WWF and Dalberg advisors estimated that the ‘true’ costs of plastics are 10 times higher than its production value, mainly because of losses in marine ecosystem services due to littering effects. Assessment of the external costs for inclusion in the price of products is extremely important. We agree these external costs are significant. But we also observe the difficulty to come to an accurate assessment in a situation with severe data paucity can result in taking wrong or ineffective measures and/or favouring less sustainable alternatives. For this reason, we would like to start the discussion about these uncertainties and how to deal with them.

Environmental impact of plastics in the (marine) environment is a field with a lot of unknowns. This is the main reason it has been missing in assessments of external environmental costs (or ‘true’ costs) of plastics. In the Dalberg study for WWF study (‘Plastics: the costs to society, the environment and the economy’, WWF 2021), a first top-down assessment concerning the external environmental costs of plastics in the marine environment has been executed. This can be seen as a first approach to assessing the ‘true’ costs of plastic, which is estimated at a staggering 3.7 trillion dollars by the WWF. At TNO, we have been working at bottom-up estimations of damage of plastics to the ecosystem and like the WWF study, we ask governments to ensure that all actors in the plastic system are held accountable for the costs imposed by the plastic lifecycle on nature and people. Therefore , we agree that external costs should be included in the price of products (see our White paper ‘Don’t waste it! Solving the dark side of today’s plastics’, TNO 2020).

However, in the end this accountability must be based upon reliable data and a sound scientific approach. In our opinion, there are still too many uncertainties, estimates and inconsistencies in the published study. The impact of plastics is estimated with a crude methodology and highly uncertain data, due to the many knowledge gaps. This introduces a negative bias towards plastics with respect to other materials and products, such as metal, glass, or paper, which are not accounted for marine ecosystem damage. Below, we discuss several points concerning the approach and data of the WWF study into more detail.

1) The marine ecosystem services for society, not only food provision but also leisure and recreation, are under multiple threats. Not only by plastic waste entering the system, but also by fishery, shipping, oil and gas production,  offshore wind parks and emissions of other materials and chemical substances. According to the WWF almost 30% of fish stocks commercially fished are over-fished, and over 60% of fish stocks are fully fished. Besides fishing as an important threat, other studies show that shipping is another main threat. The study by WWF and Dalberg assumed an annual loss of 1% of ecosystem services by plastics alone which is not substantiated by facts. This assumed 1% of an exceedingly high number (the total global ecosystem service value) determines the size of the plastic damage, which is therefore also highly uncertain. The assumed repetitiveness of the damage of the plastic for 400 years results after discounting in an, again, very uncertain multiplication factor of 50 of the damage over the lifetime in the marine environment. Before drawing conclusions this way, a proper assessment of to which extent marine plastic waste and other threats that lead to a loss in ecosystems is needed, as well as the degradation mechanisms and the residence time of the plastic.

2) Estimates of plastic losses used in the study are obtained from scientific modelling studies. When values are taken out of the context of the study, crucial details and assumptions can get lost. Eventually, these can give incorrect results, including the vast overestimation of plastic losses and stocks in the marine environment. At first, the modelling study that estimated a stock of 74 million tonnes of plastic in the ocean is based on a ‘closed system’, where no plastic is removed and all produced plastics are being turned into waste. This is unrealistic and too simple to be used in a study like this. Not all produced plastics immediately become waste, because they are used for multiple years or due to recycling. Also, plastics can be removed from the ocean systems when they settle and form sediments.  Additionally, outdated data can increase the error of margin. Improved modelling studies find not 11 million tonnes to enter the ocean yearly (a study from 2015), but more recent estimates find between 0.8 – 2.7 million metric tons that enter rivers per year, of which only a fraction will enter the ocean (Meyer et al., 2021).

3) There is a bias towards the marine environment when it concerns plastic pollution. Plastic pollution to the environment mainly takes place close to human activity, on land and in rivers. Hence, terrestrial and freshwater ecosystems are under much higher threat from unwanted consequences of plastic pollution. Additionally, 70% of our planet is ocean, 30% land. Only 3% of all water is freshwater. At last, freshwater and terrestrial ecosystems give even higher ecosystem services. However, only limited studies focus on the freshwater and terrestrial effects of plastic pollution, and unfortunately the WWF study addresses neither of these.

In our opinion, there is not yet a definitive answer on the magnitude of external costs of plastics. However, it is already possible to assess external costs with Life Cycle Assessment (LCA) through applying environmental (shadow) prices. Environmental prices include impacts like climate change, acidification, air quality and even human and ecotoxicity – although it is not included in ISO standards due to introduction of a “subjective” element. At TNO, we have been working at bottom-up estimations of damage of plastics to the ecosystem using environmental prices of ecotoxic components and estimating the clean-up costs of plastics. We include not only marine and freshwater, but also terrestrial ecosystems. Notably, the physical effects of plastics (like entanglement or ingestion) are not addressed since these are not known yet. Knowing that this is an underestimation, our first analysis indicates a total ‘hidden’ costs estimate in the order of equal to production costs. This is a factor two, which is significantly lower than the factor ten of the WWF study. It is not our purpose to claim that TNO has the definitive answer here, but we would like to illustrate that the uncertainty of this type of estimations is still significant. Hence, further research is needed to make definitive statements.

Concluding, we highly appreciate the study of WWF and Dalberg to assess external costs for inclusion in the price of products to give insight of the negative impacts of plastics. In our opinion the study is not perfect, plastic pollution being a “wicked”, and multifaceted problem. The top-down assessment in a situation with severe data paucity is risky and more research is needed. Additionally, it might introduce a bias to plastics in comparison to other materials, potentially leading to less sustainable alternatives to contribute to a constructive public debate. It could also give a bias in problem perception, focusing on the marine environment, leading to ineffective and less sustainable solutions. In our view, it would help to assess external costs in a bottom-up way by including toxicity effects, physical effects for multiple ecosystems – in line with Life Cycle Impact Assessment.  TNO is setting up such assessments and we offer to contribute to substantial progress on the road to sustainability by discussing the facts and the unknowns of plastic pollution and making available results with a good indication of their validity.

Esther Zondervan-van den Beuken, Program Manager Circular Plastics bij TNO