Chemicals and pieces of plastic produced through the use of packaging are migrating into food and harming plants and soil ecosystems, scientists warn.
Ecologists from the Free University of Berlin contributed one of three evidence-based essays exploring the problem of microplastics and how best to tackle them.
The German team, led by Matthias Rillig, they suggest that microplastic pollution appears to be interfering with the ‘very fabric of the soil environment’.
They have called for a major concerted effort among scientists and governments to understand the pervasive effects of plastic particles on soils and ecosystems.
Chemicals and pieces of plastic produced through the use of packaging are migrating into food and harming plants and soil ecosystems, scientists warn
MICROPLASTICS CAN PASS FROM PREGNANT MOTHERS TO A BABY
Tiny plastic particles have been discovered in the organs of unborn baby rats, the first time microplastics have been seen to cross the placenta in live mammals.
Researchers found the particles inhaled by the mother travelled across the placenta and into the developing lungs, brain and heart of the foetus.
The study also revealed that nanoparticles of polystyrene were able to reach the foetus within 90 minutes of the mother being exposed.
One day before the foetuses were due to be born, the babies of mothers who had been exposed to plastic were seven per cent smaller than expected.
Scientists do not yet know if the findings also apply to human pregnancy but the findings are a cause for concern, they say.
Some 8,300 million tons of plastics have been manufactured since production exploded in the 1950s, with more than 75% ending up as waste, they found.
Plastic waste fragments into increasingly smaller but environmentally persistent ‘microplastics,’ with potentially harmful effects on people, wildlife and ecosystems.
Plastic production increased from two million metric tons a year in 1950 to 380 million metric tons by 2015 and is expected to double by 2050.
The plastic pollution crisis will worsen, experts say, as petrochemical companies shift from fossil fuels to fracking, which produces the plastic feedstock ethane.
Microplastics are found in environments, including terrestrial ecosystems, planetwide and so far most research has focused on ecotoxicology, examining effects on performance of soil biota in controlled settings.
As research pivots to a more eco- system and global change perspective, questions about soil-borne biogeochemical cycles become important.
Rillig and colleagues say microplastics can affect the carbon cycle in numerous ways, for example, by being carbon themselves and by influencing soil microbial processes, plant growth, or litter decomposition.
‘Great uncertainty surrounds nano-sized plastic particles, an expected by- product of further fragmentation of microplastics,’ said Rillig.
‘Our knowledge of microplastic effects in soils is quite limited—considering that the first papers describing effects on soils appeared only a few years ago—but rapidly increasing,’ the study author added.
‘A major concerted effort is required to understand the pervasive effects of microplastics on the functioning of soils and terrestrial ecosystems,’ the team say.
As part of their essay, Rillig says future research needs to capture the immense diversity of these particles in terms of chemistry, ageing, size, and shape.
Ecologists from the Free University of Berlin contributed one of three evidence-based essays exploring the problem of microplastics and how best to tackle them
URBAN FLOODING IS FLUSHING MICROPLASTICS INTO THE OCEANS FASTER THAN THOUGHT
Urban flooding is causing microplastics to be flushed into our oceans.
Waterways in Greater Manchester are now so heavily contaminated by microplastics that particles are found in every sample.
This pollution is a major contributor to contamination in the oceans, researchers found.
This debris – including microbeads and microfibres – are toxic to ecosystems.
Scientists tested 40 sites around Manchester and found every waterway contained these small toxic particles.
It has long been known they enter river systems from multiple sources including industrial effluent, storm water drains and wastewater.
Most rivers examined had around 517,000 plastic particles per square metre, according to researchers from the University of Manchester.
Following a period of flooding, the researchers re-sampled at all the sites.
They found levels of contamination had fallen at the majority of them, and the flooding had removed about 70 per cent of the microplastics.
This demonstrates that flood events can transfer large quantities of microplastics from rivers to oceans.
The fact that microplastics are particles that contain a lot of carbon, typically around 80% , makes them fairly unique in relation to other global change factors, including greenhouse gas emissions and deforestation.
Microplastic carbon is already present in our soils, probably still making up only a tiny proportion of total soil organic matter carbon in most cases, but Rillig says this is expected to change in the future.
The study authors say future studies should examine ways these plastics can be removed from the soil, as longer term they could have a serious impact.
They could affect plant growth in a number of ways, including by changing soil structure and bulk density, which can affect root penetration resistance, changes in water holding capacity, and others.
This could have a long term, detrimental affect on the availability of plants and foodstuff for animals throughout the planet.
This is one of three essays published in the journal PLOS Biology, exploring pressing challenges in a range of health and policy areas related to microplastics.
The different papers explore the difficulty of developing health protective policies to reduce the impact the plastics will have on human bodies.
They also look at the migration of toxic and undisclosed plastic additives into food and understanding how microplastics impact carbon in soils.
‘Plastic, for all its uses, has left a trail of debris from the deepest ocean trenches to the remotest polar reaches,’ wrote Liza Gross in a foreword for the studies.
‘Researchers are finding microplastics in the gut or tissue of nearly every living thing they examine, including the placentas of unborn children.’
Gross said microplastics are everywhere and researchers are just starting to get a handle on how to study the influence of this emerging contaminant on diverse environments and organisms.
‘But as the contributors to this collection make clear, the pervasiveness of microplastics makes them nearly impossible to avoid,’ the author wrote.
‘And the uncertainty surrounding their potential to harm people, wildlife, and the environment, they show, underscores the urgency of developing robust tools and methods to understand how a material designed to make life easier may be making it increasingly unsustainable.’
The collection of three papers are published in the journal PLOS Biology.
WHAT FURTHER RESEARCH IS NEEDED TO ASSESS THE SPREAD AND IMPACT OF MICROPLASTICS?
The World Health Organisation’s 2019 report ‘Microplastics in Drinking Water’ outlined numerous areas for future research that could shed light on how far spread the problem of microplastic pollution is, how it may impact human health and what can be done to stop these particles from entering our water supplies.
How widespread are microplastics?
The following research would clarify the occurrence of microplastics in drinking-water and freshwater sources:
- More data are needed on the occurrence of microplastics in drinking-water to assess human exposure from drinking-water adequately.
- Studies on occurrence of microplastics must use quality-assured methods to determine numbers, shapes, sizes, and composition of the particles found. They should identify whether the microplastics are coming from the freshwater environment or from the abstraction, treatment, distribution or bottling of drinking-water. Initially, this research should focus on drinking-water thought to be most at risk of particulate contamination.
- Drinking-water studies would be usefully supplemented by better data on fresh water that enable the freshwater inputs to be quantified and the major sources identified. This may require the development of reliable methods to track origins and identify sources.
- A set of standard methods is needed for sampling and analysing microplastics in drinking-water and fresh water.
- There is a significant knowledge gap in the understanding of nanoplastics in the aquatic environment. A first step to address this gap is to develop standard methods for sampling and analysing nanoplastics.
What are the health implications of microplastics?
Although water treatment can be effective in removing particles, there is limited data specific to microplastics. To support human health risk assessment and management options, the following data gaps related to water treatment need to be addressed:
- More research is needed to understand the fate of microplastics across different wastewater and drinking-water treatment processes (such as clarification processes and oxidation) under different operational circumstances, including optimal and sub-optimal operation and the influence of particle size, shape and chemical composition on removal efficacy.
- There is a need to better understand particle composition pre- and post-water treatment, including in distribution systems. The role of microplastic breakdown and abrasion in water treatment systems, as well as the microplastic contribution from the processes themselves should be considered.
- More knowledge is needed to understand the presence and removal of nanoplastic particles in water and wastewater treatment processes once standard methods for nanoplastics are available.
- There is a need to better understand the relationships between turbidity (and particle counts) and microplastic concentrations throughout the treatment processes.
- Research is needed to understand the significance of the potential return of microplastics to the environment from sludge and other treatment waste streams.
To better understand microplastic-associated biofilms and their significance, the following research could be carried out:
- Further studies could be conducted on the factors that influence the composition and potential specificity of microplastic-associated biofilms.
- Studies could also consider the factors influencing biofilm formation on plastic surfaces, including microplastics, and how these factors vary for different plastic materials, and what organisms more commonly bind to plastic surfaces in freshwater systems.
- Research could be carried out to better understand the capacity of microplastics to transport pathogenic bacteria longer distances downstream, the rate of degradation in freshwater systems and the relative abundance and transport capacity of microplastics compared with other particles.
- Research could consider the risk of horizontal transfer of antimicrobial resistance genes in plastisphere microorganisms compared to other biofilms, such as those found in WWTPs.
Can water treatment stop microplastics entering our water supplies?
Although water treatment can be effective in removing particles, there is limited data specific to microplastics. To support human health risk assessment and management options, the following data gaps related to water treatment need to be addressed:
- More research is needed to understand the fate of microplastics across different wastewater and drinking-water treatment processes (such as clarification processes and oxidation) under different operational circumstances, including optimal and sub-optimal operation and the influence of particle size, shape and chemical composition on removal efficacy.
- There is a need to better understand particle composition pre- and post-water treatment, including in distribution systems. The role of microplastic breakdown and abrasion in water treatment systems, as well as the microplastic contribution from the processes themselves should be considered.
- More knowledge is needed to understand the presence and removal of nanoplastic particles in water and wastewater treatment processes once standard methods for nanoplastics are available.
- There is a need to better understand the relationships between turbidity (and particle counts) and microplastic concentrations throughout the treatment processes.
- Research is needed to understand the significance of the potential return of microplastics to the environment from sludge and other treatment waste streams.
