Water contamination: Can we stop the world’s biggest killer?
It may be surprising to some, but water-borne
diseases are the leading cause of death in the world. There are an estimated
3.4 million deaths a year according to the World Health Organisation (99% of
which occur in developing countries (Prüss-Üstün et al., 2008)), whilst
four-fifths of illnesses in developing countries are caused by contaminated
water (Fonyuy, 2014). Clearly the problem of water
pollution and contamination is now one of the most pressing issues for
developing countries.
So how does water get polluted? Surface water
is more commonly contaminated, and this can pose a high risk as many public
waterways are used for drinking and cooking water as well as sanitation.
However, a lack of infrastructure in towns and cities can lead to sewage and
garbage being dumped straight into these waterways. Groundwater is usually
safer as it gets filtered as it passes through underground layers of sand, clay
and rock (Kjellstrom et al., 2006). Nevertheless, industry and mining can affect
the mineral and pH levels of both ground and surface water. Arsenic (especially a problem in southern Asia, including Bangladesh)
and fluoride, can leech through the soil into groundwater from both natural and
anthropogenic sources, and are seen as the most dangerous inorganic
contaminants in the world (Farooqi, 2015).
The overriding contamination of freshwater comes from nitrogen and phosphurus, which are carried into the water from agricultural runoff. This leads to eutrophication of water bodies, and enhanced productivity of algae to form toxic algae blooms. A consequence of the increased respiration rates is that it depletes the water of oxygen, which can create 'dead zones' with devastating effects on local fauna.
The overriding contamination of freshwater comes from nitrogen and phosphurus, which are carried into the water from agricultural runoff. This leads to eutrophication of water bodies, and enhanced productivity of algae to form toxic algae blooms. A consequence of the increased respiration rates is that it depletes the water of oxygen, which can create 'dead zones' with devastating effects on local fauna.
It is not just freshwater reserves which are
being increasingly contaminated. Go to any beach in Britain and it’s easy to
see the amount of waste and debris washed up onto our shores. There are billions
of pieces of plastic floating around are oceans, right down to microscale which
can have a devastating effect on wildlife. The BP oil spill in the Gulf of
Mexico is a well-known example of water pollution, where 780,000 cubic metres
of oil were released into the ocean, causing havoc to marine wildlife as well
as the local fishing and tourism industries. Meanwhile, Diaz and Rosenburg, 2008 report more than 400 marine dead zones, caused by toxic algae blooms and oxygen depletion.
Why is
freshwater contamination such an issue in developing countries, whilst in
general richer ones are able to get around the problem? The answer, inevitably,
focuses around money. Many developing countries lack the finances to build the
necessary infrastructure, such as pipes, treatment plants and wells. The
problem is being exacerbated in many African countries by high population
growth rates, meaning increased use of unsafe water for drinking, cooking and
sanitation.
However the developed world has its problems
as well. Recently in the USA there have been reports of contaminated
groundwater due to deposition of waste water from the hydraulic fracturing, or
fracking, process of extracting natural gas. Although natural gas has been
hailed as a cleaner alternative to coal, and a transition fuel whilst the world
switches to a future which utilises renewable energy sources, it brings its own
environmental impacts. Methane concentration has been found to rise with
proximity to fracking sites (Holzman, 2011). This video shows an example
of how methane levels are so high in some US drinking water supplies that they
are actually flammable:
This has led to a backlash against fracking
in regions which are experiencing water pollution. Developed nations have
higher expectations with regard to their water supply and are typically willing
to take steps to protect the quality of that water.
How realistic is it though, to expect to
radically reduce water contamination in developing countries? Historically
poorer agricultural countries are often the ones experiencing the most rapid
economic growth, driven by increased globalisation and growing demand for
minerals and other commodities. This
typically involves rapid expansion of cities, including the building of new factories
and roads, but often without the infrastructure to support dealing with
contaminated water.
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