Plastic pollution has been an area of growing public concern in recent years. Plastics and, in particular, microplastic pollution have been making headlines around the world and policymakers and regulators are increasing activity in this area. But what is the risk to our health and the environment? What do we know already and what research is necessary to better assess risk and guide practical policymaking?
These questions and more were debated at the recent 21st Annual Workshop of the Cefic Long-range Research Intitiative (Cefic-LRI) in Brussels. Opening the debate, Dr Jens C Otte from BASF noted that a search of scientific journals for the term ‘microplastics’ yielded some 2,486 articles with a clear increase in the number of papers published since 2010 and also a shift in context since then from an engineering focus to areas such as environmental sciences and human toxicology.
Plastic vs. particle: toxic for humans?
According to Dr Stephanie Wright of King’s College London, the topic of microplastics first emerged in the health field around 2004. There is a wide range of estimates with respect to our exposure to microplastics. Exposure to microplastic particles through ingestion range from 39,000 to 52,000 particles per person per year, with an additional exposure of 4,920 to 46,453 microplastic particles or fibres via inhalation. At the high end, our intake of such products “represents 15% of the calorific intake of the typical western diet” said Dr Wright. One of the few studies on exposure to microplastics through inhalation, identified an exposure rate of 123 microplastic particles a day for an individual while the actual particle number concentration (outdoor) was determined in another study to be as high as 10,000 particles of any nature and origin (PM10) per cm³. This indicates a rather low level of inhalation of microplastics, when looking at the overall particle load.
But is there a potential risk in terms of toxicity? The majority of available studies on the potential toxicity of microplastics are concerned with Nylon flock workers disease, a work-related interstitial lung condition, that was widely studied from 1998 to 2007. The studies did not clearly identify whether this was related to toxicity due to the polymer per se or a particle effect.
This question of plastic versus particle effects appears as a common theme in analysis of studies, yet they do not shed light on whether there is a toxicity issue or if adverse outcomes are determined by the size and/or shape of the particle.
Plastic microparticles themsleves are usually described as poorly soluble and of low toxicity, but we know that some synthetic fibres with a specific structure (for example, asbestos fibres and carbon nanotubes) cannot be digested by macrophages and therefore are not removed from biological systems.
Dr Wright stated that currently studies are skewing towards hazard assesment, but she believes that more relevant exposure studies at appropriate concentrations of microplastics are needed. And the inclusion of negative controls is essential to investigate the plastic versus particle conundrum.
Microplastics in the environment: assessing data
Work to develop and apply an environmental risk assessment framework for microplastic particles was described by Dr Todd Gouin of UK-based company EnvironResearch. In November 2018 the International Council of Chemical Associations (ICCA) held a symposium in California to consider what science was required to better comprehend the potential risk and to ensure that any future regulation was both effective and efficient.
It became apparent that there are a number of knowledge gaps , which call for enhanced collaborative work. Currently standard test methods are missing or not truly applicable to the search for the effects of microplastics. In addition, the infrastructure for data management is not adequate; meaning that there are doubts about the quality of some data, which allows for a wide interpretation of similar results by different stakeholders.
From a regulatory viewpoint the recent Science Advice for Policy by European Academies (SAPEA) Report on Microplastics summarises the current tools for microparticles within REACH, EU Waste regulations and environmental legislation. Unfortunately, the different instruments address varying aspects of the potential concerns associated with plastic microparticles. “There is a need to clarify the problem we are trying to address,” said Dr Gouin. “Are we looking to reduce risk? Or reduce harm? Or reduce the release of plastic?”
On the general question of risk of the adverse impact of plastic microparticles in the aquatic environment, the current concentrations are lower than those associated with adverse endpoints. So the data suggests no risk. But the big question is: “Are we measuring the right data?” Hence the need for a comprehensive open framework to properly assess today and project into the future. In particular, there is a need to better understand exposure and fate pathways for these particles, the natural degradation processes and their true effects.
Future research
Dr Gouin outlined two recently commissioned Cefic-LRI projects that are working in this area. Project LRI ECO 48 ‘Nano2Plast’, led by Professor Matthew MacLeod at Stockholm University, will estimate increasing concentrations of microparticles in the environment and embraces a flexible approach to cope with existing data gaps. The project should deliver a tool to start to understand the fate of plastic microparticles in the environement.
Project ECO 49 ‘METAS’ will look at microplastic effect thresholds for aquatic species under Professor Bart Koelmans at Wageningen University. The project will develop a QA process for data already out there with the aim of assessing if microparticles have an intrinsic toxicity or adverse effects are due to an indirect ‘bulk’ issue; where, for example, the ingestion of plastics is displacing nutrition for an organism.
Dr Gouin also stressed the need for work on effects using relevant species to develop better tests to understand the effects of exposure to plastic microparticles. And the physiochemical properties of the particles also need to be better characterised in terms of their size and shape distribution and chemical composition. This was essential to be able to relate intrinsic properties to possible effects. The two new LRI projects can help guide the complex matrix of testing that may be required and provide a practical testing context.
In terms of regulatory action, Dr Gouin thought that current moves were reacting to public pressure and not addressing true causes. All stakeholders need to work together. There is a real opportunity to innovate with plastic microparticles in terms of how we do risk assessment effectively and collaboratively.
Speaking of future research… Dr Nowak won this year’s Cefic-LRI award for her proposal to develop a fast and cost-efficient screening method for testing the persistence of chemicals in complex environments. Watch the video here.
Presentations of the Cefic-LRI workshop are available here.
Click here to see the photo gallery.
