Microplastic Pollution: Everyone’s problem - but what can be done about it?
Dec 20 2017
Author: Tom Lynch on behalf of Tom Lynch - Independent Analytical Consultant
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That was the question posed to over 70 delegates for the one-day workshop held at the Royal Society of Chemistry (RSC) in London on the 16th October 2017.
The day was organised by the RSC Water Science Forum (WSF) and featured presentations from leading experts in microplastic pollution from marine and freshwater backgrounds (Figure 1). The event was endorsed by the Institute of Chemical Engineers (IChemE) Water Special Interest Group and the Society of Chemical Industry (SCI).
The aim of the workshop was to share the latest information and review the current understanding of the risks and knowledge gaps in this highly topical area.
Delegates were welcomed by Adrian Clark from the RSC WSF who introduced an opening video address by Dr Therese Coffey, the UK Parliamentary Under Secretary of State for the Environment and Rural Life Opportunities, who reinforced the UK government’s support for tackling the issues associated with microplastic pollution.
The main scientific programme was introduced by Prof Richard Thompson from the Plymouth University who gave an excellent introduction and overview of microplastics. He began by clarifying the definition of microplastics based on their size and, although many define them as particles of < 1 mm, he quoted the USA Dept. of Commerce National Oceanic and Atmospheric Administration (NOAA) definition of particles < 5 mm as the now more generally accepted upper size limit. The lower bound size limit of microplastics is not defined, but the perceived risks associated with microplastics are mainly associated with particle ingestion and so particle sizes down to the micron level and lower were considered potentially important. It has been reported that ~75% of marine debris found on beaches originates from plastics and that ~10% of literature reports on plastics in the environment concerned microplastics. Prof Thompson mentioned similar quantities of plastic debris have also been found in the deep ocean (1).
Prof Thompson then discussed the primary and secondary routes by which microplastics are formed and enter a body of water (Figure 2). Primary microplastics consist of manufactured raw plastic material, such as virgin plastic pellets, scrubbers, and microbeads that enter the ocean via runoff from land. Secondary microplastic introduction occurs when larger plastic items enter a beach or ocean and undergo mechanical, photo and/or biological degradation. This degradation breaks the larger pieces into progressively smaller plastic fragments which eventually become undetectable to the naked eye. Microfibres from textiles were also highlighted as becoming increasingly prevalent in marine environments and was up to four orders of magnitude more abundant (per unit volume) in deep-sea sediments from the Atlantic Ocean, Mediterranean Sea and Indian Ocean than in contaminated sea-surface waters (1). He then went on to discuss the proposed sources of risk from microplastic ingestion by species. In addition to the physical risks from the polymer particles there are also chemical risks posed by the base polymer, its degradation products and chemical additives, such as antioxidants, which are added to improve polymer performance in use. Also, the oleophilic nature of many plastics mean they have the potential to absorb hydrophobic chemical contaminants present in the water and may provide a mechanism to transport concentrated contaminants to organisms. Prof Thompson then gave an overview of recent studies (2, 3, 4) into these areas of concern and also stated that there needs to be a harmonisation of monitoring procedures, that exposure studies should use concentrations which are environmentally relevant, and the impact evaluation should utilise recognised risk matrix analysis techniques.
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