Sequestration and Redistribution of Emerging and ... - ACS Publications

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Chapter 10

Sequestration and Redistribution of Emerging and Classical POPS by Polystyrene: An Aspect Overlooked? Najat Ahmed Al-Odaini1 and Narayanan Kannan*,2 1Department

of Chemistry, Faculty of Science, Sana’a University, Sana’a, Yemen 2AIMST University, Semeling 08100, Bedong, Kedah Darul Aman, Malaysia *E-mail: [email protected]. Current Address: Institute for Graduate Studies, Taylor’s University (Lakeside Campus), No. 1, Jalan Taylor’s, 47500, Subang Jaya, Selangor Darul Ehsan, Malaysia.

Plastics are useful products produced from petroleum based styrene monomer. Polystyrene (PS) is the raw material for expanded PS (EPS), extruded PS foam (XPS), and extruded PS that forms a galaxy of plastic products around the world. These ‘miracle products’ have a darker side that is being identified recently. Plastics and the additives when released into the environment threatens life through their toxic properties. Dying marine organisms caught in the fishing nets are few examples of physical damage through PS. However, the fact that weathering plastics ending up as micro and nano particles threatening life, especially marine life, is new. Plastics in addition sequestrate persistent organic pollutants from water and pass them on to marine food web. An international pellet watch program has been initiated based on this property of PS. Several emerging pollutants such as HBCDs, TBBPA, BTBPE and DBDPE are found in buoys that are used in aqua culture. Finding toxic phthalates and UV stabilizers in consumer products having moisture contact (like bottles with short use) raises concern over human health. Hence it is important to document the production, use and chemodynamics of polystyrene; their biological

© 2016 American Chemical Society Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.

impacts and the risks associated with it. The magnitude of damage PS products could incur on the environment and their chemical/biochemical interactions (in-situ, in-vitro, additive, cumulative, synergistic, and inhibitive) with the biosphere is slowly emerging.


Polystyrene and the Products Polystyrene (PS) is a petroleum-based plastic made from the styrene monomer. Polystyrene foam was first created by Dow Chemicals in the 1970’s as an insulation device. It is commonly known as Styrofoam, which is actually the trade name of a product used for housing insulation. There are three types of plastics made from polystyrene that are available in the global market namely expanded PS (EPS), extruded PS foam (XPS), and extruded PS (1). EPS and XPS are injection moulded and extruded foams, respectively, while extruded PS is a hard plastic commonly used to make a variety of consumer products, such as disposable cutlery, and mobile phone holders (Figure 1). XPS is formed by adding gas during extrusion. A well-known use of XPS is the vacuum formed polystyrene trays and cutlery. The extruded polystyrene foam is a fine laminate that is only 2-3 mm thick. EPS is a rigid cellular plastic containing an expansion agent. EPS has many attractive properties that may explain its wide and immense consumption. It is very versatile and can be cut into the shape or size required by the construction project and consumable products. EPS is 98% air making it the lightest packaging material available. The excellent mechanical and thermal properties are unaffected by humidity because EPS does not absorb water or water vapour. Because of its very good insulation properties, it is used in all types of products from cups that keep beverages hot or cold, to packaging material that keep devices safe during shipping. The unique ability of EPS to resist compression makes it ideal for packing large items such as cookers and washing machines. EPS is not altered by external agents such as fungi or parasites as they find no nutritional value in the material. In addition all PS types are considered to be the most durable thermoplastic polymer towards biodegradation (2). PS plastics are ageing resistant and most of the properties listed above are retained over the whole of the material’s life. Asia is the overall leader in production and consumption of polystyrene plastic, with 50% of total world production and 46% of total consumption of polystyrene in 2014. North America and Western Europe follow distantly at about 15–20% of total production and consumption (1). The largest single defined end use for GP/HIPS is in packaging applications, accounting for 37% of world consumption in 2014. Applications include a variety of products ranging from food containers and trays, to one-time use disposable cutlery, as well as non-food packaging, such as clear bottles, plastic lids, and jewel cases used to protect CDs. Electronics and appliances represent the second-largest market for GP/HIPS; this market has been following the appliance industry’s move to Asia over the past decade (1). 220 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


Figure 1. Various polystyrene products (EPS=1-14, XPS= 15-26 and extruded PS= 27-34). Source: (3). The global production of PS in 2008 reached 15.4 million tons, and around 20% of this arose from China. The Asia-Pacific region, including Korea, Japan, and China, has shown the most rapidly growing consumption of PS in the past decade (4). Most of the PS products are made for a single use which means a huge amount of these products are continuously made, disposed and dumped into the environment. PS plastics especially EPS is not easily recycled thus it pose a serious waste management issue. The ultimate fate for dumped EPS will be the oceans, they are carried into water by wind or wave action. When PS plastics and other type of plastics reach the oceans they are causing a serious environmental problem known as marine debris (5–7). Sources of marine debris are multiple, in addition to the inland sources, marine debris can come from activities at sea and on the shore. Several activities can contribute marine debris such as tourism, agriculture, aquaculture, fisheries and industry. Marine debris that are initially deposited on the shore can be pulled into the sea by tides, wind or rain run-off. In coastal waters with large rivers an important fraction of marine debris comes from land-based activities, which can be far away from the coast. Large amounts of marine debris from land-based sources are also flushed into coastal waters by hurricanes, storms, or tsunamis. Sea-based activities such as shipping, fishing, aquaculture or oil/ gas extraction also contribute much (8). Due to widespread release of plastic materials (including styrene polymers) into the environment, united nation’s environmental protection agency recognised the marine debris problem as an emerging global pollution issue (9). GESAMP has come up with a comprehensive report on the sources, fate and effects of micro plastics in the marine environment from a global point of view (10). Although PS 221 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.

polymers have many attractive properties and wide applications, there is a wide range of negative impacts of PS on human and environment alike which will be discussed in detail in this chapter.


Environmental Impact of PS Production Manufacturing of polystyrene products produces air pollution, hazardous waste and solid waste. Firstly, Polystyrene products are from petroleum and polystyrene is made from the styrene monomer, which is a priority pollutant and is listed as toxic substances by the USEPA, ATSDR and OSPAR (11). It is considered to be carcinogenic, mutagenic or toxic for reproduction. Polymerization reactions are rarely complete and unpolymerized residual monomers can migrate off the plastic to the surrounding environment (12). It was also reported that some hazardous chemicals may be produced as by-products during the manufacturing of PS foam such as Poly Aromatic Hydrocarbons (PAHs) that are legacy environmental pollutants (13). The production of Extruded polystyrene (EPS) is linked to Greenhouse effect because EPS is usually made with hydrochlorofluorocarbons (HFCs) as blowing agents may have effects on ozone depletion and on global warming. Even though their ozone depletion potential is greatly reduced relative to chlorofluorocarbons (CFCs) which were formerly used, it still has 1000 times greater effect on global warming than carbon dioxide (14). In 1986 the EPA released a report that listed the polystyrene manufacturing process as the fifth largest creator of hazardous waste. The process of making polystyrene pollutes the air and creates large amounts of liquid and solid waste. Fifty-seven chemical by-products are released during the manufacturing process of polystyrene, polluting the air, land, water and communities that live near the facilities (15). The use of hydrocarbons in polystyrene foam manufacture releases the hydrocarbons into the air at ground level; there, combined with nitrogen oxides in the presence of sunlight, they form tropospheric ozone, a serious air pollutant at ground level (16). Ozone is a pollutant. EPA (17) says: “Breathing ozone can trigger a variety of health problems, particularly for children, the elderly, and people of all ages who have lung diseases such as asthma. Ground level ozone can also have harmful effects on sensitive vegetation and ecosystems.” Finally, the majority of PS products are generally used once before disposed. Given that there is a huge amount of energy embodied in foam products causing air pollution.

PS Products as Solid Waste Huge amount of PS products is used as packaging material for consumable products such as food sold in supermarkets, fast food, disposal food plates, cutlery and cups that only used once and disposed and is often dumped into the environment as litter. In USA alone, each year Americans throw away 25 billion Styrofoam cups. 222 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


Polystyrene foam is biologically inert and can survive in the environment for hundreds if not thousands of years. Once in a landfill, experts estimated that the PS materials would last for 500 years to decompose and it takes up to 25-30% of our world’s landfills. Though it’s possible to recycle polystyrene, the lack of a market for recycled polystyrene foam makes recycling impossible or impractical in most places. In most cases recovery of this plastic waste is not economically feasible (18). The Society for Plastics Industry’s (SPI) code for Polystyrene plastic is 6, indicating the difficulty associated with its recycling. However, there are several challenges and risks associated with the recycling of polystyrene. Although the technology to recycle polystyrene to produce a variety of products is well known, its recycling is limited by transportation problems due to its low density to volume ratio. This makes it uneconomical to collect, store and transport over long distances. Moreover, there are limited incentives to promote recycling due to lack of investment in infrastructure, compaction equipment and logistical systems. Due to its high stability arising from the presence of phenyl groups and single C-C bonds, the decomposition or depolymerisation process into its monomers is energy-intensive requiring high temperatures and pressure (18). Therefore, a large portion of used EPS and HIPS is disposed of in landfills or by incineration in developed countries, through open burning and waste dumps in developing countries. This is because EPS and HIPS are relatively inexpensive and conventional recycling methods turn them into lower value materials like fuel oil or recycled resin. Polystyrene can be recycled into new packing materials or other plastic products. However, recycled Styrofoam has very little market value and can only be used to make a small range of products, most of which cannot be recycled themselves (19). There are many issues related to PS recycling. The volume of polystyrene foam makes it difficult to collect and transport. According to the plastics industry (American Chemistry Council), PS food packaging is typically not clean enough to be recycled and it is economically not realistic to recycle it. Polystyrene can be remade into items such as packing fillers and cafeteria trays, but not into cups or food containers. Containers that have previously been used for food storage create a massive food hygiene issue for recyclers. Whilst the technology does exist in some countries to recycle polystyrene, the market for recycling is small and shrinking. EPS has a very low recycling rate. According to a 2004 study by the California Integrated Waste Management Board, of the 377,580 tons of polystyrene produced in the state, only 0.8% is recycled. Of that, only 0.2% (310 tons) of polystyrene food service packaging is recycled (19). For these reasons, and due to the shrinking market for the recycled products, many recyclers do not accept polystyrene. Due to its low density, polystyrene can easily be scattered by wind in the environment, creating a visible nuisance. EPS and XPS are brittle substances, which break into tiny pieces and contributes disproportionately to litter problems on streets and in parks and can reach to the river and oceans through winds or waterways. Once reached to waterways and oceans, PS waste is an important fraction of marine debris that presents a danger to the health of marine environment which will be discussed in next sections. 223 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


PS as Marine Debris Poor waste management, low recycling rate in combination with the extensive use of plastics has created serious pollution problems such as marine debris in oceans and coastal aquatic environments throughout the world. While the majority of this waste is discarded via landfill, incinerated, or recycled, immense quantities of improperly disposed plastic waste are entering the aquatic environment via littering, sewage, runoff, landfill leachates, and illegal dumping (20). Marine debris is defined as solid materials of human origin discarded at sea or reaching the sea through waterways. It consists of various man-made wastes and can be found in almost all beaches, ocean surfaces and seafloors, even in isolated islands and unpopulated coastlines (7). Regardless of their origin, plastics have been manufactured to be durable, a fact that allows them to remain for years in the environment. Due to their resistance to physical, chemical and biological degradation, marine debris are considered to be stable materials and are widely considered not to decompose at low temperature, through light or wave action (21). This is particularly true in the marine environment, where the plastic degradation may take decades (22). The first report about polystyrene as a marine debris was in 1972. The report drew the attention of the presence of polystyrene spherules in coastal water of southern New England (23). The problem has not got enough attention for many decades. Recently, a number of environmental monitoring studies have quantified the environmental occurrence of MPs in surface waters (24), coastal sediments (39), beach sands (8), and deep-sea environments (20). Marine debris become ubiquitous and is now a local and global issue causing various problems through its effect on local scenery, the ecosystem, tourism development and marine economies. According to the United Nations Environment Program, “Marine litter currently poses a dire, vast and growing threat to the marine and coastal environment” (9). Once in the environment plastics undergo abiotic and biotic weathering processes that cause their degradation and fragmentation into increasingly smaller particles, (25). PS debris in marine environment has been found in all kind of sizes including macro, micro and nano that range in size from many square meters to only a nano meters. The microplastic/micro debris are known as anything less than 5 mm in diameter and 0.333 mm is usually the lower limit. Anything larger than 5 mm in diameter are macroplastic/macrodebris and anything smaller than 0.333 mm as nanoplastic/nanodebris. A particular ecological problem with micro and nanoplastic is the ease with which it may be mistaken as food or passively ingested by organisms at the lower end of the food chain (24). In the marine environment, the existence of plastic debris, including primarily classes of polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC), proliferate, migrate, and accumulate in natural habitats from pole to pole and from the ocean surface to the bottom of the sea (22). However, polystyrene (PS) is one of the most problematic materials as a marine debris (4). One unique feature of Styrofoam as a marine debris is that it has a light weight and it is durable yet brittle and appear to be broken up into smaller and smaller fragments over time. These features enable Styrofoam to fly by wind and reach 224 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


far away distance from place to place acting also as an air pollutant. Styrofoam can breakdown during degradation to form nanoparticles that increase in number over time. It was found that 1.26 x108 particles are formed for every ml (average particles size 224 nm) of the PS coffee cup. The environmental impacts of nanoplastics will be different to those presented by microplastics, because of their smaller size makes tissue penetration and accumulation in organs a possibility. This is a potentially important issue given the current concerns regarding the environmental behaviour and ecotoxicity of engineered nano-materials (25).

PS as Source and Sink for Legacy and Emerging Pollutants Because of their physical and chemical properties, plastics accumulate a complex mixture of chemical contaminants present in the surrounding seawater adding to the cocktail of chemicals already present from manufacturing. Persistent, bioaccumulative and toxic substances (PBTs), which include those listed as POPs by the Stockholm Convention, generally have a low water-solubility (i.e. are hydrophobic) and tend to partition out of the water column and onto another environmental matrix with similar hydrophobic properties (e.g. sediment, organic matter). Thus, when PBTs encounter plastic debris they tend to sorb to this material (25). As early as in 1970s a study reported that the PS debris in marine environment can absorb pollutants such as polychlorinated biphenyls (PCBs) from ambient seawater (23). Concentrations of organic contaminants are found at concentrations up to 500 times greater than underlying waters which means floating plastic debris could easily accumulate relatively large concentrations of chemical contaminants from this sea-surface microlayer, and may be one reason why we find large concentrations of chemicals on floating plastic debris recovered globally, including in remote regions. While some contaminants may be lost due to biological or physical degradation, leaching of chemicals back to the environment may be of concern in remote and more pristine regions where sources of chemical contaminants are sparse. Laboratory studies have found that plastics with sorbed POPs release a considerable amount of these chemicals upon being placed in clean water. In general, the longer the plastic is in the water, the greater concentrations of chemical contaminants it will accumulate or release suggesting that plastic debris may become more hazardous the longer it remains at sea (12). Research has shown that marine plastic debris may act as both a sink and a source for contaminants in the marine environment, including their transfer into marine food webs. In fact, of the chemicals listed as priority pollutants by the US EPA, 78 % are associated with marine plastic debris. Therefore, Marine plastic debris is associated with a ‘cocktail of chemicals’, including chemicals added or produced during manufacturing and those present in the marine environment that accumulate onto the debris from surrounding seawater. This raises concerns regarding the environmental fate of these chemicals to and from plastics in our oceans and how this mixture affects wildlife, as hundreds of species ingest this material in nature (12). 225 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


Classical Persistent organic pollutants (POPs) such as PAHs, PCBs and DDTs were found in marine debris including PS in eight beaches around San Diego County, California. The greatest concentration of PAHs (1900 ng/g) was found in PS foam. PAH concentrations were consistently high in all PS foams and relatively greater than in plastic fragments and pellets. PCBs, DDTs, and chlordanes were detected in all samples confirming that these POPs persist and accumulate in the environment despite their ban in the United States (22). To find out plastic debris as vectors of chemical contaminants in marine environment, a study conducted at KIOST, Korea revealed hydrocarbons, ultra-violet (UV)-stabilizers, antioxidants, plasticizers, lubricants, intermediates, compounds for dyes and inks, flame retardants, etc. Finding of toxic phthalates and UV stabilizers in those products having moisture contact (like bottles with short use) raised concern to human health (26). Flame retardant chemicals are added to all types of PS plastic to reduce their flammability and the risk of fire. Flame retardants such as HBCDs, TBBPA, BTBPE and DBDPE were detected in 34 samples of variety of products made from EPS, XPS, and extruded polystyrene. The concentration of HBCDs found varied much among products and highest concentration was measured in EPS samples 960000 ng/g (3). These flame retardants are additive which means they are not bound to the products and can easily leach out from the product during use, disposal or as a marine debris. In another study, EPS buoys used for aquaculture farming was found to be the source of the emerging flame retardants in the marine environment. Marine sediments from South Korea shows that emerging flame retardants such as HBCDs are found at high concentrations nearby aquaculture farms where EPS buoys are used for farming. The study also shows that the levels of HBCDs in the external part of the buoys are less than the inner part confirming the leaching of HBCDs from the buoy to marine environment. Other flame retardants such as TBBPA, BTBPE and DBDPE were also detected in both sediment and buoys samples. It is then confirmed that PS debris in marine environment can act as a diffuse source of emerging pollutants to marine environment (27). Moreover, the use of expanded polystyrene buoys in aquaculture was also found to be a potential source of HBCDs in bivalves that are highly consumed among Koreans. HBCDs exhibit typical POP properties (i.e., persistence, bioaccumulation, and toxicity), a global ban on HBCDs was recently approved under the framework of Stockholm Convention on POPs (28). The decomposition products of PS were recently reported as new emerging pollutants in marine environment. They clearly show a new threat of global contamination by styrene-related compounds such as styrene monomer, styrene dimers and styrene trimer generated from the decomposition and/or elution of PS debris. They were found to be widely distributed in samples of sand and seawater from the shorelines of the North-West Pacific Ocean (4). Similar findings were reported from beach sand and seawater taken from the coastlines of the North-East Pacific Ocean and Hawaii State. All samples were found to be contamination by styrene monomer, styrene dimers, and styrene trimmers. The Western Coastlines of the USA proved more severe than in Alaska and other regions and seem to be affected by both land- and ocean-based pollution sources; the data suggest a 226 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


possible proportional relationship between PS pollution and population as well. These results confirm the presence of new global chemical contaminants derived from PS in the ocean, and along coast lines (21). Monitoring results of seawater and sand on the oceans for styrene monomers and styrene oligomers were found globally from 21 countries covering north, west and east pacific ocean at concentrations that are higher than those expected based on the stability of PS. Styrene oligomers appear to persist to varying degrees in the seawater and sand samples collected from beaches around the world. The most persistent forms are styrene monomer, styrene dimer, and styrenetrimer. Sand samples from beaches, which are commonly recreation sites, are particularly polluted with high styrene oligomers concentrations. Styrene oligomers along with other endocrine disrupting chemicals are a threat to human health (29). In a realistic natural exposure conditions where organisms as well as the media water, sediment and plastic were brought at or close to equal chemical fugacity, no or limited (i.e. within a factor of two) increases or decreases in chemical transfer of toxicants were found. Several studies even showed beneficial effects of microplastic ingestion by reducing bioaccumulation due to sorption of chemicals to the plastic (30).

International Pellet Watch International Pellet Watch (IPW) is a volunteer-based global monitoring program for persistent organic pollutants (POPs) including oil pollution molecular markers PAHs and hopanes and flame retardant PBDEs, using plastic resin pellets. Resin pellets are industrial feedstock of plastic products and can be spilled into the environment during production, packaging, and transportation. Typically, such pellets are in the shape of a cylinder or disk with diameters

Sequestration and Redistribution of Emerging and ... - ACS Publications

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