutrition, inflammation, and death.
Their effects on the human body are still being studied but there is concern about the accumulation of MPs and NPs in the human bodies.

MPs and gut microbiome

Microplastics can affec the bacteria in the intestines, altering the balance between the different strains that live in the gut. This can cause bloating, abdominal pain and other gastrointestinal issues like IBS

Humans ingest roughly 0.1 to 5 grams of microplastics per week. "equivalent to the weight of a credit card." (4) Up to nine different types of plastic have been found in human stool, polypropylene and PET are predominant.The quantity excreted in feces is 20 particles of MPs every 10 g of stool. With a total amount of 0.1 to 14.6 mg per person.

Lungs

Inhaled MPs can affect the lungs and airways causing inflammation, asthma,s lower absorption of oxygen, coughing, sneezing, shortness of breath and a higher risk of chronic obstructive pulmonary disease.

The most frequently found MPs beside particles are fibers. They have been found in autopsies of human lung tissue.

Skin

Nanoplastics from textiles don't seem to be able to penetrate the skin, neither do the NPs in tainted water. However, they may be able to get across the skin barrier if their are injuries or using sweat glands and hair follicles.

Other effects

They can cause endocrine disruption, infertility and miscarriage. A study found MPs in the placentas of pregnant women.

Tests in mice show that microplastics cause inflammation, and oxidative stress producing reactive oxygen species that harm cells and DNA.

In mice they also alter the liver and intestinal microbiota, it caused damage to their brains leading to neuron damage and cognitive dysfunction.

Nanoplastics

Minute particles less than 1μm across, and down to nano sizes (1000 times smaller than a micrometer). They pass through all tissue barriers, penetrating the bloodstram and dispersing across the body. Some of them are water-repelling (hydrophobic) and this has an impact on the metabolism of cells. (4)

Closing Comments

Microplastics are a serious issue. Once they are released into the environment they can't be retrieved. Once they enter your body, part of them are absorbed and fixed. With health effects that are still being studied.

Recycling, replacing plastics by other materials (glass, metal, wood, paper) and controlling the fate at the end of the life of plastic articles (tires for instance) can reduce the amount of plastics entering the environment.