This story was originally published by The Guardian and appears here as part of the Climate Desk collaboration.

Pollution at Australia’s largest Antarctic research station, Casey, has exceeded international guidelines for close to 20 years, new research shows.

Analyzing marine sediment levels around Casey station between 1997 and 2015, Australian and Canadian scientists found that levels of multiple contaminants exceeded international quality guidelines.

These included arsenic, toxic metals such as lead and cadmium, and persistent organic pollutants such as polychlorinated biphenyls — highly carcinogenic compounds that have been banned from global production since 2001 but last for long periods in the environment.

Casey is the largest of three research stations managed by the Australian Antarctic Division and one of 112 research stations on the southern continent.

“Antarctic research stations such as Casey are likely to pose a moderate level of long-term ecological risk to local marine ecosystems through marine pollution,” the research found.

The study showed “there can be quite significant impacts from our stations locally,” said Jonathan Stark, the lead author and a principal research scientist at the Australian Antarctic Division.

The sediment quality guidelines had been developed for temperate and tropical ecosystems, Stark said. “We don’t really have equivalent guidelines for Antarctica, so in a way, it’s a best guess.”

Environmental management practices on Antarctica have improved since the protocol on environmental protection to the Antarctic treaty came into force in 1998. But historical practices have “resulted in a legacy of environmental contamination,” the research noted.

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The construction of Casey started in 1964 as a replacement for Wilkes station, which was abandoned in 1969 and contains contaminated sites and legacy waste.

Until 1986, solid waste from Casey was disposed in a waste site at the foreshore of Brown Bay. “We wouldn’t dream of doing that sort of thing these days,” Stark said. “But in the 1960s and 1970s, that was the accepted practice, to dump all your waste in a convenient shoreside location and when that got too big, to bulldoze it into the sea.”

Samples from the site adjacent to the former waste disposal dump had the highest contamination levels of all sediments tested.

There was a large peak in contaminant levels there in the late 1990s, which “declined quite dramatically” after a large cleanup operation in 2003-04 that removed 1,800 cubic metres of waste material, Stark said. “But since then, there’s been a slight, gradual increase.”

Prof. Susan Bengtson Nash of Griffith University, who was not involved in the research, said sources of legacy chemicals included fuel spills and leaching of metals from abandoned equipment.

But scientists were still “bringing consumer products that will leach chemicals into the environment,” she added.

“Fire is a big threat… Should you lose shelter in Antarctica, it’s a big deal. We have used perfluorinated firefighting agents and water-repelling agents and certainly also brominated flame retardants — some of these [persistent organic pollutant] chemicals are covered in [the] paper.

“Few Antarctic programs have prioritized monitoring — yet that is the golden goose that will keep on laying for us if we can get standardized long-term monitoring in place.”

Guardian Australia revealed recently that the “cleaner Antarctica program,” remediation work that would provide a “cleanup strategy for Australia’s contaminated sites,” would be restricted in the 2023-24 season.

Internal documents seen by Guardian Australia have suggested the project will not proceed at Mawson station due to budget constraints at the Australian Antarctic Division.

“There is some remediation work happening at Casey, [which is] part of a longer-term program, and that is still going ahead,” Stark said.

There are also concerns about the environmental impacts of booming Antarctic tourism. A record 105,331 people visited the continent over the 2022-23 season.

Black carbon from ship exhaust is accelerating snowmelt on Antarctica, research has shown, while scientists have expressed concerns about damage to local flora and the potential introduction of foreign species.

The study was published in the journal Plos One.