Microplastics and Nanoplastics: Tiny Particles, Big Impact

Here we look at what we know so far about micro(nano)plastics: what they are, how they affect human health and what we can do about it.

��Los #microplásticos y #nanoplásticos se han convertido en un nuevo problema para el #medioambiente y la salud, uno de los retos medioambientales más importantes del siglo XXI.

¿Qué sabemos de ellos?����

��https://t.co/3v5yPPvboD pic.twitter.com/De4sxKgP8p

— ISGlobal (@ISGLOBALorg) January 11, 2024

Over the past decades, every facet of our modern lives has become highly dependent on plastic. Today, microplastics and nanoplastics constitute an emerging environmental and health concern and they have emerged as one of the most significant environmental challenges of the 21st century. Yet, our primary exposure routes to micro and nanoplastics and their additives, as well as their effects on environment and health, remain largely unknown. Here, we will shed light on the knowledge we possess thus far surrounding micro(nano)plastics: exploring what they are, how they impact human health and what we can do about it.

What are microplastics and why are they a problem?

Plastics are complex and highly heterogeneous synthetic compounds that originate from fossil fuels. Plastics are composed of a carbon-based polymer framework and encompass an array of additional chemicals intentionally added during production to confer distinct characteristics.

Micro(nano)plastics (MNPs) are tiny particles of plastics that are less than 5 millimeters in size. They can be classified into two main categories based on their source:

• Primary MNPs are plastic particles that are intentionally manufactured to be small, such as microbeads used in personal care products like exfoliating scrubs and toothpaste. They are also used in industrial processes and products like abrasive blasting or as a raw material to produce other plastics.
• Secondary MNPs are a result of the degradation of larger plastic items such as plastic bags, bottles, and fishing nets, that end up in the environment. These larger plastic items can break down over time due to physical, chemical, or biological processes, such as exposure to sunlight or the mechanical force exerted by sea waves.

Microplastics and nanoplastics are a growing concern because they can persist in the environment from decades to centuries so that, year after year, they accumulate in the environment. It is estimated that 22 megatons of plastic waste enters the environment annually, adding on to the 6 gigatons of plastic waste that have accumulated since 1950. Furthermore, the production of plastic is accountable for approximately 3.7% of worldwide greenhouse gas emissions, exceeding the emissions of an entire nation such as Brazil. If present trends persist, this proportion is expected to rise to 4.5% by the year 2060.

The microscopic size of MNPs makes them highly mobile. They can be found in every place on Earth from the Himalayan mountains, to glaciers and the deepest parts of the ocean. They can be absorbed by most living organisms from crops to marine creatures and even humans. Their accumulation in the environment and potential impacts on human health raise considerable environmental and public health concerns.

How can microplastics enter the body?

The human body is exposed to microplastics and nanoplastics through ingestion of food and drinks contaminated by MNPs, inhalation of MNPs suspended in the air and by dermal contact when microplastics are contained in personal care products, synthetic textiles, dust, etc. The ingestion route is currently considered the major route of human exposure to microplastics.

Microplastics can end up in our food and drinks by different ways:

• Through accumulation in the food chain:

Plastic debris contaminates both aquatic and terrestrial ecosystems. Hence, primary trophic levels (plants) can take up microplastics and transfer them along the food chain. In addition, animals of higher trophic levels can also accidentally swallow plastic that will accumulate in their tissues. As a consequence, plastics have been identified in hundreds of species in all major taxa, including species consumed by humans. Drinking water is also a major source of MNPs exposure.

• During the food and drinks production process:

Manufacturing processes often involve cutting, grinding, molding, and other mechanical operations that can generate microplastic particles that will end up in the food. Another example would be the plastic pipes delivering households tap water that can release MNPs.

• From plastic packaging:

Plastic is the most commonly used food package, which might release plastic particles in contact with food. A single plastic tea bag at brewing temperature can release up to 11.6 billion microplastics into a single cup of beverage.

What are the possible effects of microplastics and plastic additives on human health

In vitro studies identified multiple biological effects ranging from inflammatory response to carcinogenicity or neurotoxicity. In vivo studies on rodents showed that MNPs could accumulate in different organs (liver, spleen, kidney, brain, lungs and gut) and present adverse effects on mice and their offsprings including altered gut microbiome, toxicity for the liver, oxidative stress, reproductive toxic effects that could lead to infertility, etc.

Recently, there have been reports of MNPs found in various human body tissues including the gastrointestinal tract, lungs, bloodstream, and reproductive system (placental tissue, male testis, mammary glands). In addition, many plastic additives such as BPA or phthalates are proved to be highly toxic. These compounds are endocrine disruptors that affect various systems of the human body. For example, human epidemiological studies have shown a significant association between phthalate exposures and adverse reproductive outcomes in women and men, type II diabetes and insulin resistance, overweight/obesity, allergy, and asthma. However, neither the magnitude of human exposure to microplastics nor the possible health consequences associated with the accumulation of microplastics in the human body are known. More epidemiological research such as the one being currently done at ISGlobal (AGBAR, EXaMINA) is needed to elucidate this knowledge gap.

What should we do to reduce microplastic pollution and our exposure to it?

MNPs have become of great concern as a potential threat to human health and urgent actions need to be taken to protect the health of ecosystems and people. Globally, plastic disposal is highly inefficient. Plastic recovery and recycling rates below 10% and vast quantities of plastic waste are exported each year from high-income to low-income countries, contributing to environmental injustice. Hence, the most efficient way to cut down plastic pollution is to reduce plastic production from its source. Certainly, single-use plastics, which currently account for 35-40% of the current plastic production, stand out as the fastest-growing segment within the plastic manufacturing industry.

On a personal level, there are several effective practices to reduce plastic pollution and minimize our own exposure to it. These include:

• Buy as little food packaged in plastic as possible
• Don't use single-use plastic and purchase plastic items secondhand
• Avoid heating food in plastic containers or wrapped in plastic
• Keep your general environment clean (take off shoes when you enter your house, clean dust deposits, ventilate the house every day, )
• Wash your hands frequently and always before you eat

While our personal contributions undoubtedly hold value, it's essential to recognize that corporations and governmental bodies possess substantial influence in tackling this concern. Advocating for the endorsement of the forthcoming international legally binding treaty on plastic pollution, currently under development by the United Nations Environment Assembly, is a meaningful step towards change. If you perceive room for improvement in a company's packaging practices, consider voicing your concerns and initiating a dialogue with them.

Co-benefits of reducing plastic pollution

Reducing plastic pollution brings many additional benefits. This endeavor will not only promote our well-being but also contribute to addressing climate change and safeguarding the biodiversity of our ecosystems, which are vital for humanity's sustenance, oxygen supply, livelihoods, and overall welfare.