Microplastics, the tiny plastic fragments less than 5mm in size, are increasingly being found everywhere – in the oceans, freshwater systems, soil, air, and even in our food.
As these tiny plastic pieces spread unabated into the environment, scientists are concerned about their effects on human health.
Key facts:
- Over 6,000,000 tons of microplastics are produced globally each year, from a variety of sources like cosmetics, synthetic textiles, tire dust, and the breakdown of larger plastics.
- Microplastics contain hazardous chemical additives like bisphenol A (BPA), phthalates, heavy metals, and flame retardants that can leach out. Many of these are endocrine disruptors linked to cancer, reproductive issues, and other diseases.
- Microplastics have been detected in various foods and drinks – salt, bottled water, beer, shellfish and more. Humans are exposed through ingestion, with estimates of ingesting 74,000-121,000 microplastic particles annually.
- Besides food, microplastics can also enter the lungs through breathing. Evidence shows respiratory inflammation, distress and autoimmune disorders from inhaled microplastic fibers and particles.
- Once ingested, microplastics less than 150 microns in size can penetrate organs and even cellular membranes, though current estimates are that only 0.3% of ingested microplastics are absorbed into the body.
- Nanoplastics less than 100 nm can penetrate skin, while microplastics are unlikely to be absorbed transdermally. Inhalation of nanoplastics is of greater concern.
- Within the body, microplastics can cause inflammation, cellular damage, allergic reactions and toxicity from their chemical additives. Their small size also makes them more bioavailable.
- Studies show threats to the gastrointestinal tract, liver, cellular DNA, immune system and even the brain. The full extent of effects on human health remains to be determined.
Source: Int J Environ Res Public Health
The Rise of Microplastics
The mass production of plastics only began in the 1950s, but plastics now pervade almost every aspect of modern life.
From packaging and electronics to clothes, toys and automobiles, both synthetic polymers and plasticizers have become essential industrial materials.
However, plastic waste is notoriously resistant to degradation. Larger plastic items in the environment break down into smaller and smaller fragments over time, until they become microplastics – particles smaller than 5 mm in size.
There are two types of microplastics:
- Primary microplastics are intentionally manufactured small, like the microbeads in cosmetics or the nurdles used in plastic production.
- Secondary microplastics result from the degradation of larger plastics, through mechanical action and weathering processes.
Some of the major sources of secondary microplastics include fibers shed from synthetic fabrics, tire dust from wear while driving, microfragments of larger plastic waste, and degradation of plastic litter from unsound waste management.
Global plastic production has now reached over 400 million tons annually.
All this plastic eventually makes its way into the environment, leading to widespread pollution by microplastic particles.
Research is still ongoing, but early estimates suggest there are already over 150 million tons of microplastics spread across the oceans alone.
Microplastics have now been found in all environmental realms – freshwater bodies, terrestrial soils, arctic ice, and even the atmosphere.
Their small size allows microplastics to be readily transported.
Wastewater systems are a key transmission route, discharging microplastics from urban centers into rivers and oceans.
But atmospheric transport also accounts for spreading microplastics far and wide.
Nowhere on Earth remains untouched by plastic pollution.
Microplastics are the most abundant form of plastic debris in the environment.
Their prevalence and persistence poses risks for human health that we are only just beginning to grasp.
The Cocktail of Chemical Additives in Plastics
Plastics are rarely composed of pure polymer resins.
A multitude of chemical additives are mixed in during manufacturing to enhance the properties and functionality of plastic products.
Unfortunately many common additives are known to be toxic for human health.
As plastic particles degrade in the environment, these hazardous chemicals can leach out and be released.
Some of the most concerning chemical additives in plastics include:
Bisphenol A
Bisphenol A (BPA) is widely used to make polycarbonate plastics for food containers, reusable bottles, CDs and electronics.
It is known to mimic estrogen, and has been linked with obesity, infertility, reproductive disorders, and breast cancer.
Phthalates
Phthalates like DEHP and DBP are plasticizers used to make plastics more flexible.
They are common in toys, food wrap, cosmetics and more.
Phthalates are endocrine disruptors that can damage reproduction and development.
Heavy Metals
Heavy metals like cadmium, lead, mercury and chromium are added to plastics as pigments, stabilizers and biocides.
They are toxic metals that can accumulate in organs and tissues, causing DNA damage and disorders of the kidney, bones and brain.
Flame Retardants
Brominated flame retardants (BFRs) prevent plastics from catching fire, but have been shown to disrupt thyroid hormones and become toxic PBDFs and PBDDs when combusted.
Studies have confirmed that these known toxicants do leach from microplastics out into their surroundings, and can then be absorbed by organisms upon exposure.
Food and drink are contaminated with microplastics both directly and through bioaccumulation in marine life.
When humans consume this, we are inevitably exposed to a cocktail of plastic additives that pose health hazards.
Human Exposure Pathways
There are three main routes by which humans can be exposed to microplastics – ingestion, inhalation and skin contact.
Ingestion or consumption of microplastic contaminated food and water is currently the best researched exposure pathway.
Ingestion
A number of studies have now analyzed various food items and bottled water for microplastic contamination.
Shellfish like mussels and oysters ingest large quantities of microplastics from the marine environment they live in.
Significant levels of microplastics have also been found in commercial salt, beer, honey, sugar, alcohol and bottled water.
Fish and shellfish sold for human consumption are also often contaminated after ingesting microplastics themselves.
One study estimates the average person may be ingesting 74,000 to 121,000 microplastic particles from food sources annually.
Vegetables also risk microplastic contamination accumulated in agricultural soils.
Gastrointestinal absorption of microplastics under 150 microns in size has been proven in mammalian studies.
Persistent microplastics are known to cause inflammation in organs.
Chemical additives being released in the body also increases their bioavailability and toxicity.
Inhalation
Microplastic fibers and particulates are ubiquitously present in indoor and outdoor air.
Inhalation of microplastics from atmospheric dust and pollution has now emerged as a significant exposure route lacking adequate research.
Workers handling synthetic textiles are at particular occupational risk of lung damage from inhaled plastic microfibers.
But microplastics in the air we breathe daily also pose worrying health impacts like respiratory distress, irritation, inflammation and exacerbated allergies.
Nanoplastics can penetrate deep into lung tissue to enter the bloodstream after inhalation.
Further translocation to the brain is also likely. Inhaled non-biopersistent microplastics still lodge in the lungs to cause chronic toxic effects.
Skin Contact
Some microplastics found in facial cleansers, shower gels and exfoliating scrubs can directly enter our bodies through the skin.
However, given the barrier function of the skin, transdermal absorption of microplastics is very unlikely.
Nanoplastics less than 1 micron may permeate into skin, but in general microplastics do not pose great risk of entry through dermal contact.
Inhalation and ingestion are more relevant exposure pathways.
Toxic Effects of Microplastics on Human Health
The toxicity mechanisms of microplastics are related to both their physical particle properties, as well as their chemical additives.
Unfortunately the miniscule size of microplastics increases bioavailability as well as transport through cell barriers.
Potential toxic effects from microplastic exposure include:
Cellular Toxicity
Oxidative stress damages cell membranes and DNA.
Nanoplastics directly interact with cellular organelles.
Particles remaining in tissues can cause chronic inflammation.
Immune Dysfunction
Ingested microplastics concentrate in immune tissue of the gut.
This can trigger allergic reactions, release of cytokines and chemokines.
Metabolic Disorders
The liver filters microplastics entering the bloodstream, leading to liver stress.
Endocrine disrupting additives also increase risk of obesity and diabetes.
Developmental Toxicity
Microplastics crossing the placental barrier and blood-brain barrier can impair fetal development and cause neurotoxicity.
Cancer
Carcinogenic additives like heavy metals and BPA may leach from ingested microplastics.
Inflammation triggers tumor formation.
Nanoplastics entering cells also display genotoxicity.
The full spectrum of microplastic related toxicity is still an emerging area of research.
But early studies have flagged sufficient harms to warrant precaution regarding human exposure through environmental contamination.
Mitigating the Health Risks of Microplastics
There are measures that can be taken at both industrial and individual levels to reduce health risks from plastics:
- Eliminate unnecessary uses of plastics, especially single use packaging and disposable items. Choose reusable non-plastic alternatives.
- Improve waste management systems to prevent plastic pollution through effective sorting, recycling and safer disposal. Implementing extended producer responsibility can also incentivize sustainable design.
- Use more natural fiber clothing over synthetics to reduce microfiber shedding. Install filters on washing machines.
- Avoid seafood known to ingest large amounts of microplastics, like mussels and oysters. Remove digestive tracts of fish before eating.
- Use safer personal care products without microbeads and other forms of microplastics as exfoliants or shower gel additives.
- Reduce direct sources of microplastics at home by dusting and vacuuming frequently, using doormats and avoiding plastic-bottled drinks.
- Improve filtration systems to remove microplastics from tap and bottled water. Use water filters when washing vegetables.
The perils of plastic are now plainly evident.
From governments to industries and individuals, we all must act decisively to curb the proliferation of plastics throughout the environment.
This will reduce microplastic pollutants and their risks to the human body.
Human health is intimately intertwined with planetary health.
Solving the plastic crisis is an essential step towards creating a safer, cleaner and more sustainable future for all.
References
- Study: A detailed review study on potential effects of microplastics and additives of concern on human health
- Authors: Claudia Campanale et al. (2020)
