Anticipating on plastic pollution in the North Sea despite the lack of scientific urgency

Anticipating on plastic

pollution in the North Sea

despite the lack of scientific

urgency

Students: Mas Bais (11318562)

Carlijn Bouwer (11769505)

Puck van der Mark (11671998)

Course: Interdisciplinary Project

(Future Planet Studies, semester 1, year 3)

Tutor: Njal van Woerden

Supervisor: Alison Gilbert

Word count: 6760

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Abstract

There is plenty of reason to take action against plastic pollution. Actual risks of plastic pollution on the marine organisms in the North Sea and on humans are known-unknowns, and bring about a lot of uncertainties. This research focuses on how to appropriately handle plastic pollution in the North Sea to prevent possible future threats to marine organisms and humans despite the lack of scientific urgency. The focus is on nano- and microplastics because these contribute most to pollution. Through literature research it was found the scientific urgency to tackle plastic pollution was not that high, but through the use of a survey it was found that non-experts of the Dutch society perceived this differently. This, together with the precautionary principle, resulted in executing a SWOT analysis to determine which measure provides the best way to tackle plastic pollution to prevent future threats to marine organisms and humans.

Inhoudsopgave

6. Optimization of the measures ... 18

7. Conclusion, discussion & recommendation ... 19

References ... 20

Appendix A Transcript of interview with Annemarie van Wezel ... 24

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1. Introduction

Considerable amounts of the plastic waste end up in oceans each year (Geyer, Jambeck & Law, 2017). Plastics are very persistent in the marine environment (Kershaw, Katsuhiko, Lee & Woodring, 2011), because they are resistant to natural decay (Pruter, 1987). However, larger plastics can fragment into nano- and microplastics (NMPs) (Andrady, 2011). The larger plastics themselves pose a threat to marine organisms for example because of the possibility of entanglement and ingestion (Wright, Thompson & Galloway, 2013). The NMPs can also be ingested by marine organisms (Andrady, 2011). Furthermore, because of this, they are also present in the marine organisms that humans consume (A. van Wezel, personal communication, October 2, 2019). Once ingested, they can cause adverse effects to marine organisms and humans, both physically and chemically (Bouwmeester, Hollman & Peters, 2015).

What these actual consequences are, however, remains largely uncertain. In a research by Koelmans et al. (2017) it was noted that even though this is the case, the overall idea in society is that plastics are a major threat to humans and marine organisms. According to them, this is mostly due to incomplete and biased information spread by media and scientists. The result of this is that there is a difference between how the non-experts in the Dutch society and scientists perceive the risks of plastic pollution in marine environments (A. van Wezel, personal communication, October 2, 2019). Therefore, the urgency to take action against plastic pollution differs between the groups (A. van Wezel, personal communication, October 2, 2019).

Despite the uncertainty and the difference in urgency, various measures have already been taken to reduce plastic pollution and its consequences. Therefore, this research will focus on the reasoning behind these measures. Furthermore, these measures will then be analysed in order to understand their role in tackling plastic pollution in marine environments. More specifically, the North Sea is the case study in this research.

Therefore, the research question for this research is: How to appropriately handle plastic pollution in the North Sea to prevent possible future threats to marine organisms and humans despite the lack of current scientific urgency?

To answer this research question, it was divided into multiple subquestions: What are the actual risks of plastic pollution on marine organisms in the North Sea and humans?; What are the drivers behind taking preventive measures?; How do the non-experts in the Dutch society perceive plastic pollution and its consequences?; What are some implemented measures that are taken to reduce plastic pollution? and What are the strengths, weaknesses, opportunities and threats of these measures?.

First, in a Theoretical Framework the first two subquestions will be answered (section 2). After that, a problem definition will be given (section 3). Then, in section 4, the methods that were used to gather the data to answer the research question are discussed. In the Results section (section 5), the final three subquestions are answered. Section 6, discusses how the analysed measures can be optimized. Finally, in the conclusion an answer will be given to the research question. The shortcomings of this research and further recommendations will then be discussed (section 7).

2. Theoretical framework

In this section, first the findings of previous disciplinary researches on the potential risks of plastics for marine organisms in the North Sea and for humans are presented. After that, this knowledge is combined with relevant theories to assess the actual risks. Furthermore, the scientific urgency to tackle plastic pollution, the perception of non-experts, the pressure on the government to undertake action and the underlying reasons and theories for all of these are discussed. Lastly, more related theories and concepts are explained.

2.1 Potential risks of plastics for marine organisms and humans

Macroplastics pose the biggest threat to marine organisms in the North Sea. They can lead to direct consequences such as entanglement and starvation (Gregory, 2009; Sheavly & Register, 2017). However, macroplastics are irrelevant for humans when looking at consequences of plastics as they pose no direct threat to them (Koelmans et al., 2017). As the disciplinary researches examined the risks for both marine organisms and humans, this research focuses on nano- and microplastics (NMPs) to be able to compare the two accurately.

2.1.1 Potential risks of NMPs for marine organisms and humans

NMPs can be harmful to marine organisms and humans in multiple ways. Firstly, the physical presence of NMPs in bodily tissues can lead to adverse effects such as local inflammation (Bouwmeester, Hollman & Peters, 2015). Another possibility is that the additives leach out of the plastics and subsequently disrupt the endocrine system (Bouwmeester, Hollman & Peters, 2015). Next to being endocrine disruptors, additives are also associated with various diseases, such as cancer and cardiovascular diseases (Galloway, 2015). Lastly, because of their charged surface, plastics are often contaminated with other chemicals such as persistent organic pollutants (POPs), heavy metals and hydrophobic organic contaminants (HOCs) (Koelmans et al., 2017; Wright & Kelly, 2017). These chemicals can desorb from the NMPs and are then released to the environment they are in. Thus, if contaminated NMPs are ingested and the chemicals desorb, they end up in the bodies of marine organisms or humans. These chemicals are for example carcinogenic, endocrine-disrupting, immunotoxic and mutagenic (Franco, Nardocci & Günther, 2008; Wright & Kelly, 2017).

Thus, a lot of potential effects of NMPs in both marine organisms and humans are already known. However, plastics may also have other unexpected effects that scientists are unaware of right now (Jahnke et al., 2017).

2.2 Risk assessment

Now that the potential risks of plastic pollution for marine organisms in the North Sea and for humans are discussed, it should be assessed whether these potential risks that are found in laboratory tests are realistic.

2.2.1 The dose makes the poison

The concentrations at which the discussed adverse effects were measured, are not the concentrations that occur in the environment and in the seafood (Koelmans et al., 2017; A. van Wezel, personal communication, October 2, 2019). In laboratory tests, unrealistically high concentrations of plastics or unrealistic exposure scenarios are used (Koelmans et al., 2017). “The dose makes the poison” (A. van Wezel, personal communication, October 2, 2019), meaning that everything can become poisonous eventually depending on the dose, is

6 applicable to these tests. The fact that adverse effects have been observed in laboratory tests does not mean that these effects will always occur in marine organisms in the North Sea and in humans. Therefore, it is logical that in studies on North Sea fish from Foekema et al. (2013) and Rummel et al. (2017) no effects of NMPs, additives and other chemicals were found. This supports that adverse effects are only observed with a higher concentration of NMPs and that this concentration was not found in the North Sea fish in 2017, and therefore most likely also not right now.

2.2.2 Actual concentration of NMPs in marine organisms and seafood

Thus, the concentration of NMPs in the North Sea is not alarmingly high. However, it is hard to establish what the actual concentration of NMPs is in the marine organisms in the North Sea and in seafood. In 2013, Foekema et al. found that only 33 (2.6%) of the 1203 investigated fish contained plastic particles. Moreover, only 6 of those 33 fish contained more than one particle. This indicates that the concentration of NMPs in the North Sea fish is very low. Subsequently, it is likely that the concentration of NMPs and associated chemicals in seafood from the North Sea is also low. However, there is still a lot of uncertainty regarding the concentration of NMPs and chemicals in marine organisms in the North Sea. It is also still uncertain how much NMPs are actually consumed by humans through dietary exposure (SAPEA, 2019). Because of this, because of the high concentrations in toxicity tests and because of the possibility of unexpected effects, it is uncertain what the actual effects of NMPs are for marine organisms in the North Sea and for humans.

2.3 Scientific urgency

Despite the uncertainties discussed in the previous section, it is evident that the concentration of NMPs that causes the effects observed in laboratory tests do not resemble the current concentration of NMPs in the North Sea and therefore, from the scientific point of view there is no urgency to tackle the plastic pollution problem immediately (A. van Wezel, personal communication, October 2, 2019).

In spite of the lack of current scientific urgency, it needs to be taken into account that the macroplastics that are in the North Sea right now, can fragment into micro- and nanoplastics (Jahnke et al., 2017). Therefore, the exposure to NMPs may increase for marine organisms in the North Sea and for humans. The risk of something is the hazard times the exposure. The hazard, in this case, says something about at which concentration the plastic particles and their additives are harmful (A. van Wezel, personal communication, October 2, 2019). Thus, the risk for marine organisms in the North Sea and for humans increases when the exposure increases. Therefore, it is necessary that the plastic pollution is tackled, even without the scientific urgency.

2.4 Public perception and pressure

There is a lot of information available for everyone about the effects of plastic pollution. This includes gray literature, opinions and misperceptions (Koelmans et al., 2017). Furthermore, the mechanism of publication bias is visible in the available information. Publication bias is “the tendency of researchers and journal editors to prefer some outcomes rather than others (e.g., results showing a significant finding)” (Koelmans et al., 2017, p. 11514). Because of this, information becomes available about for example the potential effects based on unrealistic concentrations of NMPs (Koelmans et al., 2017). This can then be picked up by mainstream

and social media and subsequently the non-experts who hear this will assume that the consequences of the plastic pollution are already very severe. In addition to this, there are a lot of photographs showing the most cruel consequences of the plastic pollution on marine organisms and these are shared on for example social media by influential people. This in combination with all the available information influences how people perceive the impact of plastic pollution, being that most people are worried about the effects of plastic pollution (A. van Wezel, personal communication, October 2, 2019). This results in the Dutch government being under pressure from society, because they are worried and want the government to take action against plastic pollution (A. van Wezel, personal communication, October 2, 2019). Politicians are more likely to undertake action against something when they are under societal pressure (Popp, Hafner & Johnstone, 2011; A. van Wezel, personal communication, October 2, 2019). Therefore, the perception of the non-experts and the pressure on the government that results from this can influence policy making. This explains why various measures have already been taken to reduce the magnitude of plastic pollution, such as the ban on free plastic bags in 2016, even without scientific urgency. Because the public perception can have an impact on policies against plastic pollution, the perception of the non-experts in the Dutch society is researched in this research, to determine if the majority is indeed worried. This will be elaborated in section 5.1, Survey Results.

2.5 Known-unknowns

The risks of plastic pollution for marine organisms in the North Sea and for humans can be labelled as known-unknown risks, according to the definition by Donald Rumsfeld (Logan, 2009). Known-unknowns are “things that we now know we don’t know” (Logan, 2009, p. 712). This applies to the effects of plastic pollution because it is known that there are potential consequences, but what the magnitude of these consequences will be is still uncertain. The known risks, as mentioned in section 2.1, provide evidence that plastic pollution can be a threat to marine organisms in the North Sea and to humans, but this evidence appears to be anecdotal evidence (Derraik, 2002). More research is needed to assess the actual risks and provide better evidence to scientists (Syberg et al., 2015). At the moment it is unknown how these risks will develop and the data from which to draw conclusions about impacts of plastic debris is limited (Wilcox et al., 2016). Assessing the part that is unknown can provide data in addressing the problem and provide input for management and policy (Derraik, 2002).

2.6 How to cope with known-unknowns?

Thus according to section 2.5, the the risks of plastic pollution for marine organisms in the North Sea and for humans are known-unknown risks. Knowing that there are known risks with unknown consequences makes it difficult to make policies and take measures. Some principles that can be implemented to form policies are based on dealing with these uncertainties, for example the precautionary principle (see below). An alternative for the precautionary principle is doing nothing until all uncertainties are gone. This alternative will be elaborated in section 2.6.2.

2.6.1 Precautionary principle

Thus, there are possible risks for the marine organisms in the North Sea and for humans, but it is highly uncertain about whether these risks will actually take place. According to Holbrook

8 & Briggle (2013), this is exactly what is required in order to invoke the precautionary principle. The precautionary principle is determined as:

“When an activity raises threats of serious or irreversible harm to human health or the environment, precautionary measures that prevent the possibility of harm shall be taken even if … the causal link is weak and the harm is unlikely to occur.” (Holm & Harris, 1999, p. 398).

Thus, the precautionary principle is applied to form policy when the evidence of certain risks occurring is lacking and when the risks are not yet realistic. This is the case for plastic pollution in the North Sea organisms and the humans that consume the seafood.

2.6.2 Alternative to the precautionary principle

The extreme alternative to using the precautionary principle to form policy would be not doing anything to tackle the plastic pollution in the North Sea until there is no uncertainty anymore about the effects of NMPs on marine organisms in the North Sea and on humans (Koelmans et al., 2017). However, because the effects are mostly dependent on the concentration of the NMPs and chemicals, this does not seem to be a logical approach as the concentration will increase when nothing is done. Moreover, this approach has for example caused a delay in the tobacco legislation and is still impeding restriction of greenhouse gas emissions (Koelmans et al., 2017). This all indicates that this is not the desired approach for dealing with the plastic pollution in the North Sea.

2.7 Implications of the theories and concepts

What is known now is that there are various potential effects of NMPs for marine organisms in the North Sea and for humans, but because these are not yet realistic, the immediate scientific urgency to tackle the plastic pollution in the North Sea is lacking. However, there is a high degree of uncertainty surrounding the (future) concentration of NMPs and their effects in the North Sea. In addition, there is a possibility that the amount of NMPs will increase. Because of this, because of the fact that there is pressure on the government and because the precautionary principle justifies taking action in order to prevent harm to the environment and human health, there is plenty of reason to take action against plastic pollution, despite the fact that the direct scientific urgency is lacking.

3. Problem definition

3.1 Knowledge gap

As discussed in section 2.4, due to the non-scientific, incomplete and/or incorrect information that is available about the effects of plastic pollution on marine organisms and on humans, many people are worried about the consequences of plastic pollution. The scientists that research this topic, however, are less worried. The results from numerous scientific researches on the effects of NMPs showed that even though marine organisms and humans being in contact with NMPs can result in various harmful effects, these effects are only measured at high concentrations that are not present in the current natural environment. Hence, according to this there is not really a reason to worry if the NMPs do not reach these harmful concentrations in the natural environment, and thus in the seafood humans are exposed to. This indicates that there is a rather big knowledge gap between non-experts and scientists.

3.2 Justification of research question

Because of the knowledge gap discussed in the previous section, it is difficult to decide what kind of policy fits best. On one hand, due to the widespread imaging of marine organisms that are harmed by plastic pollution, the pressure on the government to undertake immediate action is high (Popp, Hafner & Johnstone, 2011; A. van Wezel, personal communication, October 2, 2019). On the other hand, from a scientific point of view there is no urgency to tackle the problem right now. However, both do agree that something needs to happen, only the urgency differs between the two groups (A. van Wezel, personal communication, October 2, 2019). Another complicating factor is the high degree of uncertainty surrounding the (future) concentration of NMPs and their effects. The research question of this research is therefore “How to appropriately handle plastic pollution in the North Sea to prevent possible future threats to marine organisms and humans despite the lack of current scientific urgency?”

3.3 Complexity of the problem

The plastic pollution problem is complex, multiple factors influence each other. Therefore, it is also a complex system. Complex systems are systems that consist of multiple properties. The different parts in complex systems are connected with each other and they form a network (Menken & Keestra, 2016). In the plastic pollution problem, policy can have an influence on the state of the pollution problem. Policies that reduce the use of plastics, influence the amount of plastics that end up in the marine environment. Therefore, the chosen policy determines the magnitude of the problem and thus the actual effects, depending on how radical the policy is. Moreover, the policy that is chosen is determined by for example the amount of pressure from society or scientific evidence. Thus, there are a lot of connections between different aspects of this issue, which makes it complex. Another aspect of complexity is that complex systems can be robust and resilient, but that they can also become unstable after a critical threshold. Moreover, they can unexpectedly collapse or switch from one state to another (Menken & Keestra, 2016). As of right now, there has not been a collapse in the ecosystem because of plastic pollution. However, this could change when the concentration of NMPs in the marine environment reaches harmful concentrations or in other words, when a critical threshold is exceeded. This also indicates that aspects of the problem are complex. A complex

10 problem requires an interdisciplinary approach, because a complex problem should be observed from multiple perspectives as there is not one perspective that can explain the problem, but multiple perspectives together are needed to gain an understanding of the situation. Therefore, an interdisciplinary approach is chosen for this research.

4. Methods

This section elaborates on how the data used to answer the research question is obtained. First, it is explained why Annemarie van Wezel was interviewed. After that, the method of the survey is discussed. Lastly, the methods used for the analysis of the different measures against plastic pollution are described.

4.1 Interview: Annemarie van Wezel

An interview with Annemarie van Wezel was conducted (Appendix A) in addition to the literature research that was done to gain more information about the effects of plastic pollution on both marine organisms and humans that eat marine organisms and about the difference in perception between non-experts and scientists. Annemarie van Wezel, the director of IBED (Institute for Biodiversity and Ecosystem Dynamics), was chosen because she has experience as a scientist in environmental toxicology and chemistry, risk assessment and environmental policy and this was very relevant for this research. Moreover, she was also chosen because of her contribution to the article Risks of Plastic Debris Unravelling Fact, Opinion, Perception and Belief in Environmental Science and Technology (2017). This article was a source of inspiration for this interdisciplinary research.

4.2 Survey: Perception of plastic pollution

The perception of non-experts concerning plastic pollution is an important factor to acknowledge in order to tackle the issue. In order to confirm if non-experts are indeed worried about the effects of plastic pollution for marine organisms and themselves, an anonymous survey was conducted (Appendix B). The answers of the 169 respondents were used to create a general impression of how the Dutch society perceives plastic pollution. The survey consisted of 10 questions. Starting with questions about age and education made it possible to examine the background of our respondents. Subsequently, the questions aimed to display the perception of the respondents concerning plastic pollution and its consequences. Questions like “How big do you think the effects of plastic pollution in the oceans are on the animals in the oceans” and “How big do you think the effects of plastic pollution in the oceans care on people who eat fish, crustaceans or shellfish from the oceans” are asked to determine how severe the respondents think that the consequences are. The question “Are you worried about the impact of plastic pollution on the animals in the oceans and/or on the health of people who eat fish, crustaceans or shellfish” is asked to investigate about what the respondents are worried the most. The complete set of posed questions can be found in Appendix B. The survey was made with my.survio.com and distributed on social media. The responses on the questions were visualised in Microsoft Excel.

4.3 Analysis of measures against plastic pollution

According to section 2, measures should be taken with the aim of tackling plastic pollution and its consequences. Therefore, already taken measures are studied by means of a literature research to clarify their role in tackling plastic pollution in marine environments. The measures will be analysed with a SWOT analysis.

4.3.1 SWOT analysis

In this research, the SWOT analysis is used to compare the measures against plastic pollution to each other. SWOT is an acronym for Strengths, Weaknesses, Opportunities and Threats. More specifically; current positive aspects are Strengths, future positive aspects are

12 Opportunities, current negative aspects are Weaknesses and future negative aspects are Threats (Chermack & Kasshanna, 2007). The SWOT analysis will identify the factors that help or hinder the measures (Chermack & Kasshanna, 2007).

According to Dyson (2004), the strengths and weaknesses are internal factors, they can be controlled and changed. The opportunities and threats are external factors, the opportunities can be used to take advantage of and it is possible to protect against threats, but it is not possible to change them. Optimizing the measures implies that advantage should be taken of the opportunities building upon the strengths. The (effects of) threats must be opposed or avoided and weaknesses should be eliminated (Chermack & Kasshanna, 2007;

Dyson, 2004).

Eventually, the outcomes will be analyzed to conclude whether the measures, are able to appropriately tackle plastic pollution and prevent future risks.

5. Results

This section discusses the results of the survey and will shed light on various measures that are taken to reduce the plastic pollution in the marine environment, specifically the North Sea. These measures will be discussed in general and it will be justified why these were chosen. This is followed by a SWOT analysis of these different measure.

5.1 Survey results

As discussed in section 4.2, the perception of the Dutch society was investigated by means of a survey. The visualization of the results will be displayed below, the complete visualization of all the responses can be found in Appendix B.

The survey is filled in by people (169 respondents) in every age group and with every education level (see Appendix B). Almost every respondent (98%) thought that the plastic pollution is a big problem with large consequences for the health of marine organisms, see Figure 1. A slightly smaller proportion (73%) of the respondents thought that the plastic pollution poses a big threat for human health too, see Figure 2.

Figure 1. Pie chart of the question: “How big do you think the effects of plastic pollution in oceans are on the animals in the oceans?”. 98% of the respondents think that the consequences are big. 2% of the respondents think that these are small.

Figure 2. Pie chart of the question: “How big the effects of plastic pollution in oceans are on people who eat fish, crustaceans or shellfish from the oceans?”. 73% of the respondents think that the consequences are big. 26% of the respondents think that the consequences are small. 1% of the respondents think that there are no consequences.

The majority (84%) of the respondents were worried about the impact of plastic pollution on both the marine organisms and the humans who consume seafood, see Figure 3. Only 9% of the respondents were not worried at all, the rest was worried about only one of the issues.

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Figure 3. Pie chart of the question: “Are you worried about the impact of plastic pollution on the animals in the oceans and on the health of people who eat fish, crustaceans or shellfish?” 84% of the respondents are worried about both. 9% of the respondents was not worried at all. 5% was only worried about the health of marine organisms and 2% was only worried about the human health.

The majority of the respondents (68%) viewed the ingestion of microplastics as the largest threat for marine organisms, instead of entanglement in and ingestion of macroplastics. Subsequently, 79% of the respondents also thought the NMPs in the seafood humans consume were the biggest threat to humans, rather than the additives in plastics.

These results show that the majority is aware of and worried about the problems relating to plastic pollution. Therefore, how the scientists perceive this problem differs from how non-experts perceive this problem, being that the non-experts are more worried than the scientific evidence suggests they should be.

5.2 Measures

Three measures with the aim to tackle plastic pollution are discussed. Measures against single use plastics were chosen because of their relevance in reducing the plastic waste in oceans. Measures for cleaning up oceans are relevant for reducing plastic pollution, because they reduce the waste present in marine environments. Despite the fact that no such measure is being implemented in the North Sea at the moment, it is known that the The Ocean Cleanup is the only organization that provides such technologies on a global scale and therefore this measure is taken into consideration. The measures of recycling are included because they reduce the need for plastic production.

5.2.1 Against single use plastics

Measures against single use plastics in the Netherlands started in 2016, when the ban on free plastic bags in shops is implemented. This way, they met the obligation of the EU to reduce the use of plastic bags (Rijksoverheid, n.d.). Various bans on other single use plastics are already present and more will come from 2021 onward (Europees Parlement, 2019). Products that are being banned include plastic plates, cutlery, straws and cotton buds (Europees Parlement, 2019).

5.2.2 Cleaning up oceans

Another measure to limit the emergence of more plastic waste is cleaning up the plastics that are already present in the oceans. Plastics accumulate in the oceans after they sink to the sea floor (Cressey, 2016). This ‘missing’ plastic is scattered all over the world and the numbers are estimated to lead up to millions of tonnes of plastic (Cressey, 2016). There are technologies developed to clean up this plastic waste. The Ocean Cleanup is an organization that creates and invests in such technologies. The goal is to remove plastic particles from the oceans (The Ocean Cleanup, n.d.-a). The North Sea is currently being used as a location for

testing prototypes and in the future the Ocean Cleanup system might be executed in the North Sea (Tjallema, 2019).

5.2.3 Recycling

Recycling is the third type of measures that is used to reduce plastic pollution. Recycling is the process where plastic waste is processed into useful products (Leblanc, 2019). European waste policy focuses on the separation of plastic waste by households, this is thus also being done in the Netherlands (Gradus, 2019). This collection of plastic waste is in the Netherlands managed at a municipal level. Some municipalities have a waste dispersal service where the waste is collected door to door, other municipalities residents have to take their waste to a local collection point.

5.3 SWOT analysis

As explained in section 4.3.1, this research provides SWOT analyses for the three categorized measures. Each category of measures will be discussed separately. 5.3.1 Measures against single use plastics

Strengths

● Considerable part of the pollution ● Reduction in use of plastic bags ● Impact on behaviour of consumers ● Increase in use of reusable bags

Opportunities ● Awareness Weaknesses ● Selective ban Threats ● Non-environmental friendly alternatives

● Attitude of the consumers ● Different impact depending on

income

Figure 4. SWOT analysis of the measures against single use plastics.

The first category includes the measures against single use plastics, such as bans and levies, and has various strengths (Figure 4). One of these strengths is that according to Schnurr et al. (2018) single use plastics contribute to 60-95% of global marine plastic pollution. Thus, a considerable proportion of the source of plastic pollution in the marine environment will be tackled when these measures are implemented. Another strength of this measure is specific for measures against plastic bags, being that bans and levies of plastic bags have proven to reduce plastic bag use (Schnurr et al., 2018; Xanthos & Walker, 2017). Furthermore, another strength is that consumers are directly confronted with levies on plastic bags, so this potentially alters the behaviour of consumers regarding use of plastic bags (Foster, 2013). Instead of plastic bags made for single use, reusable bags take their place. The increase in use of reusable bags is therefore another strength of a ban on single use plastics (Taylor & Villas-Boas, 2016).

Despite the strengths of these measures, there is also a weakness (Figure 4). Namely, the ban on single use plastics in the EU starting in 2021 is only applied on those single use plastics that already have plastic-free alternatives (Europees Parlement, 2018). An

16 within the society about marine pollution which can lead to non-legislative actions (Schnurr et al., 2018).

A possible threat (Figure 4) is that the plastic-free alternatives are not always better for the environment. For example, paper is a common alternative to plastic, but according to KPMG (2019), some aspects of paper production and its degradation are worse for the environment. Another threat is that, mostly the wealthy people, are not stimulated to not take a plastic bag for a low levies, e.g. 0.25 cents per plastic bag. In addition, some consumers tend to adopt behaviours that are relatively undemanding (Tilikidou & Delistavrou, 2008). Bringing a (reusable) bag is more demanding than buying a plastic bag. The last threat is that people with low income are more impacted by these levies compared to people with high income (Foster, 2013).

5.3.2 Cleaning up oceans Strengths ● Effective

● Macro- & microplastics

Opportunities

● Removal before fragmentation ● Relative reduction of costs Weaknesses

● Not for nanoplastics ● Symptom control ● Time consuming ● Limited locations

● Other locations might be more optimal

Threats ● Expensive technology

● No plastic removal on ocean floor

Figure 5. SWOT analysis of the measure cleaning up oceans.

A strength (Figure 5) of the second category, cleaning up oceans, is that once this measure is implemented, it is an effective way of cleaning up plastics in oceans (The Ocean Cleanup, n.d.-a). It is expected that 50% of the total amount of plastic in the Great Garbage Patch will be removed each five years (The Ocean Cleanup, n.d.-b). Another strength is that both macro-and microplastics can be removed by The Ocean Cleanup (The Ocean Cleanup, n.d.-a).

However, a weakness (Figure 5) is that nanoplastics are too small to be removed. Furthermore, this measure only tackles the symptoms of plastic pollution, instead of the cause (Kraaijvanger, 2018). If The Ocean Cleanup will indeed be able to remove 50% of the plastic in 5 years, then this equals 40.000 tonnes of plastic taken out of the Great Pacific Garbage Patch. However, if we continue to pollute the oceans at the same rate as now, in those 5 years approximately 40 million tonnes will end up in the ocean (Kraaijvanger, 2018; Billard & Boucher, 2019). Moreover, this measure is only implemented in the Pacific Ocean at the moment (The Ocean Cleanup, n.d.-a). It takes time before the measure is implemented all over the world and the plan is to implement it only in the five ocean garbage patches around the world, none of these being the North Sea. Another weakness is that according to Sherman and Sebille (2016), more microplastics are removed when the removal system is placed closer to shore, instead of in ocean garbage patches.

An opportunity (Figure 5) of this measure is that it removes macroplastics before they are able to fragmentate, so this avoids the formation of more NMPs (The Ocean Cleanup, n.d.-b). Another opportunity concerns the costs of The Ocean Cleanup. The costs of plastic pollution, in terms of damage to industries worldwide, are expected to be 13 billion US dollars

(UNEP, 2014). The costs of The Ocean Cleanup are lower (Slat, 2018). Therefore, cleaning up the plastics will reduce costs.

Finally, this measure also has threats (Figure 5). The first one is that the design, development, production, assembly and the monitoring of the system are expensive. System 001 cost 21 million Euros (Kart, 2018). This may jeopardize the process. The last threat is that there is also a lot of plastic on the ocean floor (Kershaw, Katsuhiko, Lee & Woodring, 2011). This technology is not suitable for removing this plastic (The Ocean Cleanup, n.d.-a). Therefore, this plastic remains in the oceans.

5.3.3 Recycling

Strengths ● Reduce of plastic pollution ● Less virgin plastic production

Opportunities ● Awareness

● Circular economy

Weaknesses ● Fines on residual waste ● High collection costs

Threats ● Socio-economic status ● Waste disposal service

Figure 6. SWOT analysis of the measure recycling.

The third category, recycling, has multiple strengths (Figure 6). The first one is that recycling reduces the amounts of plastics ending up on landfills (Siddique, Khatib & Kaur, 2008). Accumulated plastic debris on landfills can transfer to marine environments (Barnes et al., 2009). Recycling will therefore reduce the stream of plastic going to marine environments. Another strength of recycling is that less virgin plastic material is needed, and thus recycling reduces the production of virgin plastic (Gradus et al., 2017).

A weakness (Figure 6) of this measure is that many municipalities in the Netherlands carry out fines for high amounts of residual waste, in order to encourage recycling. However, to dodge these fines, some people put plastic in their vegetable, garden and fruit waste (VGF waste). 1-2% of the VGF waste consists of plastics and when this waste is turned to compost, the plastics can end up in surface waters and eventually in the North Sea (NOS, 2017). Furthermore, the collection costs of plastic waste are seven times higher than the collection costs of mixed waste. The treatment and process costs of recycling are also high (Gradus et al., 2017).

An opportunity (Figure 6) of recycling is that it raises awareness for environmental problems, which increases the participation rate of the society (Evison & Read, 2001). Another opportunity is that recycling is eventually able to contribute to a circular economy. A circular economy would signify no waste and this reduces plastic pollution (Worm et al., 2017).

Lastly, this measure has two threats (Figure 6). People with a low socio-economic status are less likely to recycle plastic, for example due to limited available space to store separate waste (Martin, Williams & Clark, 2006). This lowers the recycling rate and is therefore a threat to the recycling measure. Moreover, when the waste disposal service is not convenient, people are less likely to recycle and more likely to throw everything away together at home (Martin, Williams & Clark, 2006).

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6. Optimization of the measures

In this section, the results of the SWOT analysis will be analysed and it will be discussed how each measure can be optimized in order to reduce the consequences in the North Sea. As stated in section 4.3.1, the strengths must be remained, advantage should be taken of the opportunities, the effects of threats must be avoided and weaknesses should be eliminated.

6.1 Measures against single use plastics

The SWOT analysis of these measures showed that they are effective and can reduce use of single used plastic. However, more plastic-free alternatives for single use plastic items need to be developed so that the ban can be extended to those items as well. Moreover, as current alternative materials can negatively affect the environment as well, alternative materials that are less harmful should be developed.

Furthermore, the awareness that is created due to these measures could be used to stimulate more people to use the plastic-free alternatives.

Lastly, to eliminate the threat that people with low incomes are more impacted by the levies on plastic bags for example, an option would be “giving bag credits for free bags to families with annual incomes below a defined level” (Foster, 2013, p. 6).

6.2 Cleaning up ocean

The Ocean Cleanup is currently able to reduce the amount of plastics in the Great Pacific Garbage Patch, but the system will not be installed in the North Sea. However, the knowledge behind the system may be helpful in order to develop a system that is placed closer to shore, and thus potentially also in the North Sea, as according Sherman & Sebille (2016) more microplastics are removed there. Prototypes of The Ocean Cleanup have already been placed in the North Sea, to test whether they were resistant to the extreme weather conditions there (Tjallema, 2019). This indicates that such a system can be installed in the North Sea, despite the fact that it is a busy sea (Krause, Von Nordheim, Bräger, 2006).

Despite all these possibilities, it is important to note that this measure alone will not be sufficient to reduce plastic pollution, but that it should be combined with pressures that reduce the formation of plastic waste.

6.3 Recycling

Carrying out fines for high amounts of residual waste can potentially work counterproductive, so other possible ways to stimulate recycling must be developed. Waste disposal services should be improved and it should be made easier to recycle plastics. For example, plastic waste should be collected on the same day each week and this should be implemented in the entire country. When recycling becomes more accessible, people with a lower socioeconomic status hopefully will be stimulated as well.

7. Conclusion, discussion & recommendation

7.1 Conclusion

“How to appropriately handle plastic pollution in the North Sea to prevent possible future threats to marine organisms and humans despite the lack of current scientific urgency?” It was found that the actual risks of plastic pollution on the marine organisms in the North Sea and on humans are known-unknowns. Furthermore, the consequences of plastic pollution depend on the concentration of the NMPs.

There is plenty of reason to take action against plastic pollution, despite the fact that scientific urgency is lacking, because of multiple findings. First, the consequences are known-unknowns and the amount of NMPs may increase. Secondly, the precautionary principle justifies taking action in order to prevent harm to the environment and human health. Lastly, the Dutch society puts pressure on the government to take action. This was substantiated by the results of the survey, as these indicate that the majority of the non-experts in the Dutch society are worried about the consequences of the plastic pollution.

The SWOT analyses showed that all measures are efficient, but that each measure has limitations. However, when these measures are optimized as discussed in section 6, then they can all contribute to reducing plastic pollution in the North Sea. The measure ‘cleaning up oceans’ is not sufficient to reduce plastic pollution, as the source of plastic pollution should also be tackled. The other two measures do this. Therefore, a combination of the three measures is recommended in order to appropriately handle plastic pollution in the North Sea.

7.2 Discussion & Recommendations

The executed research has a few shortcomings. First, the potential risks of plastic pollution on marine organisms in the North Sea were reviewed with the use of only two available studies. This might be seen as non-representative and therefore more research should be done for the effects in the North Sea.

Secondly, the public perception and thereby the level of societal pressure was determined through the means of a survey. This survey was the only data on the perception of non-experts in the Dutch society. Despite the large number of respondents (169), and the fact that they were all from different age groups and education levels, they were not evenly distributed and therefore the results may not be representative for the whole Dutch society.

In addition to that, the results from the survey might not represent the Dutch society because of its distribution. The survey was only distributed on social media and therefore people who are not on social media were not able to participate. If different or multiple methods of distribution had been used, the results might have been different.

Thirdly, a major point of discussion is the fact that only three measures were discussed. By choosing these three, various other measures, such as measures in education and cleaning up land, were excluded. In further research, other measures need to be taken into account when looking at how to appropriately handle plastic pollution.

Furthermore, despite extensive literature research, the SWOT analyses may not discuss every strength, weakness, opportunity and threat of each measure. More literature research is recommended to provide a better and more extensive analyses.

Lastly, the optimization of the measures might not be completely feasible due to various contributing factors.

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Appendix A Transcript of interview with Annemarie van Wezel

Interviewed by: Puck (P) en Carlijn (C)

P: Ik wilde eigenlijk beginnen met vragen, wat zijn de meest schadelijke stoffen in plastics, voor mensen en dieren?

AvW: Er wordt redelijk veel onderzoek gedaan aan de effecten van plastic zelf en dat is dan vaak zonder allerlei additieven, dus echt de polymeren. Dat gebeurt vaak met laboratorium studies, maar je ziet dus dat plastics wel negatieve effecten kunnen hebben op dieren, daar is het vooral op getest. Vaak liggen de concentraties waarbij negatieve effecten worden gemeten veel hoger dan de concentraties die in het milieu voorkomen. Daarom concludeert ook dat rapport dat het onwaarschijnlijk is dat er op dit moment veel negatieve effecten in het milieu zijn, omdat je dan hoge concentraties nodig hebt. Aan de andere kant weten we ook dat plastics heel persistent zijn, dus als we op deze manier doorgaan met het gebruiken zijn er in de toekomst wel meer schadelijke effecten te verwachten. Plastics is een containerbegrip, want je hebt veel verschillende polymeren, heel veel verschillende groottes en vormen enzovoorts. Je hebt oude plastics waar biofilms omheen kunnen zitten met bacteriën erin. Het lijkt er wel op dat hoe kleiner ze zijn, meer naar de nanoplastics, dat die relevanter zijn. We zien ook dat het bijvoorbeeld ontstekingsreacties teweeg kan brengen. Er was ook al een nieuw itempje over, daar zijn heel hoge dosissen gebruikt bij sommige van die testen.

P: Over die immuuncellen?

AvW: Ja en ik zeg dan altijd "the dose makes the poison", voor giftigheid is en relevant wat zijn de inherent schadelijke stofeigenschappen van een stof en hoe wordt je blootgesteld. Nou als je maar genoeg ergens bij gooit, dan vind je altijd wel wat negatiefs en dat hoeft niet relevant te zijn voor de echte wereld omdat de concentraties daar veel lager zijn. In ieder geval lijkt het er dus op, hoe kleiner, hoe vervelender. Daarnaast bevatten plastics allerlei additieven, zoals parabenen, BPA... En daarvan weten we van een boel van die additieven dat ze schadelijke effecten hebben en ook hormoonverstorende effecten. Veel van die additieven weten we van dat ze schadelijk zijn en we weten ook dat ze als die plastics in het milieu zijn, dat die stoffen die daarin zitten ook weer oplossen in het water. Dan treden ze ook uit die plastics en kunnen ze in opgeloste vorm hun giftige werking doen.

P: En ik las ook veel over het effect van de nanodeeltjes zelf, dat die ook denaturerend kunnen werken eventueel?

AvW: Ja, ontstek-, kijk vroeger had je de asbest, wordt het ook wel mee vergeleken. Dat zijn gewoon lichaamsvreemde deeltjes in het lichaam en daar krijg je immuunreacties voor. Dus Reactive Oxygen Species zijn in feite gevolg van ontstekingsreacties en dat lijkt dus een belangrijk werkingsmechanisme te zijn. Maar voor de mens weten we niet heel veel, behalve uit workers industrie, dus bijvoorbeeld in de textielvezels, hè polyester kleren bijvoorbeeld, da's natuurlijk ook een polymeer. Daar zijn wel gegevens, meer epidemiologisch, van wat gebeurt er wanneer mensen lang worden blootgesteld daaraan.

AvW: Additieven zelf is juist wel vaak veel over bekend. P: Ah oké, ook in de mens?

AvW: Nou ja voor iedere stof die in Europa gebruikt wordt, die moet worden aangemeld, bijvoorbeeld bij de Europese chemicaliën autoriteit. Dan moet je altijd een dossier aanleveren over studies, dus naar het aquatisch milieu, maar ook soms als het om grote volumes gaat muizen studies of in vitro celsystemen. Nou ja we weten daarvan vaak wel op wat voor manier deze stoffen toxisch zijn. Van veel van die plastic additieven weten we dat ze hormoonverstorend kunnen zijn.

P: Maar dan ook in zulke hoge concentraties dat dat nu nog niet echt voorkomt?

AvW: Nee, die hormoonverstorende stoffen, dat komt niet alleen uit plastics, daarvan weten we wel dat dat in concentraties voorkomt die milieu-relevant zijn. De milieu relevante concentraties kunnen ook al negatieve effecten veroorzaken.

P: Oké en weet u iets over de waarschijnlijkheid dat we microplastics en die additieven binnenkrijgen via het eten van vis?

AvW: Ja, dat is zeker. Dus als je vis en mosselen, daar zijn verschillende studies voor, als je die gaat meten dan vind je plastics. Dat is zeker, die krijg je binnen.

P: Vooral bij schaal- en schelpdieren was dat toch?

AvW: Die filteren, dus daar vind je het zeker in, maar je vind het ook in vissen. Maar het is niet dat er al een hele uitgebreide dataset is met allerlei soorten voedsel. Maar er zijn wel verschillende studies waar het van vissen en schelpdieren wordt gemeten.

P: En weet u iets over het specifieke effect van bepaalde stoffen? Dus inderdaad dat, dat had ik gelezen, BPA endocrien verstorend werkt. Zijn er nog speciale voorbeelden?

AvW: BPA is inderdaad een belangrijk voorbeeld, maar ook ftalaten, de weekmakers, daar is altijd veel over te doen geweest. Buigzame plastics zitten ftalaten in en ook die hebben een endocriene werking. Soms wordt het gecombineerd met biocide, dat mensen niet willen dat er schimmeltjes of zoiets op groeien, nou die hebben natuurlijk ook weer hun eigen werkingsmechanismen. Er wordt van alles en nog wat door plastics heen gemengd die weer negatieve consequenties kunnen hebben. Maar van al die stoffen, dus als je het CAS nummer van een stof weet en je die intypt bij ECHA, krijg je het dossier van die stof te zien, althans het dossier op hoofdlijnen, dus dan krijg je ook wat te zien over wat weten we nou over de giftigheid van de stof en ook het gedrag in het milieu.

P: Dat is wel een goede. Weet u ook iets over dat, ik las een artikel en daar stond er dat die nanoplastics door de darmwand opgenomen kunnen worden, maar dat er nog niet veel bekend is over wat er daarna dan mee gebeurt.

AvW: Ja, daar gaan ook weer allerlei nieuwe projecten over van start. Het probleem is dat wij, dat detectielimieten van de kleine plastic deeltjes nog niet goed zijn uitgekristalliseerd, zelfs

26 voor de grotere nog niet, maar daar zijn we nog wel verder mee dus daar is al best veel literatuur over. Maar juist die kleine plastic deeltjes kunnen we nog niet goed analyseren en dat betekent ook dat het best lastig is om te traceren waar ze precies blijven. Maar we weten wel van andere typen nanodeeltjes, dat die inderdaad, de kleine, wel lichaams barrières kunnen passeren. Dus dat zou je dan ook bij plastics verwachten.

P: Oké. Carlijn wil jij nog iets vragen?

C: Ja, want in uw artikel over risk of plastic debris, daar hebben we ook voornamelijk het idee voor ons onderwerp vandaan gehaald, van wat is nou de perceptie van mensen en hebben ze ook het idee dat ze invloed hebben. En hebben zij eigenlijk ook last van plastics, dus voornamelijk uit vissen of in het ecosysteem. Daar stond ergens in, dan moet ik hem heel even terugvinden, stond er wel iets over bioaccumulatie, maar hoe erg is dat dan ook in de mens?

AvW: Dat weten we volgens mij nog niet heel goed. Het is begonnen met voorkomen in het mariene systeem, om te meten, nou toen is het een beetje naar zoet water gegaan en naar inderdaad wat soorten voedsel zoals bijvoorbeeld die schelp- en schaaldieren. Nu komt er meer onderzoek naar plastics op land, dus echt op de bodem zeg maar, en in het bodemecosysteem en in de mens, maar het is toch nog een heel jong veld. Wat hebben mensen er voor last van? Het publiek maakt zich heel erg zorgen hierover, veel meer dan over bijvoorbeeld de weekmakers of de endocriene stoffen. Dat heeft ermee te maken dat het heel zichtbaar is, je kunt het zien. Dat relateert eigenlijk net zoals gewone stoffen aan je eigen gedrag, want ga maar eens na hoe vaak jij plastic verbruikt, dat is heel moeilijk om te vermijden. De mensen maken er zich zorgen over en er is best veel publiciteit over en je ziet het aantal nieuwsitems enorm oplopen en mensen beseffen dat het met hun eigen gedrag te maken heeft, maar tegelijkertijd vinden ze het toch heel lastig om dingen te veranderen. Ja, dus nu worden die single use plastics zo langzamerhand verbannen, de rietjes mogen niet meer, gratis tasjes... Maar 40% van ons plastic zit 'm in de verpakkingsindustries. Nou als je boodschappen gaat doen bij de Albert Heijn krijg je gewoon enorm veel plastic. Naar de groenteafdeling kun je nog wel je eigen zakje meenemen, maar als je een biefstukje daar wil kopen, ja dan is het verpakt. Ja, dus het zit gewoon heel diep in ons systeem en de mensen zeggen ook vaak, wat moet je er dan aan doen? Maar we hebben eigenlijk nog helemaal geen sluitende massabalans, we weten natuurlijk hoeveel we produceren en we weten grosso modo, ja er zijn mooie statistieken over van waar we het allemaal voor gebruiken, nou verpakking is dus heel belangrijk. Overigens zijn bijvoorbeeld banden en de bandenslijtage ook heel belangrijk, die zien we ook veel in het milieu terug. Maar je kan het je voorstellen dat elk gebruik weer z'n eigen emissie route naar het milieu toe. En soms worden dingen ingezameld, dus iedereen zegt bijvoorbeeld biodegradable plastics, ja leuk, ga jij eens even hier bij de kantine een studie doen wat er nu gebeurt met die zogenaamd biodegradable lepeltjes, of die uiteindelijk echt bio-gedegradeerd worden op de manier zoals dat wenselijk is, want dat betekent namelijk dat ze ook in hun eigen stroom bij elkaar moeten blijven, want als je het gaat mengen met allerlei materiaal werkt het niet. Dus kortom, de hele logistiek daaromheen is gewoon niet georganiseerd op dit moment, dus dat werkt nog niet heel goed. Dus, minder plastic zou toch ook heel erg helpen en ja je hebt natuurlijk ook technologieën om plastics, vooral grote plastics, ergens uit te halen. Denk aan de filters bij de wasmachine bijvoorbeeld. Dus nou ja eigenlijk hebben we nog niet de goede analyse van hoe zijn nou precies die stromen, hoeveel komt er nou uiteindelijk in het milieu, want wat we terugvinden in de oceanen is maar minder dan 1% van de productie, waar blijft al dat plastic dan? Weten

we dat niet, is dat naar de bodem gezakt, is dat helemaal gedegradeerd, dus dat weten we nog niet. Zolang je dat niet goed in kaart hebt en zolang je niet weet wat de meest schadelijke plastics zijn, is het ook heel lastig om te zeggen waar gaan we onze maatregelen prioriteren. C: En eerst begreep ik dit plaatje niet helemaal uit datzelfde artikel, maar wat wordt hier met clean microplastics bedoeld?

AvW: Clean betekent in dit geval dus de schone, originele... kijk dus je hebt zeg maar intentionally added microplastics, dus die je bijvoorbeeld vroeger in je scrub crèmepjes had, daarvan is nu een voorstel om ze te verbannen vanuit de ECHA. Heel bijzonder is dat, want er is dus eigenlijk geen risico-indicatie op dit moment, maar ze zeggen dat doen we alleen maar omdat we weten dat het zo persistent is. Maar heel veel plastics zijn dus ook degradatieproducten van oorspronkelijk grote kopjes, flesjes, tasjes, enzovoorts en die zijn ergens op hun weg in het milieu in stukjes gebroken en daar groeien bacteriën op en dat is ook absorptiemateriaal, dus allerlei andere stofjes sorberen ook in dat polymeer, die vinden het net als een sedimentdeeltje lekkerder om daar te zitten dan om in het water te zitten. Dus er is van alles en nog wat mee gebeurt, dat is niet meer het product waarvan ooit het flesje gemaakt was.

P: En dat verschil tussen perceptie, dat dus heel veel mensen zich veel zorgen maken, en de wetenschap, waar denkt u dat dat vandaan komt?

AvW: Ik vind het ergens ook wel weer goed, want het slaat natuurlijk ook terug op allerlei andere stoffen die ook problematisch zijn, dus dat leidt toch wel tot een bewustwording van wat doe je nou eigenlijk allemaal in je dagelijks leven en hoe vervuilt dat het milieu, dus ik vind het niet per se verkeerd. Ik denk dat het vandaan komt dat er heel veel beeldmateriaal is van de zeeschildpadden helemaal in plastic netjes en het zeepaardje dat zo'n wattenstaafje heeft, die staan op ieders netvlies gebrand, dus het beeldmateriaal is erg overtuigend. Er zijn ook weer celebrities, Leonardo DiCaprio geloof ik, die dan tweet daarover, dus dat zeg maar de sociale media en de sterren die maken zich er ook zorgen over en die maken zich er ook zorgen over en die hebben een groot bereik. Maar ook de politici willen wat doen. Dat was heel grappig we hadden een rapport gemaakt en dat was voor de Europese Commissie en normaal als je zo'n rapport maakt zijn de politici van 'nou leuk dankjewel' en nemen het in ontvangst en hier was het van 'nee we zijn blij dat het er is, want we willen echt aan de slag'. Ze willen gewoon aan het publiek laten zien dat ze wat doen, omdat de publieke druk groot is. Vanuit de wetenschap willen we er veel meer van weten, maar daar wordt dus met heel hoge doseringen gewerkt. In de wetenschap is er best een consensus dat het een probleem kan worden en dat het relevant is om verstandige dingen te gaan doen, maar niet dat morgen de wereld ervan vergaat.

C: En denkt u dat die wetenschappers die hoge concentraties gebruiken dat voornamelijk doen om nog meer subsidie te krijgen, van ga onderzoek doen?

AvW: Nee, je ziet dat heel veel toxiciteitsstudies gebeuren bij niet-milieu relevante concentraties.