As more reactors fail, or if there's another disruption at Fukushima (say, an earthquake that causes a containment vessel failure), more monitoring will be needed. Up to now, probably not a big deal.

Not sure if this has been mentioned before, but the Skapa Flow, north of Scotland, was the site of a mass sinking of WW1 German ships. Most of them were salvaged, but there's still a business in recovering steel bits from them for the purpose of constructing scientific instruments where steel is required that does not have radioactivity from the atomic bomb era. All modern steel (and everything else) is radioactive.

6000 atoms doesn't sound like many to me...