We will be breaking from our normal practice of commenting on economic issues to address something that is bigger and more important today. That is growing panic over radiation from Japan. Trace levels of radioisotopes have been detected in water and food near the Fukushima plant site. In one case, it exeeded the legal limits so if you are in Japan, you should take some precautions - and especially so in Northern Japan. The governments involved have no one to blame but themselves since they have destroyed their own credibility and many people won't believe them even when they tell the truth. As of today, the truth is this:
There is no threat of radiation in North America and with a couple tiny of exceptions, there is no measurable increase above background levels.
One of the sources I see quoted often by the panic-mongers is Radnet - a data gathering program of the EPA. But most people have no idea what the data means and there are many problems with the data itself. The most serious problems with the Radnet data are as follows:
1) Collection is by volunteers and by agencies that often specialize in other things. For instance, most of the California data is gathered by regiona agencies like the Bay Area Air Quality Management District. BAAQMD certainly knows what it is doing with regard to routine air pollution issues but they are hardly specialists in radiation exposure.
2) Inconsistency of the data due to the varied and non-specialist nature of the data gatherers. The data should be comparable over time at any given location but may not be comparable between different locations gathered with varying practices.
3) Timeliness is weak. The typical collection method is to use air filters to gather particulate matter and then apply a radiation detector after a 5-hour field deployment period.
4) The data is difficult to interpret. Because of we do not know with certainty the exact equipment used to measure beta and gamma exposure at a given location, we cannot be certain what conversion factor should be used for CPM to millirems or milliseiverts.
Also, the gamma exposure is divided into energy ranges. Due to the normal slope, we can feel confident that the lower ranges are lower-energy (longer wavelength) gamma rays. This is a typical pattern for background radiation. In fact, many of the less energetic "gamma rays" detected by a typical geiger counter are not technically gamma rays at all. Quite often the detection threshold for a geiger is 20 kEv or less - at a wavelength more associated with X-rays so the lower bands of gamma reported by Radnet are actually mostly X-rays. Even so, I cannot locate a chart showing the frequency or wavelength with which each gamma energy range is associated.
Nevertheless, Radnet can be a valuable tool to measure changes over time in a single location. If better data were not available, I would be forced to use it for other purposes as well. Fortunately, we have something run by people who are focused on radiation and the only real weakness is that the network is only regional.
The Department of Energy and the Desert Research Institute maintain a network of radiation monitoring stations across Nevada and western Utah known as the Community Environmental Monitoring program. The explicit purpose of CEMP is to monitor sites downwind of the underground nuclear test site in Nevada. Thus, CEMP is "focused like a laser" on radiation. Most stations update every 10 minutes and the rest do so hourly.
The data is comparable between stations and presented in an easily analyzed format. Exposure dosages are measured in microrems per hour (uR/hr) and measured constantly. The only downside is that only gamma radiation is measured, not beta but this is not a severe drawback in my opinion. There is even a tab on the display for each monitoring station that allows you to display the data from the past week in graphical format.
I checked a sampling of the monitoring stations and all of them showed gamma radiation steady as a rock for the past week. There is NO EVIDENCE of any increase in ambient radiation in Nevada or Utah at least.
The website can be found here:
I want everyone to be safe and informed. Don't panic out of ignornace. If the data call for you to take precautions you should absolutely do so but rationally and based on facts. Good luck.