Grasshopper effect

Global distillation or the grasshopper effect is the geochemical process by which certain chemicals, most notably persistent organic pollutants (POPs), are transported from warmer to colder regions of the Earth, particularly the Poles and mountain tops. Global distillation explains why relatively high concentrations of POPs have been found in the Arctic environment and in the bodies of animals and people who live there, even though most of the chemicals have not been used in the region in appreciable amounts.^[1]

 –Wikipedia