Natural Radiation in the Rocks, Soils, and Groundwater of Southern Florida with a Discussion on Potential Health Impacts

Southern Florida is underlain by rocks and sediments that naturally contain radioactive isotopes. The primary origin of the radioactive isotopes is Miocene-aged phosphate deposits that can be enriched in uranium-238 and its daughter isotopes. Nodular phosphate containing radionuclides from the Miocene has been reworked into younger formations and is ubiquitous in southern Florida. When the nodular phosphate is exposed to groundwater with geochemical conditions favorable for its dissolution, uranium, radium, and radon may be released into the groundwater system. Uranium concentrations have been measured above the 30 µg/L drinking water standard at only one location in Lee County. Radium226/228 exceedances of the drinking water standard have been documented in numerous wells in Sarasota County. Indoor radon activities have exceeded the 4 piC/L guideline in five southern Florida counties. The exceedance of radioactivity standards in drinking water does not occur in municipal drinking water supplies, but rather only in some domestic self-supply wells. Health risks for exposure to radiation from domestic self-supply wells could be mitigated by testing of well water and, if necessary, switching to the use of a different aquifer or treatment process. While the risk of exposure to radon in indoor air in southern Florida is generally low, some areas are enriched in soil radon that migrates into structures, which could be addressed by improved ventilation

A novel insect defensin mediates the inducible antibacterial activity in larvae of the dragonfly Aeschna cyanea (Paleoptera, Odonata)

The injection of low doses of bacteria into the aquatic larvae of dragonflies (Aeschna cyanea, Odonata, Paleoptera) induces the appearance in their hemolymph of a potent antibacterial activity. We have isolated a 38-residue peptide from this hemolymph which is strongly active against Gram-positive bacteria and also shows activity against one of the Gram-negative bacteria which was tested. The peptide is a novel member of the insect defensin family of inducible antibacterial peptides, which had so far only been reported from the higher insect orders believed to have evolved 100 million years after the Paleoptera. Aeschna defensin is more potent than defensin from the dipteran Phormia, from which its structure differs in several interesting aspects, which are discussed in the pape