Microplastics as freshwater contaminants

The issue of microplastic in the marine environment has gained global media attention in response to the discovery of large accumulations of plastics in the oceanic gyres, so called garbage patches. Microplastic has also been found in the environment more generally. Recently, a German television program detected microplastics in beer (previously reported on by the FPF). The source of contamination was hypothesized to be the freshwater used in the manufacturing process. Now researchers from the University of Frankfurt, Germany and colleagues from other institutions reviewed the science on microplastic as freshwater contaminant and conclude that microplastics in freshwater are of emerging concern (Wagner et al. 2014). The study was published online on July 9, 2014 in the scientific journal Environmental Sciences Europe. The authors argue that the presence of microplastics in freshwater systems is problematic because microplastics may bioaccumulate throughout the food web and act as vector for other organic pollutant adsorbed on to the microparticles or absorbed therein. The researchers report that 70% to 80% of microplastic found in the oceans originates from inland sources including wastewater treatment plants (WWWTPs), beach litter, fishery, cargo shipping, harbors and industrial plastic production. They hypothesize that freshwater contamination has similar sources and may additionally arise from sewage sludge. So far, microplastics have been detected in lake surface waters and sediments in the US, Canada and Italy. Average levels in the Great Lakes surface waters amounted to 43 000 items/ km². The majority of particles found at lake shores consist of polystyrene (PS), polyethylene (PE), and polypropylene (PP), all of which are also used in food contact materials (FCMs). Levels ranged from 0 to 1 100 items/m². Microplastic particles were also detected in Californian rivers and the Danube in Europe, though no research has so far been carried out on river sediments. Microplastics have been found to be ingested by a variety of freshwater invertebrates as well as the gudgeon, a freshwater fish. According to research, microplastics adsorb metals and persistent, bioaccumulative and toxic compounds (PBTs), which may have adverse effects when ingested. The authors stress that the vector hypothesis deserves further investigation to corroborate first results. Further, microplastics may serve as new habitat for exotic species and pathogens which develop biofilms on microplastic particles. In Europe, microplastic contamination in marine waters is addressed by the European Marine Strategy Framework Directive EC 2008/56. Under the Water Framework Directive EC 2000/60 Member States further have the obligation to monitor anthropogenic pressures on waters systems in the European Union. Additionally, the Directives on packaging waste EC 2004/12, waste EC 2008/98, landfills EC 1999/31, urban wastewater EEC 91/271, sewage sludge EEC 86/278, and shipment source pollution 2005/35/EC address potential sources of microplastic contamination of freshwaters. The European chemical regulation REACH (EC 1907/2006) addresses plastic monomers and additives produced in relevant quantities. The authors of the review reach the conclusion that microplastic in freshwater are emerging as contaminants of concern and identify 6 areas deserving further study:

1. presence of microplastics in freshwater systems
2. sources and fate of microplastics in freshwater
3. exposure to microplastics
4. biological effects of microplastics exposure
5. interaction of microplastics and other freshwater contaminants
6. development of risk assessment framework for microplastics

Reference

Wagner, M. et al. (2014).“Microplastic in freshwater ecosystems: what we know and what we need to know.” Environmental Sciences Europe.