Selv ferskvandsøer kan være forurenet med plast. Der blev i 2013 fundet ligeså høj koncentration af plastaffald i [[Genevesøen]] som i [[Middelhavet]].
<ref>[http://www.sciencedaily.com/releases/2013/05/130529092902.htm École Polytechnique Fédérale de Lausanne (2013, May 29). Microplastic pollution prevalent in lakes, too. ScienceDaily] Citat: "..."We were surprised to find such high concentrations of microplastics, especially in an environmentally aware country like Switzerland," says first author Florian Faure from EPFL...In this preliminary study, the amount of debris caught in Lake Geneva using the manta trawl was comparable to measurements made in the Mediterranean Sea..."</ref>
Kemi Vand