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Since the mass production of plastics began in the 1940s, the versatile polymers have spread rapidly across the globe. Although plastics have made life easier in many ways, disposing of the materials is a growing problem. Now, researchers in the ACS journal Environmental Science & Technology estimate that the average American consumes more than 70,000 particles of microplastics per year, though the health effects of that consumption are unclear.
Microplastics are tiny (often microscopic) pieces of plastic that can arise from multiple sources, such as the degradation of larger plastic products in the environment, or the shedding of particles from food and water containers during packaging. Humans can inadvertently take in the materials when eating food or breathing air containing microplastics. The health effects of ingesting these particles are unknown, but some pieces are small enough to enter human tissues, where they could trigger immune reactions or release toxic substances. But how much microplastics do humans consume? That's the question Kieran Cox and colleagues wanted to tackle.
To do so, the researchers reviewed 26 previous studies that analyzed the amounts of microplastic particles in fish, shellfish, added sugars, salts, alcohol, tap or bottled water, and air. Other foods were not included in the analysis because the data were lacking. The team then assessed approximately how much of these foods men, women and children eat from the recommended dietary intakes of the 2015-2020 Dietary Guidelines for Americans. From this analysis, the estimated microplastic consumption ranged from 74,000 to 121,000 particles per year, depending on age and sex. People who drink only bottled water could consume an additional 90,000 microplastics annually compared with those who drink only tap water. Because the researchers considered only 15% of Americans' caloric intake, these values are likely underestimates, they say. Additional research is needed to understand the health effects, if any, of the ingested particles.
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The authors acknowledge funding from the Natural Sciences and Engineering Research Council of Canada and the Liber Ero Foundation.
Expert Reaction
These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.
Microplastics are everywhere in the food chain: There is no doubt that microplastics are already in our food chain, but more importantly everywhere in our ecosystems, oceans, lakes, rivers, streams, soil, air, everywhere!
All animals can ingest microplastics: We know from a long time ago that invertebrates (mostly eaten by fish) are able to ingest microbeads in laboratory studies. Those early studies were fascinating, because they were looking at the ability of invertebrates to “taste” and such they coated microbeads with various substances and fed them to the invertebrates. The funny thing is that in the mind of scientist 30-40 years back, there was no doubt that these invertebrates were able to ingest microbeads!
Is the next stop the human brain? The key and serious question before us is: what is the impact of microplastics once they are inside the human body? We know that humans can ingest or inhale microplastics, there is no doubt anymore about this one. The key question, is what happens next? What are the physical impact of particles travelling inside the bloodstream? Where is the next stop? Human brain? Many questions for the scientist to try to answer in a short period of time because this is urgent.
When we say 'the environment', we mean humans too: The irony is that we have been saying that microplastics are everywhere in the environment, in the scientist mind humans are part of the environment. So we meant, humans as well. But it seems that there is some perceived separation between the environment and humans. Now with this evidence, it may start being too close for comfort and hopefully we could see some real action. It’s only a matter of time.
Dr Paul Harvey is an environmental scientist (pollution specialist) and science communicator. He is the owner of Environmental Science Solutions, and often engages with audiences under the name "Doc PJ Harvey"
This new study once again highlights the pervasive nature of microplastics in the global environment. While once thought to be limited to impacts on the natural world, microplastic pollution is beginning to become a detriment to humans too.
The study emphasises a number of disturbing trends that show that humans are consuming vast amounts of microplastic material through diet.
Humans are highly mobile, so ingestion and then excretion of food and water containing microplastics presents an opportunity for humans to act as vectors to further spread microplastics around the world.
Not only this, ingesting microplastics may be placing humans at risk of exposure to the various chemicals found within the plastic compounds. This is particularly problematic and concerning for those who are more sensitive to environmental toxins including children and pregnant mothers.
The work clearly highlights that micro-sized plastic pieces are pervasive pollutants and not only confined to the world’s oceans, and it is a valuable stepping stone in understanding human exposure.
Humans are certainly exposed to microplastics through food and air. It is important to understand that the particle exposure numbers presented are a current best guess based on a narrow number of studies. The authors rightly point out the large amount of variation in their estimates and make known current limitations in the methods used to quantify plastic exposure in consumed items.
For this to be addressed, we need measurement techniques that can quantify the smaller particles, and we need to understand the measurement uncertainty associated with microplastic analysis. Without a knowledge of the uncertainty, it is impossible to know what confidence can be placed on the reported data and it is challenging to assess the comparability of different measurements.
This is an emerging but rapidly progressing field of science where improved techniques for assessing exposure levels and burdens is key. Once we better understand human exposure levels then we can begin to comprehend whether there are any health effects from consuming microplastics.
Dr Lauren Roman is a CSIRO Postdoctoral researcher at CSIRO Oceans and Atmosphere
Plastics in the environment are a serious environmental issue. Wildlife is killed by ingesting plastic, usually due to (macro)plastic causing blockages in their stomachs.
There is some evolving research into health effects due to plastic ingestion at the cellular level in wildlife studies. Usually the exposure-to-plastic levels in wildlife to detect these cellular effects are quite high (much higher than I expect you would find in humans).
Irrespective of the accuracy of this human exposure estimation, whether environmentally relevant exposure causes health effects is key. Regarding human health effects, to the best of my knowledge in the scientific literature, there is currently no credible scientific evidence linking human dietary exposure to microplastics in their diet (shellfish, plastic bottles etc) to negative health effects.
This doesn't mean that there are no negative health effects, it's possible there are and they just haven't been found, but imminent danger is very unlikely.
Oliver Jones is Professor of Chemistry at RMIT University in Melbourne, Australia
This is an interesting and well-reasoned study predicting the possible level of exposure of humans to microplastics (particles of plastic less than 5 millimeters long) via food and drink.
However, while the numbers might at first sound quite scary it should be kept in mind that this work is only an estimate of possible consumption, in the USA, and is based on extrapolation rather than direct measurements. And the authors are good enough to admit there is also a lot of variation in the data.
Even if the values for microplastic consumption are correct, they tell us nothing about any potential health effects, if any.
No harm has yet been demonstrated to humans from microplastics. Indeed, previous research estimated that humans get more exposure to microplastics from dust than food.
That said, the data are certainly a wake-up call to the potential scale of the problem. Microplastics are an area where more science is welcome as we simply don’t yet know enough about the issue to make robust conclusions about the possible risk.
This report provides an alarming indication of the wider impacts of plastic pollution. It’s a crisis that is not only blighting our landscapes and oceans but affecting the food we eat and the water we drink.
Its findings mirror those of a larger report undertaken by the University of Newcastle in collaboration with WWF launching next week, which looks at the issue at a global level and proposes a path towards ending the disastrous leakage of plastic across nature by 2030.
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