Parts of the sea floor near Australia's Casey research station are as polluted as the harbour in Rio de Janeiro, Brazil, according to a study published in PLOS One in August1.

The contamination is likely to be widespread across Antarctica's older research stations, says study co-author Jonathan Stark, a marine ecologist at the Australian Antarctic Division in Hobart.

Research stations started to get serious about cleaning up their act in 1991.

Much of the damage had already been done - roughly two-thirds of Antarctic research stations were built before 1991.

There are already more than 100 research stations or national facilities, and most of the buildings are located in ice-free areas, where they jostle with wildlife for a foothold on the most viable land.

"The stations have quite a large footprint for the number of people that are there," says Shaun Brooks, a conservation scientist at the Commonwealth Scientific and Industrial Research Organisation in Hobart who co-authored the study.

Each nation is responsible for its own environmental monitoring around research stations, and practices vary, says Brooks.