Threshold values for marine litter : general discussion paper on defining threshold values for marine litter.
Date: 2020-06-16
Institutions: Joint Research Centre
Subjects: biodegradability, decision (EU), environmental impact, environmental indicator, environmental monitoring, environmental protection, environmental standard, marine ecosystem, marine environment, marine life, marine pollution, prevention of pollution, research report

Threshold Values for Marine Litter 

General discussion paper on 
defining threshold values for 
marine litter 

Stefanie Werner, Elke Fischer, David Fleet, 
François Galgani, Georg Hanke, Sue Kinsey, 
Marco Mattidi 

MSFD Technical Group on Marine Litter 

2020 

EUR 30018 EN 

 
 
 
 
 
 
 
 
 
 
 
 
 
This publication is a technical report by the Joint Research Centre (JRC), the European Commission’s science and knowledge service. It aims 
to provide evidence-based scientific support to the European policymaking process. The scientific output expressed does not imply a policy 
position of the European Commission. Neither the European Commission nor any person acting on behalf of the Commission is responsible 
for the use that might be made of this publication. 

Title: Threshold Values for Marine Litter 

Authors: Stefanie Werner, Elke Fischer, David Fleet, François Galgani, Georg Hanke, Sue Kinsey and Marco Mattidi 

TG ML was supported by Arcadis and the Coastal & Marine Union (EUCC), under framework contract ENV.D.2/ 
FRA/2018/791850. 

Final editing was done by Stefanie Werner (co-chair, UBA), David Fleet (LKN-SH) and Annemie Volckaert (Arcadis). 

Contact information  
Name: Georg Hanke 
Address: Via Enrico Fermi 2749, I-21027 Ispra (VA), Italy 
Email: georg.hanke@ec.europa.eu 
Tel.: +39-0332-785586 

EU Science Hub 
https://ec.europa.eu/jrc 

JRC114131 

EUR 30018 EN 

PDF 

ISBN 978-92-76-14179-2 

ISSN 1831-9424 

doi:10.2760/192427 

Luxembourg: Publications Office of the European Union, 2020 

The reuse policy of the European Commission is implemented by the Commission Decision 2011/833/EU  of 12 December 2011 on the 
reuse of Commission documents (OJ L 330, 14.12.2011, p. 39). Except otherwise noted, the reuse of this document is authorised under the 
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All content © European Union 2020, except image on front page kindly provided by Peter Hübner (Germany)  

How to cite this report: Werner S., Fischer E., Fleet D., Galgani F., Hanke G., Kinsey S. and Mattidi M., Threshold Values for Marine Litter , EUR 
30018 EN, Publications Office of the European Union, Luxembourg, 2020, ISBN 978-92-76-14179-2, doi:10.2760/192427, JRC114131. 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Contents 

1  Background .......................................................................................................... 5 

2  Scope of setting threshold values ................................................................................. 6 

3  General concepts of threshold setting .......................................................................... 10 

3.1  Harmful effects of marine and beach/coastal litter...................................................... 10 

3.2  Marine and coastal litter as a pollutant ................................................................... 11 

3.3  Requirements and uncertainties related to TVs .......................................................... 11 

3.4  Risk assessment ............................................................................................ 12 

3.5  Existing threshold values for marine litter ................................................................ 12 

4  Options for setting threshold values ............................................................................ 14 

4.1  The zero option ............................................................................................. 14 

4.2  Points-of-no-return and tipping points .................................................................... 14 

4.3  Precautionary approach .................................................................................... 14 

4.4  Cut-off values ............................................................................................... 15 

4.5  Lowest endpoint ............................................................................................ 15 

4.6  Non-deterioration ........................................................................................... 15 

5  Towards thresholds for marine litter ............................................................................ 16 

6  Thresholds for individual MSFD COM DEC (EU) 2017/848 Descriptor 10 criteria ............................ 17 

6.1  Litter on the coastline (beach litter) ....................................................................... 17 

6.2  Surface layer of the water column ........................................................................ 17 

6.3  Seafloor litter ............................................................................................... 17 

6.4  Micro-litter (beach/coastal, sea surface, seafloor) ....................................................... 18 

6.5 

Ingested litter ............................................................................................... 19 

6.6  Entanglement or other forms of injury/sub-lethal effects or death .................................... 19 

6.7  Thresholds for individual litter items/types ............................................................... 20 

7  Conclusions and recommendations ............................................................................. 21 

References ............................................................................................................ 22 

List of abbreviations and definitions ................................................................................ 23 

i 

 
 
Abstract 

The revised Commission Decision 2017/848/EU requires EU Member States to establish threshold values for 
criteria  of  Descriptor  10  on  marine  litter.  Threshold  values,  which  are  now  mandatory  through  the  new 
provisions,  are  intended  to  contribute  to  Member  States’  determination  of  a  set  of  characteristics  for  Good 
Environmental Status and enable their assessment of the extent to which Good Environmental Status is being 
achieved under the Marine Strategy Framework Directive (MSFD). 

The MSFD Technical Group on Marine Litter has been mandated, through the MSFD 2016-2019 work program 
of  the  Common  Implementation  Strategy,  to  develop  approaches  for  setting  threshold  values  and  to  work 
towards agreed threshold values. This document sets out the scope of setting threshold values for marine litter 
criteria, explores general concepts of threshold setting and how those concepts can be translated to address 
the various hazardous effects of marine litter. It evaluates potential options for setting threshold values and 
their suitability for use with marine litter. 

While thresholds for marine litter criteria in different environmental compartments may follow the same basic 
concepts,  they  may  each  require  specific  approaches and  need  to  be  discussed  separately.  Therefore,  basic 
thoughts are presented and questions are raised, which should be addressed when defining threshold values 
for litter in the different marine compartments and for marine litter impacts. In conclusion, recommendations 
for marine litter threshold setting are made. 

2 

 
Foreword 

The Marine Directors of the European Union, Acceding Countries, Candidate Countries and European Free Trade 
Association (EFTA) Countries have jointly developed a common strategy for supporting the implementation of 
the Directive 2008/56/EC, “the Marine Strategy Framework Directive” (MSFD). The main aim of this strategy is 
to  allow  a  coherent  and  harmonious implementation  of  the  Directive.  Focus is on  methodological  questions 
related to a common understanding of the technical and scientific implications of the MSFD. In particular, one 
of the objectives of the strategy is the development of non-legally binding and practical documents, such as 
this report, on various technical issues of the Directive. 

The MSFD Technical Group on Marine Litter led by the Directorate-General for Environment and chaired by the 
European  Commission  Joint  Research  Centre,  the  German  Environment  Agency  and  IFREMER,  is  delivering 
thematic  technical  reports  such  as  Guidance  for  Monitoring  of  Marine  Litter,  Harm  caused  by  Marine  Litter, 
Identifying  Sources  of  Marine  Litter,  and  Riverine  Litter  Monitoring  –  Options  and  Recommendations.  These 
thematic reports are targeted at experts, who are directly or indirectly implementing the MSFD in the marine 
regions. 

This Technical  Report  should  further  support  European  Member States  in  the  implementation  of  monitoring 
programmes and programmes of measures to act upon marine litter. 

3 

Acknowledgements 

The authors would like to acknowledge the discussions within the MSFD Technical Group on Marine Litter and 
the contributions and comments from individual members of the group. 

Authors 

This report was prepared by the following authors within the MSFD Technical Group on Marine Litter: 

Stefanie Werner, German Environment Agency (UBA), Germany 

Elke Fischer, University of Hamburg, Germany 

David M. Fleet, LKN-SH, Germany 

François Galgani, IFREMER, France 

Georg Hanke, EC JRC, Ispra, Italy 

Sue Kinsey, MCS, United Kingdom 

Marco Mattidi, ISPRA, Italy 

4 

 
 
1  Background 

Descriptor 10 of the Marine Strategy Framework Directive (MSFD, 2008/56/EC) requires EU Member States (MS) 
to ensure that “Properties and quantities of Marine Litter (ML) do not cause harm to the coastal and marine 
environment.”  The  process  toward  reaching  this  state  includes  the  definition  of  Good  Environmental  Status 
(GES),  target  setting,  monitoring,  assessment  and  the  implementation  of  measures.  Assessing  the  current 
environmental  status  requires  a  comparison  between  a  reference  (expected/usual/normal)  state  and  an 
impacted one. Thus, it is necessary to define the reference values for indicators against which the actual or 
potentially changed situation can be compared. Therefore, by definition, the determination of GES as required 
by the MSFD, implies a condition, which has been or can  be compared against an anthropogenically altered 
state, where effects can be demonstrated (Borja et al., 2013). 

The  MSFD  Commission  Decision  (EU)  2017/848  (COM  DEC),  which  lays  down  criteria  and  methodological 
standards on GES of marine waters, specifies that Threshold Values (TVs) for the criteria of Descriptor 10 (D10) 
on ML,  should  be agreed through cooperation at EU-level. This should  be done  within  the framework of the 
Common Implementation Strategy (CIS) set up by the MS and the European Commission (EC) for the purposes 
of the MSFD. 

The MSFD Technical Group on Marine Litter (TG ML) has been mandated, through the MSFD 2016-2019 CIS 
work program, to develop approaches for setting TVs and to work towards agreed TVs for Descriptor 10. This 
document compiles available information and identifies topics for further discussion in order to derive an agreed 
strategic approach and to facilitate progress towards the setting of TVs for ML Criteria. 

5 

 
2  Scope of setting threshold values 

The revised MSFD COM DEC (EU) 2017/848 follows to some extent a different concept in comparison to the 
requirements  of  the  previous  Commission  Decision  (2010/477/EU).  The  revised  decision  requires  the  use  of 
quantified threshold values for ML criteria instead of trends for assessing the achievement of MSFD aims. 

Box 1. MSFD Commission Decision 2017/848/EU 

Article 2 

Definitions 

(5)  `threshold  value’  means  a  value  or  range  of  values  that  allows  for  an  assessment  of  the  quality  level 
achieved  for  a  particular  criterion,  thereby  contributing  to  the  assessment  of  the  extent  to  which  good 
environmental status is being achieved. 

Article 4 

Setting of threshold values through Union, regional or subregional cooperation 

1. Where Member States are required under this Decision to establish threshold values through Union, regional 
or subregional cooperation, those values shall: 

(a) be part of the set of characteristics used by Member States in their determination of good environmental 
status; 

(b)  be  consistent  with  Union  legislation;  18.5.2017  L  125/47  Official  Journal  of  the  European  Union  EN  (1) 
Regulation  (EU)  No  1143/2014  of  the  European  Parliament  and  of  the  Council  of  22  October  2014  on  the 
prevention and management of the introduction and spread of invasive alien species (OJ L 317, 4.11.2014, p. 
35); 

(c)  where  appropriate,  distinguish  the  quality  level  that  reflects  the  significance  of  an  adverse  effect  for  a 
criterion and be set in relation to a reference condition; 

(d)  be  set  at  appropriate  geographic  scales  of  assessment  to  reflect  the  different  biotic  and  abiotic 
characteristics of the regions, subregions and subdivisions; 

(e) be set on the basis of the precautionary principle, reflecting the potential risks to the marine environment;  

(f) be consistent across different criteria when they relate to the same ecosystem element; 

(g) make use of best available science; 

(h) be based on long time-series data, where available, to help determine the most appropriate value; 

(i)  reflect  natural  ecosystem  dynamics,  including  predator-prey  relationships,  and  hydrological  and  climatic 
variation, also acknowledging that the ecosystem or parts thereof may recover, if deteriorated, to a state that 
reflects prevailing physiographic, geographic, climatic and biological conditions, rather than return to a specific 
state of the past; 

(j)  be  consistent,  where  practical  and  appropriate,  with  relevant  values  set  under  regional  institutional 
cooperation structures, including those agreed in the Regional Sea Conventions. 

The calculation of reduction-rates, as requested in the previous COM DEC 2010/477/EU, can still be used as a 
basis for achieving a given operational TV. Reduction targets, used in this sense, can be especially suitable if 
they are set for the most frequent litter items/types found in the marine environment in order to validate the 
effectiveness of reduction and removal measures taken. 

TVs, which are now mandatory through the new provisions of the revised COM DEC (2017/848/EU), are intended 
to contribute to MS’ determination of a set of characteristics for GES and enable their assessment of the extent 
to which GES is being achieved. TVs are used to distinguish  between GES being achieved and GES not being 
achieved, the latter triggering a need for targets and measures. ML, as considered through MSFD Descriptor 10, 
represents  a  pressure  to  the  marine  environment.  Borja  et  al.  (2013),  proposed  that  it  might  be  easier and 
cheaper to determine GES as the `absence of pressures` (or a reference condition allowing a certain amount 
of litter as long as it does not cause harm) in a region rather than the `presence of good environment`. 

6 

 
Resource management and efficiency, with associated reduction targets, which have been proposed and set by 
MS and other international agreements, aim to reduce the input of ML into the marine environment as well as 
the amount already in the sea within a reasonable and  achievable time frame. However, even a significant 
reduction of e.g. 50 % could leave high litter concentrations in the marine environment in some areas, where 
litter pollution is elevated well above acceptable levels. Therefore, absolute numeric thresholds are not only 
required by the COM DEC (2017) but are also beneficial to the well-being of the marine environment. Given that 
zero litter levels are no-longer achievable, especially due to the high persistence of plastic litter already present 
in the sea, the central challenge is to define “sustainable” levels, which ensure that the amounts and types of 
litter, which occur, do not cause significant impacts on or risks to marine biodiversity, marine ecosystems, human 
health or legitimate uses of the sea as specified in Art. 1(2)(b) of the MSFD. 

The setting of TVs commits to a level of litter pollution above which it is agreed that GES has not been achieved. 
This is related to its potential for causing harm, as discussed in the TG ML report on “Harm caused by marine 
litter” (Werner et al., 2016). The risk caused by ML is a function of its spatial distribution and quantity  within 
the potential impact area as well as its potential to cause harm. Harm can be to marine organisms and habitats, 
e.g. through entanglement, ingestion and other forms of biological impact, as well as to humans, e.g. socio-
economic harm, human perception of litter and potential consequences to human health. According to Descriptor 
10  of  the  MSFD,  GES  is  achieved,  when  “marine  litter  does  not  cause  harm  to  the  coastal  and  marine 
environment.” This objective prescribes a low threshold of harm requiring the application of the precautionary 
principle in line with Art. 4, 1. (e) of the COM DEC (EU) 2017/848, which reflects the potential risks of litter to 
the marine environment. The precautionary principle means setting TVs at a level, where it is certain that litter 
pollution will not cause harm to the marine environment. This might need to be adjusted  at a later stage, if 
research shows that, at that particular level, harm does not occur. However, it could also infer that combating 
the highest levels of litter should be first priority and the levels, which cause harm, should be defined, once 
there is enough evidence available. 

While the MSFD provides a legal commitment for MS to address the problem of ML, including micro-litter, as 
one of the qualitative descriptors for GES of marine waters, the investigation of litter sources and increased 
awareness of this type of pollution has also led to the consideration of litter as a topic relevant to other EU 
policies. These policies include the European Strategy for Plastics in a Circular Economy (COM(2018) 28 final), 
with  its  related  Directive  (EU)  2019/904  on  the  reduction  of  the  impact  of  certain  plastic  products  on  the 
environment  as  well  as  the  Water  Framework  Directive  (2000/60/EC),  the  Waste  Framework  Directive 
(2018/851/EC amending Directive 2008/98/EC on waste), the Landfill Directive (1999/31/EC), the Urban Waste 
Water  Treatment  Directive  (91/271/EEC),  the  Port  Reception  Facility  Directive  (2000/59/EC),  the  Eco-design 
Directive  (2005/32/EC),  the  Drinking  Water  Directive  (98/83/EC)  and  the  EU´s  Water  reuse  and  Food 
Protection/Safety policies. Because litter pollution is a cross-cutting issue, the establishment of thresholds for 
D10 MSFD criteria will need to refer to these policies in order to strive for compatible approaches and resource 
efficient working processes. An efficient working arrangement could e.g. mean to have agreed TV in the marine 
environment, where the litter ends up and targets for measures implemented under various policies to work 
towards the reductions of marine litter pollution. Although these policies should be referred to under the MS 
Programmes of Measures (PoMs), the setting of TVs should primarily relate to scientific data and risks (“harm”) 
within the marine environment. Therefore, ecologically relevant targets leading to the reduction in litter levels 
required to achieve a GES, which is based on ecologically relevant values for “harm”, should only be developed 
within the context of the MSFD. 

Consultation  processes  and  scientific  research  are  ongoing.  Therefore,  this  discussion  paper  cannot  be 
conclusive on some aspects, but aims to consolidate the discussion towards the setting of TVs for ML criteria. 
Before developing actual TVs for the different criteria, the next steps are to determine how litter is measured 
in  the  different  marine  compartments  and  biota,  which  types  of  metrics  are  involved  and  which  statistical 
instruments are available for providing baselines and TVs.  

A explained above, the TVs to be defined, should be set at a level that does not cause harm to the coastal and 
marine environment by setting concentration levels (D10C1 and D10C2), levels corresponding to impact levels 
(D10C3) or to impacts directly (D10C4) that should not be exceeded. D10C1 and D10C2 are to be established 
at  Union  level,  D10C3  and  D10C4  at  a  regional  or  subregional  level  (see  Box  2  &  3).  However,  as  already 
highlighted, a concerted approach is to be developed within TG-ML for all D10 criteria. 

7 

 
 
Box 2. MSFD Commission Decision 2017/848/EU 

Preamble (8)  

 “For  each  of  the  qualitative  descriptors  listed  in  Annex  I  to  Directive  2008/56/EC,  and  on  the  basis  of  the 
indicative lists in Annex III to that Directive, it is necessary to define the criteria, including the criteria elements 
and, where appropriate, the threshold values, to be used. Threshold values are intended to contribute to Member 
States' determination of a set of characteristics for good environmental status and inform their assessment of 
the extent to which good environmental status is being achieved. It is also necessary to set out methodological 
standards, including the geographic scales for assessment and how the criteria should be used. Those criteria 
and methodological standards are to ensure consistency and allow for comparison, between marine regions or 
subregions, of assessments of the extent to which good environmental status is being achieved.” 

Annex: Criteria for D10 on Marine Litter 

D10C1 — Primary: The composition, amount and spatial distribution of litter on the coastline, in the surface 
layer of the water column, and on the seabed, are at levels that do not cause harm to the coastal and marine 
environment.  Member  States  shall  establish  threshold  values  for  these  levels  through  cooperation  at  Union 
level, taking into account regional or subregional specificities. 

D10C2  —  Primary:  The  composition,  amount  and  spatial  distribution  of  micro-litter  on  the  coastline,  in  the 
surface layer of the water column, and in seabed sediment, are at levels that do not cause harm to the coastal 
and marine environment. Member States shall establish threshold values for these levels through cooperation 
at Union level, taking into account regional or subregional specificities. 

D10C3 — Secondary: The amount of litter and micro-litter ingested by marine animals is at a level that does 
not adversely affect the health of the species concerned. Member States shall establish threshold values for 
these levels through regional or subregional cooperation. 

D10C4 — Secondary: The number of individuals of each species which are adversely affected due to litter, such 
as by entanglement, other types of injury or mortality, or health effects. Member States shall establish threshold 
values for the adverse effects of litter, through regional or subregional cooperation. 

Box 3. MSFD Commission Decision 2017/848/EU 

Preamble (13)  

 “Threshold values should reflect, where appropriate, the quality level that reflects the significance of an adverse 
effect for a criterion and should be set in relation to a reference condition. Threshold values should be consistent 
with  Union  legislation  and  set  at  appropriate  geographic  scales  to  reflect  the  different  biotic  and  abiotic 
characteristics of the regions, subregions and subdivisions. This means that even if the process to establish 
threshold values takes place at Union level, this may result in the setting of different threshold values, which 
are  specific  to  a  region,  subregion  or  subdivision.  Threshold  values  should  also  be  set  on  the  basis  of  the 
precautionary principle, reflecting the potential risks to the marine environment. The setting of threshold values 
should accommodate the dynamic nature of marine ecosystems and their elements, which can change in space 
and  time  through  hydrological  and  climatic  variation,  predator-prey  relationships  and  other  environmental 
factors. Threshold values should also reflect the fact that marine ecosystems may recover, if deteriorated, to a 
state that reflects prevailing physiographic, geographic, climatic and biological conditions, rather than return to 
a specific state of the past.“ 

Preamble (15) 

“It is necessary to lay down TVs which will be part of the set of characteristics used by MS in their determination 
of  GES  in  accordance  with  Article  9(1)  of  the  Directive  2008/56/EC,  and  the  extent  to  which  TVs  are  to  be 
achieved. TVs therefore do not, by themselves, constitute MS` determination of GES.” 

While the setting of qualitative or quantitative reduction targets provides an overall ambition to move towards 
GES, the efforts needed in different geographical areas will vary. The effort is also dependent on the decision 
to set consistent thresholds for all regions at EU level or not. However, TVs should be set on a scientific basis 
without considering the measures required to reach them, which is a task for managing at a later stage. 

The  definition  of  scientifically  derived  TVs  enables  the  identification  of  a  desirable  situation  across  Europe 
considering regional and subregional specificities, which is approved by MS at the Marine Strategy Coordination 

8 

 
Group (MSCG) based on TG-ML proposals and which provides an equal level of protection from harm throughout 
Europe.  In  the  framework  of  the  MSFD  the  ecological  threshold  concept  is  closely  linked  to  adaptive 
management  as  a  tool  for  addressing  environmental  pressures.  In  adaptive  management,  measures,  as 
solutions  to  problems,  are  proposed  and  implemented.  However,  specifications  are  constantly  re-evaluated 
based on actual ecosystem response to management. As requested by the MSFD, monitoring/measurements in 
the  marine  and  coastal  environment  are  used  as  a  tool  for  supporting  iterative  management  decisions 
concerning the implementation of PoMs. Monitoring is the means of assessing the current status, which then 
drives the need (or not) for measures. 

Although the thresholds for D10C3 and D10C4 will vary between subregions due to the spatial distribution of 
appropriate species, it is proposed to discuss the approach of setting thresholds for both criteria at the EU level, 
in order to provide coherence, a common base for further work and to avoid duplicating work. It is therefore of 
prime importance to involve experts from MS, the scientific community, environmental NGOs and Regional Sea 
Conventions (RSCs) in the discussion. 

While thresholds will need to be adopted at the national level, ML is a transboundary problem and litter crosses 
national borders. Achieving TVs will require close collaboration between neighbouring countries, especially in 
the framework of RSCs, including those outside the EU. Therefore, although ideally TVs are to be set at European 
level, there is also need for cooperation within a global framework. International agreements are needed e.g. 
with  United  Nations  (UN)  agencies,  like  the  International Maritime  Organization  (IMO),  to  tackle  sources like 
shipping.  If thresholds and targets to reduce litter in the marine environment  have already been adopted in 
other fora, targets and thresholds defined under the MSFD should ideally be compatible and comparable. 

The  COM  DEC  (EU)  2017/848  states  explicitly  that,  in  cases  where  TVs  have  not  been  defined,  MS  should 
establish TVs through Union, regional or subregional cooperation. Furthermore, the decision stresses that  TVs 
should be set at appropriate geographic scales to reflect the different biotic and abiotic characteristics of the 
regions and subregions, which may result in the setting of TVs, which are specific to a region or subregion. If 
the TVs for each of the D10 criteria do vary between regions or subregions, the ongoing work  will primarily 
focus on discussing and proposing a common approach on how to set these values. The equal level of protection 
across Europe should be ensured by the definition of a common/harmonized approach  to setting TVs  while 
considering the physical and biological specificities of regions and subregions.  

9 

3  General concepts of threshold setting 

Box 4. General definitions of the meaning of thresholds for discussion 

Oxford dictionary (https://en.oxforddictionaries.com/definition/threshold) 

“The magnitude or intensity that must be exceeded for a certain reaction, phenomenon, result, or condition to 
occur or be manifested.” 

Groffmann et al., 2006 

“The point at which there is an abrupt change in an ecosystem quality, property or phenomenon, or where small 
changes in an environmental driver produce large responses in the ecosystem.” 

Rosenthal, 1997 

“The dose of the toxicant below which no adverse effects will occur.” 

The setting of TVs assumes that specific values of a parameter can be derived in a quantitative way in order 
to provide protection against adverse effects. This is not always possible, due to lack of knowledge, inaccuracy 
of quantification or the nature of adverse effects and cumulative unknown effects of several pressures acting 
together. Furthermore, analysis of thresholds is complicated by nonlinear dynamics and multiple factor controls 
that operate at diverse spatial and temporal scales (Groffmann et al., 2006). 

3.1  Harmful effects of marine and beach/coastal litter 

The effect of a toxic substance is typically described by the endpoints, i.e. the biochemical pathways and the 
mode-of-action through which the substance acts on the metabolism. A toxicity endpoint is the result of a study 
conducted to determine how dangerous a substance is. However, the toxic component is just part of the range 
of  impacts  caused  by  ML.  Therefore,  in  the  following,  an  attempt  is made  to  translate  the  concept  of  toxic 
endpoints to address the various hazardous effects of ML, namely: 

●  Toxicological action mode (lethal and sublethal) 

●  Physical damage such as entanglement, intestinal obstruction (lethal and sublethal) 

●  Disturbance of human activities (sublethal) 

●  Human health implications (sublethal and lethal) 

An overview of “Harm caused by marine litter” is provided in a report published by the TG ML (Werner et al., 
2016). The general conclusions of this report are: 

●  The numbers of animals affected by negative interactions with ML and the associated suffering that 
affects  animal  welfare,  in  combination  with  the  extent  of  encounters  which  in  some  represent  a 
substantial  proportion  of  a  population,  clearly  show  that  reductions  in  further input  and of  existing 
amounts of ML are urgently needed. 

●  The relative importance of plastic as a solid environmental contaminant is likely to increase over time. 
Even if the introduction of large items of litter into the marine environment ceases, the abundance of 
micro-plastics will continue to increase because of the fragmentation of larger plastic items (legacy 
items).  What  we  do  today  will  strongly  influence  future  quantities  of  micro-  and  potentially  nano-
particles. 

●  About the quality of evidence, it can be concluded that monitoring of impacts on biota is challenging, 
but there is clear evidence of harm to individuals and, to a lesser extent, assemblages of organisms 
and populations of some species. There is evidence that increasing numbers of species are experiencing 
encounters with ML with manifold consequences. 

The report provides available evidence of relevant impacts of ML and some specific conclusions, which includes 
information  on  entanglement,  ingestion,  chemical  transfer,  ML  as  a  vector  for  biota,  marine  litter 
altering/modifying assemblages of  species, levels of  biological organization affected,  animal welfare, socio-
economic harm and risk assessment for ML. 

10 

3.2  Marine and coastal litter as a pollutant 

Article 1(2)(b) of the MSFD requires prevention and reduction of inputs into the marine environment, in order to 
phase out pollution as defined in Article 3(8), so as to ensure that there are no significant impacts on or risks 
to  marine  biodiversity  (also  in  microbial  communities),  marine  ecosystems,  as  well  as  socio-economic 
implications. 

Thresholds are used to protect the environment and humans against detrimental disturbances/pollution levels 
of  substances  of  concern.  The  setting  of  thresholds  for  ML  and  its  effects  appears  similar  to  this  type  of 
application. Therefore, concepts from chemical pollution could be relevant for setting TVs for ML and are being 
discussed regarding their applicability. In this context and referring to the scope of Article 3(8), litter should be 
considered as a pollutant causing physical and chemical harm to biodiversity, human health, uses of the sea, 
etc. 

One should also keep in mind that plastic pollution in the marine environment is being considered as a planetary 
boundary threat. From a stratigraphic perspective, there is a clear Anthropocene threshold between pre-plastic 
and post-plastic systems, but for a chemical pollutant to pose a planetary boundary threat, its environmental 
exposure and/or its disruptive effects must be poorly reversible. Plastic pollution in the marine environment will 
always fulfil this condition, as the ultimate end-fate of most mismanaged plastics is that they end up deposited 
and  compartmentalised  in  the  ocean  (Villarrubia-Gomez  et  al.,  2017).  Given  the  long  timeframes  for  the 
degradation of plastics, we do not know if the disruptive effects (e.g. smothering of seafloor, ecotoxicological 
effects from nano-plastics) are, in the end, reversible or not. 

The pollution of the environment by chemical substances has been addressed by setting TVs based on scientific 
knowledge and experimental data. For example, the Water Framework Directive (WFD) provides a scheme for 
the  setting  of  environmental  quality  standards  for  chemical  pollutants  in  the  freshwater  and  marine 
environment: WFD TGD EQS setting1. Litter (including macro, meso and micro-litter) could be regarded in this 
way too. As already highlighted, the introduction of litter into the marine environment causes chemical vector 
effects.  However,  ML  is  causing  additional  impacts  such  as  physical  harm/damage  of  marine  species  and 
habitats and disturbance of human activities as well as socio-economic harm, which need to be addressed, too. 

Threshold concepts of toxicological concern are based on the possibility of establishing an exposure TV below 
which no significant risk is to be expected. By  determining the “no observable adverse effect level” and the 
“lowest observable adverse effect level”, the (absolute) threshold must lie between these two doses (Rosenthal, 
1997). However, in case of uncertainty about the caused  effects, the  concept of “thresholds of no  concern” 
(which is a conservative approach using levels where effects were not observed or expected to be observed) 
has been applied in the food safety area2. 

The outputs of relevant projects, such as JPI Oceans (Intergovernmental platform Joint Programming Initiative 
Healthy and Productive Seas), will be considered once they become available. 

3.3  Requirements and uncertainties related to TVs 

While thresholds are expressed as numerical values, it should be kept in mind that they have been derived from 
underlying data, with uncertainties. These uncertainties must be considered in TV developments. In practical 
applications, this is often taken into consideration by applying ample safety factors to the TVs in order to take 
gaps in knowledge and uncertainties in the data into account. However, uncertainty becomes more of an issue, 
when measured levels are very close to a GES threshold, where it is then unclear if GES is achieved or not. If 
GES is clearly out of reach, there is a need to act (take measures) and the degree of uncertainty is less of an 
issue. 

A basic pre-requirement for the setting and  compliance checking with TVs is the availability of a monitoring 
framework for data collection  that supports representative quantitative assessments  of litter in appropriate 
environmental compartments and that delivers data with a known uncertainty allowing for comparison against 
TVs. The potential costs in case of non-compliance with agreed TVs are supposed to create a joint incentive to 
comply with them.  

The concept of thresholds assumes that there are levels of pollutant concentrations that, according to scientific 
studies, do not cause significant impacts on or risks to marine biodiversity, marine ecosystems, human health 
or legitimate uses of the sea as specified in Art. 1(2) b of the MSFD. This implies the ability to identify amounts 

(1)   https://circabc.europa.eu/sd/a/0cc3581b-5f65-4b6f-91c6-433a1e947838/TGD-EQS%20CIS-WFD%2027%20EC%202011.pdf 
(2)   https://www.efsa.europa.eu/en/topics/topic/threshold-toxicological-concern 

11 

                                           
or concentrations of litter in areas with an affected environmental status, but where litter does not significantly 
impact the marine or coastal environment. This will not work for all types of ML, e.g. those especially prone to 
cause entanglement. The setting of quantitative thresholds requires monitoring data of sufficient quality and 
in agreed matrices, in order to allow compliance checking against TVs. This applies to the unit of measurement, 
as well as to the environmental compartment or species, and the harmonization of micro-litter quantification. 
Properties that ML thresholds should have, are listed below: 

● 

Ideally, they should be based on scientific evidence and long-time series of data. 

●  They should be set so that they are achievable, but always in relation to a harm level. If the scientific 
evidence clearly demonstrates the need to set very low thresholds, this should be done, regardless of 
the  achievability.  There  will  be  litter  reductions  that  are  more  easily  achieved  than  others  (cost, 
practicality, societal willingness), but to prevent harm to the marine environment has priority in defining 
TVs, whereas achievability comes secondary.  

●  They should enable compliance checking through existing and implemented monitoring protocols. 

●  They should be numerical values and be based on a comparable expression of litter quantities and 

effects for the different marine reporting units. 

●  They should be based on the precautionary principle, reflecting the potential risks to the marine and 

coastal environment. 

●  They  should  be  set  in  relation  to  reference  conditions,  a  probable  effect  situation  or  a  no-effect 

situation. 

●  They should be based on reference conditions, which will be very dependent on the chosen geographic 

scale; EU, regional, subregional or local. 

●  They  should  be  consistent  with  thresholds  set  under  other  criteria  for  the  same  element  (species, 

habitat). 

●  They should be set at appropriate geographical scales of assessment and be consistent, where practical 
and appropriate, with relevant TVs set under regional institutional cooperation structures within an EU 
framework as well as with those agreed in the RSCs. 

3.4  Risk assessment 

TVs should represent a pressure level, which ensures that there are no significant impacts on, or risks to marine 
biodiversity,  marine  ecosystems,  ecosystem  functioning,  species,  habitats,  individuals/populations,  human 
health,  societies  or  economics  or  legitimate  uses  of  the  sea.  These  provisions  require  the  identification, 
quantification and prioritization of harmful effects. This also includes the identification of significant versus 
non-significant risks of  harm, the societal agreement on  acceptable risk levels, and thus the introduction of 
quantitative  evaluation  criteria.  While  there  is  longstanding  experience  of  environmental  and  human  risk 
assessment,  e.g.  for  chemical  contaminants,  such  approaches  for  ML are  still  under  development.  The  risks 
related to ML and the concept of using a risk assessment approach for  ML have been described in a TG ML 
report on harm (Werner et al., 2016). A quantitative risk assessment approach for ML, in the sense that risk of 
harm is used to set TVs, should be discussed (analogous to contaminants). 

The assessment of risk is also relevant to the prioritization of measures against specific litter types, because 
some litter types pose a greater threat to the marine environment than others do. This implies that thresholds 
should be set for individual litter types, groups of litter types or sub-criteria elements, which could be used to 
set operational reduction targets and hence measures and actions. 

3.5  Existing threshold values for marine litter 

There are currently few established TVs for ML. One exception is the objective of the OSPAR indicator on plastic 
particles in the stomachs of the Northern Fulmar Fulmarus glacialis. The monitoring program uses corpses of 
beached birds or individuals accidentally killed. OSPAR has a long-term objective of less than 10 % of fulmars 
exceeding a level of 0.1 gram of plastic in their stomach contents. This is regarded as a pressure TV correlated 
with impacts. Other potential TVs correlated to impacts or  directly representing impacts are presently under 
discussion e.g. (i) the number of plastic pieces in turtle stomachs occur below levels that might affect the body 
condition and cause mortal effects, and (ii) plastic litter used as nesting material in seabirds’ breeding colonies 
is  below  amounts  observed  in  least  polluted  areas  in  order to  reduce  mortality  rates  due  to  entanglement. 

12 

Thresholds should also take population level effects into account by considering the state of the population as 
a whole. If the population of a species is already threatened by other factors, then an even lower litter impact 
should  be  aimed  for.  For  instance,  some  harbour  porpoise  Phocoena  phocoena  populations  are  already 
threatened and a threshold for by-catch of zero individuals in active fishing gear is proposed. This has to be 
taken into account when assessing entanglement/mortalities in Derelict Fishing Gear. 

In addition, litter reduction targets (Art 10 MSFD) have been defined by some countries/regions in the framework 
of Regional Action Plans on ML and the MSFD PoMs. These are based on a percentage reduction over time in 
the amount of litter entering the marine environment and/or the amount of litter already present in the marine 
environment as well as microplastics applied in products and industrial processes.  

13 

4  Options for setting threshold values 

As already expressed, harm caused by marine litter is manifold. Depending on the type of harm (e.g. ingestion, 
entanglement, habitat alteration, socio-economic etc.), different levels of litter pollution must be considered for 
threshold setting and possibly also different thresholds for different types of litter. 

Different options and concepts for setting of thresholds are presented  below. These are provided as a non-
exhaustive list with the aim of stimulating discussion (the order does not represent a prioritization). 

4.1  The zero option 

ML items are mainly made up of artificial polymers, which, by definition, do not exist in nature. Some litter items 
are made from other materials, though their origin is still anthropogenic. The ultimate goal for avoiding harm 
caused by litter could be a waste free environment. However, plastics are widely used and are currently very 
abundant  in  the  marine  environment.  The  ubiquity  of  marine  plastic  litter  and  the  unfeasibility  of  its  total 
removal  from  the  marine  environment,  especially  in  the  case  of  micro-particles,  means  that  exposure  is 
essentially irreversible (Villarrubia-Gomez et al., 2017). On the short-term or even the intermediate to long-
term, it will be impossible to prevent all input of litter to, or remove all litter from, the marine environment. 
Thus, the setting of a TV of zero litter, even on the long-term, may not be a realistic/operational option, because 
it would not be achievable. However, it can still be treated as a reference condition considered as the ultimate 
goal to achieve. 

4.2  Points-of-no-return and tipping points 

Points-of-no-return are system condition parameter values that indicate a level, which, when surpassed, will 
lead  to  irreversible  alterations  in  system  conditions  (playground  slide  effect).  A  point-of-no-return  might  be 
reached if, due to ML, a population declines beyond recovery. This could also include declines as a result of 
cumulative  effects  with  other  detrimental  factors.  However,  population-level  effects  have  been  difficult  to 
quantify  for  ML.  All  factors  affecting  a  population  need  to  be  studied  to  determine  how  much  additional 
mortality or reduced fitness the population can tolerate, before a threshold for litter-based effects can be set. 

Tipping points are system condition parameter values that indicate a level, which, when surpassed, will alter 
system  conditions  drastically  (see-saw  effect).  These  effects  may  occur  in  cases  of  extremely  high  litter 
concentrations. 

Both approaches, point-of-no-return and tipping points, are only applicable to population-level effects. Since 
they both refer to a status that is opposite to GES, being points of no return in terms of values, above which 
harm  is already  occurring,  they  are  not  options  for  setting  ML thresholds.  In  addition,  there  is  currently  not 
enough data available to support such an approach. Once this data becomes available, it would be necessary 
to use safety factors/uncertainty factors to prevent irreversible alterations. 

4.3  Precautionary approach 

There is clear evidence of harm to many marine species caused by ML, largely on individuals and to a lesser 
extent on assemblages of organisms and populations (Werner et al., 2016). There is evidence that increasing 
numbers  of  species  are  experiencing  encounters  with  ML  with  multiple/numerous  consequences.  However, 
conclusive scientific knowledge on the quantitative relationship between the amount and the exact rate of harm 
caused by ML is currently only partially available, especially regarding sub-lethal effects. As research is currently 
unable to provide clear TVs, an initial approach to setting TVs should make use of the precautionary principle, 
thus providing the maximum protection against adverse effects by introducing large safety margins. This could 
be based on an expert judgement approach (a subjective opinion based on scientific evidence), by eliciting the 
expertise of a wide range of qualified contributors to make sure that such judgement is demonstrably robust 
and  explicitly  stated.  Currently  models  for  using  expert  judgement  are  under  development,  especially  in 
quantitative risk assessment. This approach should be used especially for micro-plastics, tackling their input 
from various sources 

A threshold based on the precautionary principle may e.g. allow the setting of thresholds if the quantitative 
concentration/risk relation is not known, but there are indications of risk. Another way is the concept of using 
litter  pollution  levels from pristine  or near-pristine  areas as TV,  as  was  done  for  the  OSPAR  litter in  fulmar 
stomachs indicator. This means accepting a slight deviation from the reference (pristine) condition by using the 
situation of least pollution found elsewhere in the environment of concern. 

14 

4.4  Cut-off values 

There  is  societal  agreement  on  the  need  to  reduce  the  amount  of  litter,  especially  plastic  litter,  in  marine 
ecosystems. The presently high litter pollution levels are not considered tolerable. The tolerance of certain levels 
of  pollution  by  the  public  is  the  key  element  to  be  considered  here.  Disturbance  of  human  wellbeing  is  a 
component of socio-economic harm. It might be possible to define levels of pollution linked to targets, which 
are  acceptable  to  society.  People  envisage  the  environment  as  degraded,  when  they  see  litter  or  hear  that 
marine animals have litter in their digestive systems. While scientific research is still investigating the physical 
and chemical effects as well as toxicological properties and impacts of litter, areas of potentially high impact 
can already be predicted based on concentration/abundance mapping. In addition to available information on 
highly polluted regions, increased surveillance  is providing comparable and representative data for  areas of 
lower impact. Assessing litter abundance of specific litter types or groups of litter types (e.g. single-use plastics) 
should allow the identification of heavily polluted versus near-pristine areas, taking also cross-border processes 
and transport into account. This information will then enable the  prediction of litter concentration thresholds 
that, while not yet based on quantitative harm/impact data, can minimize litter impact, and can be conceived 
as tolerable to society. 

Such cut-off values could be defined as a proportion or a percentile in relation to reference conditions, averages 
or maximum concentrations.  The rationale for this approach is that the lower concentrations, which already 
exist in certain areas, should be the goal for other areas. This concept would be supported by the requirement 
of an equal level of protection in all areas and seas. 

4.5  Lowest endpoint 

In this case the threshold is set to the lowest concentration causing an adverse effect on one of the specific 
types  of  harm.  For  ML  this  denotes  that,  while  it  might  be  difficult  or  impossible  to  decide  on  the  relative 
importance of different adverse effects such as toxicological, entanglement or socio-economic, the lowest TV 
will be most relevant. Thus, if a TV, based on a perceived disturbance by beach visitors, is occurring at a lower 
litter abundance level than other impacts, it would determine the threshold level. However, this option requires 
substantial knowledge of the different adverse effects before it can be applied in practice. 

4.6  Non-deterioration 

While the application of reduction percentages does not foresee an increase of litter concentrations and impacts, 
the MSFD goal to prevent deterioration of the marine waters and coastal environment should be addressed. 
According  to  MSFD  Article  1(2)  EU  MS  shall  protect  and  preserve  the  marine  environment,  prevent  its 
deterioration  or,  where  practicable,  restore  marine  ecosystems  in  areas  where  they  have  been  adversely 
affected. Similar to the WFD, the non-deterioration approach could usefully be combined with other options of 
setting TVs. The setting of absolute TVs at an EU-level should not allow increases in litter pollution in countries 
where  litter  pollution  levels  are  already  below  the  TV.  This  will  be  especially  important  as  we  struggle  to 
determine thresholds for micro-plastics. There is no consensus yet on how risk assessment for micro-plastics 
should be conducted, and attempts are currently hampered by a lack of data. It is therefore important to stress 
that, especially for micro-plastics, there should be no allowances for increases. 

A combined approach of non-deterioration, based on existing data, alongside a precautionary approach, with 
proposed TVs, which are reviewed, when new scientific and monitoring data are available, could be a possibility.  

15 

 
 
 
 
 
 
5  Towards thresholds for marine litter 

The discussions on thresholds for ML in TG-ML will not be straightforward due to the current limited state of 
knowledge. It will certainly require initial exchange of information between MS. The COM DEC (EU) 2017/848 
provides options for bridging the time until jointly set TVs are set: 

Box 5. MSFD Commission Decision 2017/848/EU 

Preamble (12) 

“In cases where no threshold values are laid down, Member States should establish threshold values through 
Union, regional or subregional cooperation, for instance by referring to existing values or developing new ones 
in  the  framework  of  the  Regional  Sea  Conventions.  In  cases  where  threshold  values  should  be  established 
through cooperation at Union level (for the descriptors on marine litter, underwater noise and seabed integrity), 
this will be done in the framework of the Common Implementation Strategy set up by the Member States and 
the  Commission  for  the  purposes  of  Directive  2008/56/EC.  Once  established  through  Union,  regional  or 
subregional cooperation, these threshold values will only become part of Member States' sets of characteristics 
for good environmental status when they are sent to the Commission as part of Member States' reporting under 
Article 17(3) of Directive 2008/56/EC. Until such threshold values are established through Union, regional or 
subregional cooperation, Member States should be able to use national threshold values, directional trends or 
pressure-based threshold values as proxies.” 

It might be advisable to attempt to reach agreement on provisional thresholds at EU-level, rather than moving 
towards a situation with many different national approaches across Europe. This might include setting values 
for  levels,  which  would  be  clearly  unacceptable  considering  the  precautionary  principle.  These  TVs  could  be 
adjusted in the future, as evidence on harm improves. 

The derivation of provisional thresholds could be done by compiling information on the current state of marine 
and coastal litter pollution, including patterns across regions and their change over time and, where sufficient 
data  is  available,  by  considering  the  baselines  and,  in  a  final  step,  by  defining  the  methods  used  for  data 
processing. It could be helpful to use intermediate/provisional TVs/directional trends for criteria that do not yet 
allow for the setting of  ultimate TVs. Proposals for possible intermediate thresholds should also  include the 
option of non-deterioration 

Furthermore, the COM DEC only refers to two types of indicators: the absolute level type and the type stating a 
required percentage reduction. However, in other descriptors, where knowledge is currently insufficient to define 
levels for one of the two types, the requirement is simply that a significant trend over a specified period should 
occur.  This  option, which  lies  somewhere  between  a  percentage  decrease  and  non-  deterioration,  should  be 
considered  for  use  with  ML.  However,  in  order  to  detect  a  trend,  long  time  series  of  data  are  usually  a 
prerequisite and such data is not yet available for ML in all areas, since many countries only started monitoring 
around 2015. 

The contribution of stakeholders from different backgrounds will be beneficial to the further process of defining 
TVs. For instance, the involvement of behavioural scientists could add significant value to this discussion. 

16 

6  Thresholds for individual MSFD COM DEC (EU) 2017/848 Descriptor 10 

criteria 

While thresholds for ML in the different marine compartments (coastline, surface layer of the water column, 
seabed)  may  follow  the  same  basic  concepts,  they  might  each  require  specific  approaches  and  need  to  be 
discussed separately. 

In  the  following,  basic  thoughts  and  questions  are  raised,  which  should  be  discussed  further  taking  into 
consideration the approaches set out above, when working on the definition of TVs for the different ML criteria. 

6.1  Litter on the coastline (beach litter) 

●  TVs should be based on data on the abundance of litter recorded during beach surveys. TVs should be 
cut-off  values  (absolute/percentiles)  determined  through  expert  judgement.  TVs  for  groups  of  litter 
types (i.e. all plastic items, all packaging items) as well as individual litter types should be defined in 
order  to  be  able  to  assess  the  efficiency  of  measures and instruments  aimed  at  reducing  ML.  TVs 
developed for litter types or groups of litter types, should be based on the identification of a “near-to-
pristine” condition (Schulz et al., 2013), which, would strive towards a status where less harm is caused. 

●  There is a potential conflict between ‘based on expert judgement’ and ‘near-to-pristine’, as the latter 
may intrinsically involve expert judgement. The term ‘near-to-pristine’ needs to be defined more clearly, 
but may be linked to litter occurrence in remote areas, as e.g. the Arctic.  

● 

Interim targets  toward  achieving  the  TV  could  be  based  on  reduction  trends for the  six-year MSFD 
assessment cycle. The calculation of an interim target could be performed by defining a baseline and 
setting a  reduction target of a  given  percentage or a  downward trend from that baseline for a set 
period. The baseline can be calculated from existing data from beach litter surveys. A 30 % reduction 
from  a  baseline  of  e.g.  60  items/100  m  would  give  a  target  value  of  42  items/100  m.  An  annual 
reduction of 10 % over a six-year period from a baseline of 60 items/100 m would give a target value 
of 31.89 items/100 m (i.e. for a six-year period, an annual 10 % reduction is about the same as a total 
50 % reduction). Interim reduction targets need to be ambitious in order  to achieve a prescribed TV 
within a couple of MSFD cycles e.g. a 10% reduction per year from 60 items would take about 14 years 
to reach a TV of 13 items/100m. 

● 

It is important to determine cut-off values using a sound analysis of reliable data. 

●  A focus should be on  plastic litter, which is dominated by single-use and fishery-related items and 
linked to the Plastics Strategy and the associated directive on the reduction of the impact of certain 
plastic products in the environment. 

6.2  Surface layer of the water column 

●  For  litter  on  the  surface  layer  of  the  water  column  far  less  data  is  available  than  for  beach  litter. 
Nevertheless, the same approach  as for beach litter could be used by  analysing existing data  sets, 
where available, and determining a close-to-pristine state using percentile values of those data sets. 
The analysis of data and definition of TVs could be done at a sea-basin level. 

● 

If litter in the stomachs of seabirds, such as the Northern Fulmar, are used as an indicator of litter on 
the water surface, a draft TV is already available for the North Sea (OSPAR indicator). However, birds 
do not ingest all litter types and ingestion is generally limited to smaller litter items (meso & micro) 
and  thus  the  type  of  litter  assessed  is  not  representative  of  litter  on  the  sea  surface  overall. 
Additionally, for some areas (e.g. the Baltic Sea), indicator species have yet been identified. Although 
it is accepted that the birds, which are used as samples, are representative of the marine waters, where 
they are collected, information on where the individual birds, live, feed, breed and die is limited. 

●  Abandoned, lost and otherwise discarded fishing  gear (ALDFG), which also can occur in the  surface 

layer of the water column, also needs to be considered, when defining TVs. 

6.3  Seafloor litter 

●  Seafloor litter data is mostly available from bottom-trawl-net fishing. 

●  The availability of information on the dynamics of litter on the seafloor is limited. 

17 

●  Monitoring methods are lacking for large areas of the seafloor, where bottom trawling is not possible. 
For such areas, innovative methods need to be developed and implemented. Since bottom trawling is 
destructive to the seabed, data must only be collected as a by-product of other scientific surveys e.g. 
fish-stock assessments (platforms of opportunity). 

●  Certain areas of the seafloor are final sinks for litter. Under the assumption that most ML is highly 
persistent material, in some areas litter quantities on the seafloor are unlikely to diminish over time. 
In this respect, the removal of ML by Fishing-for-Litter (FFL) activities is probably relatively negligible 
in most areas and the proportion of seafloor litter, which is washed up on the coastline, is unknown. 

●  Hotspots, accumulation zones and sinks need to be considered, when collecting data on seafloor litter. 
For  monitoring  chemicals,  specific  accumulation  zones  are  used,  which  are  believed  to  be 
representative of a larger area such as a sea basin. This idea could be applied to seafloor litter. 

●  Thresholds could be derived for certain litter types, prioritising litter types, which are especially harmful 
(e.g.  lost  and  discarded  fishing  gear  such  as  nets  and  remains  of  nets).  That  implies  the  need  for 
improvement  in  monitoring  especially  in  areas  where  trawl  surveys  are  not  possible.  The  use  of 
innovative methods for monitoring seafloor litter, such as side-scan-sonar or ROVs, could support the 
development of TVs for this marine compartment.  

6.4  Micro-litter (beach/coastal, sea surface, seafloor) 

Box 6. Shortlist of prerequisites needed for threshold setting for micro-litter 

—  Set-up and/or extension of a reliable database providing comparable data including: 

—  Determination of environmental compartment(s) to be investigated (beach sediment, seabed sediment, surface water, 

water column, biota) 

—  Definition of reference sampling sites based on regional or subregional level 

—  Definition on temporal resolution of surveys 

—  Agreement on harmonized methods for sampling, sampling design, sample preparation and identification 

— 

Identification of further basic parameters (such as meteorology, morphology, sediment parameters, etc.) 

—  Agreement on reference units and reporting values (size, weight, shape, colour, etc.) 

—  Central documentation and statistical evaluation 

● 

It is currently difficult to derive TVs based on the toxicological and other properties of marine micro-
litter.  There  is  a  need  for  a  combined  approach  considering  societal  concerns  and  especially  the 
inability, in many cases, to exclude impacts, as no conclusive information on potential harm is available. 

●  However, information is available for mechanical/physical impacts; ongoing literature reviews (e.g. by 

the ECHA/JPI Oceans) should be consulted. 

●  Monitoring frameworks and QA/QC schemes are under development, as well as monitoring schemes 

and strategies. 

●  The latest scientific findings should be considered (development is ongoing). 

● 

● 

It may not be possible to derive toxicology-based thresholds for marine micro-litter at present. 

It  is assumed  that  the  major  part  of  micro-litter is resulting  from  degradation  of  macro  litter.  It  is 
extremely challenging to set TVs for such secondary micro-plastics. 

●  According to the COM DEC (EU) 2017/848, micro-litter shall be monitored in a way that can be related 
to  point-sources  for  inputs  (such  as  harbours,  marinas,  waste-water  treatment  plants,  storm-water 
effluents), where feasible. 

●  Focus should be on input from sewage, rivers and estuaries.  Atmospheric and sea-based sources as 
well as fragmentation processes should be second priority. Whether the focus should be on wastewater 
treatment and/or on microplastics out at sea, needs clarification. 

18 

   
●  Fluxes  between  sources,  pathways  and  sinks  (even  temporary  sinks)  need  to  be  considered.  Since 
seabed sediments are final sinks for microplastics, TVs for their concentration in sediments could be 
the most relevant approach. However, it could be better to wait until effects of microplastics on benthic 
organisms are better known. 

●  Sediment sampling also allows for the assessment of different size fractions and could potentially also 

be used to assess the litter flux from the water column. 

●  Reference sites need to be identified for monitoring trends. 

●  A precautionary approach needs to be applied to pathogens, which might severely impact on the marine 
environment. However, although some initial evidence is available, it is too early to draw conclusions.  

● 

In some countries, the proposal for (large) micro-litter is to set thresholds similar to the OSPAR indicator 
on plastic particles in the stomachs of the Northern Fulmar i.e. that a certain percentage of the area 
of a compartment of the marine environment, e.g. beach, water surface, seafloor, should not contain 
more than a certain amount of micro-litter. 

6.5 

Ingested litter 

●  The amount of litter ingested and potentially causing entanglement must be reduced drastically; D10 

criteria 1 and 2 support this. 

●  The approach for quantification of ingestion if ML by different target species is still under development. 

●  The approach for Northern Fulmar in the North Sea (OSPAR common indicator) is available and has 
been used for many years. The TV could aim at the same goal as the OSPAR indicator, which relates 
to close-to-pristine conditions. 

●  Thresholds for ingestion of litter by turtles, based on the work of Matiddi et al. (2017), were developed 

during the INDICIT project and are available. 

● 

In some areas (see also Werner et al., 2016) it could be feasible to set thresholds for individual species 
because around 40 % of the individuals of some populations ingest ML. 

●  Numerous results are now available for benthic and pelagic fish species, for example from the ICES 
fish disease surveys. Although these surveys include a bias since they are only possible in areas with 
a certain sediment, which will need to be corrected for, they have potential as good indicators, if the 
right species are chosen. 

●  Effects of micro-plastic exposure on predator-prey interactions have not yet been established in the 
marine environment. However, there is abundant evidence that animals do consume plastics, possibly 
mistaking litter and plastic particles for prey (De Sa et al., 2018). 

●  Micro-plastics have been shown to alter feeding behaviour as well, and feeding preferences can affect 

propensity to ingest plastics (Mizraji et al., 2017). 

●  Upcoming monitoring of micro-plastics should include sentinel species such as filter feeders, which are 

known to ingest plastic particles (e.g. blue mussels). 

●  The achievement of GES with regard to Criterion D10C3 has the potential to fail when populations are 
simultaneously in- or decreasing, e.g. through successful measures taken  or measures not taken to 
combat  other  pressures.  Therefore,  the  work  on  this  criterion  should  initially  aim  to  monitor  the 
proportion (%) of individuals impacted by ingestion of ML relative to the total number of individuals in 
the  studied  population,  while  taking  into  account  information  available  for  other  anthropogenic 
pressures. 

6.6  Entanglement or other forms of injury/sub-lethal effects or death 

 

 

The approach for quantification of entanglement events is still under development. Entanglement was 
included as a secondary criterion in the revised COM DEC in 2017. Only a few monitoring approaches 
have been tested so far.  

The protocol to assess entanglement in seabird colonies, which is recommended by TG Litter, has been 
applied in the Gannet colonies on the islands of Helgoland in the North Sea and Grassholm off the 

19 

coast  of  Wales.  Options  for  thresholds  could  be  the  number  of  entangled  birds/unit  of  colony  and 
calculated mortality rates from entanglement. 

●  The link between seafloor litter and entanglement requires further discussion (e.g. with regards to rates 

of interaction between animals and ML). 

6.7  Thresholds for individual litter items/types 

As reduction measures will target specific litter types, or groups of litter types, as well as sources and pathways, 
thresholds could also be set for these different levels (e.g. plastic drink bottles, plastic bags, packaging, pre-
production pellets, fishing nets, sewage-related litter or single use plastics). These litter type or litter group-
related  TVs  should  be  derived  in  relation  to  measures, e.g.  for specific  litter types or  groups  of  litter items. 
However, they should still be based on risk for harm to the marine environment, and the assessment should 
then inform on the need for measures under relevant legislation. This must consider EU-level legislation, related 
to the EU Plastics Strategy, as well as RSCs in order to be aligned with the operational reduction targets, which 
exist within the framework of the Regional Action Plans on ML. 

20 

7  Conclusions and recommendations 

Based  on  the  discussions  within  the  TG  ML,  the  following  recommendations  for  ML  threshold  setting  are 
proposed: 

●  Threshold values define agreed borderlines which contribute to the definition of GES. 

●  The COM DEC (EU) 2017/demands the development of thresholds for ML criteria to protect the marine 
environment and human activities against all types of harm caused by litter, which include physical 
damage, toxicological responses, disturbance of human activities as well as socio-economic harm. 

●  Before discussing individual TVs, agreement on the concept and approach should be reached. 

●  Thresholds for ML should ideally be set at EU-level in order to provide equal protection across the EU. 
However, there may be sound reasons for setting (sub-)regional values, e.g. where different species 
are involved. 

●  ML is a global problem. Nevertheless, TVs need to be set at a specific geographic scale and assessed 
at that scale or possibly finer spatial scales. For instance, TVs could be set at a regional scale (if it is 
not appropriate to have them set at EU-level) and then assessed at finer spatial scales e.g. to assess 
whether the threshold has only been achieved by some MS or even in part of a MS marine waters. 

●  Thresholds for ML can only be set if it is possible to check compliance against quantitative values from 

monitoring. 

●  Thresholds for ML are to be set for the individual criteria as defined by the COM DEC (EU) 2017/848 

and specifically for defined litter size-fractions and possibly also for litter types/categories. 

●  The  derivation of thresholds  for  ML requires the  distinction between  significant and  non-significant 
risks of harm as well as a societal agreement on acceptable risk levels and, thus, the introduction of 
quantitative evaluation criteria. 

●  TVs for ML should be set at the appropriate spatial scale which should be compatible with other litter-

relevant spatial scales, such as those used for the calculation of baselines. 

●  Although monitoring of impacts on biota is challenging, there is clear evidence of harm to individuals. 
To a lesser extent, there is evidence of harm on assemblages of organisms as well as on populations 
of some species. It is, therefore, in some cases, possible to set TVs for ML based on biological dose-
response relationships. 

● 

It is currently not possible to set agreed TVs for ML based on quantitative toxicological  dose-effect 
relationships. 

●  Due  to  the  transboundary  nature  of  ML  pollution,  the  compliance  with  thresholds  may  require 

multilateral measures and international as well as regional cooperation. 

●  The natural state of the seas, which is the ultimately desired state, is a litter-free environment. 

●  The present level of litter pollution in the marine environment of the EU is considered unacceptable, 
because it reduces wellbeing, generates high costs to local communities, can cause  harm to human 
health and hinders the use of the sea for recreational use. 

●  The setting of TVs at litter pollution levels in least contaminated areas appears reasonable. 

●  For  criteria  that  do  not  yet  allow  the  setting  of  quantitative  TVs,  which  are  based  on  established 
baselines, intermediate targets could be established, based on the precautionary principle aiming at a 
downward trend or non-deterioration. 

21 

 
 
References 

Borja A., Elliott M., Andersen J.H., Cardoso A.C., Carstensen J., Ferreira J.G., Helskanen A.-S., Marques J.C., Neto 
J.M., Teixeira H., Uusitalo L., Uyarra M., Zampoukas N. 2013. Good Environmental Status of marine ecosystems: 
What is it and how do we know when we have attained it? Marine Pollution Bulletin 76 (1-2) 

De Sa  L., Oliveira  M., Gomes Ribeiro F., Futter M.N.  2018.  Studies of the effects of  microplastics on aquatic 
organisms:  What  do  we  know  and  where  should  we  focus  our  efforts  in  the  future?  Science  of  the  Total 
Environment (2018) 645; 1029-1039 

Groffmann P.M., Baron J.S., Blett T., Gold A.J., Goodman, I., Gunderson L.H., Levinson B.M., Palmer M.A., Paerl H.W., 
Peterson  G.D.,  LeRoy  Poff  N.,  Rejeski  D.W.,  Reynolds  J.F.,  Turner  M.G.,  Weathers  K.,  Wies  J.  2006.  Ecological 
Thresholds:  They  Key  to  Successful  Environmental  Management  or  an  Important  Concept  with  no  Practical 
Application? Ecosystems (2006) 9: 1-13 

Matiddi M., Hochsheid S., Camedda A., Baini M., Cocumelli C., Serena F., Tomassetti P., Travaglini A., Marra S., 
Campani T., Scholl F., Mancusi C., Amato E., Briguglio P., Maffucci F., Fossi M. C., Bentivegna F., de Lucia G. A. 
2017.  Loggerhead  sea  turtles  (Caretta  caretta):  A  target  species  for  monitoring  litter  ingested  by  marine 
organisms in the Mediterranean Sea. Environmental Pollution 230, 199-209. 

Mizraji R., Ahrendt C., Perez-Venegas D., Vargas J., Pulgar J., Aldana M., Ojeda P.F., Duarte C., Galban-Malagon C. 
2017. Is the feeding type related with the content of microplastics in intertidal fish gut? Marine Pollution Bulletin 
116(1-2): 498-500 

Rosenthal, H.  1997. Environmental issues and the interaction of aquaculture  with other competing resource 
users, p. 1-13. In AAC Special Publication No. 2. St. Andrews, Aquaculture Association of Canada. 

Schulz M., Neumann D., Fleet D.F., Matthies M. 2013. A multi-criteria evaluation system for marine litter pollution 
based  on  statistical  analyses  of  OSPAR  beach  litter monitoring  time  series.  Marine  Environmental  Research, 
Volume 92, pp 61-70 

Villarrubia-Gomez P., Cornell S.E., Fabres J. 2017. Marine plastic pollution as a planetary boundary threat – The 
drifting piece in the sustainability puzzle. Marine Policy, https://doi.org/10.1016/j.marpol.2017.11035 

Werner  S.,  Budziak  A.,  van  Franeker  J.,  Galgani  F.,  Hanke  G.,  Maes  T.,  Matiddi  M.,  Nilsson  P.,  Oosterbaan  L., 
Priestland E., Thompson R., Veiga J., Vlachogianni T. 2016. Harm caused by Marine Litter. MSFD GES TG Marine 
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22 

List of abbreviations and definitions 

ALDFG 

 Abandoned, lost and otherwise discarded fishing gear 

CIS 

 Common Implementation Strategy 

COM DEC  Commission Decision 

D10             Descriptor 10 

DG ENV 

 Directorate-General for Environment 

EC 

 European Commission 

EFTA 

 European Free Trade Association 

EU 

FFL 

GES 

IMO 

JPI 

JRC 

ML 

MS 

 European Union 

 Fishing-For-Litter 

 Good Environmental Status 

 International Maritime Organization 

 Joint Programming Initiative 

 Joint Research Centre 

 Marine Litter 

 Member State 

MSCG 

 Marine Strategy Coordination Group 

MSFD 

 Marine Strategy Framework Directive 

OSPAR 

 Oslo Paris Convention for the Protection of the North Atlantic and North Sea 

PoM 

RSC 

 Programme of Measures 

 Regional Sea Convention 

TG ML 

 MSFD Technical Group on Marine Litter 

TV 

UN 

 Threshold Value 

 United Nations 

WFD 

 Water Framework Directive 

23 

 
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