The Arctic Ocean has long been considered a habitat virtually untouched by humans. But new measurements show that a large portion of the lead released into circulation by leaded gasoline and other anthropogenic sources also ends up in the Arctic Ocean from the North Atlantic. In some cases there is already so much lead in the seabed that organisms could be harmed. In the future, the toxic heavy metal could dissolve from the sediments and endanger other Arctic marine zones, the researchers warn.
Lead (Pb) is a toxic heavy metal that can accumulate in habitats and living things. If it enters the human body through the food chain, it can damage the nervous system and cause cancer. The heavy metal gets into the atmosphere and from there into nature through man-made processes, among other things. The Phoenicians and Romans already processed lead-containing ores and caused this form of environmental pollution. At the beginning of industrialization, thousands of tons of lead were emitted every year through the smelting of metals. In the 20th century, it even reached hundreds of thousands of tons annually, mainly due to the burning of leaded gasoline by cars in North America and Europe.
This lead, now banned in gasoline, was then blown away by the wind and deposited in even the most remote regions of the world. However, most of it ended up in the nearby North Atlantic and its sediments. But to what extent was the heavy metal transported from there by ocean currents to neighboring ocean basins such as the supposedly untouched Arctic Ocean?
Lead entry through Arctic-Atlantic straits
Researchers led by Stephan Krisch from the TU Braunschweig have now investigated this. To do this, they undertook three expeditions through the Arctic-Atlantic straits: the Fram Strait, the Barents Sea opening and the Parry Channel. There they took water and sediment samples and analyzed them for their lead content. From this they then reconstructed how much lead-containing water flows from the Atlantic into the Arctic. They also used isotope analyzes to determine from which sources the lead came. “This is possible because global production of tetraethyl lead, used in leaded gasoline, was based on only a few lead ores with unique geological features,” explains co-author Arianna Olivelli from Imperial College London.
The evaluation showed that a surprising amount of lead has accumulated and is still accumulating in the Arctic Ocean. About half of it currently comes from natural sources such as Arctic rivers. “This natural input occurs, for example, through the weathering of rocks or minerals,” explains Krisch. However, the lead in the Arctic Ocean is still largely due to man-made lead emissions: “This lead input can keep up with the natural input of lead for decades after the end of the use of leaded gasoline in Europe and North America,” says Krisch.
According to the data, lead input was highest at the end of the 1980s – around five times higher than in 2015. With the gradual abolition of leaded gasoline, emissions and the further transport of the heavy metal into the Arctic Ocean also fell. In total, around 75,000 tons of lead from anthropogenic sources such as gasoline from the North Atlantic entered the Arctic Ocean between 1970 and 2015, as the team reconstructed. Compared to the North Atlantic, where hundreds of thousands of tons of lead are stored in the sediments, this is small. “However, this lead entry explains the large-scale contamination of Arctic deep-sea sediments with lead,” says Krisch.
How is climate change changing lead distribution?
The new measurements and previous analyzes show that in some places the seabed in the Arctic already has such high lead concentrations that it could be harmful to bottom-dwelling organisms. Marine researchers also fear that toxic lead could dissolve from the sediments as a result of climate change and then endanger even more ocean inhabitants. “The rapid loss of sea ice and the increase in sediment erosion on the shelf may promote the renewed release of lead from Arctic sediments – with as yet unknown consequences for the lead content in seawater and in the marine biodiversity of the Arctic,” said Krisch. “We therefore hope that future expeditions will address the effects of climate change on the lead cycle in the Arctic.”
Source: Technical University of Braunschweig; Specialist article: Nature Communications, doi: 10.1038/s41467-025-67620-9