Trucost calculated the quantity of additives per type of plastic based on an Organisation for Economic Co-operation and Development report focusing on plastic additives.175
LEACHING Data regarding the leaching of additives from plastic into its environment is nascent and the results are highly uncertain. Furthermore, few data points exist on the leaching rate of plastics’ constituents into a marine environment. Hence, Trucost used the leaching rate calculated by Organisation for Economic Co-operation and Development for plastics “outdoor, leaching to environment”.175 The annual leaching rate is 0.16% per year. At this rate, it would take 625 years for 100% of the additives to be released from the plastics. Trucost discounted the total natural capital cost using this timeframe, thereby producing what is believed to be a conservative estimate of the impact. Future studies may reveal more accurate leaching rates, including in the marine environment, which would likely revise upwards the impacts calculated in this report.
VALUATION OF TOXIC IMPACTS Depending on whether plastic is likely to reach marine environments or not (see table 5), Trucost either quantified marine, land or freshwater toxicity impacts. Lifecycle analysis characterization models calculate the human, terrestrial, freshwater and marine toxicity of thousands of substances when released in different media. Trucost used a global adaption of Recipe by EUSES-LCA to model the marine and human impacts additives.182,183,184,185,186 Human toxicity impacts are expressed in Disability Adjusted Life Years (DALYs) and terrestrial, freshwater and marine toxicity are expressed in Ecosystem Damage Potential (EDP). These toxicity impacts were then valued using same methodology as for land and water pollutants (described earlier).
MARINE LITTER Important quantities of plastic reach the ocean every year. Media’s attention has been particularly focused on entanglements from fishing nets or ingestion of plastic bags. More and more reports and scientific literature assess these impacts which are diverse, economic as well as ecological, and come from plastics as well as microplastics. The objective of this methodology is to obtain a value in monetary terms per kilo of plastics reaching the ocean.
STEP 1: IDENTIFYING THE IMPACTS OF PLASTICS IN THE OCEAN The impacts of plastics into the ocean are complex for various reasons: •
Plastics degrade very slowly over time, and this degradation depends on the type, shape and location of the plastics. As a consequence, plastics accumulate and it is difficult to quantify the amount of plastic which is today in the ocean.
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Macroplastics and microplastics have some overlapping and some distinct impacts.
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Water flows makes it challenging to track plastic geographically. For this reason, Trucost built a global average valuation of plastic rather than a location specific one.
Due to the complexity of plastics impacts, Trucost built a valuation model based on a simplified interpretation of these impacts. The figure below presents these impacts. Light arrows represent potential impacts which have been excluded from the valuation. For example, the valuation excludes primary microplastics impact for lack of adequate data, even though this area of research has been receiving more attention recently.
Where do microplastics come from? There are primary and secondary forms of microplastics. Primary forms of microplastics are found in personal care products such as toothpaste and skin care products, synthetic textiles such as blankets, fleeces or shirts, and industrial sources such as plastic resin pellets used in industrial feedstocks. These primary microplastics are problematic as they are not filtered during sewage treatment and can be released directly into the ocean or other water bodies (e.g. personal care products and textiles) or lost through poor management operations and during transport (e.g. pre-production plastic resin pellets). Secondary microplastics are formed when plastic items fragment and disintegrate; the rate at which fragmentation occurs is highly dependent on the environmental setting.193 In the marine environment larger plastic items can break into secondary microplastics through combined effects of wave action and photo-degradation from sunlight. The key to stemming flows of plastic debris to the ocean is to prevent this debris entering the environment. Larger items are much easier to identify and potentially to control than small ones.
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