anything that is done in extremely large scale can be dangerous for the environment where we live.

According to the information from the internet, the extraction and refining process of 157 tons of U 308 for nuclear power plants, leaves 155,000 tons of tailing that still contain 60 to 80 percent of the radioactive uranium. In other words the tailings are radioactive, but not as highly radioactive as the fuel rods that go into the reactors or the very highly radioactive material of the spent fuel rods.
Australia alone exports 10,000 tons of refined uranium per year.
There are about 440 or more nuclear power reactors around the world that produce electricity, plus there are many nuclear reactors that are not classified as generating electrical power, but they, never the less, use nuclear material, which means that they are generating alpha beta and gamma radiation.

Since all these operations happen in the atmosphere and the radiation is spread into the atmosphere, it is no wonder that the background radiation is increasing, and it will not surprise me if the air molecules would leave the atmosphere never to come back again.

Good info on nuclear reactors around the world.

http://en.wikipedia.org/wiki/List_of_nuclear_reactors

http://www.euronuclear.org/info/encyclopedia/n/nuclear-power-plant-world-wide.htm

Effects of iron dust in the ocean.

http://t.news.ca.msn.com/canada/haida-gwaii-ocean-iron-dump-investigation-to-proceed-1