November 29, 2019

expert reaction to report on microplastics in freshwater and soil

A report, published by The Royal Society, reports on microplastics in freshwater and soil, and discusses the evidence and action required. 

Prof Iseult Lynch, Chair of Environmental Nanoscience, University of Birmingham, School of Geography, Earth and Environmental Sciences, said:

“The Royal Society report provides a comprehensive and balanced summary of the current state of knowledge regarding microplastic pollution in the environment, and its potential hazards including for human health.  Importantly, the report places the current heightened concerns regarding microplastics into the broader context of other environmental threats such as climate change, nutrient and chemical pollution, sewage, land-use change and many more.

“The consideration of three potential means by which microplastics may affect organisms and humans, either through direct effects from the particulates themselves, through release of additives some of which have been shown to have endocrine disrupting properties, or through adsorption of other pollutants present in the environment and enhanced bioavailability of these but only if they are subsequently released inside organisms, provides a very balanced overview of the potential risks that need to be assessed and ranked.   It is notable that all three of these potential effects are similar to those arising from other anthropogenic particles such as diesel exhausts or mining dusts, where the effects are often a result of leeching and/or adsorption of other chemicals in addition to impacts from their particulate nature which can result in inflammatory responses and/or persistence in the body.

“The report correctly notes that there are significant discrepancies between observational field data and controlled laboratory experiments, many of which are performed at unrealistically high concentrations (a common concern in toxicological studies where establishment of a dose-response curve is needed) and under idealised conditions that miss much of the complexity of real environments. Such studies may thus significantly under or over-estimate the toxicity to the target organism in the absence of competing sinks such as other organisms that may compete better for the microplastics / food or natural transformation processes such as biofouling which can change the properties of the microplastics and thus their persistence in the water column, for example.

“Harmonised sampling, recovery / isolation, and detection and characterisation methods are missing, especially for particles at the smaller end of the microplastics size spectrum and for nanoscale plastic waste particles.

“In terms of terminology, it would be more appropriate to refer to microplastics as microscale plastic waste, and by extension, to nanoscale plastic waste, in order to distinguish clearly that the majority of the particles arise from the breakdown of macroscale plastic waste.  This is an important distinction as it indicates that these materials are regulated via waste legislation rather than via chemicals or consumer product legislation.  Indeed, as the report clearly states, the greatest potential to address the issue of microplastic pollution is via enhanced recycling of macroscale plastics, and thus to prevent the formation of microscale plastic waste in the first place.

“Given the scale of the research gaps, prioritisation should be given to understanding hotspots of accumulation in order to prioritise assessment of impacts on organisms in these areas, and on understanding longer term exposure effects in individual organisms, in populations and in terms of ecosystems services provided by the most sensitive organisms.”

Alice Horton, Anthropogenic Contaminants Scientist (Microplastics researcher), National Oceanography Centre (NOC), said:

“This is a balanced and informative report which clearly highlights some of the key gaps in our knowledge surrounding the ecological and human health risks posed by microplastics.

“As identified here, in order to understand these risks, it is essential that we look to understand not only the current status of microplastic pollution within the environment, but the possible future scenarios. This is especially important given that concentrations of microplastics in the environment will likely continue to increase, and high concentrations of microplastics have been shown to have adverse effects on a range of organisms.

“There is already evidence that microplastics have spread into remote regions around the world.

“Given that plastics can take tens or hundreds of years to degrade, ecosystems worldwide will be chronically exposed to microplastics. We do not yet know the implications of this long-term exposure.

“With further research and greater knowledge we can better assess possible harm that could be caused by the ever-increasing amounts of microplastics spread throughout the environment, and take measures to reduce this harm.

“It will not be possible to ‘clean’ the environment of all current plastics, therefore preventing more plastic from entering the environment is key. All parts across the supply chain must take responsibility for managing production, demand, usage and waste management.”

‘Microplastics in freshwater and soil, an evidence synthesis’ by the Royal Society was published at 00:01 UK time on Friday 29 November. 

Declared interests

Prof Iseult Lynch: No conflict of interest

Alice Horton: No conflicts of interest