In October 2018, a highly media study was made public that confirmed the presence of microplastics in human feces. Although many people would put their hands to their heads, the results of this work should not surprise us, since we know that we live surrounded by these small particles: they are found on our clothes, in the air we breathe, they land in food and, obviously, they end up in our digestive tract.
They are increasingly present in our lives, but what exactly are these microplastics that so much is talked about? In 2015, the Netherlands Institute for Public Health and the Environment proposed a very detailed definition that describes microplastics as solid, synthetic particles smaller than five millimeters in size. Furthermore, they are insoluble in water and have a very low ability to degrade.
Microplastics come from very diverse sources: mainly due to the degradation of larger plastic materials , but also from cosmetic products, paints, tires, cleaners …
For some years now, the scientific community has had microplastics in their sights, since we are talking about a global environmental problem: according to a 2015 report in the journal Science , about eight million tons of plastic enter the oceans of the world per year. Many of these wastes are outrageously visible, like the famous Pacific garbage island, but in other cases, like microplastics, the contamination is more difficult to detect. A study published in the journal Royal Society Open Science in 2014 already warned that the deep sea is becoming a large deposit of microscopic plastic debris and, more recently, Nature Communications echoed an analysis of the accumulation of microplastics in the Arctic ice, a worrying fact in a very sensitive region whose environmental problems can have an impact on the entire planet.
Although the effects of microplastic pollution on ecosystems are not well understood, we are talking about an emerging problem on which it is necessary to investigate more and, above all, apply the precautionary principle, both in terms of environmental risks as well as food safety. We are talking about particles that, although in principle inert, are very easily dispersed and also persist and accumulate in the environment. Much more research is therefore needed to characterize the behavior of microplastics and also to quantify their presence, not only in the ocean, but also in terrestrial ecosystems.
Andreu Rico is a researcher at IMDEA Agua (Madrid) and participates in the IMPASSE project, which studies the impact of microplastics on agricultural systems and river ecosystems. The team is conducting different experiments in order to better understand the dynamics of microplastics in agricultural lands and their role as possible sources of pollution in runoff waters.
How do microplastics get to cultivated land? One of the main contributions comes from sewage sludge, which is very often used as fertilizers in agriculture. In a first phase, the IMDEA Agua researchers have quantified the concentration of microplastics present in the water before and after passing through the treatment plants, which are effectively very effective in eliminating this pollutant: “between 60 and 95% it stays in the mud ”, explains Andreu Rico. But it is a double-edged sword: microplastics are deposited in the sludge, yes, but these, as we have already mentioned, very frequently end up being used as agricultural fertilizers.
The next step is, therefore, to investigate the dynamics of this possible contamination by microplastics once the sludge is added to the crop fields. “In another of the experiments we have underway, we are comparing what happens in plots cultivated with barley and those that have been treated with sewage sludge with other control plots without treatment,” Rico explained to us. It will be necessary to quantify the accumulation of microplastics in the soil and also evaluate how much of them ends up leaving the system in the runoff water. In addition, another of the project activities will evaluate the effects on different species of invertebrates present in the soil.
Are there risks to human health?
It is precisely about the possible risks to organisms – and, by extension, to human health – that is where there seems to be great confusion: are we talking about a food safety problem?
Microplastics can enter the food chain in many ways and, as we have already seen, they are so present in our lives that we ingest them through everyday events such as drinking tap water or adding salt to stew. ” You have to bear in mind that the world is full of plastic: we ingest plastic continuously “, Marco Vighi, researcher at IMDEA Agua and local head of the IMPASSE project reminds us. “There is plastic in water, in food, even in the air! In fact, we have many problems so that the control plots – those that are not treated with sewage sludge – of our experiment are not contaminated with microplastics: just by walking by, we are already releasing them through the fibers of Our clothes”.
This is why, if we eliminate mussels or fish from our diet, we will not prevent microplastics from reaching the intestine. “There is a lot of confusion when it comes to ‘bioaccumulation’,” explains Vighi. “Microplastics do not accumulate, because they cannot cross cell membranes. The problem may be, however, in nanoplastics, they are much finer particles that could enter cells. We are trying to analyze this, but at a methodological level it is much more complicated than studying microplastics ”.
According to a report published in 2017 by the Spanish Agency for Consumption, Food Safety and Nutrition, “the presence of these particles in food is already identified as an emerging risk in the European Union, but there is still a lack of information about them, and in particular, on its toxicity and toxicokinetics ”. For example, another aspect that needs to be studied to better understand the health effects of microplastics has to do with their possible role as ‘Trojan horses’. Under certain conditions, microplastics could be both vehicles to which certain toxic particles adhere, as well as releasing agents, and there could really be the real problem of microplastics.
The fight is against plastic
At the beginning of 2018, the United Kingdom announced the implementation of a measure to prohibit the marketing of cosmetics containing microplastics. This is an important step that clearly indicates that there is general concern about the problem. According to a study published in 2009 in the journal Marine Pollution Bulletin , most facial cleansers contain polyethylene microplastics that are not captured by sewage plants and most likely end up in the ocean.
However, the fraction of microplastics that comes from cosmetics is very small and, as we have already seen, the greatest contribution comes from the degradation of larger plastics. If we want to fight against microplastics, we will have to fight against plastics, there is no other way. In this sense, the European Union has taken a giant step forward by announcing the ban on single-use plastics. This measure is part of the first European strategy on plastics, presented by the European Commission at the beginning of 2018. Although in Spain we still do not have specific legislation in this regard, the Ministry of Ecological Transition informs us that the matter is in progress. the future government roadmap and will try to move forward with the European Union.
In any case, and after many years of insistence and denunciation by environmental organizations and the scientific community, it seems that finally the environmental problem posed by plastics and, therefore, microplastics, is already on the political agenda. “We can do many things as consumers on a personal level”, researcher Marco Vighi reminds us, “but it is necessary to legislate to change the use we give to plastic today, that is the important thing. That is what is going to really change the world and our habits ”.
Advisors: Andreu Rico and Marco Vighi, researchers at the IMDEA Water Institute; Press Office of the Ministry of Ecological Transition.
Photography: Wolfram Burner
