EXPERT REACTION: We consume over 74,000 microplastic particles a year

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.

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.

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.

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.

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.

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.