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At the beginning of January of the year 2021, a huge storm named Filomena left the biggest snow storms that Spain had experienced in the last half century . And in addition to really inhospitable weather, the storm also brought a new type of denial. As the streets were flooded with snow, social networks were flooded with people collecting snowballs and burning them using matches, lighters or kitchen torches. They were surprised that no water dripped, that the area where the flame had touched the snow was blackened, and that there was a burning smell. The so-called “conspiracy theories” soon spread their message through the networks: “Snow is plastic.”
Of course, snow is not made of plastic. But leaving aside the absurdity of this approach, what is certain is that there is plastic in the snow , but in such small particles and in such small quantities that it would be very difficult to find it in a single snowball .
But the microplastics are there. In the atmosphere, on the ground and in the sea, waiting for precipitation in the form of rain or snow to drag these particles and deposit them.
What is a microplastic?
Microplastics are tiny pieces of non-biodegradable plastics. In general, they come from larger pieces of plastic , which living beings are unable to degrade and metabolize in any way, and due to erosion, they end up breaking into smaller and smaller fragments . Microplastics are considered all fragments measuring less than 5 millimeters , and can reach up to 10 microns (ten thousandths of a millimeter).
Among these microplastics there is everything: polyamides, polycarbonates, polyesters, polystyrenes, polyethylenes, polypropylenes, polyvinyls, and more substances that start (or not) with “poly-“.
Since we began to discard plastics, they have been accumulating, fragmenting, disintegrating and dispersing everywhere imaginable, until they have become ubiquitous . They are found in the soil, in rivers, in the seas, in glaciers, floating in the atmosphere … we have found them inside the tissues of plants, and even in our blood .
What do microplastics do in the rain or snow?
If microplastics are found on land and in water, it only takes a bit of wind for them to end up suspended in the atmosphere. In fact, the atmosphere is the most important factor in the long- distance transport of microplastics, ahead of ocean currents.
In several cities, the concentrations of microplastic particles reach alarming levels. Only the plastics that precipitate dry – not dragged by water or snow – exceed 500 particles per square meter per day in Hamburg. However, in the polar regions the concentration is much lower.
When it comes to precipitation in the form of rain or snow, the amount of microplastics that precipitate is directly related to that in the atmosphere. In some places in Bavaria, Germany, up to 145 000 plastic particles per liter of precipitation , although the European average is around 24,600 particles per liter. Unfortunately, there are no specific data for Spain , at least for now.
What harm can it do?
Of the microplastics present in the atmosphere, a person can consume more than 1 000 microplastic particles per year, and more than 3,000 if it is a child . Not counting those that enter our body through food or with some cosmetics.
We know that these particles can reach the blood —through the digestive system, from mucosal contact, or through the lungs. The human placenta is permeable to certain types of microplastics, and bioaccumulation has been observed in the liver, kidneys, and intestine .
In pharmacy, certain polymeric carriers are used so that certain drugs can cross the blood-brain barrier —and pass from the blood to the nervous system—. If these microplastic particles, administered in a controlled manner, can do it, there is nothing to suggest that others of a similar nature, but obtained from the environment, are also capable of doing it.
The effect of the consumption of microplastics on human health has not yet been well studied , but in general, the expected results are not encouraging. There are three ways in which they could generate negative impacts .
On the one hand, physical damage ; the particles could erode living tissue, and the smallest could cross cell membranes and cause damage inside the cell. Effects related to oxidative stress, cell damage and inflammation associated with the presence of microplastics have been observed.
On the other hand there is the possibility of chemical toxicity . The particles can generate effects of disruption in the endocrine system , either by the plastic itself, or by substances previously adsorbed and later released in the human body.
Furthermore, toxic effects can occur unexpectedly ; If a plastic particle encapsulates a toxic substance and transports it to an organ where it would not normally be able to reach—for example, the nervous system through the blood-brain membrane—it could produce effects that are not even contemplated .
Third, many microorganisms find refuge in porosities and recesses of plastic particles . In this way, microplastics can become vectors for pathogens and parasites .
REFERENCES:
Bergmann, M. et al. 2019. White and wonderful? Microplastics prevail in snow from the Alps to the Arctic. Science Advances, 5(8), eaax1157. DOI: 10.1126/sciadv.aax1157
Evangeliou, N. et al. 2020. Atmospheric transport is a major pathway of microplastics to remote regions. Nature Communications, 11(1), 3381. DOI: 10.1038/s41467-020-17201-9
Klein, M. et al. 2019. Microplastic abundance in atmospheric deposition within the Metropolitan area of Hamburg, Germany. Science of The Total Environment, 685, 96-103. DOI: 10.1016/j.scitotenv.2019.05.405
Leslie, H. A. et al. 2022. Discovery and quantification of plastic particle pollution in human blood. Environment International, 107199. DOI: 10.1016/j.envint.2022.107199
van Weert, S. et al. 2019. Effects of nanoplastics and microplastics on the growth of sediment-rooted macrophytes. Science of The Total Environment, 654, 1040-1047. DOI: 10.1016/j.scitotenv.2018.11.183
Vethaak, A. D. et al. 2016. Plastic Debris Is a Human Health Issue. EnvironmentalScience & Technology, 50(13), 6825-6826. DOI: 10.1021/acs.est.6b02569
