Monday, May 20, 2024

How dangerous are Microplastics?

Microplastics are tiny plastic particles less than five millimeters (one fifth of an inch) in diameter.  They are now ubiquitous in the environment and are found in large quantities in our oceans, land, food, water and air. They have been found in the organs of fish, human placentas, dust, rice, tea, salt, honey, sugar, vegetables and soft drinks.  Health experts have yet to come to a definitive conclusion about the danger of microplastics to human health. 

How do microplastics enter the environment?

8 million tonnes of plastic waste end up in our oceans each year – that’s the equivalent of a truckload of plastic being dumped into the sea every minute.

It enters the ocean via rivers, storms, winds or floods.  A high proportion of ocean plastic consists of fishing gear such as plastic nets which have been tossed overboard from trawlers.

Larger pieces of plastic become brittle and gradually break down due to the action of sunlight, oxidation, friction or by animals nibbling on the plastic.   A similar process happens on land.

This plastic breakdown process goes on forever, although the speed depends on the circumstances – some plastics can take many hundreds or even a thousand years to break down completely.

As a result of the ongoing breakdown process, the number of micro- and nanoplastic particles increases exponentially.

Due to their low density, most of these microplastics float at the ocean surface.

The wear and tear of rubber car tyres is also a significant source of microplastics, which are then carried by winds over land and sea and then breathed in by mammals.  In the Netherlands, seventeen million kilograms of car tyre rubber enters the environment every year – around 1 kilogram per inhabitant.

Microplastics are also generated when we wash our clothes.   A large proportion of our clothing is made from synthetics such as nylon, polyester and acrylic.  Five kilograms of synthetic clothing (a typical large wash load) releases an average of 9 million microfibres that are carried down the drain with the rinse water.

Microplastics or ‘microbeads’ are also contained in personal care products such as facial scrubs, cosmetics and toothpaste.  These are rinsed away with wastewater during use.  Many countries have now banned the use of microbeads in products.

It ‘rains’ microplastics every day, even in the most remote regions of the world.   Microplastics have been found in the deepest places on earth – at depths of 11 kilometers below the surface of the water.

Animals and fish

Fish, marine mammals and seabirds often mistake floating plastic for prey, and many die as a result of ingesting it.  At least 267 different species of fish are known to have been affected by plastic pollution, while up to 90% of seabirds are thought to have pieces of plastic in their stomachs.

A study carried out by marine scientists at NUI Galway found that 73% out of 233 deep water fish from the Northwest Atlantic Ocean had ingested plastic particles.  

To further complicate matters, microplastics in the ocean can bind with other harmful chemicals before being ingested by marine organisms.  These are then fragmented by freshwater invertebrate animals as part of their digestive process.  The ingestion of microplastics by these animals may cause internal physical damage, inflammation of intestines, reduced feeding and other effects.

How do Humans ingest microplastics?

More than half of the fish species found to have ingested microplastics are eaten by humans.

Microplastics have also been found in fruit and vegetables.

Plastic food containers and bottles also provide a route for microplastics to enter the human digestive system. 

A recent study by researchers from Trinity College Dublin (TCD) discovered that high levels of microplastics are released from infant feeding bottles during the sterilisation and preparation of baby formula.

A study also found high levels of microplastics in tap water.  A recent study by researchers from the University of Newcastle in Australia found that the average person consumes about 5 grams of plastic every week from water.

An analysis of some of the world’s most popular bottled water brands found that more than 90% contained tiny pieces of plastic.  The study found an average of 325 plastic particles for every litre of water being sold.  In one bottle of Nestlé Pure Life, concentrations were as high as 10,000 plastic pieces per litre of water.

New research suggests 136,000 tons of microplastics are ejected from the ocean each year, ending up in the air we breathe.  The oceans were estimated to be the source of about 10% of the airborne plastics in western US.

Microplastics can also be inhaled. These plastics, whipped up into the air by road traffic and carried by winds, are likely to include particles from tyres and brake pads on vehicles, and plastics from litter that had been ground down.  

A team from Macquarie University in Sydney took samples of airborne dust from homes and found about 40% of it was plastic, about a quarter of which was composed of particles small enough to be inhaled.

How can microplastics affect human health?

While the World Health Organization’s stance is that ingesting microplastics poses no known threat to human health, not everyone agrees.

“Nobody really knows the answer,” says environmental contamination expert Professor Mark Taylor of Macquarie University, Sydney. “But the absence of evidence is not evidence of absence”, he said in a recent article in The Guardian.

Dr. Douglas Rader, chief oceans scientist at the Environmental Defense Fund, points out that many microplastics contain chemicals linked to reproductive and hormonal disruption and cancer.  Some of these particles are toxic to humans — they can carry carcinogenic or mutagenic chemicals.

Plastic comes in many forms and contains a wide range of additives such as pigments, ultraviolet stabilizers, water repellents, flame retardants, stiffeners such as bisphenol A (BPA), and softeners called phthalates, all of which can leach into their surroundings.

Some of these chemicals are considered endocrine disruptors—chemicals that interfere with normal hormone function.  Flame retardants may interfere with brain development in foetuses and children.  Other compounds that cling to plastics can cause cancer or birth defects.

The inhalation of particles can be irritating to lung tissue and lead to serious diseases.

Tim Spector, professor of genetic epidemiology at King’s College London and author of The Diet Myth, has commented that he suspects microplastics will have a negative impact on the gut microbiome.  As the diversity of our gut microbiome is linked with our immune system this may have an impact on our overall health.

There is also growing evidence that human infertility – particularly male infertility – is increasing, and it is known that some micro- and nanoplastics mimic female hormones in the male body.

In 2017 Shanna Swan, professor of environmental medicine and public health at Mount Sinai school of medicine in New York documented how average sperm counts among western men have more than halved in the past 40 years.

Her study found that younger women had experienced a bigger increase in infertility than older age groups.  She also noted that there is compelling evidence that the risk of miscarriage has been rising among women of all ages.

Swan says that chemicals play a major causal role.  Phthalates, used to make plastic soft and flexible, are of paramount concern.  “They are in everybody and we are probably primarily exposed through food as we use soft plastic in food manufacture, processing and packaging. They lower testosterone and so have the strongest influences on the male side, for example diminishing sperm count, though they are bad for women, too, shown to decrease libido and increase risk of early puberty, premature ovarian failure, miscarriage and premature birth”, she says.

Bisphenol A (BPA), used to harden plastic and found in cash-register receipts and the lining of some canned-food containers, is another chemical of concern.  It mimics oestrogen and so presents risks in terms of fertility, and can also affect men.  Men occupationally exposed to BPA have shown decreased sperm quality, reduced libido and higher rates of erectile dysfunction.  

“By 2045 we will have a median sperm count of zero.  This means that most couples may have to use assisted reproduction”, Professor Swan says.

Can we remove microplastics from the environment?

On a positive note, there are a number of different projects underway which attempt to remove microplastics from the environment. 

Oil and Magnets (Fionn Ferreira, Cork/Ireland):

Fionn Ferreira, a student from county Cork, invented a device which removes microplastics from water using a combination of oil, magnetite powder and magnets.  The oil, which binds with microplastics, is infused with magnetite.  When the microplastics bind with the oil a magnet can then be used to attract the particles and remove them.  In 1,000 tests, Ferreira was able to remove over 87% of microplastics from water samples.  The next step would be to scale this up to produce a device that will work on filtration systems such as those in wastewater treatment plants.  This would prevent microplastics contained in effluent from domestic and industrial sources from ever reaching waterways and the ocean.

Fionn Ferreira

Ferreira also plans to test whether he could use the device to make a self-cleaning filter for ocean engines.  The filter could be built into the already existing water intake and outlets of the ships used to cool the engines, so as they’re taking in the water and as they’re driving around the oceans, they could be cleaning the water that passes through those engines.  In autumn 2020, Suzuki Motor Corporation announced plans to introduce a microplastic filter into its watercraft outboard motors using similar logic.

Living ‘vacuum cleaner’ organisms (Dr. Juan José Alava):

Dr Juan José Alava studies organisms he calls “living vacuum cleaners”.  These include bottom feeders such as sea cucumbers, as well as bacteria that are able to break down synthetic material, some of which originally evolved to metabolize naturally occurring polymers such as lignin and wax, and others which evolved to eat plastic.

The idea is to identify communities of bacteria and try to stimulate them to break down plastic.  When an organism can eliminate more plastic than it accumulates in its body or waste, it becomes “our best ally” in the fight against microplastics, says Alava.

Static-charge screen filter for beach sand (Marc Ward):

On beaches, microplastics are visible as tiny multicoloured plastic bits in sand.  There are beaches where you not only see large pieces, but also countless fragments, coloured or faded — the smallest pieces can no longer be distinguished from grains of sand.

Marc Ward

Marc Ward began surveying beaches in both South America and near his home of coastal Oregon, sifting through sand with a static-charged screen able to capture plastic particles as small as 50 microns – essentially plastic dust.  In some areas, he found 10 pounds of microplastic in each square meter of beach.

Ward now works with a team to filter thousands of pounds of plastic out of Oregon’s beaches every year as part of his non-profit, Sea Turtles Forever’s Blue Wave initiative.

Water filter mesh (VTT Research Centre, Finland):

A new kind of water filter made from plant-derived nanocellulose mesh has been created by scientists at the VTT Technical Research Centre of Finland.

The porous, colloidal structure of cellulose allows it to bind to nanoplastics without using any chemical or mechanical interaction.

Cellulose filters can help researchers study nanoplastics, as well as keep them out of our water when integrated into wastewater filtration systems, or even laundry machines, where they could catch the tiny microfibers from synthetic clothing.   This short video illustrates the technology.

Carbon nano-tube catalysts (University of Adelaide):

A team at the University of Adelaide created coils half the width of a human hair in size to create chemical reactions that convert plastic into carbon dioxide and water.

To decompose the microplastics, the researchers had to generate short-lived chemicals called reactive oxygen species.  These chemicals trigger chain reactions that chop the various long molecules that make up microplastics into tiny and harmless segments that dissolve in water.

Reactive oxygen species are often produced using heavy metals such as iron or cobalt, which are dangerous pollutants in their own right, but the researchers found a greener solution – carbon nanotubes laced with nitrogen.

They worked so well that over the course of just eight hours the researchers were able to remove a significant fraction of microplastics from water samples in their lab.

Nano coils

To make them work even better, the team made the nano-coils magnetic by including a small amount of manganese buried deep inside the nanotubes to prevent it from leaching into the water.  This makes it easy to collect the nanotubes after they have been used in real life situations such as waste water treatment plants or the environment.

While these developments do look promising, it is important that we continue to cut down on the amount of plastic packaging we consume in the first place, with the eventual aim of eliminating it from our lives altogether.  Adopting a zero waste lifestyle and buying food from refill shops is a great start, as is buying toiletry products with zero packaging.  Advancements in technology will hopefully be able to remediate the damage done to the environment by plastic over the past decades. 


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