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Plastic Pollution and Downstream Impacts
In recent years, there has been an increase in interest in marine
plastics.However,fewstudieshavefocusedonplasticaccumulation
in freshwater systems and rivers, despite their important role in
transporting plastics to the sea (Williams and Simmons, 1997;
Galgani et al., 2000; Acha et al., 2003; Rech et al., 2014).
Plastics production reached 300 million tons in 2014 (Plastics
Europe, 2015). Plastic has many applications and advantages
and is used in almost all economic sectors because of its specific
characteristics – its low cost, durability, strength and lightness.
Unfortunately, it is precisely these characteristics that make
plastics so persistent and widespread in the environment,
causing huge challenges in terms of impact and management
(UNEP and GRID-Arendal, 2016).
Plastic litter is generally subdivided into larger macroplastics and
smaller microplastics, which measure less than 5mm (GESAMP,
2015). Microplastics are either purposefully manufactured (for
example, microbeads in abrasives or in cosmetics) or are the
result of erosion and fragmentation of larger plastic items. The
degradation of plastics depends on physical, chemical and
biological conditions but is enhanced by exposure to ultraviolet
light and air. Fragmentation into smaller particles increases the
dispersal of plastics into the environment.
Environmental concerns over plastic are not only related to
the volume or aesthetics of waste, but mainly to the impact
they might have on humans and other living organisms. Both
terrestrial and marine organisms can experience mechanical
problems, resulting from ingestion and entanglement. Even
when plastic disintegrates into smaller pieces, the polymer
within may not completely break down into its natural chemical
elements. Most plastics also contain additives to improve their
properties such as flame retardants and plasticizers (for example,
phthalates), which can easily leach out to contaminate the
One of the far-reaching implications of waste in mountains, particularly waste that is unmanaged
or poorly managed, is that it might not always stay in the mountains. Solid waste can end up in
rivers, lakes or wetlands after it enters sewage systems, is washed down by rainwater, or blown
away by wind. Lakes, including artificial lakes and reservoirs, can act as temporary storage facilities
for all kinds of litter, but it is rivers that are the key pathways to lowlands and coastal areas – for
water, sediments, pollutants and litter. Once rivers have discharged their content into the ocean, it
becomes ‘marine litter’. Waste that was once disposed of on a mountain can find itself on the floor
of submarine canyons (Tubau et al., 2015).
surrounding environment. Some of these substances are known
to be toxic and cause endocrine disruptions and other potential
risks to living organisms (Oehlmann et al. 2009; Teuten et al.,
2009) including humans (Talsness et al., 2009).
Plastic pollution can also clog drainage systems, which are very
important for channelling excess water and preventing flooding,
especially after heavy rainfall. When water pipes are blocked by
plastic debris, the diverted water can cause local flooding, which,
in turn, has the potential to transport more plastics.
Plastic pollution is directly linked to human activity, population
density and the quality of waste management (Jambeck et al.,
2015). Without proper waste management, even low-density
populations can heavily pollute freshwater systems with plastics.
While there are major uncertainties about the actual quantities
of plastic debris in lakes and rivers, high concentrations of
microplastics have been found even in remote water bodies.
Examples include Lake Hovsgol, a remote lake in a mountainous,
sparsely-populated region of Mongolia (Free et al., 2014); in
fish from Lake Victoria (Biginagwa et al., 2016); in sediments of
remote lakes in the Tibetan Plateau (Zhang et al., 2016); in lake
sediments in Italy (Fischer et al., 2016); in the Laurentian Great
Lakes (Driedger et al., 2015); in the Yangtze (Zhao et al., 2014);
and in the Danube (Lechner et al., 2014).
The lack of available data does not allow for a comprehensive
assessment of the long-term impacts of plastics on mountain
ecosystems and human health. Further research is needed, but
prevention, mitigation and adaptation strategies and policies
should be urgently designed to address identified sources and
pathways to prevent further plastic contamination – including
the dispersal of persistent organic pollutants in freshwater
systems on which human populations depend for drinking water
and food resources.