PLASTIC POLLUTION: SOURCES, PATHWAYS AND IMPACTS
REPORT PREPARED FOR THE PLASTIC POLLUTION WORKING GROUP (PPWG) OF THE UK & EIRE SPILL ASSOCIATION ‘GOAL 1’
REPORT PREPARED BY ORACLE ENVIRONMENTAL EXPERTS LTD
PPWG - Goal 1 Report
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DOCUMENT CONTROL RECORD
Project: Microplastics R&D
Project Reference: OEE R&D 2101
Report Title: Plastics: Sources, Pathways and Impacts
Authors: Kif Cullerne BSc (Hons)
Environmental Consultant – Oracle Environmental Experts Ltd
Dr Jon Burton BSc PhD FGS MCIWEM CSci MAE
Managing Director - Oracle Environmental Experts Ltd
Checked and Approved By: Joshua Doran MSci MCIWEM FRGS
Environmental Consultant - Oracle Environmental Experts Ltd
Version No: 1
Issue Status: Issued
Date Issued: 12 July 2022
OEE Microplastics R&D Page 3 of 45
Plastics: Sources, Pathways & Impacts
APPENDICES
Appendix A: Wyre Council (2021) Summary Report on Pollution incident January 2021 - Plastic Tide Pollution Events
Appendix B: Environment Agency Briefing on Micro-plastics: Small Plastic Pellet Pollution
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Plastics: Sources, Pathways & Impacts
1.0 INTRODUCTION
1.1 Understanding the Problem
1.1.1 According to the Plastics Industry Association, the first man-made plastic was created by Alexander Parkes who publicly demonstrated it at the 1862 Great International Exhibition in London. The material, called Parkesine, was an organic material derived from cellulose that, once heated, could be moulded and retained its shape when cooled. This development was the first step on the road to the development of a wide range of different plastics and to humanities current obsession with the material. According to UNEP (2020) in 2018, global production of plastics reached 360 million metric tonnes, and this figure is even higher if plastics used in manufacturing synthetic textiles, synthetic rubber, and plastic additives were included. The majority of this plastic ends up in landfills, open waste sites and littered throughout the environment, with an increasing proportion ending up in rivers, lakes and oceans.
1.1.2 There is a rapidly increasing amount of research on the sources and impacts of plastics on human health and on the natural world, and the extent of the problem is gaining much more attention. Once in the environment, plastics tend to breakdown into smaller particles through natural weathering processes, and in time, can become microplastics.
1.1.3 Microplastics is a term commonly used to describe extremely small pieces of plastic debris in the environment which result from the disposal and breakdown of plastic-based products and waste materials (Hann et al., 2018). Microplastics are regarded as an emerging pollutant and are now ubiquitous in the environment, present in food, water, air and even identified in human blood (GESAMP, 2015; Boucher and Friot, 2017; Baztan et al 2017; SAPEA, 2019; Stothra Bhashyam et al., 2021; Leslie et al., 2022). Their presence has been identified in rivers, lakes, coastlines and the open ocean, and even in snow in the polar regions of the globe (Bergmann et al., 2019; Auta et al., 2017). UNEP (2020) highlight that the potential hazards associated with microplastics come in three forms: physical hazards from the particles themselves; chemical hazards due to the ability to carry toxic unbound monomers, additives and sorbed chemicals; and microbial hazards from pathogenic microorganisms attaching and colonize microplastics surfaces
1.1.4 In the UK there have been several incidents in the last few years which have resulted in plastic pollution of shorelines over several kilometres. Examples include incidents in 2020 and 2021 in the north west of England where, following storms, plastic particles washed up on the shoreline of the coastline in the Wyre Council area.
1.1.5 The plastic particles washed up along the shoreline and made up of small brightly coloured pieces of different shaped plastic which created a plastic strandline. The size of the particles in this case was between 1 mm – 5 mm, but mainly about 3 mm and angular shaped (Photo 3).
1.1.6 The council provided a summary of their experiences and lessons learned during the incident This highlighted the difficulty in recovery of the material due to its size and behaviour with the material floating on the tide and mixing in the strandline (refer to Appendix A)
1.1.7 The Environment Agency (Environment Agency, 2015) have also completed research on the sources, fate and impacts of microplastics (refer to Appendix B) and are investigating the distribution of microplastics in the environment and they are working with businesses and academics to investigate the types and quantities of plastics, including various small plastic pellets, entering the environment This research is intended to aid the production of plans to tackle this type of pollution at source
1.1.8 Large plastic pollution incidents such as the recent X-Press Pearl incident in Sri Lanka, which involved a ship containing an estimated 1,680 tonnes of pre-production plastic pellets commonly known as ‘nurdles’, caught international attention with respect to the initial cleanup of the coastline, as well as assessment of the longer-term impacts (Rubesinghe et al., 2022). Manual recovery of plastics, as seen in Sri Lanka, is laboursome, lengthy, and costly. As seen in the oil spill response industry, an effective response plan, quick response and use of tried and tested recovery techniques, can successfully mitigate impacts and can also save money. Not only is plastic pollution a visual nuisance, but the smaller microplastics have also been identified to be damaging to fauna and flora accumulating in food chains (Stothra Bhashyam, 2021).
1.1.9 Clearly there is a need to prevent plastics from entering the environment in the first place, and to identify appropriate techniques to recover plastics pollution from once present
1.2 The Plastic Pollution Working Group
1.2.1 To better understand the issues involving plastic pollution, the UK & Ireland Spill Association and several of its members, formed the Plastic Pollution Working Group (PPWG) in March 2021. The group has set itself 10 ambitious goals to improve the understanding of where plastic pollution originates, the impacts it has on the environment, how to deal with plastic pollution incidents and prevention.
1.2.2 The 10 goals of the PPWG are as follows:
1. Understand the problem – Understand the sources, pathways and impacts of plastic pollution from rivers to the oceans
2. Identification of the most effective equipment for the recovery of macro and microplastics from shorelines and nearshore environments
3. Establish agreed methods for the assessment of ecological impact of plastics recovery operations
4. Establish agreed methods for qualitative (e.g. SCAT) and quantitative (e.g. laboratory analysis) assessment of macro and microplastics in sediments and waters and effective sampling and monitoring techniques
5. Assessment of environmental and health risks associated with macro and micro plastics to assist in clean up end point determination
6. Develop effective approaches for the surveillance and modelling of macro and microplastics to aid in response efforts, prediction of plastic movement and source identification
7. Develop approach to sustainability assessment with respect to plastics recovery endpoints and final destination of recovered plastics / debris
8. Share information gained through the group through webinars, demonstration days, technical publications and liaison with other appropriate organisations (e.g. EA, IMO, Councils, NGOs)
9. Work with International Spill Accreditation Scheme (ISAS) to ensure the Module for Shoreline Plastic Pollution and Marine Debris Recovery is formally released.
10. Identification of effective tools and equipment for controlling plastics at source (e.g. on site, in drains and in rivers)
1.3 Report Aim
1.3.1 This report aims to present a review of available information on the sources, pathways, and impacts of plastic pollution, from rivers to oceans, to address Goal 1 of the PPWG.
2.0 DEFINITIONS
2.1 General Definitions
2.1.1 Plastic debris (i.e. plastic items found in the natural environment), is most commonly categorised in scientific literature according to size (Hartmann et al., 2019). A review of the scientific literature on plastic pollution confirms the wide range in definitions for categorising plastics as shown in Figure 1 from Hartmann et al. (2019)
Figure 1: Examples of differences in the categorization of plastic debris according to size as applied (and/or defined) in scientific literature and in institutional reports (from Hartmann et al., 2019)
2.1.2 Table 1 provides further examples of the different definitions of plastics sizes in the available literature, which includes additional references published after Hartmann et al., (2019) Table 1: Differences in the definitions of plastics sizes in the available literature (units in mm).
2.1.3 Despite the publication of an International Standard on the subject (i.e. ISO 2020 Plastics Environmental aspects State of knowledge and methodologies – ISO/TR 21960), it is not clear if there is currently a universally accepted definition for plastics based on their size.
2.1.4 For the purposes of this report, the definitions outlined in ISO (2020) have been used.
2.2 Macroplastic Definition
2.2.1 This report aims to understand the sources, pathways and impacts of microplastics in the environment, however, an understanding of the sources and distribution of macroplastics is essential, as they are a major source of microplastics through their degradation and breakdown ISO (2020) define macroplastics as “any solid plastic particle or object insoluble in water with any dimension above 5 mm.” The ISO (2020) standard also adds the following notes: “Note 1: Typically, a macroplastic object represents an article consisting of plastic or a part of an end-user product or a fragment of the respective article, such as cups, cup covers. Note 2 to entry: The defined dimension is related to the longest distance of the particle.”
2.3 Microplastic Definition
2.3.1 ISO (2020) define microplastics as “any solid plastic particle insoluble in water with any dimension between 1 µm and 1 000 µm (=1 mm) Note 1: This term relates to plastic materials within the scope of ISO/TC 61. Rubber, fibres, cosmetic means, etc. are not within the scope. Note 2: Typically, a microplastic object represents a particle intentionally added to end-user products, such as cosmetic means, coatings, paints, etc. A microplastic object can also result as a fragment of the respective article. Note 3: Microplastics may show various shapes. Note 4: The defined dimension is related to the longest distance of the particle.”
2.3.2 The ISO (2020) further defines “large microplastics” as “any solid plastic particle insoluble in water with any dimension between 1 mm and 5 mm. Note 1: Microplastics may show various shapes. Note 2: Typically, a large microplastic object represents an article consisting of plastic or a part of an end-user product or a fragment of the respective article. Note 3: Microplastics in this size range are, for example, plastic pellets as intermediates for further down-stream processing such as moulding, extrusion, etc. resulting to semi-finished products which are not final end-user products.”
2.3.3 ISO (2020) define nanoplastics as plastic particles smaller than 1 µm. Nanoplastics are not discussed further in this report, however, they are likely to be a focus of future research as the scientific community learns more about their extent and impact on human health and the environment.
3.0 SOURCES
3.1 Sources of Macroplastics in Marine Environments
3.1.1 In 2020, 367 million tonnes (Mt) of plastic were produced worldwide (Tiseo, 2021) which is expected to double in the next 20 years (Lebreton and Andrady, 2019)) Statistics published by PlasticsEurope (2019) show that in 2018, in Europe, 61.8 Mt of plastic was manufactured which is equates 17.2% of the global production, with the packaging industry found to be the largest contributor of macroplastic waste, accounting for 39.9% of the total produced, while the construction industry produced 19.8%, the automotive industry 9.9%, the electronics industry 6.2%, household and leisure use 4.1%, and agriculture 3.4%.
3.1.2 Currently, it is estimated that 19-23 Mt of plastic enter aquatic ecosystems annually from land-based sources (UNEP, 2021). Global marine studies place plastic bags, containers, bottles including bottlecaps, packaging straps, nets, ropes and fishing lines, as the most common macroplastic pollution items within the ocean (Leemans, 2016). While in the UK, beach studies identify cigarette butts, food wrappers, bottle caps and fishing line as dominant macroplastic items along coastlines (www.coastalcleanupdata.org).
3.1.3 Napper & Thompson (2020) highlight that macroplastics can enter the environment from many sources, generally split into oceanic or land-based sources. Oceanic sources include fishing, boating, and shipping. Land-based sources include primary industry, litter, sewage, and storm water, ISO (2020). Sources of plastics were further reviewed by ISO (2020) which presents the findings of a model developed for the assessment of land-based sources of plastic in Germany which enter the North Sea (Lindner, 2015). Figure 2 taken from ISO, 2020, distinguishes the different sources of plastic pollution in the sea into sea-sourced and landsourced litter.
3.2 Sources of Microplastics in Marine Environments
3.2.1 Microplastics are considered to originate from two broad sources: those that are manufactured specifically for particular industrial or domestic applications such as exfoliating facial scrubs, toothpastes and resin pellets used in the plastics industry (primary microplastics), and those formed from the breakdown of larger plastic items (secondary microplastics) such as the gradual breakdown of rope and even polymer-based paints from the shipping industry (OSPAR, 2017). Being able to make the distinction between primary and secondary microplastics helps indicate potential sources, and identify mitigation measures to reduce their input to the environment (GESAMP, 2015).
3.2.2 OSPAR (2017) confirmed that microplastics sources across the Northeast Atlantic region under the OSPAR region (Belgium, Denmark, Finland, France, Germany, Iceland, Ireland, Luxembourg, The Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom) include pre-production pellets, cosmetics, abrasive cleaning agents, rubber infill on artificial sports fields, road runoff of car tyre wear, laundry fibres, and paints. The estimated source emissions of microplastics across the OSPAR region are shown in Figure 3
(OSPAR 2017)
3.2.3 The OSPAR (2017) report identified that the largest sources of microplastics to the OSPAR catchments are tyre wear and (macro) litter, with estimated amounts of around 100,000 tonnes/year. However, it was noted that the estimated emissions were difficult to validate with monitoring data because the origin of the microparticles found could often not be traced back to a particular source.
3.3 Primary Microplastic Sources
3.3.1 Microplastics can be manufactured for a range of domestic and industrial applications. The majority of primary microplastics (98%) are generated from land-based activities (Boucher & Friot, 2017). These include plastic particles used in facial cleansers (also known as microbeads), exfoliants and cosmetics (Zitko and Hanlon, 1991) Microplastic particles can be found in: eyeshadow, deodorant, make-up, shaving cream, baby products, bubble bath lotions, hair colouring, insect repellents and sunscreen (Castañeda et al., 2014; Fendall and Sewell, 2009; Cole et al., 2011; Costa et al., 2010; Duis and Coors, 2016) Others include abrasives found in cleaning products, drilling fluids or as air-blasting media (Gregory, 1996), whilst their use in medicine as vectors for drugs is increasingly reported (Patel et al., 2009). Figure 4 visually represents the wide range of sources of microplastics which enter the environment.
3.3.2 Under the broader size definitions of a microplastic, pre-production plastic pellets, also known as ‘mermaids tears’, (typically 2–5 mm in diameter) can also be considered primary microplastics, although their inclusion within this category has been criticised (Andrady, 2011, Costa et al., 2010). Pre-production plastic pellets are used as feedstock in the manufacture of plastic products and can be lost during handling, or through spillages during production or transportation such as the recent X-Press pearl incident, where 87 shipping containers carrying several types of plastic pellets were lost from a container ship which ran aground and caught fire off the coast of Sri Lanka in May 2021. A total of around 1680 tonnes of nurdles were released to the ocean as a result of that incident (UNEP, 2021a, Rubesinghe et al., 2022) and the clean-up of the nurdles has continued over a year since the incident.
3.3.3 An estimated 99 % of plastics worldwide, including pre-production plastic pellets, are derived from fossil fuel sources with 1% derived from biomass based sources (UNEP, 2021). This is expected to increase in the near future as biomass raw materials provide alternative sources to fossil fuel raw materials. Being bio-based, however, does not necessarily make the plastic biodegradable; in fact, bio-based resins are developed to mirror the properties of their conventional counterparts and would thereby have the same potential pollution issues associated with them (GESAMP 2015).
3.3.4 According to Hann et al., (2018), the European Union (EU) produces between 58
70.6 Mt of plastic pellets per year and this equates to up to 1,400 billion pellets entering the environment per year. Within OSPAR countries, plastic demand amounts to 31 Mt per year (OSPAR, 2018).
3.3.5 OSPAR (2018) presented a research document which introduces the issue of pellet loss, provides an overview of existing initiatives and identifies possible measures that could reduce the amount of pellets that enter the environment They highlighted several steps in the supply chain that present a high risk for plastic pellet loss including the following:
• General handling: pellets spills can occur because of defective packaging or during filling processes;
• Pellet transport: pellets spills can occur during vehicle cleaning, loading and the sealing of vehicles, as well as during storage, and the unloading of bulk containers;
• Shipping: pellets can be spilt directly into the ocean from damaged or lost shipping containers or from damaged bags;
• Waste disposal: plastic pellets can be disposed of with mixed residual waste or blown away from bins stored outside
3.3.6 Measures to reduce pellet loss to the environment proposed by OSPAR (2018) and initiatives such as Ocean Clean Sweep include the following:
• Eliminate pellet loss across the supply chain by implementing best practice guides and toolkits and information sharing on global scale
• Implement monitoring and auditing programmes to assess measures implemented to reduce pellet loss
• Implement loss prevention, containment and clean ‐ up procedures including improvements in storage and transport of pellets
• Provide appropriate training to those responsible for storing, transporting and using pellets
3.4 Secondary Microplastic Sources
3.4.1 Over time, larger pieces of plastic debris on sea and land, fragment into smaller particles when exposed to UV radiation and physical weathering, until they end up as microplastics (Brate et al., 2014), and these are referred to as ‘secondary microplastics’
3.4.2 Secondary microplastics are produced through physical, chemical or biological degradation of plastic debris (Germanov et al., 2018; Lehtiniemi et al., 2018; Wolff et al. 2019). A culmination of these processes reduces the structural integrity of macroplastic debris, which leads to fragmentation (Cole et al., 2011) Secondary microplastics and are thought to be among the most common sources of microplastic pollution (Boucher & Friot, 2017). Embrittled plastics can release microplastics long before they themselves become small enough to be classified as microplastics (GESAMP 2015).
3.4.3 Around 60% of all microplastics entering marine environments globally are thought to originate from two sources: the laundering of synthetic textiles and from the abrasion of automotive tyres (Boucher & Friot, 2017; Duis and Coors, 2016).
3.4.4 The total microplastics generated from the wear of automotive tyres in the EU alone is estimated to be 503,586 tonnes per year (Hann et al, 2018). In the UK, studies have shown that a significant proportion of the microplastic particles entering the marine environment originate from brake and tyre wear from motor vehicles, including from electric vehicles marketed as ‘greener’ vehicles (Smith, 2022). A study conducted in the UK, further identified road-derived particles such as road-marking paints or road surface coatings, a previously undescribed source of secondary microplastics, as a significant contaminant source (Horton et al., 2016). These findings are consistent with those reported by OSPAR (2017) who identified that the largest sources of microplastics to the OSPAR catchments are tyre wear and (macro) litter. Due to their high polymer content, particle size, low solubility and low degradability, tyre wear particles are considered as microplastics. The particle size of tread wear particles range from < 10 µm to several hundred micrometres. The amount of microplastics released from tyres depends on a number of factors including vehicle type, road type, tyre age/tread thickness and vehicle operation. Table 2 shows the tyre wear emissions from different vehicles from various studies across Europe (OSPAR, 2017).
3.4.5 Based on the review of the available data and extrapolating across the OSPAR region, OSPAR (2017) estimated an average of 167,000 tonnes of tyre wear particles are released to the water environment every year.
3.4.6 In terms of microplastic generation through synthetic textiles, abrasion during laundry, as well as exposure to chemicals and detergents, causes the breakdown of synthetic fibres into smaller microfibres (Browne et al., 2015). They found that up to more than 1900 fibres per garment, per wash, (100‐300 fibres per litre effluent) could be released. It is estimated that up to 700,000 microfibres can be lost in a single wash cycle (Napper & Thompson, 2016) and it is further estimated that microplastics from synthetic textiles comprise up to 35% of the total secondary microplastics found in marine environments (Henry et al, 2019, Boucher & Friot, 2017).
3.4.7 OSPAR (2017) provide a detailed review of the sources of microplastic fibres across the OSPAR region and review the efficiency of sewage treatment plants to remove the fibres. They identified that the removal rate of microfibres from laundry effluents in sewage treatment plants is variable. Leslie et al., (2017) studied influent and effluent concentrations of microplastics at 7 municipal waste water treatment plants (WWTPs) in the Netherlands and found a mean retention of microplastics in sewage sludge of 72% (standard deviation 61%). OSPAR (2017) reported the findings of the study of Talvitie et al., (2017) which identified that most of the microlitter (97%) entering sewage treatment plants was removed during the pretreatment and activated sludge treatment further decreased the microlitter concentration. It was further identified that the overall retention capacity of studied WWTPs was over 99% after secondary treatment.
3.4.8 In the OSPAR (2017) study, it was estimated that approximately 33% of laundry fibres were retained in sewage sludge. They reported that depending on national policies on the spreading of sewage sludge on land, these emissions could enter the environment, and could be redistributed to surface water through runoff. From their review, and based on a number of assumptions, they estimated the fibre emissions across the OSPAR region as shown in Table 3.
3.4.9 Following their calculations, OSPAR (2017) note that a subsequent EU wide project (EU funded Mermaids project) estimated a total emission of 29,215 tonnes synthetic fibres from domestic laundry in the EU. After correction for population numbers OSPAR reported that this would equate to approximately 15,700 tonnes in laundry effluents in the OSPAR catchment area.
3.5 Environmental Microplastic Sources
3.5.1 In the current literature, certain environmental pathways are also referred to as sources. For example, atmospheric deposition can be considered a microplastic source for land, freshwater systems and the oceans, and microplastic release from rivers can often be considered a source to marine systems (Dris et al., 2015).
3.5.2 Wastewater treatment plants are considered a source or entry pathway of microplastics for freshwaters and soils as a resulting of spreading of sewage sludge on land (Mason et al., 2016; Talvitie et al., 2015; OSPAR 2017; SEPEA 2019;).
3.5.3 Koelmans et al., (2019) completed a critical review of data on the presence and types of microplastics in freshwater and drinking water. They concluded that microplastic is frequently present in freshwaters and drinking water with fragments, fibres, film, foam and pellets being the most frequently found microplastics in surface water samples. The relative abundance of polymer types found across the various studies reviewed, reflected plastic production and polymer densities.
4.0 PATHWAYS
4.1 Introduction
4.1.1 Once plastics are released into the environment, there are a number of pathways that they can take towards the marine environment and several sinks along these pathways that can retain them. Plastic waste enters waterways through processes influenced by wind or raininduced surface/road runoff, littering or direct disposal or via wastewater treatment systems and wind transfer (Boucher & Friot, 2017; Hann et al., 2018). A summary of the global sources of microplastics from Boucher & Friot (2017) is reproduced in Figure 5.
4.1.2 OSPAR (2017) highlight that the spatial distribution and accumulation of litter, and probably of microplastics in the ocean, is influenced by hydrography, geomorphological factors, prevailing winds and anthropogenic activities. They further identified that hotspots of litter accumulation include shores close to populated areas, particularly beaches, but also submarine canyons, where litter originating from land accumulates in large quantities.
4.1.3 The review of the available literature by OSPAR (2017) identified that microplastics can reach marine waters directly from marine activities or recreational activities at sea, on shores/beaches, or indirectly through riverine inputs or discharges of sewage treatment plants. Figure 6 shows the main potential pathways for microplastic particles entering the environment published by OSPAR (2017).
4.2
Rivers
4.2.1 Rivers have consistently been identified as one of the most important transport pathways for all sizes of plastic debris (Stothra Bhashyam et al., 2021; Boucher & Friot 2017). Rivers are highly dynamic environments connecting land to sea and along their course (Horton et al , 2018; Stothra Bhashyam et al., 2021). Globally, it is estimated that between 1.15 and 2.41 Mt of plastic waste currently enters the ocean every year from rivers (Lebraton et al., 2017).
4.2.2 In the UK, there have been relatively few studies conducted concerning microplastics and their behaviour in rivers and freshwater systems. A recent government report (Water Quality in Rivers, 2022) highlighted concerns that emerging pollutants such microplastics are not being systematically monitored or measured. A study on the presence of microplastics in the tributaries of the River Thames, further identified the presence of microplastics in UK freshwater systems, highlighting rivers as potential major transport pathways for the transfer of microplastic particles from terrestrial sources to the oceans (Horton et al., 2017). In addition, studies show that rivers are not only a pathway to the marine environment, but that
river sediments can also act as potential sinks for microplastics (Hann et al., 2018, Nel et al., 2018).
4.2.3 McGoran et al., (2020) published a study of the prevalence of plastic ingestion by crabs in the Thames Estuary and reported that plastic accumulates near estuarine inputs to marine habitats. Thousands of pieces of plastic have been found flowing along the Thames riverbed, including fragmented carrier bags, sanitary pads, cellophane cigarette wrappers and food packaging (Morritt et al., 2014). McGoran et al., (2020) further highlighted that these items can break up into smaller fragments (Barnes et al., 2009; Andrady, 2011), eventually becoming microplastics
4.2.4 McGoran (2020) reported that the River Thames that it has a large catchment of 16,000 km2 encompassing 15 million residents (Environment Agency, 2016) and it passes through major urban centres (e.g. Oxford, Reading and London). McGoran (2020) stated that the River Thames is in constant use by pleasure craft, ferries, passenger transport, cargo vessels and trans-oceanic shipping. Currently, the tidal Thames, eastward of Teddington Weir, Middlesex, also receives huge quantities of untreated sewage overflow discharged from an antiquated Victorian sewerage system. Consequently, the Thames is vulnerable to domestic and industrial wastewater pollution and microplastics have been reported throughout the Thames watershed (Horton et al., 2017; Santillo et al, 2019; Rowley et al., 2020) being one of the most microplastic-contaminated rivers in the UK. Rowley et al., (2020) sampled the water column of the River Thames at two sites, Putney and Greenwich, and assessed the material composition of the microplastics identified in the samples and their findings are shown in Figure 7
Figure 7: A stacked bar chart showing the percentage material composition for each form. Polymer forms were identified using FTIR at a 70% minimum spectral library match. 63 samples were analysed; 21 fragments, 31 films, 2 nurdles, 4 glitter particles and 5 microbeads (Rowley et al., 2020)
4.2.5 Rowley et al., (2020) also identified a clear positive relationship between the amount of sewage discharged from a combined sewage overflow into the Thames and the concentration of microplastics in the Thames. This relationship is illustrated in Figure 8 reproduced from Rowley et al , (2020)
4.2.6 Rowley et al., (2020) studied the concentrations of microplastics on the ebb and the flow tides of the River Thames. They observed that on peak ebb tides just after high water, there were approximately 35,000 microplastic particles per second being discharged downstream at Putney, and 94,000 microplastic particles being discharged downstream at Greenwich. The majority of plastics found in the River Thames water column were secondary microplastics, films and fragments. During peak ebb tides, at Greenwich, secondary microplastics contribute to an estimated 92% of all microplastics, while at Putney this was estimated to be 90%.
4.3 Surface and Road Runoff
4.3.1 Surface and road runoff have been identified to be significant pathways for microplastic pollution (Werbowski et al., 2021; Seigfried et al., 2017; OSPAR, 2017). Runoff is a complex mixture of precipitation, suspended sediment, natural and anthropogenic debris, and chemical pollutants that are washed off the urban landscape during rain events (Werbowski et al., 2021), all of which can contain significant amounts of microplastics which are then subsequently washed into watercourses.
4.3.2 Road runoff and the associated tyre-wear particles have been highlighted as the main pathway for microplastic loss to the environment (Boucher & Friot, 2017, Seigfried et al., 2017; OSPAR,2017). Microplastics present in road runoff can consist of tyre wear particles, road markings and pellet spill incidents (Boucher & Friot, 2017; OSPAR,2017). Tyre and road wear particles washed into road drainage systems are calculated to be the largest sources of microplastic found in European rivers, and account for 42% of the total exported microplastic load (Knight et al., 2020). In the UK, Highways England (2020), identified motorways and high traffic highways to be a significant contributor to microplastic runoff.
4.4 Wastewater Treatment Plants / Sludge Application
4.4.1 Studies indicate that sewage from WWTPs play an important role in releasing microplastics to the environment (Browne et al., 2011; OSPAR, 2017; Sun et al., 2019; Karapanagioti and Kalavrouziotis, 2019; Koutnick et al., 2021; Lofty et al., 2022; Harley-Nyang, et al., 2022). Larger debris that enters WWTPs is removed in the treatment plant, but the plants are not specifically designed to retain microplastics. Microplastics in WWTPs are released into the environment by the discharge of effluent, from the release of untreated sewage (Woodward et al, 2021), or through the application of sewage sludge (a by-product from the treatment of wastewater) to agricultural land (Browne et al., 2011; Harley-Nyang et al., 2022).
4.4.2 Microplastics have been found in WWTPs in high concentrations (Harley-Nyang et al., 2022) and are thought to be initially effective at removing microplastics via a combination of primary and secondary treatment processes (Karapanagioti and Kalavrouziotis, 2019, Harley-Nyang et al, 2022) Studies demonstrate that WWTPs retain 87–99% of the microplastics entering them (Rezania et al., 2018). However, these systems are expensive and are not common in many countries (GESAMP, 2016). In addition, even after effective processing, some removed microplastics are incorporated into sewage sludge which is often used as fertiliser for agriculture.
4.4.3 In a recent study by Lofty et al., (2022), it is estimated that the UK recycles the most microplastics to agricultural soils through the use of sewage sludge as a fertiliser in Europe with between 500 – 1000 microplastic particles found per m2 of agricultural land per year as seen in Figure 9
4.4.4 In a study of a WWTP in the UK, Harley-Nyang et al., (2022) identified that microplastics were detected in all samples taken from across the treatment process with concentrations ranging from 37.7–286.5 number of microplastics/g of sludge (dry weight). The microplastic load in the final biosolid products produced at the site ranged from 37.7–97.2 particles of microplastics/g of sludge (dry weight). The wastewater treatment works in the study produced 900 tonnes of anaerobically digested sludge cake and 690 tonnes of lime stabilised cake per month. Based on the results from this study, Harley-Nyang et al., (2022) concluded that the application of these biosolids to agricultural land as fertilisers could potentially release 1.61 × 1010 and 1.02 × 1010 microplastics in anaerobically digested and lime stabilised sludge respectively, every month (equivalent to the same volume as >20,000 plastic bank cards).
4.5 Agricultural Runoff
4.5.1 Plastic products are used extensively in agriculture for various purposes. Agricultural plastics are used to improve crop yields and are found in irrigation equipment, greenhouse and tunnel covers, mulch to cover soil, shade cloths and pesticide containers (UNEP 2021). It is estimated that between 6.5 and 9 Mt of plastics are used in agriculture every year (reference). Agricultural plastics are often difficult to recycle because of contamination by other products such as pesticides and fertilisers. As a result, they are often buried in fields or abandoned in
watercourses (UNEP, 2021). Macroplastics can be released into the wider environment from agricultural land through wind transportation and are carried by surface water runoff during heavy rainfall and storm events. In addition, these plastics are often exposed to sunlight for many months and break down into microplastics thus contaminating the surrounding soils. These can again enter watercourses through runoff with the microplastics ultimately ending up stranded in river sediments or in the marine environment (SAPEA, 2019).
4.5.2 In addition to the deliberate use of plastics in agriculture, a recent study by Lofty et al., (2022), suggests that 31,000 to 42,000 tonnes of microplastics are spread on European farmland soils each year through the application of sewage sludge as a fertiliser. It is suggesting that agricultural soils are potentially large sinks for microplastics where they can then be reintroduced into marine environments via surface runoff (Harley-Nyang et al., 2022; Koutnick et al., 2021; Hurley et al., 2018). Microplastic fibres have been reported in agricultural fields up to 15 years after sludge was applied, still maintaining their original properties (Zubris & Richards, 2005).
4.6 Atmospheric Transportation
4.6.1 Microplastics have been detected in the atmospheres of remote areas far away from any microplastic sources, suggesting that windblown, atmospheric transport of microplastics is an important potential pathway (Zhang et al., 2020; Allen et al., 2019).
4.6.2 Wright et al., (2020) highlighted that microplastics have been measured in atmospheric fallout in the megacities of Paris, France (Dris et al., 2016) and Dongguan, China (Cai et al., 2017) with average deposition rates of 110 ± 96/m2/d and 53 ± 38/m2/day in total atmospheric deposition collected at urban and suburban sites in Paris, respectively (Dris et al., 2015). In Dongguan City, China, an average deposition rate of 36 ± 7/m2/d was reported (Cai et al., 2017) and microplastics were measured at a remote, pristine mountain catchment (French Pyrenees) at a comparable daily rate (365/m2/d) (Allen et al., 2019).
4.6.3 Microplastics have been reported in suspended particles, atmospheric fallout, road dust and wet precipitation around the world; these microplastics may cause potential harm to humans (Yao, 2022; Zhang et al., 2020) and are thought to be an emergent component of air pollution (Zhang et al., 2020). Microplastics have been found in indoor air samples where they have been shown to be elevated in comparison to concentrations in outdoor air (ISO, 2022).
4.6.4 Studies suggest that suspended atmospheric microplastics are an important source of microplastics pollution in the oceans, especially the pollution caused by textile microfibres (Lui, 2019) However, this is an emerging area of research and there are an increasing number of studies on the subject (Munyaneza et al., 2022; Zhang et al., 2020; Dris et al., 2016) and there are published studies on atmospheric microplastic transportation and deposition of microplastics in the UK (Wright et al., 2020).
5.0 DEPOSITS
5.1 Plastic Deposits
5.1.1 Given their high mobility and long residence times, microplastic deposits are found globally and it is becoming increasingly evident that are few environments on Earth that have escaped microplastic pollution
5.1.2 Plastic litter is not only a problem because it breaks down into microplastics, macroplastics are a major problem on their own. It is estimated that by 2050, there will be approximately 12 billion metric tonnes of plastic litter in landfills, open dumps and the natural environment (Geyer et al., 2017), with a significant amount of this plastic finding its way to rivers, lakes and oceans.
5.1.3 Plastics have been observed in many different parts of the marine system, including in near surface ocean waters, in the garbage patches of the subtropical gyres, and in other marine hotspots such as the Mediterranean Sea (SEPEA, 2019). Furthermore, microplastics have been found in sediment samples from shoreline areas (Thompson et al., 2004, Browne et al., 2011), estuaries (Malli et al., 2022) and the abyssal ocean (Woodall et al., 2014).
5.1.4 Although plastics in the marine environment have received worldwide attention and have been studied extensively, studies of terrestrial deposits of microplastics are less common. However, most marine plastic pollution is derived from land-based sources; one study estimates that the true amount of plastic release to terrestrial environments could be four to 23 times more than is found in marine environments (Horton et al., 2017). Terrestrial microplastic deposits have been detected in agricultural soils, urban cities and industrialised areas across the globe (Campanale et al., 2022).
5.1.5 UNEP (2021) provide a useful illustration of the sources, pathways and sinks for plastics waste and this has been reproduced in Figure 10
5.2 Oceans
5.2.1 Plastics have been found in every ocean of the world, including remote regions such as Antarctica and the deep sea and it is estimated that 12.2 Mt of plastic enter the ocean each year (Eunomia, 2016). There have been many detailed reviews of the nature and extent of impacts associated with marine plastics (e.g. UNEP, 2016; Andrady, 2011; Bergmann et al., 2015; GESAMP, 2015; Boucher & Friot, 2017; Napper & Thompson, 2020; Stothra Bhashyam et al., 2021) Once plastics enter the ocean, they can become widely transported due to their durability and buoyant properties (Napper & Thompson, 2020). A large proportion of plastics normally float on the surface as they are less dense than seawater. However, the buoyancy and density of plastics may change once they begin to degrade at sea due to weathering and biofouling These therefore spread across surface with denser particles transferring vertically through the water column and collecting in sediments at the bottom of the ocean (Ye and Andrady, 1991; Morishige et al., 2007; Woodall et al., 2014). Plastics are then transported in marine systems by processes such as tides, winds and currents. High concentrations of floating
macroplastic debris have been reported in subtropical ocean gyres, which are thought to act like a conveyor belt for the collection and accumulation of plastics.
5.2.2 Stothra Bhashyam et al., 2021 reported that “Gyres are convergence zones where large quantities of floating plastic litter are known to accumulate. According to recent estimates, the North Pacific Gyre accumulates between 1.1. and 3.6 trillion plastic plastics weighing 79,000 tonnes. Consistent efforts to monitor other gyres, such as the North Atlantic Gyre, close to the Azores archipelago in Portugal, has been undertaken in recent years, and results show that gyres represents an important pathway of microplastics in the region and a possible input for other areas further north, where transport is promoted by ocean currents.”
5.2.3 With respect to plastic inputs to oceans, Eunomia (2016) identified that over 80% of the annual input comes from land-based sources and they highlighted the following:
• 94% of the plastic that enters the ocean ends up on the sea floor. There is now on average an estimated 70kg of plastic in each square kilometre of sea bed.
• Barely 1% of marine plastics are found floating at or near the ocean surface, with an average global concentration of less than 1 kg/km2 . This concentration increases at certain mid-ocean locations, with the highest concentration recorded in the North Pacific Gyre at 18 kg/km2
• The amount estimated to be on beaches globally is five times greater, and importantly, the concentration is much higher, at 2,000 kg/km2 .
5.2.5 To note the statement presented in GESAMP (2019) “Although microplastics greatly outnumber large plastic items in marine systems, they still make up only a small proportion of the total mass of plastics in the ocean (Browne et al. 2010). This means that even if we were able to stop the discharge of macroplastic litter into the sea today, on-going degradation of the larger litter items already at sea and on beaches would likely result in a sustained increase in microplastics for many years to come.”
5.3 Coastlines
5 3.1 As a result of the washing up of floating plastic debris, coastlines across the globe can contain significant amounts of plastic debris. Lebreton et al., (2019) estimate that the total amount of macroplastics released to coastline environments between 1950 and 2015 could be 82 Mt, whereas it is estimated that 40 Mt of microplastics have been released to coastlines in the same time period. Macroplastic and microplastic deposits on coastlines have been reported on beaches at numerous locations worldwide where they accumulate mostly on beaches close to heavily populated areas (although not exclusively) and within the drift lines on the surface of the sandy beaches (Browne et al., 2011; Turra et al., 2014; Tunnell et al., 2020). There is also some evidence that microplastics are distributed three dimensionally in beach sediments (Turra et al., 2014). However, there is relatively little available information on the levels of microplastics on non-beach sediments (e.g. mangroves, tidal marshes or rocky shores) (SEPEA, 2019). Globally, a significant proportion of microplastics debris deposited on beaches and shoreline areas comprise pre-production pellets (nurdles) (Tunnell et al., 2020; Hann et al.,
2018). A UK based study by Cole & Sherrington (2016) estimated the loss of industrial resin pellets to the environment in the UK alone to be between 105 – 1054 tonnes per year.
5.3.2 GESAMP (2019) highlighted that there is virtually no information on weathering of plastics stranded on shorelines, floating in seawater (Andrady 2011; Muthukumar et al. 2011) and especially submerged in seawater or sediment. The effects of variables such as mechanical impact, salinity, temperature, hydrostatic pressure, presence of pollutants such as oil in seawater and bio-fouling (reducing UV exposure) on the rates of weathering according to various types of plastic items are virtually unknown.
5.3.3 Researchers have identified that plastic accumulates in coastal zones where it can be colonized by macro- and microbiotic communities in what has been termed by some authors as the plastisphere (Stothra Bhashyam et al., 2021; Amaral-Zettler et al., 2020). It has also been identified that several species attach and colonise plastics, most of them harmless, but there are other species (e.g., Vibrio spp.) that are potentially pathogenic. Due to their lightweight nature, plastics float in the ocean, and are often regarded as a transport vector for invasive species into remote ecosystems, across continents (e.g. Amaral-Zettler et al., 2020)
5.4 Freshwater Environments
5.4.1 Studies have demonstrated that microplastics are widely distributed in freshwater bodies in concentrations at least similar to marine systems (SAPEA, 2019). Globally, microplastics have been found in and below water surfaces and in sediments of lakes, rivers and estuaries (Medrano et al., 2015; Malli et al., 2022).
5.4.2 Where microplastics are present within sediments, they may be trapped for long periods, although wave action and beach erosion can release particles from at least shallow water sediments. Microplastics might be more readily re-suspended from bottom sediments than larger plastic items simply because they are small and of low density compared to natural sediment, and hence more easily disturbed by wave action, currents or bioturbation (GESAMP, 2019)
5.5 Soils
5 5.1 Soils may represent the largest global environmental reservoir of microplastics, larger even than the oceanic basins (Hurley & Nizzeto, 2018) and it is considered likely that microplastics are ubiquitous in soils around the world (Yang et al., 2021).
5.5.2 Microplastics entering soils are stored (potentially over very long periods of time), translocated, degraded, leached to groundwater and can enter watercourses through surface runoff, thus threatening organisms and further effecting human health (Hurley & Nizzeto, 2018). However, this is an emerging area of research and there are relatively few studies on the occurrence and distribution of microplastics in soils (He et al., 2018, Yang et al., 2021, Blasing & Amelung, 2018) particularly in respect to the UK.
6.0 IMPACTS
6.1 Impacts of Plastics
6.1.1 The mismanagement of plastic waste has led to global widespread contamination of microplastics Microplastics are highly persistent, non-degradable, toxic and have a tendency to sorb pollutants or release additives (Anik et al., 2021; Rehse et al., 2016); they can persist for years in the environment and have been recorded at almost every location on the globe (PlasticsEurope, 2019)
6.1.2 Microplastics are of particular concern as a pollutant in environmental systems because their small size and variable buoyancy makes them readily available for uptake by a wide range of organisms (Miller et al, 2020) Given the ubiquity of plastics and microplastics in the environment, exposure to humans and other species through water, air, soil and food is rapidly increasing (UNEP 2020)
6.1.3 The potential environmental and biological health impacts of microplastics are relatively new areas of research, and there is currently a large degree of uncertainty surrounding this issue (GESAMP 2015). However, it is widely agreed that the presence of microplastics in the environment has the potential to cause harm to human health, living organisms in the aquatic environment as well as causing harm to other environments such as rivers and soils (Auta et al., 2017; GESAMP, 2015; SEPEA, 2019).
6.2 Physical Impacts on Marine Biota
6.2.1 Severe impacts of macroplastic litter have been well documented for many marine organisms. These impacts include, among others, entanglement, strangulation and clogging of intestines (Thevenon et al., 2014). On the microscale, however, such devastating effects are less obvious but seem to be replaced by other adverse effects on the level of organs and cells. It has been observed that ingested microplastics can induce immune responses and inflammatory cell reactions in marine organisms such as mussels (Saborowski & Gutow, 2016).
6.2.2 Due to their small size, microplastics are thought to be ingested by a wide variety of species, ranging from protozoans to marine mammals. A UN report documented 800 animal species contaminated with plastic via ingestion or entanglement (UNEP 2016). Of these 800 species, 220 have been found to ingest microplastic debris (Smith et al., 2018). Plastics may be ingested by marine life directly or indirectly through trophic transfer (Smith et al., 2018).
6.2.3 Microplastics are thought to move through food chains and bioaccumulate, with predators higher up the food chain ingesting the most plastics. Ingestion of microplastics by marine organisms may have a negative effect on food consumption, growth, reproduction and survival, especially vulnerable marine species such as filter feeders, zooplankton and juvenile fish (Duis & Coors, 2016; SEPEA, 2019; Miller et al., 2020). The review of the available literature on the subject by Miller et al., (2020) confirmed that microplastic contamination
occurs across all five main trophic levels in a general marine food web. Bioaccumulation of microplastics occurs in numerous individual marine species across four main trophic levels representing consumers Miller et al., (2020) concluded that microplastic bioaccumulation appears to be more strongly linked with feeding strategies, rather than trophic levels, of marine species and their study did not support the biomagnification of microplastics from lower to higher trophic levels.
6.2.4 Evidence is mounting to suggest that if plastic concentrations continue to increase as expected, microplastic ingestion and ingestion of associated chemicals, will pose a serious threat to marine ecosystems in the future (GESAMP, 2016; Rochman, et al., 2015).
6.3 Physical Impacts on Human Health
6.3.1 Microplastics may directly or indirectly impact human health by acting as physical stressors or as vectors of environmental contaminants (Hartmann et al., 2017) and may enter the human digestive, respiratory and circulatory systems (Barboza et al., 2018; Hartmann et al., 2018). It is estimated that globally, on average, humans may ingest 0.1–5 g of microplastics weekly through exposure pathways (Senathirajah et al., 2021) such as ingestion and inhalation, while nanoparticles may also be able to enter through the skin (Prata et al., 2020).
6.3.2 One of the main exposure pathways is thought to be through ingestion of contaminated drinking water and foodstuffs such as seafood (Rochmann et al., 2018) and through other less familiar food sources such as beer, honey and salt (EFSA, 2016; Kosuth et al., 2018; Lusher et al., 2017). A further pathway for the ingestion of microplastic particles is via ingestion of microplastics associated with atmospheric deposition (e.g. microplastics present in outdoor and indoor air) (SAPEA, 2019).
6.3.3 In spite of this, the human body’s excretory system is thought to eliminate >90% of micro and nanoplastics via faeces (Rochmann et al., 2018). However, although the physical effects of microplastics are still not fully understood, research has shown that the physical effects include enhanced inflammatory response, respiratory problems, size related toxicity of plastic particles, disruption of the gut biome and compromise immune cells (Rochmann et al., 2018; Wright et al., 2017; SAPEA, 2019)
6.4 Chemical Impacts on Biota and Environments
6.4.1 A range of chemicals (known as additives) are added to plastics during the manufacturing process, some of which are known to be are highly hazardous to human health, marine biota and the environment (Lithner et al., 2011; Stenmarck et al., 2017; Wiesinger et al., 2021). Additives are added to give the plastic certain characteristics (UNEP, 2021) and many different chemicals are used as plastic additives: typical additives include stabilisers, fillers, plasticisers, colourants and fire retardants. These substances may be released to the environment as the plastic degrades over time, resulting in biological and environmental exposure to potentially hazardous chemicals.
6.4.2 In addition to additives added to plastics, for some plastics, the monomer that makes up the polymer itself is classified as hazardous. For example, polyurethane foam, PVC, polycarbonate and high-impact polystyrene, are considered carcinogenic, mutagenic/toxic for reproduction (Rochman, 2015, Lithner et al., 2011).
6.4.3 Furthermore, due to their chemical composition, microplastics can easily adsorb toxic chemicals and trace metals from the surrounding environment (Campanale et al, 2020; Rochman & Hentschel 2014). Marine plastic debris is recovered globally with measurable amounts of persistent organic pollutants (POPs) and other persistent bioaccumalative and toxic substances (Rochman, 2015). As a result, microplastics may act as vectors for sorbed pollutants
6.4.4. Miller et al., (2020) found that “While chemical additives have been detected in a few marine species collected in situ, results from laboratory exposures indicate that environmental exposure to chemical additives per se affects bioaccumulation more strongly than exposure to chemical additives associated with microplastic (MPs).”.
6.5 Chemical Impacts on Human Health
6.5.1 Chemicals such as phthalates and bisphenol A (BPA), added to plastics in the production process as plasticisers, are known to act as endocrine (hormone) disruptors (Sohoni & Sumpter, 1998; Halden, 2010). Recent studies have associated endocrine disrupting chemicals with human health conditions such as hormonal cancers, reproductive problems, metabolic disorders, diabetes, asthma and neurodevelopmental conditions (Campanale, 2020). The contamination of food from BPA has been estimated to be responsible for 12,404 cases of childhood obesity and 33,863 cases of newly incident coronary heart disease in 2008 (Campanale et al., 2020).
6.5.2 Other hazardous chemicals used in the production of plastics include brominated flame retardants (BFRs) and lead heat-stabilisers. BFRs are compounds that have been found to interfere with thyroid hormone homeostasis and neurodevelopment and have been linked with human health conditions such as diabetes, neurobehavioral and developmental disorders, cancer, reproductive health effects and alteration in thyroid function (Kim et al., 2014). However, it is still unclear whether microplastics play an important role in uptake of chemicals into organisms; a recent study by Nor et al., (2021) suggests that the contribution of microplastics for the transfer of chemicals into the body is small to negligible based on a study of four common chemicals associated with plastics.
6.6 Microplastics as Vectors for Microbial Pathogens
6 6.1 As plastic pollution continues to increase, an emerging threat is the potential for microplastics to act as carriers (or vectors) for microbial pathogens (Hou et al., 2021). Microplastics possess a number of qualities that make them a unique substrate for microbial colonization; they have
hydrophobic hard surfaces, have a high surface area to volume ratio and are transported for long distances. As a result, once microplastics enter aquatic environments, organic matter, biomolecules and nutrients, sorb to the polymer surface and are rapidly colonized by complex microbial communities (Pinto et al., 2019), creating a slimy coating substance known as a ‘biofilm’.
6.6.2 Analysis of macro and microplastic biofilms have highlighted a broad spectrum of diverse bacteria, fungi, symbiotes and diatoms. This diverse microbial community has become commonly referred to as the ‘plastisphere’- a term first coined by Zettler et al., (2013). The plastisphere provides a protective environment that could facilitate the increased survival, transport and distribution of pathogens and therefore increase the likelihood of pathogens coming into contact with humans and aquatic life (Metcalf, 2022). Figure 11 summarises the interaction of Vibrios pathogens (bacterial genus) with microplastic particles compared with natural particles in sea water.
6.6.3 Human pathogens have been identified within the plastisphere of several different plastic polymers, including polyethylene, polypropylene and polystyrene (Metcalf, 2022). Commonly detected pathogens within plastisphere communities include Vibrios spp. (Laverty et al., 2020), which causes diarrhea, cellulitis and septicemia in humans, and is responsible for significant levels of mortality in developing countries where medicine and resources are less available (Heng et al., 2017) Other human pathogens identified within plastisphere
communities, include E.Coli, Salmonella and Providencia rettgeri, which can cause diarrhea and gastrointestinal, urinary tract and eye infections (Shi et al., 2021).
6.6 4 In addition, recent research has suggested that microplastics can act as hubs for enriching antibiotic resistant bacteria (ARB), antibiotic resistant genes (ARG) as well as pathogens (Pham et al., 2021; Shi et al., 2021), posing a pressing concern to both aquatic biota and human health. The World Bank's "One health: operational framework for improving human, animal, and environmental public health systems" has identified ARGs as a major issue (White and Hughes, 2019). More than 200 ARG subtypes have been discovered in the aquatic environment across the globe, most of which are linked with commonly used antibiotics such as tetracycline (Liu et al., 2021). It has been estimated that about 10 million people will die across the world by 2050 due to rising antibiotic resistance of pathogens (Dadgostar, 2019)
6.6.5 Microplastics can act as vectors of pathogens which can not only affect humans but marine life as well. Pathogenic bacteria such as Vibrios spp are large contributors to disease in organisms such as fish and shellfish (Haldar, 2013), often causing mass mortality in cultured populations. In fact, bacterial infections in fish, shellfish, molluscs, and crustaceans are the leading cause of economic loss in aquaculture settings (Lafferty, 2015).
7.0 CLOSING REMARKS
7.1 This report is intended to present a review of available information on, and highlight the sources, pathways, and impacts of microplastic pollution, in rivers and oceans, to address Goal 1 of the UK & Eire Spill Association PPWG, which was to “Understand the problem –Understand the sources, pathways and impacts of plastic pollution from rivers to the oceans.”
7.2 The goals of the PPWG as outlined in section 1.2 of the report are intended to give members of the UK & Eire Spill Association an understanding of the issues presented by plastic pollution, and to assist member companies to develop services and products that can help reduce the impact that plastic pollution has on the environment and on human health.
7.3 Given the issues faced by Wyre Council, the Environment Agency during the X-Press Pearl Incident in Sri Lanka, a key focus of the PPWG will be the development of techniques for the recovery of microplastics from shoreline environments.
7.4 Further research will be needed to assess the impacts that those recovery techniques have on the shoreline environment, to establish suitable disposal or recycling options for recovered plastics, and determination of suitable end-points for clean up operations based on a net environmental benefit analysis (NEBA) approach.
7.5 As detailed in Goal 10 of the PPWG priority also has to be the prevention of the entry of plastics into the environment in the first place, and without a massive reduction in plastic production and use, and a concurrent reduction in the entry of plastics to the environment, there is likely to be major and long-lasting effects to the environment and human health.
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