9 Other common additives include dyes and nucleating agents . Colourants and pigments are considered “non-functional” additives, but are widespread in the production of plastics (Rochman et al., 2019). In PS foam, some of the most common colours reported are white, pink and blue. Nucleating agents typically are used to increase resin clarity and reduce processing times (Hahladakis et al., 2018). Flame retardants are commonly added to PS foam to give fire resistance and are of concern for their environmental and human health effects (Marvin et al., 2011). Prior to 2015, Hexabromocyclododecane (HBCDD) was the principal brominated flame retardant added to PS to make it flame resistant (Rani et al., 2013). It has been estimated that primary application of HBCDD (over 90 % worldwide) is in extruded (XPS) and expanded (EPS) PS foam, into which it is reportedly added at concentrations of 0.7 % and 2.0 % by weight, respectively (European_Commission, 2011, Marvin et al., 2011). Concentrations of flame retardants have been found in different PS foam materials (Jang et al., 2016; Rani et al., 2013). HBCDD has been found in docks and floats as well as packaging foams, ice boxes and food trays (Jang et al., 2016; Rani et al., 2013). It has been hypothesized that production facilities that are not fully cleaned from one production run to the other can contaminate other products that do not require flame retardants (i.e. floats) (Jang et al., 2016). HBCDD has been banned since August 2015 (Ibo Osterreichisches Institut Fur Baubiologie Und-Okologie, 2016; Su et al., 2017). The EPS industry was granted a two-year grace period until 2017 (Ibo Osterreichisches Institut Fur Baubiologie Und-Okologie, 2016). There is also no limiting period for the stocks and stored goods that remain, and it is unclear whether these replacement chemicals are also found in docks and floats. Due to the long-shelf life of EPS, it is likely that EPS containing HBCDD is still in use. Other brominated flame retardants used in foam include Tetrabromobisphenol A (TBBP-A) and Polybrominated diphenyl ethers (PBDEs) (Eljarrat and Barceló, 2011). Intermediates and catalysts In addition to monomers and additives, other substances such as intermediates and catalysts are used in plastic manufacturing. Certain chemicals are used in the reactions to produce PS foam. For example, dicumyl peroxide is a chemical that is commonly used in XPS for the copolymerization of styrene. This compound also gives slight flame resistant properties (Ibo Osterreichisches Institut Fur Baubiologie Und-Okologie, 2016). 2.4 Adsorbed chemicals from the surrounding environment It is well understood that PS and other microplastics can adsorb metals ions, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and antibiotics (Graca et al., 2014; Guo et al., 2019; Llorca et al., 2018; Rochman, 2013; Velzeboer et al., 2014). Rochman et al (2013) found that PS floating on the sea surface had a large potential for adsorbing polycyclic aromatic hydrocarbons (PAHs), and this was greater than polypropylene (PP), polyethylene terephthalate (PET), and polyvinylchloride (PVC). These chemicals can be passed onto animals when ingested, where they can bioaccumulate in animals and have negative effects, including hepatic stress (Rochman et al., 2013). Graca et al. (2014) observed the high accumulation of mercury in EPS debris stranded on beaches, which can then be transferred to soil. Research has also shown that in some cases, microplastics can have higher adsorption capacity in freshwater compared to seawater because of fewer sodium ions in freshwater. Higher adsorption in freshwater has been shown for antibiotics (Li et al 2018) and per- and polyfluoroalkyl substances (PFASs) (Llorca et al 2018), which could make microplastics in freshwater more of a risk to adsorb and pass on contaminants to wildlife. PS foam can also absorb fuel and oil. In a few instances, PS docks have been reported to catch fire. This can occur when foam in docks forms a thick sludge when mixed with oil and fuel, causing PS to become flammable (ERDC, 2009). The US Army Corps of Engineers have documented marina gas docks with PS foam floatation catching fire after a fuel spill (ERDC, 2009). Absorption vs. Adsorption: Absorption is the process where one substance enters the volume of another substance. For example, a sponge absorbs water. Adsorption occurs on the surface of a substrate due to intermolecular forces that cause molecules to be held to a surface. For example, metal ions or chemical contaminants can adsorb onto the surface of plastic.