Dhaka, Aug. 28 -- Rising tourist numbers and expanding research projects are contributing to pollution in Antarctica, posing new threats to one of Earth's most pristine environments already affected by climate change, scientists said Wednesday.

In areas of human activity, fine particles containing heavy metals are now 10 times higher than 40 years ago, according to an international research team. Over the past two decades, annual tourist visits have jumped from 20,000 to 120,000, the International Association of Antarctica Tour Operators reported.

"The growing human presence raises concerns about pollutants from fossil fuels used by ships, aircraft, vehicles, and infrastructure," the study published in Nature Sustainability noted. Ships...