There is not yet enough evidence to conclude that microplastics do or do not cause harm to the environment, scientists said following a review of over 300 global studies. However, other studies believe that plastic pollution has become an epidemic which threatens our environment, and causes serious dangers to the marine biology.
The research team believes that future research into the impact of microplastics needs to be much more focused, after the study revealed a large mismatch in the types of microplastics measured in the environment to those tested for effects in the laboratory.
There is increasing scientific and public concern over the presence of microplastics in the environment, with microscopic plastic beads, fragments and fibres found in waterways around the globe – from rural streams to major oceans. A review of 320 studies by the University of York revealed that monitoring tends to focus only on a fraction of the microplastic size range – leading to “major knowledge gaps” concerning our understanding of the impact they have on the environment.
Microplastics have been defined as plastic particles less than five mm in size. They can come from several sources, including cosmetics, tyres, and clothing such as fleece. The review concludes that the concentrations of particles detected in the natural environment are orders of magnitude lower than those reported to affect feeding, reproduction, growth, tissue inflammation, and mortality in organisms.
However, the review found that environmental monitoring studies typically look at larger particles, down to 100th of a mm, while the effects studies often look at much smaller particles, down to 10000th of a mm. Polystyrene is the material that has been most analysed in laboratory effects studies, whereas in the real environment these particles make up only 5% of the monitored materials. This makes it problematic to conclude what the real impacts are.
The authors of the report said that there is an urgent need for more studies to plug the gaps in our scientific knowledge. The study revealed that fragments and fibres dominate, with beads accounting for only 3% of the detected microplastic types.
Alistair Boxall, from the University of York’s Environment and Geography Department, said: “Based on our analysis, there is currently limited evidence to suggest microplastics are causing significant adverse impacts.” Boxall added that, however, currently, he and his team are trying to compare apples to pears when it comes to comparing monitoring data, with effects data.
The researcher explained further that there is an urgent need for better quality and more holistic monitoring studies, along with more environmentally realistic effects studies on the particle sizes, and material types that are actually in the environment.
“We believe regulations and controls may be focusing on activities that are having limited impact, and ignoring the most polluting activities such as releases of small particles from tyres on our cars,” said Boxall.
Much of that plastic waste ends up in oceans, where it is responsible for killing one million seabirds and 100,000 marine mammals annually, according to the UN Environment. The enormous quantities of plastic particles can be found in the water in virtually every river, sea, and ocean. It harms the marine life by the tiny plastic particles floating in the water. One other problem happens when fish, seabirds or marine mammals mistake the particles for food and consume them, and these fish could be consumed by humans.
Another recent study which shed light on the danger of microplastic pollution in our oceans revealed that microplastics were found in the stomachs of nearly three out of every four mesopelagic fish caught in the Northwest Atlantic, one of the highest levels globally.
According to the study, microplastic contamination may also spread from organism to organism in the food-chain pyramid, where prey is eaten by predator. Since the fragments can bind to chemical pollutants, these associated toxins could accumulate in predator species.
Findings of the study published in the Frontiers in the Marine Science journal expressed concerns as the affected fish could spread microplastics throughout the ocean. The fish are also prey for fish eaten by humans, which means that microplastics could indirectly contaminate our food supply through the transfer of associated microplastic toxins.
Alina Wieczorek from the National University of Ireland, Galway, and lead author of the study said “microplastic pollution has been in the news recently, with several governments planning a ban on microbeads used in cosmetics and detergents. The high ingestion rate of microplastics by mesopelagic fish that we observed has important consequences for the health of marine ecosystems and biogeochemical cycling in general.”
Mesopelagic fish is a food source for a large variety of marine animals, including tuna, swordfish, dolphins, seals, and seabirds. Despite living at depths of 200-1,000 metres, mesopelagic fish swim to the surface at night to feed then return to deeper waters during the day. Through these vertical movements, mesopelagic fish play a key role in the biogeochemical cycling processes, which means the cycling of carbon and nutrients from the surface to the deep sea.
This means that they could spread microplastic pollution throughout the marine ecosystem, by carrying microplastics from the surface down to deeper waters, affecting deep-sea organisms, illustrates the study.
To investigate the important role of mesopelagic fish in marine ecosystems further, Wieczorek and colleagues set out to catch fish in a remote area of the Northwest Atlantic Ocean: an eddy (whirlpool) off the coast of Newfoundland. The team caught mesopelagic fish at varying depths, then examined their stomachs for microplastics back in the lab by using a specialised air filter so as not to introduce airborne plastic fibres from the lab environment.
As the researchers were extremely careful to exclude contamination with fibres from the air, they are confident that the fish had ingested the fibres in the sea. Finding high levels of fibres in the fish is significant, as some studies investigating microplastics in fish have dismissed such fibres as contaminants from the lab environment, meaning their role as a pollutant may have been underestimated.
The Nile River is one of ten rivers that are the main culprits for plastic pollution in the oceans. Those ten rivers beside the Nile and the Niger in Africa, the Yangtze, Yellow, Hai He, Pearl, Amur and Mekong in east Asia, the Indus and Ganges Delta in south Asia, according to a previous study.
The study that appeared in the Environmental Science and Technology journal, showed that those ten rivers contribute by between 410,000 and 4m tonnes a year to oceanic plastic debris, with 88 to 95% of the total plastic pollutants. The interdisciplinary research team of German hydrologists and specialists in environmental engineering analysed a global compilation of data on plastic debris in the water column across a wide range of river sizes.
One of the findings of the study pointed out that plastic debris loads, both microplastic that are smaller than 5 mm, and macroplastics that are bigger than 5 mm, are positively related to the mismanaged plastic waste (MMPW) generated in the river catchments. This relationship is nonlinear where large rivers with population-rich catchments delivering a disproportionately higher fraction of MMPW into the sea, according to the study.
Christian Schmidt, a hydrogeologist at the Helmholtz-Centre for Environmental Research (UFZ) in Leipzig, Germany, and the lead author of the study, said “It is still impossible to foresee the ecological consequences of this. One thing is certain, however: this situation cannot continue, but as it is impossible to clean up the plastic debris that is already in the oceans, we must take precautions and reduce the input of plastic quickly and efficiently.”
But on the other side, we have an earlier study which states that although microplastics are increasingly seen as an environmental problem of global proportions especially in the ocean and their effects on marine life, researchers are concerned about the lack of knowledge regarding potential consequences of microplastics in agricultural landscapes from application of sewage sludge.
Sewage sludge is in principle waste, but it can also represent a resource in agriculture and horticulture. Fertiliser based on sludge contains valuable nutrients, but sustainable use requires that the levels of undesirable substances in the sludge is kept under control. Waste water treatment plants receive large amounts of microplastics emitted from households, industry, and surface runoff in urban areas. Most of these microplastics accumulate in the sewage sludge, according to the study which was published in the journal of Environmental Science and Technology.
The researchers behind the article are Luca Nizzetto and Sindre Langaas from the Norwegian Institute for Water Research, and Martyn Futter from the Swedish University of Agricultural Sciences in Uppsala.
“We have found figures from the Nordic countries suggesting that a large fraction of all the microplastics generated in Western societies tend to end up in the sludge in wastewater treatment plants,” says Nizzetto, adding, “Via the sludge the particles are transferred to agricultural soils.”
In the same context, the smallest microplastics in our oceans, which go largely undetected and are potentially harmful, could be more effectively identified using an innovative and inexpensive new method, developed by researchers at the University of Warwick.
The research team of the study, led by Gabriel Erni-Cassola and Joseph A. Christie-Oleza from Warwick’s School of Life Sciences, has established a pioneering method to detect the smaller fraction of microplastics, many as small as 20 micrometres (comparable to the width of a human hair or wool fibre) using a fluorescent dye.
According to the study which was published in the Environmental Science and Technology journal, the dye specifically binds to plastic particles, and renders them easily visible under a fluorescence microscope. Depending on this method, scientists could distinguish microplastics amongst other natural materials and makes it easy to accurately quantify them.
The researchers took samples from surface sea water and beach sand from the English coast around Plymouth and after extracting the microplastics from these environmental samples, they applied their method and were able to quantify the smaller fraction of microplastics effectively.
According to the paper, scientists detected a much larger amount of small microplastics (smaller than 1 mm) than was previously estimated, and significantly more than would have been identified previously with traditional methods.
What makes it very important, is that these results challenge the current belief of the apparent loss of the smallest microplastics from surface seawater, and highlights the need for further research to understand the real fate of plastic waste in the oceans. “Using this method, a huge series of samples can be viewed and analysed very quickly, to obtain large amounts of data on the quantities of small microplastics in seawater, or, effectively, in any environmental sample,” said Erni-Cassola.
