Photo credit: Canva
There is an increasing body of evidence demonstrating that plastics are now ubiquitous across the biosphere, with micro-plastics now detectable in even the remotest of environments. Micro-plastics are present in deep oceans, polar ice-caps, and agricultural soils across the world, whilst nano-plastics have even been found in the tissues and fruits of food-crops. Micro-plastics (plastic pieces under 5 millimetres (mm) in size), and nano-plastics (plastic particles under 1 micrometre (μm)) are pervasive globally. These micro- and nano-plastics are the result of the breakdown and shedding of plastic objects including machinery, vehicles and synthetic fabrics, or intentionally created and added to products such as paints, cosmetics and toothpastes.
Microplastics are inside us.
Research has found that micro-plastics, including nano-plastics, are routinely inhaled in dust in homes, workplaces and the wider environment, and ingested in our food and drink. Plastics have been found in shellfish, crop plant and animal tissues, and are known to migrate up the food chain. Micro-plastics have now been found in the urine, blood, placentas, and deep in the lung tissue of living people. Studies in mice have demonstrated that exposure to micro-plastics can cause them to accumulate in living tissues.
These new and potentially alarming findings lead to urgent questions around what, if any, the impacts on human health might be.
The World Health Organisation’s recent and comprehensive study finds that whilst existing evidence is “insufficient to determine risks to human health”, this does “not…imply that exposure to NMP [nano- and micro-plastics] is “safe””.
Microplastics: a risk to human health?
Prevalent concerns around the potential human health risks posed by micro-plastics broadly fall into two groups. Direct health impacts through the exposure of people to plastics through their ingestion and inhalation, and indirect health impacts through their effects on the ecosystems on which people depend for food, clean water and air, and consequently health and wellbeing.
Direct exposure to micro-plastics.
In people, there is some evidence to suggest that micro-plastics (including nano-plastics) may affect health. For instance, workers in synthetic textile factories exposed to very high levels of airborne micro-plastic dust are more prone to lung conditions, but this does not reflect the levels that most people will experience. Lab studies, both petri-dish studies using human cells, and rodent studies, have shown evidence of cell damage from exposure to high levels of micro-plastics and reduced male fertility. However, lab studies are difficult to translate into meaningful understanding of real-world impacts.
Studies in humans suggest that micro-plastics may cause inflammation in several body systems, microbiome disruption in the gut, may disrupt immune function, and may affect cell viability and gene expression. In addition, many plastics are treated with dyes and other additives improve qualities such as flexibility or fire retardancy. These compounds tend to leach from plastics, and some, such as bisphenols or phthalates, are known endocrine disruptors, which interfere with hormonal pathways at very low quantities.
Overall, these studies are part of a body of evidence on the direct impacts of plastics on human health that is in its infancy, meaning the impacts of exposure to micro-plastics are not well established. There is cause for concern, but the picture is complicated and incomplete, with conclusive evidence difficult to attain.
Micro-plastics: the environment & human health.
Micro-plastics may also impact human health through more indirect avenues. It is estimated that the ecological risks of micro-plastics are significant. Human health and wellbeing are intimately interlinked with the health of the ecosystems and environments on which we depend. Ecosystems services such as soil water regulation are known to be impacted by soil micro-plastic content, this potentially impacting how soils respond to flooding and drought conditions. In addition, the accumulation of plastics in soils can impact soil health and impede plant growth, both areas MINAGRIS is currently conducting experiments on. These in turn, can negatively affect food security, with health outcomes for vulnerable people.
Environmental exposure of plastics could have important implications for human health. Plastics are prone to accumulating hydrophobic chemicals they come into contact with in the environment, notably persistent organic pollutants such as PCBs and DDT. This raises concerns that environmentally exposed micro-plastics may act as a ‘trojan horse’, bringing associated chemicals into the bodies of humans and other animals.
Photo credit: canva
Summary.
Overall, researchers deem that the potential risk of micro-plastics to human health might be high, but current understanding remains limited. People are exposed to a wide range of natural and artificial substances on a daily basis, so determining the role micro-plastics play in human health amongst these is difficult. There are practical and ethical challenges in the science which are yet to be resolved. Scientific studies in cells, tissues, humans, and the wider environment on which we depend need to be robust and carefully interwoven to form a comprehensive understanding of the interrelationships between micro-plastics, human and environmental health. Micro-plastics (including nano-plastics) are a major pollutant of agricultural soils but understanding their impact on the soil biota and agricultural productivity remains elusive.
Is there anything I can do?
Micro-plastics are everywhere, and ultimately, the supply of plastics of all shapes and sizes into the environment needs to be stopped to make a difference on this. We’ve pulled together some ideas on where to start here:
- Get involved.
- Know your plastics.
- Download the Beat the Bead app to avoid products which contain microbeads.
- Similarly, check out which products contain nano-plastics.
- Avoid single use plastics and synthetic textiles wherever possible.
- Pay close attention to what goes into your compost bin- if in doubt, leave it out.
Further Reading.
Plastics and the circular economy https://ellenmacarthurfoundation.org/plastics-and-the-circular-economy-deep-dive
Microplastics and Human Health, Science (2021) https://www.science.org/doi/10.1126/science.abe5041
Tissue accumulation of microplastics in mice and biomarker responses suggest widespread health risks of exposure, Nature (2017) https://www.nature.com/articles/srep46687
Microplastics are everywhere — but are they harmful? Nature (2021) https://www.nature.com/articles/d41586-021-01143-3
Microplastics: Trouble in the Food Chain, UNEP Frontiers (2016) https://wedocs.unep.org/handle/20.500.11822/36615
Dietary and inhalation exposure to nano- and microplastic particles and potential implications for human health, World Health Organisation (2022) https://www.who.int/publications/i/item/9789240054608
Microplastics in freshwater and soil: An evidence synthesis, The Royal Society (2019) https://royalsociety.org/-/media/policy/projects/microplastics/microplastics-evidence-synthesis-report.pdf
This blog was written by Honor Mackley-Ward (CCRI).
