Stock tip: invest in adult diaper companies, what with the soiling of undergarments going on about radiation levels in the US.

I’ve run across a number of stories about the worries and the run on iodine tablets, and then saw the California radiation monitoring map which led me to the EPA site. They give radiation levels for select cities, but don’t tell you what the expected background levels are, so all you have is the assurance that the detected levels are small. However, the EPA has set up a section dedicated to the Japan accident, which includes a map with the most recent data for all of their monitoring sites. I eventually found how to get historical data — you click on “Query View” over in the left column — and looked to see what I could find.

I chose Eureka, CA because it’s on the West Coast and I was excited to have found the database, and the beta count rate because that would be indicative of having fallout reach the US; many fission products are beta-emitters. (The gamma data is divided into energy bins, and would have taken longer to analyze.)

Here’s what the radiation levels look like, starting with March 10, up through a half-day’s worth of data on the 25th.

The earthquake happened in Japan on the 11th at 0542 UTC. You might think the first spike, on the 11th, might be caused by the quake/tsunami, but the cooling problems didn’t happen until about 8 hours had elapsed and it would take several days for any fallout to reach California. If you really think that either peak is significant, all you have to do is go into the database and look at a larger data set.

This graph goes back to early February. The two peaks shown on the first graph are near points 750 and 1000. We can see that the radiation levels are showing no unusual behavior.

Because the EPA has labeled levels coming from specific isotopes I have to assume that’s by looking at the spectrum, and they give numbers that are much less than a picoCurie per cubic meter. One Curie is 3.7 x 10^10 decays per second (based on the activity of a gram of Radium-226), which means that a picoCurie is about 2 decays per minute. The EPA isn’t clear that the numbers it gives for gross beta counts are for a cubic meter or a larger volume, but I think it has to be, because 0.0017 pCi (the Anaheim Cs-137 activity) is only about a quarter of a decay per hour, so I imagine they sample a much larger volume.

Vocabulary lesson: many MSM stories are confusing radiation and fallout/contamination. radiation (in this context) is the energetic particle emitted when something decays, e.g. a gamma or a beta. Fallout or contamination refers to the radioactive particles, such as particulate matter that was expelled from the reactor and contains radioactive particles. We aren’t worried about radiation reaching us from Japan, because that is diminished by distance. It would be like complaining that the lights of Tokyo are too bright and though I’m sure Sarah Palin can see them from her home, it’s simply not an issue for us. What matters is the amount of radioactive particles that might reach us, and decay when they are here. But we can’t see any effect on the radiation levels, because any increase is small compared to the background and fluctuations in the background.

To quote Hedley LaMarr, “Gentlemen, Please, Rest Your Sphincters!”