Mark, you might want as well to visit the radioactivity of the phosphates in fertilizers (source of radioactivity in bananas) we use on crops. Apparently, there are substantial areas of eastern farm lands that were used for tobacco production that are now over the "safe" radioactivity levels for food production - because of the NPK used on it over the years. "Some phosphate rock deposits are notable for their inclusion of significant quantities of radioactive uranium isotopes. This syndrome is noteworthy because radioactivity can be released into surface waters[10] in the process of application of the resultant phosphate fertilizer (e.g. in many tobacco farming operations in the southeast USA)." (
http://en.wikipedia.org/wiki/Phosphate)
Florida also has some problems with the radioactive tailings from rock phosphate fertilizer mining there. Once the largest producer of rock phosphates in the world, the US has started running out in the last decade. We're now importing about 15% of our US phosphate demand from - Morocco. We thought ME foreign oil dependence was problem - wait to we experience foreign fertilizer (food) and biofuel dependence. We're now importing over half (54%) of our food fertilizers. (
http://www.ers.usda.gov/Data/FertilizerTrade/summary.htm)
