Substances of concern: Use materials throughout the product life cycle to capture value
     In addition to polymers, plastics contain a variety of other substances. Some of these substances may have adverse effects on human health in prolonged contact with the human body, including their leakage into natural systems such as the ocean. Although the scientific evidence is not yet conclusive about the substances of concern, there is enough evidence to suggest the need to accelerate the development of alternatives to these materials. These research and innovation efforts need to be based on increasing the transparency of the different components of plastic materials and applying the precautionary principle to phase out those substances that have a negative impact. Stricter industry regulation of substances of concern and wider social concern will be the main drivers for stakeholders to take action.
   1. Substances of Concern in plastic materials Plastics are usually made by mixing polymers with a variety of additives. These additives include flame retardants, plasticizers, pigments, fillers and stabilizers that are used to improve the properties of plastics or reduce their cost.
    A variety of substances of concern are involved in plastics, for example through the use of polymer precursors and additives, as well as unwanted compounds formed from catalyst residues and side reactions. Their concentrations may be low or may be limited and do not necessarily have a negative impact on human health or the environment.
   The use of plastics may or may not be subject to specific regulations, such as those governing food packaging. These regulations are not consistent across product uses or (global) regions. This fragmented regulatory situation, coupled with the complexity of plastic materials, exacerbates the problem of lack of transparency in plastic components. In plastic applications, there are some examples of problems caused by substances of concern, including the risk of adverse effects on human health and the environment, as well as barriers to closing the loop on plastics. Phthalates, which are most commonly used as plasticizers in PVC. Due to their potential effects on human health, certain phthalates have been banned in children's toys in the European Union and the United States, thus affecting manufacturers, distributors, retailers and importers. In 2015, the EU issued a directive on preventing the recycling of phthalates: "The EU should not authorize the recycling of plastics containing the banned PVC plasticizer diethylhexyl phthalate (DHEP) as it may pose a reproductive toxic threat to workers and may render their male foetuses infertile."
    Brominated flame retardants (BFRS) are another example. Researchers investigating the presence of recycled polymer waste streams in discarded electrical and electronic equipment have found these substances of concern in the black plastic used in kitchenware. According to the Society for Cancer Prevention and Education publication, "These BFRS may have entered the product through plastic recycling processes, as these applications do not require the use of pure monomers, but prohibit their use in products intended for food preparation."

    2. Materials that do not contain substances of concern contribute to efficient recycling of plastic packaging materials
    In the design of plastic and other packaging products
    Taking into account both intended and unintended post-use pathways (such as inks and adhesives) is an important step in making these pathways effective.

   1 Effective post-use biological processes reduce the risk of soil pollution
    When ending the biological cycle, the presence of heavy metals in the packaging can hinder composting, and if the concentration of lead or cadmium used in the pigments is high, it may inhibit bacterial growth essential to the process. In addition, the presence of heavy metals is extremely damaging to the quality of compost and leads to reduced agricultural value due to its ecotoxicological effect on future plant growth. Growing food crops in contaminated soil may have the potential to introduce SoC into the food chain and pose potential risks to human health.
   "Of the possible negative effects of composting use, the potential release of toxic heavy metals into the environment and the transfer of these elements from the soil to the food chain are generally considered the most relevant."
    Standard-setting bodies aim to use plastics and packaging standards to manage these possible negative effects. So far, standards have been introduced covering biodegradation, decomposition, and the impact on the process of composting and its results. For example, the European Union's requirements for compostable and biodegradable recycled packaging, and the International Organization for Standardization's (ISO) specifications for compostable plastics. Product certification by a recognized independent third party should ensure that not only the plastic itself is compostable, but also all other accessories of the product, such as pigments, labels, inks, glues, and residues. Avoiding the use of SOCs in biodegradable plastic packaging and its associated components can improve the composting process, reduce the risk of SoC entering the food chain, and reduce the cost of complying with composting regulations.