With all the news about “radiation exposure” in the USA from the Japanese nuclear plant, I thought it might be worth having a thread that points out just how much natural radiation exposure there is in the USA already.
For the events in Japan to matter in the USA, it has a “high hurdle” to get over. For example, this map is the distribution of Uranium in soils in the USA. If you are in a dry place, like where most of it is located, well, Uranium will be “blowing in the wind”. No, not a lot. Then again, the radioactives reaching the USA from Japan are at the lower bound of measurable as well…
(Note: I’ve temporarily swapped the image from http://energy.cr.usgs.gov/images/other/uranium/uranium_concentrations.gif to the very similar map from http://www.radonattahoe.com/images/usa-uranium-map.gif as the USGS site is being grumpy)
This map is a general radioactivity map. It was made by flying over the country and measuring the radiation at the aircraft. As breakdown of the U eventually leads to Radon, it’s a rough guide to the total Radon risk of an area. Over 20,000 deaths / year are attributed to Radon in the USA.
(Note: I’ve replaced the image from http://energy.cr.usgs.gov/radon/georadon/page18.gif to the same map from the WaybackMachine as the USGS site is being grumpy. This is a high res image, so you can click on it to get the description of the rock types in each area. FWIW, I note that the “beige” empty blocks seem to be right over “interesting places”… “how to use ‘negative space’ to see where secrets are hidden, a primer.” ;-) )
There are, of course, other souces of radiation exposure in the environment. From cosmic rays to sunshine to X-rays from the old color TV, we are bathed in the stuff all day long. So unless you put a number on it, to say “there has been a radiation leak” or “we have measured radiation in California” is rather like saying “carbon dioxide detected in the air”. It’s always there, all that changes is how much. And it must rise spectacularly before it is really a health issue.
Take, for example, Thorium:
which also has some nice maps of Nevada and California showing a load of risk of exposure…
And, of course, it’s nice to know your gama ray exposure too (same source):
They also have a map of potassium locations. (Yes, it matters, as potassium has a significant level of a radioactive isotope. Potassium-40.) but putting it here would be a bit of overkill… you can click the link if you want to see it…
McGraw-Hill Science & Technology Dictionary:
(nuclear physics) A radioactive isotope of potassium having a mass number of 40, a half-life of approximately 1.31 × 109 years, and an atomic abundance of 0.000122 gram per gram of potassium.
Potassium (K) has 24 known isotopes. Three isotopes occur naturally: 39K (93.3%), 40K (0.012%) and 41K (6.7%). The standard atomic mass is 39.0983(1) u. Naturally occurring 40K decays to stable 40Ar (11.2% of decays) by electron capture or positron emission (giving it the longest known positron-emitter nuclide half-life). Alternately and most of the time (88.8%) it decays to stable 40Ca by beta decay; 40K has a half-life of 1.250×109 years.
40K occurs in natural potassium (and thus in some commercial salt substitutes) in sufficient quantity that large bags of those substitutes can be used as a radioactive source for classroom demonstrations. In healthy animals and people, 40K represents the largest source of radioactivity, greater even than 14C. In a human body of 70 kg mass, about 4,400 nuclei of 40K decay per second.
So since YOU are radioactive due to your potassium content, it seemed a bit overkill to put in a potassium soil map… then again, if you are on a ‘low sodium’ diet and eating “no salt” that is Potassium Chloride, well, you might just upset that classroom demonstration… ;-)
If you are going to complain that I didn’t put a size on that potassium risk and it really is small… well, that’s sort of the whole point I’m making. Without a number on it, “Radiation detected in USA” is roughly equivalent to “living beings detected in USA”…