Seite - 279 - in Freshwater Microplastics - Emerging Environmental Contaminants?

4 UpstreamInterventions at theSources ofFreshwater Microplastic Doingnomoreharm requires upstream intervention.The further upstreammitiga- tionoccurs, thegreater theopportunity tocollectmoreplasticwith lessdegradation andfragmentationandidentifyingsourcesbeforeenvironmental impactsoccur.For most scientists andpolicymakers,oceancleanup isnoteconomicallyor logistically feasible,moving thedebate toupstreamefforts, like zerowaste strategies, improv- ingwaste recovery, andmanagement andmitigatingpoint andnonpoint sourcesof microplastic creation and loss to the environment. MeasuringMicroplastic Sources There is wide agreement that microplastic at sea isacaseof the tragedyof thecommons,whereby itsabundance in international waters and untraceabilitymakes it nearly impossible to source to the company or country of origin. In terrestrial environments, identification to source is easier due to lessdegradation,butcapturingandquantifyingmicroplastics inanyenvironment is difficult and can easily be contaminated or misidentified [73], and in inland waterways there is the challenge of sortingdebris from large amounts of biomass. In theUnitedStatesprovisionsunder theCleanWaterActandstateTMDLs(Total Max Daily Loads) direct environmental agencies to regulate plastic waste in waterways, like California’s TMDLs, though they are often limited to>5 mm andmissmicroplastic entirely. While there are processes in the environment that degrade plastic into smaller particles(UVdegradation,oxidation,embrittlementandbreakage,biodegradation), there are other terrestrial activities and product/packaging designs that create microplastic (Table1).Thesemayinclude themishandlingofpreproductionpellets at production and distribution sites, industrial abrasives, synthetic grass in sports arenas, torncornersofsaucepackets,vehicle tiredust, tooledshavings fromplastic productmanufacture, road abrasion of plasticwaste on roadsides, unfiltered dryer exhaust at laundry facilities losingmicrofibers to the air [17], or combined sewage overflow that discharges plastics from residential sewer lines, like personal care products, fibers from textiles, and cosmetics, into the aquatic environment. These many sources lack specificmethods ofmeasurement. Thereareexamplesofobservedmicroplastic abundance in terrestrial and fresh- water environments leading tomitigations, suchas theUSMicrobead-FreeWaters Actof2015[74]andstate lawsonthebestmanagementpracticesonpreproduction pellet loss [75]. Interestingly, these two examples share three common character- istics: (a) theyarequantifiedbystandardmethodsusingnets tomeasuredischarges in waterways, (b) they are found in high abundance, and (c) they are primary microplastics, making it easier to identify responsible sources. Considering the many terrestrial activities that create small amounts of difficult to quantifymicro- and nanoplastics, often called secondary microplastics, there is a need for new methods tomeasure their significance. Microplastic:WhatAre theSolutions? 279