Consuming micro- and nanoplastics

We seem quite good at inventing ‘things’ and we rush them to market before giving enough thought to potential negative consequences. The question is will we ever learn? Ulrich Beck, a past sociology professor at the University of Munich, pointed to inherent long-term risks with new products that are often disregarded by an enthusiastic subordination of nature by science and technology. (Image by storyset on Freepik)

There are many examples of how this can backfire.

DDT was hailed as a wonder chemical that would revolutionise agriculture until Rachel Carson published her book ‘Silent Spring’ in 1962. It is now known that DDT caused direct mortality of some birds by poisoning their nervous system, caused bird eggs to have thin shells and reduced levels of a hormone necessary for female birds to lay eggs. It could indeed lead to a silent spring.

PFAS are a large, complex group of manufactured chemicals that are ingredients in various everyday products. They are used to keep food from sticking to packaging or cookware, make clothes and carpets resistant to stains, and create firefighting foam that is more effective. Now we know of numerous human health effects including altered metabolism and fertility, increased risk of being overweight or obese, and reduced ability of the immune system to fight infections. Something we have to live with as PFAS are persistent chemicals spread everywhere in nature.

Neonicotinoids are insecticides that have been repeatedly called ‘perfect’ for use in crop protection. Since their introduction in the early 1990s, neonicotinoids have become the most widely used insecticides in the world on a variety of crops. However, in a 2013 report by the European Food Safety Authority it was stated that neonicotinoids pose an unacceptably high risk to honey bees, and that the industry-sponsored science upon which regulatory agencies’ claims of safety have relied may be flawed and contain data gaps not previously considered. As bees, consisting of around 20,000 species worldwide, are one of the primary pollinators of both native plants and agricultural crops the impact of neonicotinoids could spell disaster for worldwide food production. Bumblebees are also economically important pollinators and appear to be particularly sensitive to neonicotinoid pesticides, which affect both bumblebee colony growth and foraging efficiency. It is clear that we overuse pesticides at our own peril because human and natural environments are unquestionably linked. And still many countries have no restrictions on neonicotinoid use.

Do you want some plastics with that?

And so we come to plastics, such a useful innovation for many aspects of life. Attempts to produce plastic materials started already in the middle of the 19th century. However, the world’s first fully synthetic plastic was Bakelite, invented in New York in 1907. Many chemists have since contributed to the science of developing a variety of plastic materials. Over 9 billion tonnes of plastics are estimated to have been made over the last 70 years.

The success of plastics has caused widespread environmental problems due to their slow decomposition rate in natural ecosystems. At the macro level, plastic pollution can be found all over the world creating garbage patches in the world’s oceans and contaminating terrestrial ecosystems.

Of all the plastics discarded so far, OECD calculated that only 19% had been incinerated and 9% recycled. However, the real problem can be found at the micro (or even the smallest nano) level.

Microplastics can either come from a primary source like microfibers from clothing, microbeads in cosmetics, and plastic pellets. Or there are secondary microplastics arising from the degradation of larger plastic products through natural weathering processes after entering the environment. Microplastics can now be found wherever we look and will find their way into the food we eat.

Studies have found microplastics in foods including tea, salt, seaweed, milk, seafood, honey, sugar, beer, vegetables, fruit and soft drinks. It has been estimated that 5 g of plastic particles on average enter the human gastrointestinal tract per person per week. A recent Australian survey of microplastics in rice found that consumption of a single serve of rice may contribute 3-4 mg of microplastics, equivalent to an intake of around 1 g per person annually. Even tap water contains microplastics while bottled water contains even more.

So what’s the problem?

The actual plastic polymers are not the problem although residues of the monomers used in the manufacture of the complex polymers may be toxic. What is more of a problem is the variety of additives used to change the properties of the plastic, some of which can be quite toxic. These include plasticisers, flame retardants, heat stabilisers and fillers among many others.

According to current knowledge, microplastics at 0.001 to 5 millimetres in size are considered to pose a comparatively low risk to human health as they are considered to be too ‘bulky’ to be absorbed by human cells and are largely excreted again. However, experimental studies indicate that such particles passing through the gastrointestinal tract can lead to changes in the composition of the gut microbiome and in turn the development of metabolic diseases such as diabetes, obesity or chronic liver disease.

The situation is different with smaller particles, submicro- and nanoplastics. These particles are less than 0.001 millimetre in size. A laboratory study by the German Federal Institute for Risk Assessment found that the smaller the particles, the more they were absorbed. While microplastics only “seeped” into the cell to a small extent, particles in the submicrometre range could be measured in larger quantities in intestinal and liver cells.

Whether ingested micro- and nanoplastics pose a health risk is being investigated in numerous studies but is largely unknown to date. Using specific analyses there are indications that they could activate mechanisms involved in local inflammatory and immune responses and could crucially be involved in carcinogenesis.

What to do?

Not easy to say at this stage. We could of course try to reduce the use of plastics to diminish future contamination, but this is easier said than done with the ubiquitous use of plastics for all kinds of applications.  Some reduction can be achieved by washing fruit and vegetables before consumption. Washing rice before cooking reduced the microplastic content by around 25%.

American researchers pointed out that without a well-designed and tailor-made management strategy for end-of-life plastics, humans are conducting a singular uncontrolled experiment on a global scale, in which billions of metric tons of plastic material will accumulate across all major terrestrial and aquatic ecosystems on the planet.

We can do better!