Page - 275 - in Freshwater Microplastics - Emerging Environmental Contaminants?

This subsequently catalyzed the attention, interest, and concern of the public, policymakers, industry, and science. Regional and global estimates of floating debris have come forth [9, 10]. Esti- mates of environmental concentrations have ranged from8million tons of plastic leaving shorelines globally each year [11], compared to one estimate of a quarter million tons drifting at sea [12]. This represents a huge disparity suggesting that plastics sink,washbackashore, or fragment longbefore theyarrive in the subtrop- ical gyres. Analysis of the size distribution of plastic in the oceans has found hundred times lessmicroplastics thanexpected [10, 12], supporting the suggestion that fragmented microplastics do not survive at the sea surface indefinitely and likely invade marine food chains before moving subsurface to be captured by deeper circulating currents and ultimately deposited as sediment. Recent studies have unveiled microplastics frozen in sea ice [13] and deposited on shorelines worldwide [14]andacross the seafloor [15,16], even theprecipitationof synthetic fibers as fallout from the skies [17]. Collectively, these observations suggest widespread contamination in all environments. InherentToxicity and theSorption ofPollutants While plastic products enter- ing the ocean represent a range of varied polymers and plasticizers,many absorb (taking in) and adsorb (sticking to) other persistent organic pollutants andmetals lost to the environment, resulting in a long list of toxicants associatedwith plastic debris [18].Gas stationswill sometimesusegiantmesh socks full of polyethylene pelletsdrapedaroundstormdrains toabsorbhazardouschemicalsbefore theyreach thewatershed. In the aquatic environment, plastic behaves similarly,mopping up chemicals in surroundingwater. Several persistent organic pollutants (POPs) bind toplastic as it is transported through thewatershed, buried in sediment, orfloating in the ocean [19, 20]. A single pellet may attract up to one million times the concentration of some pollutants in ambient seawater [21], and these chemicals maybe available tomarine life upon ingestion. The chemistry of plastic in consumer products raises human health as well as ecological concerns. For example, they include polyfluorinated compounds (“PFCs”) [22–24] and the pesticide/sanitizer triclosan [25, 26], also used in over- the-counter drugs, antimicrobial hand soaps and some toothpaste brands, flame retardants,particularlyPBDEs[27,28],andnonylphenols.BisphenolA(BPA), the building block of polycarbonates, and phthalates – the plastic additive that turns hardenedPVC intopliable vinyl are both knownendocrine disruptors [29, 30]. This is not surprising in the case of BPA, which was invented as a synthetic estrogen [31], yet proved tobe ausable formof plastic. Exposuremaycome from the liningofmetalcansfor foodstorage[32],CDs,DVDs,polycarbonatedishware, andreceiptpaper fromcash registers.BPAhasbeen linked tomanydevelopmental disruptions, including early puberty, increased prostate size, obesity, insulin inhi- bition, hyperactivity, and learning disabilities [33]. Phthalates are similarly prob- lematic as endocrine disruptors [34], with effects including early puberty in females, feminization in males, and insulin resistance [35]. Different phthalates Microplastic:WhatAre theSolutions? 275