Large amounts of toxic mercury are now accumulating in the Arctic tundra, as a result of coal burning, mining and industrial processes around the world.
The airborne mercury is deposited in soil and trapped in compacted ice, but with increasing global warming melting these areas, scientists are concerned that it is all ending up in the ocean.
This harmful pollutant then threatens the health and wellbeing of people and wildlife and waterways further afield.
Scientists have long reported high levels of mercury pollution in the Arctic, now a team from Massachusetts Lowell have spent two years investigating how gaseous mercury gets to such a remote region.
In the past, scientists estimated tundra runoff was responsible for around 50 to 85 tons of the heavy metal in the Arctic waters, but Professor Daniel Obrist explained it is actually more like two thirds of the mercury present.
Obrist said: “Mercury has high exposure levels in northern wildlife, such as beluga whales, polar bears, seals, fish, eagles and other birds. It also affects human populations, particularly the Inuit, who rely on traditional hunting and fishing.”
But the team were uncertain as to the source of the mercury found in the soil.
Their observations revealed that 70% of the mercury that ends up in the soil is caused by it being present in the atmosphere; lofted to the Arctic from around the world then absorbed by plants in a process similar to how they take up carbon dioxide.
In contrast, airborne mercury that is deposited on the ground through rain or snow - a more frequent focus of other studies - accounts for just 2% of the mercury deposits in the region.
Mercury is toxic to human health, posing a particular threat to the development of the child in utero and early in life. It exists in various forms, which all have different toxic effects, including on the nervous, digestive and immune systems, and on lungs, kidneys, skin and eyes.
According to the World Health Organisation, among selected subsistence fishing populations, between 1.5 people in every 1000 showed cognitive impacts caused by the consumption of fish containing mercury.
As once it is in the environment, elemental mercury is naturally transformed into methylmercury that bioaccumulates in fish and shellfish.