We are IntechOpen, the world's leading publisher of Open Access books Built by scientists, for scientists

Open access books available 5,300

130,000 155M

International authors and editors

Downloads

Our authors are among the

most cited scientists 154 TOP 1%

Selection of our books indexed in the Book Citation Index in Web of Science™ Core Collection (BKCI)

# Interested in publishing with us? Contact book.department@intechopen.com

Numbers displayed above are based on latest data collected. For more information visit www.intechopen.com

## **Polystyrene as Hazardous Household Waste**

### Trisia A. Farrelly and Ian C. Shaw Trisia A. Farrelly and Ian C. Shaw

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/65865

#### **Abstract**

Polystyrene (PS) is a petroleum‐based plastic made from styrene (vinyl benzene) monomer.Sinceitwasfirstcommerciallyproducedin1930,ithasbeenusedforawiderange of commercial, packaging and building purposes. In 2012, approximately 32.7 milliontonnesofstyrenewereproducedglobally,andpolystyreneisnowaubiquitoushousehold item worldwide. In 1986, the US Environmental Protection Agency (EPA) announced that the polystyrenemanufacturing processwas the fifthlargest source ofhazardouswaste. Styrene has beenlinked to adverse healtheffectsin humans, andin-2014,itwaslistedasapossiblecarcinogen.Yet,despitemountingevidenceandpublicconcernregardingthetoxicityof*styrene*,theproductofthepolymerisationofstyrene,*PS*, isnotconsideredhazardous.Thischapterdrawsonaseriesofmovementscalledthe'newmaterialisms'toattendtotherelational,unstableandcontingentnatureofPS,monomersand other additivesin diverse environments, and thus, we highlight the complexitiesinvolvedinthecategorisationofPSas'hazardous'andthefutilityofdemarcatingPSas 'householdwaste'.WhilelocalexamplesaredrawnfromtheNewZealandcontext,thekeymessagesaretransferrabletomostpolicycontextsanddiversegeographicallocations.

**Keywords:**polystyrene,styrene,hazardouswaste,NewZealand,materiality, carcinogen,newmaterialism

#### **1. Introduction**

Thischapteristheproductofaninterdisciplinarycollaborationbetweenasocialanthropolo‐ gistandatoxicologist.Thiscollaborationhasallowedustopresentpolystyrenewithacriticalsocialanthropologicalapproachthatisunderpinnedwiththescientificfactsaboutthisubiq‐ uitousplasticpollutant.Theanthropologicalcontributiontothischapterisitsnewmaterialistlensthroughwhichthelifeandafterlifeofpolystyrene(PS)canbemoreclearlyviewed.Tothenewmaterialists,objectsare'alive'becauseoftheircapacitiestomakedifferenceintheworld,tohaveeffectsandtoshapethewebsofinterrelationshipsofwhichtheyareapart.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Therefore, bacteria, bees, a dead dog or charcoal all have the capacity to 'animate, to act, to produce effects dramatic and subtle' [1, 2]. One notable new materialist and physicist, Karen Barad [3] brings our attention to the propensity for science to examine one or a few things (e.g. monomers or species) in isolation from their natural context. She argues that these singular foci result in limited understandings about the full and complex life of matter involved in often unpredictable relationships with other materials, biological systems and ecosystems.

PS is a petroleum-based plastic made from styrene (viny) benzene) monomer (4) (Figure 1). Since PS was first commercially produced in 1931, it has been used for a wide range of commercial, packaging and building purposes, and it has grown to be one of the world's most ubiquitous household items. Most PS is used to make rigid durable products, such as television and computer cabinets and appliances, and nearly all of the rigid PS packaging manufactured in New Zealand (NZ) is used for tood contact purposes. PS used for food packaging includes general purpose PS (GPPS) such as disposable cutlery and plates; high-impact PS (HIPS) such as yoghurt containers and single-use cold drink cups; and expanded PS (EPS) foam used as meat trays, coolers and cups [4].

Figure 1. The manufacture of PS by chemically bonding many styrene (vinyl benzene) monomer units to form a long styrene polymer chain.

EPS is made of pre-expanded closed-cell foam beads. The manufacturing process involves carrying out the styrene polymerisation in droplets suspended in water. This leads to the formation of PS beads. EPS is useful because it is an excellent insulator (e.g. used to line cool boxes or chilly bins), and it absorbs shock and so it is a good moulded or bead-based packing material for transporting fragile cargo. It is used for a wide range of food contact packaging, such as meat trays, egg cartons and 'clamshell' fast food containers. EPS is often referred to by its trademark 'Styrofoam' invented by Dow Chemical in 1941. The trademark is informally used (not only in USA and Canada but also in NZ) for all foamed PS products, although strictly it should only refer to the 'extruded closed-cell' PS foam (XPS) made by Dow Chemicals and commonly used for building insulation.

While PS is popular because of its light weight and insulating properties, there is a downside to its high rate of production, consumption and disposal. In 2012, approximately 32.7 million tonnesofPSwereproducedglobally [5].Thisfigureisconcerning,considering thelackofwastemanagementofthisman‐madematerial.Forexample,PlasticNZestimatesthatover-6784tonnesofNZ‐producedPSwereconsumedforpackaginginNZin2003,withaslittleas-450tonnescollectedforrecycling[4].TherearecurrentlynoPSresidentialcollectionservicesinNZ.Thisfigureisalsoconcerningbecauseofthehazardousnatureoftheproductanditscomponentsaswillbeexplained.

In2013,ChelseaRochman,ascientistwhostudiesthemigrationofchemicalsfromplasticswheningestedbyanimals,wastheleadauthorinanarticlein*Nature*whicharguedforthereclassi‐ ficationofsomekeyplasticsashazardoussothattheycouldberegulatedbyenvironmentalprotectionagencies[6].ThesekeyplasticsarePVC,polyurethane,polycarbonateandPS.

Today,tensoftownsandcitiesaroundtheworldprohibitthesale,possessionanddistributionofEPS,includingPortland(Oregon,USA),Toronto(Canada),Muntinlupa(Philippines),Paris (France),andTainan(Taiwan).Whileitstillhasbeenunabletoenactastatewideban,in2016, thestateofCaliforniahas65ordinances(i.e.lawsorregulationsmadebyalocalgovernmentbody)onEPS,seeRefs.[7,8](forfulllist).Thereasonscitedforordinancesbanningorregulat‐ ingEPSareprimarilybasedonitspotentialasanenvironmentalhazard:morespecifically,aconcernfortheenvironmentallypollutingpotentialofthephysicalpropertiesofonetypeofPSratherthanthechemicalinstabilityandpotentialforPS(asafamilyofplastics)toleaktoxinsinto bodies and ecosystems.

Plastics harmin two keyways: chemically,whenmonomers, plasticisers and other haz‐ ardous PS additivesleach from PS objectswhen poorlymanufactured; physically,when-PSbreaksdownintomicroplasticsintheenvironment.Themanufacture,compositionandinterrelationships of PS *in situ* are profoundly important in determining whether it is a 'hazard'[9].

Where themanufacture ofPSis complete, the resulting styrenepolymer has covalent (i.e. strong)bondsbetweenthestyrenemonomerunits;thesebondsaredifficulttobreaktoreleasestyrene.Forthisreason,styreneisnotreleasedfromPSduringenvironmentaldegradation. However,ifthePSmanufacturingprocessdoesnotresultincompletepolymerisation,freestyrenemightremainin thePSproduct.Thisfreestyreneisnotstronglybonded to thePSstructureandsocan,andlikelywill,leachoutinto theenvironmentorinto foodstoredin-PS containers. In addition to the ability of styrene toleach from PS poorlymanufacturedproducts,thischapterwillalsooutlinethehazardsresultingfromthebreakdownofPSintomicroparticles over prolonged periods.

#### **2. Styrene monomer**

While thelevelandnatureof thehazardposedbystyrenehavehistoricallybeenhotlydis‐ puted, agrowingbodyofevidenceindicatescause forpolicy action toprotectpopulationsfromitsmisuse.Forexample,in2014,theInternationalAgencyforResearchonCancer(IARC) determinedthatstyreneisapossiblehumancarcinogen.Thisisbasedonstudiesinanimalsandemergesfromresearchintostyrene'smetabolite(i.e.styreneoxide)asachemicallyhighlyreactive epoxide, which might chemically bond to DNA and thus initiate carcinogenesis (**Figure 2**).Itisnowlargelyacceptedthatstyreneoxideislikelytoberesponsibleforstyrene'scarcinogenicity, and since there arelikely to be species andinter‐individual differencesinmetabolism,therearealsolikelytobedifferencesinsusceptibilitytocarcinogenicitybetweenspeciesandindividuals[10].

TheEPANationalHumanAdiposeTissueSurveyfor1986identifiedstyreneresiduesin100% ofsamplesofhuman fat tissue takenin1982in theUSA [11],whichindicateswidespreadexposure. Inlaboratorystudies (e.g.inrats),styrenemonomerandsomeotheringredientsofPShavebeenshowntobecarcinogenicand,insomecases,affectorganismsinasimilarway tothehormoneoestrogen[9,12,13]becauseoftheirmolecularmimicryofthefemalehormone17β‐oestradiolandoccupancyandactivationofoestrogenreceptors.

**Figure 2.** Styreneismetabolised to ahighly reactive and toxicepoxide,styreneoxide,whichcaninteractwithDNAcausingamutationwhichmightinitiatecarcinogenesis.

#### TheNationalToxicologyProgramme'sReportofCarcinogensstatesthatstyreneis

reasonably anticipated to be a human carcinogen. First listed in the Twelfth Report on Carcinogens(2011)HCCH2CarcinogenicityStyreneisreasonablyanticipatedtobeahumancarcinogenbasedonlimitedevidenceofcarcinogenicity fromstudiesinhumans,sufficientevidence of carcinogenicity from studiesin experimental animals, and supporting data onmechanismsofcarcinogenesis[14].

#### TheNationalRegionalCouncilconcurredin2014:

*Review of the Styrene Assessment in the National Toxicology Program 12th Report on Carcinogens* concurswiththeNTPdeterminationthatthereislimitedbutcredibleevidencethatexposuretostyreneinsomeoccupationalsettingsisassociatedwithanincreaseinthefrequencyoflym‐ phohematopoieticcancers.Additionally,theNRCreportauthoringcommitteeindependentlyreviewed the scientific evidence from studiesin humans, experimental animals, and otherstudiesrelevanttothemechanismsofcarcinogenesisandmadelevel‐of‐evidenceconclusions. Basedoncrediblebutlimitedevidenceofcarcinogenicityintraditionalepidemiologicstudies, onsufficientevidenceofcarcinogenicityinanimals,andonconvincingevidencethatstyreneisgenotoxicinexposedhumans,thisreportfindsthatcompellingevidenceexiststosupportalistingofstyreneas,ataminimum,reasonablyanticipatedtobeahumancarcinogen[14].

More recently, on 22 April 2016, the Office of Environmental Health Hazard Assessment-OEHHAaddedstyrenetothelistofchemicalsknowntothestatetocausecancer[15].TheNZ-EPA(andsimilarly,theUSEPA)determinesthatstyreneis'possiblycarcinogenictohumans' andclassifiesthechemicalasotherwisehazardousduetoitsfollowingcharacteristics:flam‐ mable, acutely toxic, suspected human mutagen, carcinogen, and human reproductive ordevelopmentaltoxicants,toxictoorgans/systems,veryecotoxicintheaquaticenvironmenttoalgalandcrustaceans,slightlyharmfultofishandecotoxictoterrestrialvertebrates[16].

Thecategorisationofstyreneas'toxic'isunequivocalbecause,duetoitshighchemicalreac‐ tivity,itinteractswithcellsystemscausingwidespreadmetabolicdamage.Inparticular,sty‐ renecanchemicallyreactwithspecificcomponentsofDNAresultinginchanges,whichaffecttherateofdivisionofcells(**Figure 2**).Thismutationisthebasisofchemicalcarcinogenesisandexplainswhystyreneisacarcinogeninanimalstudiesandreasonablyanticipatedtobeacarcinogeninhumans[14].

TheIARC'sstatementthatstyreneisapossiblehumancarcinogenisreinforcedinstatementsmadebytheUSAandNZEnvironmentalProtectionAgencies(EPAs).TheUSAandtheNZ-EPA,amongotherEPAsglobally,classifystyreneas'hazardous'underawidevarietyofeco‐ toxicandtoxiccategories(seelaterinthischapter).TheNZEPAratestheenvironmentalhaz‐ ardsassociatedwithstyreneasfollows:9.1A(algal):veryecotoxicintheaquaticenvironment; 9.1B(crustacean):veryecotoxicintheaquaticenvironment;9.1D(fish):slightlyharmfulintheaquaticenvironmentorotherwisedesignedforbiocidalaction;9.3B:ecotoxictoterrestrialver‐ tebrates[14].Inaddition,theEuropeanUnioncurrentlyplacesstyreneinCategory1intheirlistofpotentialendocrinedisruptors,<sup>i</sup> seeRef.[17],alsoRefs.[12,18].Thesenewcategorisa‐ tionsalignwithagrowingglobalinterestinthehazardousnatureoftheingredientsusedintheproductionofplastics.Interestingly,accordingtoahazard‐rankingmodelbasedontheUnited-Nations'GloballyHarmonizedSystemofClassificationandLabellingofChemicals,thechemi‐ calingredientsofmorethan50%ofplasticshavenowbeendeterminedtobehazardous[19].

#### 3. The polymerisation of styrene

Despite building evidence and public concern regarding the toxicity of styrene, the product of the polymerisation of styrene, IS, is not listed as 'hazardous' in any policy documents. Regardless, some community groups |201 and a growing number of independent scientists |6 now treat PS as a hazardous waste item. When styrene is fully polymerised in the manufacturing process to form PS, the reactivity of the styrene component of the polymer is removed completely because the chemical bond that forms between the monomer units changes the nature of the reactive moieties of the styrene molecule. This explains why PS has very low mammalian toxicity. In addition, as discussed earlier, the monomer units are very strongly bonded together which means that styrene monomer cannot be released, in an environmental context, from its polymerised form. The bacterial degradation (e.g. in landfill) of PS does not liberate styrene, but rather produces substances such as 4-phenylvaleric acid which is of low toxicity [21].

However, if the styrene polymerisation process used in the manufacture of PS is not complete, styrene monomer might contaminate the PS (termed 'residual monomer'). This styrene can migrate into food packed in styrene-contaminated PS. Since styrene is reasonably fat soluble (LogPow [styrene] = 3.6; i.e. styrene is 103s times more soluble in fat than water), migration is greater in fatty foods (e.g. milk) in PS containers [22]. On these solubility grounds, migration of styrene into a water-based ecosystem is less likely than into fat-containing foods, but taking account of the vast quantities of water in the environment, even at low water solubility, significant transter of styrene to aqueous ecosystems will occur. Once in the aquatic environment, styrene will be rapidly absorbed via the lipid-based cell membranes of aquatic organisms and will concentrate up the food chain. Thus, styrene is more likely to affect animals at high trophic levels (i.e. predators).

Other chemicals (e.g. plasticisers) are sometimes added to PS to modify its physical properties for particular applications. For example, tris(4-nonyl-phenyl) phosphite is sometimes added as an antioxidant to prevent PS degradation. Such molecules can leach from PS and contaminate both the environment and products (e.g. food) stored in PS containers.

Regardless of whether styrene is completely polymerised or not during the manufacture of PS, all PS waste have significant implications for the environment. This is because the complete environmental degradation of PS is very slow and produces small PS particles en route. These PS particles have significations in ecosystems as they build up in, for example, marine environments. In addition to the physical hazards they pose, hydrophobic plastics such as PS are the most hazardous of plastics in fresh water and marine ecosystems because of their ability to adsorb persistent organic pollutants (POP's)—such adsorbed POP's can be released tollowing ingestion of PS microparticles by animals (e.g. fish).

#### 4. Polystyrene as an environmental hazard

While PS is highly valued for its light weight, strength, thermal insulation and shock absorbing properties, its production and disposal reveal significant threats to the environment. Today, most plastic waste goes to landfills where chemicals can leach from the plastic and contaminatesoilandgroundwater[23].TheUSEPAreportsthat'[e]achyearAmericansthrowaway25,000,000,000 [25billionor47,565perminute]Styrofoamcups.Even500years fromnow,thefoamcoffeecupyouusedthismorningislikelytosurviveintactinalandfill'[24].

ThereisnodomestickerbsidecollectionofanyformofPSprovidedbycouncilsinNZ.ThelackofPSrecyclingservicesavailable tohouseholdersinNZand thevolumeofEPSmakedisposal via council rubbish bags expensive. Consequently, littering or 'fly tipping' andhouseholdBurningofPScanbecomeresidentialalternatives,thusraisingthelikelihoodofreleasingPSanditspotentiallytoxiccombustionproductsintotheenvironment.

#### **4.1. Ecotoxicity in the manufacture of polystyrene**

In1986,aUSEPAreportonsolidwastedeclaredPSmanufacturingthefifthlargestsourceofhazardouswasteintheUSA[16].Inaddition,themanufactureofPSisenergyintensive, creatinglargeamountsofgreenhousegases(e.g.CO<sup>2</sup> )andliquidandsolidwaste.Toaddtothislife‐cycle‐basedharm to theenvironment,PSismanufactured frompetroleum: anon‐ sustainable and heavily polluting resource. Consequently, the environmental productioncostsofPShavebeenrankedthesecondworstintheUSAbytheCaliforniaIntegratedWaste-ManagementBoard[25].

It is possible that differences in manufacturing practices might lead to different levels ofmonomerresiduesremaininginthefinalproduct.Forexample,verypreliminarystudiesonpolycarbonateplasticsshowed thatverydifferentamountsofbisphenolA (BPA)monomerleachedfromdifferentplasticproductsmanufacturedinKorea,ChinaandNZ[26].Whileverypreliminary,thismightreflectdifferencesinmanufacturingprocessesandcontrolsbetweenthesecountries.AsAsiabecomestheregionofchoice(oneconomicgrounds)formanufactureofmanyplasticproducts,itispossiblethatPSproductsmadewithresidualplasticmonomerswill increase. Consequently, the risk ofmonomer leaching into the environment and intoproductsstoredinplasticcontainerswillriseasaresult.TheincreaseinfreetradeofthesePSobjectsacrossgeopoliticalboundariesmeansthatregulatingthemanufactureandresponsibledisposalofPSisverycomplexindeed[26].

#### **4.2. Physical and ecotoxic threats in marine environments**

Plasticpollutioninmarineenvironmentshasbecomesodirethattheterm'plasticpollution'isnowsynonymouswith'marinepollution'[7].A2016WorldEconomicForumreportpredictsthattheratioofplastictofishintheoceanisexpectedtobe1:3by2025[27].Currently,60–80% of waste found in marine environments is plastic [28], and in 2014, it was estimated thatmorethan226,796tonneofplasticiscurrentlyafloatatsea[29].Becauseofitslightweight, PSishighlymobileandcantransportinvasivespeciesacrossmarineboundaries.PSispreva‐ lentinNZcoastalareas:forexample,ina2016studyofmicroplasticsonCanterbury's(NZ) coastlines,themajorityofplastics(55%)foundwerePS[30].

DouglasMcCauley,amarinebiologyprofessorattheUniversityofCalifornia,SantaBarbara, USAstudiedthemechanicalandchemicalcausesofharmtomarineanimalsfromEPS.TheenvironmentaldegradationofPS(e.g.bybacteria)leadstotheproductionofsmallfragments (microplastics)whichsurviveforaverylongtimeintheenvironment(e.g.inmarinesystems) and cause physical effects. For example, fish mistake the PS particles for food and eat them. This leads to malnutrition as PS provides fish with no nutritional benefit while making them feel full, thus suppressing a desire to eat [6, 31]. Plasticisers and other additives are less common in I'S products than in other plastics (e.g. polyvinyl chloride [PVC]). However, the antioxidant tris(4-nonylphenyl) phosphite sometimes used in PS products is a potent oestrogen mimic and is part of a cocktail of estrogenic environmental contaminants that is thought to be responsible for male feminisation in animals and humans [32]. To be clear, styrene is not produced by the environmental degradation of PS but by the leaching of residual styrene from incomplete polymerisation.

As outlined above, there is a further, very important, property of PS that has a significant bearing on its environmental and human toxicity: its extreme hydrophobicity. Since, in a chemical context, like chemical properties attract like, PS attracts and adsorbs (i.e. sequesters on its surface) other hydrophobic molecules (e.g. POPs). This is important because it means that micro PS particles (produced as part of the environmental degradation of PS) will sequester and transport POPs and other hydrophobic toxins in the aquatic environment. If PS microparticles are ingested by animals (or humans), the sequestered POPs might be stripped from the PS and absorbed into the animal's system. This makes PS an excellent vector for highly toxic hydrophobic chemicals.

Seabirds that have consumed plastic waste have been found to have polychlorinated biphenyls (PCBs) and POPs in their tissues at 300% greater concentrations than in similar birds that have not eaten plastic [31]. PS is particularly good at attracting oily (i.e. hydrophobic) chemicals such as PCBs, flame retardants such as polybrominated diphenylethers (PBDEs), pesticides (e.g. DDT) and surfactants (e.g. 4-nonylphenol an endocrine disruptor). These chemicals have been estimated to be adsorbed by PS at concentrations up to a million times greater than in the surrounding water [33].

The chemicals PS attracts are regarded as 'priority pollutants':

...[C]hemicals that are regulated by government agencies, including the US EPA, because of their toxicity or persistence in organisms and food webs. These chemicals can disrupt key physiological processes, such as cell division and immunity, causing disease or reducing organisms' ability to escape from predators or reproduce [6].

Rochman and her team found that at least 78% of priority pollutants listed by the EPA and 61% listed by the European Union (EU) were associated with plastic debris (either ingredients of plastic or adsorbed from the environment) [6]. PS microplastics contaminated by these POP's enter the tood chain when eaten by marine species and might end up on our dinner tables at home [34].

Taking all of these chemical and toxicological properties of PS into account, PS per se is one of the less problematic plastics in a purely toxicological sense. However, its high rates of production, poor waste management, slow environmental degradation to form microparticles and adsorption of hydrophobic toxic chemicals have led, at the macro level, to huge quantities of PS waste presenting physical problems at all environmental levels, and, at a micro level, PS transporting adsorbed toxins to unsuspecting marine ecosystem consumers. It is clear that apolicy connectionhasnot yet beenmade between thesehydrophobicpolymer 'carriers'andprioritypollutantsinthemarineenvironment.Iftherewere,itwouldbemorelikelythattherewouldbecausetocategorisehydrophobicplasticsas'hazardous.'Growingevidence,however,continuestohighlightthepreviouslyunforeseenandcomplexrelationalbehavioursofPSanditsadditiveswithothermaterialsandbodiesinmarineenvironments. ThisgrowingevidencesupportsLiboiron's[9]argumentthatthegovernanceofplasticpollu‐ tionvia'safelevels'maynotadequatelycapturethe'afterlives'ofplasticpolymers.Thenextsectionwillfurtheradvancetheargumentthatamorenuancedandcontext‐specificapproachisneeded.This approach attends to thecomplex relationalnatureofpolymers,monomersandotheradditiveswhentheycomeintocontactwithothermatterandmaterialsindiverseenvironments.

#### **4.3. Polystyrene combustion**

Theincompletecombustion (at temperatures thatequate tohouseholdburning)ofPSpro‐ duces myriad products including styrene, PAHs, including fluoranthene which has beenshown to be carcinogenic in mouse studies [35, 36] and the IARC, have classified it as a-Group3carcinogen(i.e.notclassifiableastoitscarcinogenicitytohumans).ConcernshavealsobeenraisedaboutPSasahazardduringhouseorcommercialbuildingfiresorthedis‐ posalofPSbyburningduetothetoxinsitreleaseswhenPSiscombusted,particularlywhenincineratedashouseholdwasteinresidentialareas.TheNationalBureauofStandardsCenterforFireResearchidentified 57chemicals releasedduring thecombustionofEPS.Of these, perhapsthemosttoxicinclude,PAHs,carbonblack(i.e.thecopioussootproducedwhenPSburns)andcarbonmonoxide[11].

TheuseofextrudedXPSandEPSinbuildingconstructionisalsoafocusofconcernduetothepersistence,toxicityandecotoxicityofthebrominatedflameretardantHBCDusedinthemanufactureof thesePS foams. In response to thesegrowingconcerns, theEU (under the-StockholmConvention)bannedtheuse,importorexportofHBCDon26November2015[37].

### **5. Polystyrene and food safety**

PScanbehazardoustohumanhealthinthefollowingcircumstances:eatingmarineanimalscontaminatedwiththeresidualmonomersandadditivesinPSandthePOPsadsorbedonto-PS;inhalationofgasescreatedwhenPSisheatedorcombusted;chemicalexposurein themanufactureofPS;andexposuretotroposphericozonecausedbyHFCsinthemanufactureofPS.Inthissection,wewilldiscussthepossibilitythatPSfoodcontainersthathavebeenexposed tocertainconditions [fats (e.g.VitaminA)andheat]canincrease thepotential forstyrene contaminants to migrate into food and bodies.

Newscientificresearchisraisingsomedoubtaboutthesafetyoffoodwhenincontactwith-PS under certain conditions. One of those conditions has been recognisedin the US FDAguidelinesincontactwithfataboveambienttemperature[22,38,39].In2014,theEuropean-FoodSafetyAuthority(EFSA)'sPanelonFoodContactMaterials,Enzymes,FlavouringsandProcessingAids (CEF)conductedastudyrequestedby theFoodStandardsAgency (FDA), UK.Theyconcludedthefollowing:

…substances(butadiene,ethylacrylate,methylmethacrylate,styrene)copolymer,(butadiene, ethylacrylate,methylmethacrylate,styrene)copolymercrosslinkedwithdivinylbenzeneand (butadiene, ethyl acrylate,methylmethacrylate, styrene) copolymer crosslinkedwith 1,3‐bu‐ tanedioldimethacrylate,innanoformdonotraiseasafetyconcernfortheconsumerifusedasadditivesindividuallyorincombinationatuptoatotalof10%w/winnon‐plasticisedPVCusedincontactwithallfoodtypesatambienttemperatureorbelowincludinglong‐termstorage[40].

However,householdPSisnot alwaysusedin contactwith food at ambient temperatures; foodisoftenheatedinPScontainersinmicrowaveovens;polystyrenecupsandfoodcontain‐ ersaremostcommonlyused forhotbeverageconsumption.Thisagainraises thequestionofsafelevelsofstyrenemonomerandsafeconditionsofusewhenPSitemsareexposedtoawiderangeofuntestedconditionsintroducingatoxicrisk.

Onenotablestudyemphasisingtheneedforfurtherattentiontothepotentialleachingofsty‐ renefromPScontainersintofoodisthatofMatiellaandHsieh[41].Theresearchersreportedthatvolatilestyrenemonomerwasfoundinshellsofeggsaftertheywerestoredfor2 weeksin-PScontainersatsupermarkets.DishescookedwiththesecontaminatedeggscontainedseventimesmoreethylbenzeneandstyrenecomparedtothosepreparedfromfreshfarmeggsnotpackagedinPS.Notsurprisingly,theAmericanChemistryCouncil(representingtheplasticsindustry)vehementlydeniesanyhealthrisksposedbyPSfoodpackagingtotheUSpublic[42].

#### **6. Discussion**

ThecentraldogmaofmoderntoxicologyistheParacelsusprinciple:'thedosemakesthepoi‐ son'[43](thehigherthedose,thegreatertheeffect).However,someplasticmonomershaveahighbiologicalimpactatlowdoses(e.g.oestrogenmimicsworkat10‐5 M)meaningthattest‐ ingregimesandthepoliciestheyinformneedtochangetoaddressthesetraceenvironmentalandfoodcontaminationexposurelevels[44].Testingregimesandtheirsubsequent'safelim‐ its'significantlyinfluencewhatisdefinedas'hazardous'or'safe'.

Undercurrenttestingregimes,wecannolongerbecertainabouttheproductionofrisk‐freeobjects(arguablynothingisriskfree)[45].Laboratorytestingforsafetymaynotprovideuswithaclearindicationofhowmonomersmayactwithinavarietyofecologicalandbiologicalcontexts,andwhattheconsequencesmaybe.Specifically,toxicitytestingregimessimplydonotmimicenvironmentalsystemsandtheinterrelationshipsbetweenpollutantswellenoughforthemtogiveusareliableindicationoftheenvironmentalfateandbehaviourofcomplexplastics.

Theworkof thenewmaterialistsisvaluableinilluminating thecomplexnatureofmateri‐ als,thepoliticsoftestingregimesandtheinterpretationandcategorisationsofwhatis'haz‐ ardous'.Objects,discourses,identitiesandpoliticsemergethroughparticularrelationships. In this case,whether PSis'hazardous' or notlargely depends on how scientists establishtestingregimesandcategorise,analyse,andinterpretdata.TheethicsofcategorisingPSas'hazardous' (or not) is not fixed and predetermined; it changes and untolds as scientific findings, and their interpretations are negotiated [3].

The current approach to defining something as 'hazardous' or 'safe' involves an almost singular focus (e.g. on styrene monomer). However, if we are to safely manage PS production, consumption and disposal, we must scrutinise the life and 'afterlife' of each component that is used in the production of each PS product in the context of its fate and behaviour in the environment. This involves the engagements of its additives and intended end-products to other matter, materials and ecological and biological systems. This brings to question the term 'PS end product' and 'end of life'. If the 'end product' or the life' of the product is defined as when the product no longer serves its original function, we are missing the ongoing impacts of the product on bodies and environments long after it is considered 'defunct'. The toxicity of PS continues long after its useful life.

The new materialisms also require a mobile approach. This would involve tollowing PS objects and their interrelationships with other things. This is a call to reimagine PS in its various forms as unstable and impermanent with indeterminate consequences and trajectories. This is also a political call to scrutinise how PS is culturally constructed as 'hazardous' or 'safe' and by whom: a concern captured by what has been referred to recently as 'the politics of plastics' [46, 47]. In addition, this scrutiny might encompass the cumulative impact of substances in bodies. For example, chemicals that humans are exposed to from tood and the environment might have additive effects both physiologically and thus should be considered together rather than individually [32].

This chapter also serves as a reminder that 'household waste' is a misnomer as it implies a kind of simplistic demarcation of space, whereas PS enters the home and can only be intentionally removed intact as solid 'waste'. Yet, PS household waste items can never be fully and successfully 'managed' by waste management intrastructures to a final resting place in landfills or recycling centres where they magically disappear from our lives and no longer impact on the environment. The PS items that enter households often originate from far flung places, diverse components and industrial processes (with varying levels of regulation). They enter bodies and become entangled with other materials and matter in the household, while other PS solid objects are constructed as waste items and their invisible, ungoverned and now free-floating chemical components move on. They leave households to continue their unpredictable journeys to landfills or to impact other ecosystems and bodies. Outside the regulatory and technological structures of policy and waste management systems, the kinds of risks I'S poses become even more difficult to detect and mitigate.

#### 7. Conclusion

As Liboron reminds us, the 'atterlives' of industrially produced objects are the longest part of their lives' [7]. This means that we can no longer limit our analyses and determinations of the hazardous nature of PS within the bounded spaces of the factory, retail store, home, landfill, marine environment and their return via the food chain to the dinner plate back home. That said,shallwecontinuetotreatpolymersandmonomersasdiscretepointsofanalysisinthedevelopmentoflegislation,policyandactivismaroundhazardouswasteandfolloweachonethroughallthesespacesandbeyond?Orincombination?Andwithothermatterastheymovethroughthesespaces?Howdowedeterminesafelevels;orwhetheraPSis,orisnot,'hazard‐ ous'(consideringtheinfiniteandindeterminatecontingenciesandcontextsofPS'sinterrela‐ tionshipswithotherchemicalsandbodies)?AndwhodeterminesthesafetyofPSwhenthisdeterminationdependsonpre‐existingculturalvaluesandagendas[48]?

WhilehumanshavethecapacitytoproducePS,wecannevermakeitgo'away'whenitnolongerfulfilsits,oftenshort‐term,function.However,atcurrentratesofconsumption,another-33billiontonnesofplasticwillbeproducedby2050.Rochmanetal.suggestthatifthemostproblematicplasticswere tobeclassifiedashazardousimmediatelyandreplacedwithsafealternatives,thisratecouldbereducedto4billiontonnes[6].PVC,polystyrene,polyurethaneandpolycarbonatemakeup30%ofallplasticproduction.Theyareconsidered'priority'plas‐ ticsbyRochmanandherteambecausetheyareparticularlydifficulttorecycleandaremadeofpotentiallytoxicmaterials.However,aswehaveargued,theseplasticsmayonlybeconsidered 'hazardous'whenincertainbiophysicalorecologicalcontexts.Doesthismeanthatweshouldcontinuetoproducetheseplasticsandseekwaystoensurethesehazard‐causingscenariosdonotoccur?OrarethepossibilitiesforPStobelocatedincontextswheretheyarehazardousunavoidable,meaningthatablanketbanontheproductionoftheseplasticsistheonlyoption?

Thischapterhasraisedmorequestionsthanitcananswer.However,wehopethatitbroadensattention to the'aliveness' [1]ofPS.ThematerialqualityofPS (itsmateriality)allowsit toslipthroughthenetofhumanintention,andoutsidethewastemanagementinfrastructure, theeconomic system and thepolicies andlegislationdesigned tocontainit,profit fromit, andkeepussafe.WehavecreatedtheseroguematerialsandlikePandora'sBox,theyhaveescapedhumanmanagementsystems.Now,weneedtorecapturethem,ifonlyinourmind'seyefornow,ifwearetoacttomitigatetheirrealandfuturerisksforhumanandnon‐humanlife—insideandoutsidethehousehold.

## **Author details**

TrisiaA.Farrelly<sup>1</sup> \*andIanC.Shaw<sup>2</sup>

\*Addressallcorrespondenceto:T.Farrelly@massey.ac.nz


#### **References**

[1] BennettJ.Theforceofthings:stepstowardanecologyofmatter.PoliticalTheory.2004, **32**:347–372.doi:10.1177/0090591703260853


(butadiene,ethylacrylate,methylmethacrylate,styrene)copolymereithernotcrosslinkedor crosslinked with divinylbenzene or 1,3‐butanediol dimethacrylate, in nanoform, for use in food contact materials. EFSA Journal. 2014, **12**(4):3635, 8 p. doi:10.2903/ j.efsa.2014.3635

