ARU research on the effects of plastic pollution in aquatic and terrestrial environments has helped safeguard the environment from single-use plastics and will help prevent the substitution of conventional plastics with biodegradable alternatives before ecotoxicological effects are known.
It has been used as evidence to shape national and international policy, and reduce the single-use plastic footprint of key businesses. It has also raised awareness of plastic pollution, encouraging governments, businesses, and individuals to take action against it.
Single-use plastics account for 40% of global plastic production annually, and 50-70% of the plastic litter in marine, freshwater and terrestrial environments. Microplastics (pieces of plastic smaller than 5mm) are the most abundant solid waste on Earth.
While we have a reasonable understanding of the threat that (micro)plastic litter can pose to individual organisms, we know less about the harm it causes to biodiversity and ecosystem functioning.
We also need to increase our understanding of the effects of bio-based, biodegradable plastics, which have been increasingly adopted as an alternative to conventional, single-use plastics.
This research on microplastics was the first to evaluate how plastic pollution can affect entire communities of organisms and ecosystem functioning, rather than individual species in isolation.
Dr Green and Dr Boots conducted their research in a mesocosm (an outdoor experimental system that examines the natural environment under controlled conditions) featuring natural, flowing seawater with intact sediment cores.
They found that adding microplastics altered nutrient cycling by decreasing the flux of inorganic nutrients (including ammonium and silicate) from the sediment. They also discovered a reduction in the biomass of microphytobenthos (microscopic, primary producers in sediment).
In muddy sediment, dominated by Ostrea edulis (European flat oysters), adding microplastics caused species known to be indicators of pollution (e.g. oligochaetes) to become dominant.
The researchers also investigated the effects of smoked cigarette butts – another type of single-use plastic litter. They found that that smoked cigarette butts reduced the germination success and shoot length of Trifolium repens (white clover) by 27% and 28% respectively, and that of Lolium perenne (perennial ryegrass) by 10% and 13%.
They also found that butts reduced the root biomass of clover by 60%, and the plastic filter on its own negatively affected germination success, shoot length and root biomass.
Dr Green and Dr Boots discovered that microplastics made from polymers that are marketed as biodegradable or compostable, such as polyactic acid (PLA) can have similar effects on marine and terrestrial ecosystems to commonly-used non-biodegradable polymers, such as high-density polyethylene (HDPE) and polyvinyl chloride (PVC).
These types of microplastics disrupted the immune systems of blue mussels, filtration rates of Mytilus edulis (blue mussels) and Crassostrea gigas (Pacific oysters), and biomass of Apporrectodae rosa, an endogenic earthworm.
They also altered the biodiversity and abundance of marine organisms, decreased the biomass of algae and plants in marine and terrestrial ecosystems, and altered marine sediment nutrient cycling.
Dr Green and Dr Boots also assessed the impacts of glitter as little on freshwater ecosystems for the first time, finding that biodegradable, cellulose-based, traditional (PET) polymers, and mineral (mica) glitters all had similar effects on plants and algae. For example, cellulose-based glitter led to an increase of non-native snails.
Dr Green was nominated as a technical expert to the Risk Assessment Committee (RAC) of the European Chemicals Agency (ECHA), which implements the EU’s chemicals legislation across all 27 member states and ensures that companies comply with European law.
Dr Green made several formal interventions at ECHA RAC’s Helsinki meeting (RAC-51) on 26 November 2019, leading to two specific changes:
Since 2018, Dr Green has been the Advising Environmental Scientist on the Oceans Together business forum, led by DP World London Gateway, which aims to influence the actions of businesses in order to help them to reduce their use of single-use plastics.
Since Dr Green joined the forum, the businesses involved have used 12,800kg less single-use plastic, as her research inspired them to switch to reusable alternatives. For example:
In July 2020, Dr Green presented research on cigarette butts at a Tidy Britain All-Party Parliamentary Group meeting organised by Keep Britain Tidy on smoking-related litter.
This contributed to the introduction of voluntary extended producer responsibility (EPR) for tobacco companies, which will hold tobacco companies to account over the collection, transport, processing and safe disposal of their tobacco product waste.
Dr Green was an invited speaker at a Royal Society of Chemistry event, Microplastic pollution: everyone's problem but what can do about it? (London, 16 October 2017).
She was also an invited expert reviewer and workshop participant at a DEFRA workshop, Marine Plastic Pollution Evidence Review underpinning Policy and Gap Analysis on Marine and Fisheries Policy Area (London, 12-13 March 2019).
“She was also a lead author on the United Nations Environment Programme 2021 report From Pollution to Solution: a global assessment of marine litter and plastic pollution, and this has helped shaped global policy.
For a time, Dr Green and Dr Boots’ research on cigarette butts was in the top 5% for media attention of any research article tracked using Altmetric, scoring higher than 99% of its contemporaries and generating widespread public engagement through television, radio and online news outlets, and on social media.
Additionally, Dr Green and Dr Boots’ research on microplastics has:
We have mapped our REF 2021 impact case studies against the United Nations' Sustainable Development Goals (SDGs).
The 17 SDGs, adopted by all UN Member States in 2015, are an urgent call for action. They recognise that ending poverty and other deprivations must go hand-in-hand with strategies that improve health and education, reduce inequality, and spur economic growth – all while tackling climate change and working to preserve our oceans and forests.
This case study is mapped to SDG 12: Ensure sustainable consumption and production patterns, target 12.4.