The Russians have always been cavalier about pollution and, as much as it may be hard to believe for some Americans, even more cavalier than here in the US. Not the Russian people of course but their political systems whether Communist or post-Communist. Corruption, lack of accountability and so on. Then obviously Siberia is very large and very sparsely population and interested parties might think: big mess? No big deal.
Sort of like the intermontane west generally in the US. Wasteland, right?