time in history descended to the Arctic seabed beneath the North Pole and placed there a Russian flag made of rust-proof titanium alloy. The flag-placing during Arktika 2007 generated commentary on and concern for a race for control of the Arctic's vast hydrocarbon resources. Foreign ministers and other officials representing Canada, the Kingdom of Denmark, Norway, Russia, and the United States met in Ilulissat, Greenland on 28 May 2008 at the Arctic Ocean Conference and announced the Ilulissat Declaration, blocking any "new comprehensive international legal regime to govern the Arctic Ocean," and pledging "the orderly settlement of any possible overlapping claims." As of 2012, the Kingdom of Denmark is claiming the continental shelf based on the Lomonosov Ridge between Greenland and over the North Pole to the northern limit of the Russian EEZ. The Russian Federation is also claiming a large swath of seabed along the Lomonosov Ridge but, unlike Denmark, confined its claim to its side of the Arctic. In August 2015, Russia made a supplementary submission for the expansion of the external borders of its continental shelf in the Arctic Ocean, asserting that the eastern part of the Lomonosov Ridge and the Mendeleyev Ridge are an extension of the Eurasian continent. In August 2016, the UN Commission on the Limits of the Continental Shelf began to consider Russia's submission. Canada claims the Northwest Passage as part of its internal waters belonging to Canada, while the United States and most maritime nations regards it as an international strait, which means that foreign vessels have right of transit passage. Exploration Since 1937, the larger portion of the Asian-side Arctic region has been extensively explored by Soviet and Russian crewed drifting ice stations. Between 1937 and 1991, 88 international polar crews established and occupied scientific settlements on the drift ice and were carried thousands of kilometres by the ice flow. Pollution The Arctic is comparatively clean, although there are certain ecologically difficult localized pollution problems that present a serious threat to people's health living around these pollution sources. Due to the prevailing worldwide sea and air currents, the Arctic area is the fallout region for long-range transport pollutants, and in some places the concentrations exceed the levels of densely populated urban areas. An example of this is the phenomenon of Arctic haze, which is commonly blamed on long-range pollutants. Another example is with the bioaccumulation of PCB's (polychlorinated biphenyls) in Arctic