Is it safe to go backcountry hiking in the Tundra's of northwestern Russia, e.g. the Kola peninsula, such as the Khibin mountains? There is some heavy industry around there; can one safely go around, camp, drink from the rivers etc. as one would do in Scandinavia or the Alps, or should this rather be avoided? What about other risks that one doesn't need to worry (much) about in western or northern Europe?
The Khibin mountains and the neighboring area are very popular places to visit in Russia, especially for hiking. There is one relatively big town there - Kirovsk, and you can start your trip from there.
It has some industry, but I haven't heard of it having any bad influence on the ecology. I have drunk water from Umbozero lake and Umba river and I'm still alive :)
You can go around and camp there with no restrictions, but I would not recommend camping near any settlement in Russia. If you still want to camp anywhere near a settlement, I recommend that you keep someone from your team watching the camp while others sleep.
I think the main risk there as in many places in Russia is the absence of good infrastructure for any self-traveler. Especially a foreigner. I repeat - this region is very popular for hiking in Russia, but I don't think there is a lot of information available in English about these places.