July 5, 2016 Pollution Written by Greentumble
the Global Distillation Effect
As white and pristine as polar bears’ furs

may be, their bodies have been shown to have one of the highest levels of toxic pollutants of any creature, even though they live in remote locations away from major manufacturing and urban centres [1]. More than 200 different chemical compounds can be found in any polar bear impacting their immune system and even cognitive skills [2].

But how did those chemicals end up there in the first place?

Polar bears may live in the Arctic, far away from most sources of pollution, but due to the global distillation effect, pollutants find their way even to the most remote regions of the world such as the Arctic, and enter local ecosystems in different ways. This does not only affect polar bear populations but also other species living in the Arctic including local indigenous populations.

How does the global distillation effect happen?

The global distillation effect is the process by which certain substances are transported from warmer to colder regions. This happens when chemicals and other pollutants that are released into the environment evaporate and in the form of vapour are then transported in colder areas where the vapour condenses and the pollutants are deposited as toxic rain or snow.

Global distillation explains why relatively high concentrations of pollutants have been found in the Arctic and in the bodies of animals and people who live there, even though most of the chemicals have not been used in the region.

The process does not always involve a direct flow of pollutants from warmer regions to colder ones; pollutants may condense and then become vapour again in different places depending on climate conditions. This is why the phenomenon is also called the “grasshopper effect”.

It is also important to keep in mind that the global distillation effect is not a one-way process: atmospheric currents can carry chemicals in both directions, towards both colder and warmer regions of the planet.

But there is a net transfer of chemicals to colder regions such as the Arctic and mountain tops, because colder climates favour the deposition of pollutants in the environment. In addition, pollutants are more likely to degrade and be eliminated from our environment in warmer regions [3].

Persistant organic pollutants are to blame

Whether a substance can undergo this process primarily depends on its unique physical and chemical characteristics. Research has shown that pollutants most likely to behave in this way fall into the category of chemicals called persistent organic pollutants.

Persistent organic pollutants, or POPs, are chemicals that can stay in the environment for long periods of time, can interact with soil, water and air, can accumulate in living organisms including humans and are toxic to both humans and wildlife [4]. POPs are regulated under the UN Stockholm Convention which has regulated pesticides such as DDT and chemicals such as PCBs.

The health impacts of persistent organic pollutants

The global distillation effect is therefore particularly concerning as the properties of the chemicals that are transported through this process can cause severe health problems to the ecosystem, from smaller organisms like benthic organisms to top predators like polar bears and humans.

POPs can cause a variety of diseases ranging from cancer and damage to the central and peripheral nervous systems to reproductive disorders and disruption of the immune system that can have a transgenerational effect, affecting both parent and offspring [4].



[1] http://goo.gl/onjHcp
[2] http://goo.gl/NUWz1s
[3] http://www.ourplanet.com/imgversn/86/wania.html
[4] http://chm.pops.int/TheConvention/ThePOPs/tabid/673/Default.aspx