Washington’s Blog 
December 22, 2013
There was no background radioactive cesium  before above-ground nuclear testing and nuclear accidents started.
Wikipedia provides some details on the distribution of cesium-137 due to human activities:
Small amounts of caesium-134 and caesium-137 were released into the environment during nearly all nuclear weapon tests and some nuclear accidents, most notably the Chernobyl disaster.
Caesium-137 is unique in that it is totally anthropogenic. Unlike most other radioisotopes, caesium-137 is not produced from its non-radioactive isotope, but from uranium. It did not occur in nature before nuclear weapons testing began. By observing the characteristic gamma rays emitted by this isotope, it is possible to determine whether the contents of a given sealed container were made before or after the advent of atomic bomb explosions. This procedure has been used by researchers to check the authenticity of certain rare wines, most notably the purported “Jefferson bottles”.
As the EPA notes :
Cesium-133 is the only naturally occurring isotope and is non-radioactive; all other isotopes, including cesium-137, are produced by human activity.
What people call “background” radiation is really the amount of radiation deposited into the environment within the last 100 years from nuclear tests and nuclear accidents (and naturally-occurring substances, such as radon).
2,053 nuclear tests occurred between 1945 and 1998:
But the amount of radiation pumped out by Fukushima dwarfs the amount released by the nuclear tests.
As nuclear engineer and former nuclear executive Arnie Gundersen notes, the wave of radioactive cesium from Fukushima which is going to hit the West Coast of North America  will be 10 times greater than from the nuclear tests (starting at 55:00).
This graphic from Woods Hole in Massachusetts – one of the world’s top  ocean science institutions – shows how much more cesium was dumped into the sea off Japan from Fukushima as compared to nuclear testing and Chernobyl :
(And Fukushima radiation has arrived on the West Coast years earlier than predicted .)
The Canadian government has confirmed  in October that Fukushima radiation will exceed “levels higherthan maximum fallout” from the nuclear tests.
The party line from the Japanese, Canadian and American governments are that these are safe levels of radiation. Given that those countries have tried to ban investigative journalism  and have tried to cover up the scope of the Fukushima disaster , people may want to investigate for ourselves .
For example, Gundersen notes that the U.S. government flew helicopters with special radiation testing equipment 90 days after the Fukushima meltdown happened. The government said it was just doing a routine “background radiation” check, but that it was really measuring the amount of “hot particles” in the Seattle area  (starting at 27:00). Hot particles are inhaled and become very dangerous “internal emitters” . The government then covered up the results on the basis of “national security”.
As the Washington Department of Health noted  at the time:
A helicopter flying over some urban areas of King and Pierce counties will gather radiological readings July 11-28, 2011. [Seattle is in King County.] The U.S. Department of Energy’s Remote Sensing Laboratory Aerial Measurement System will collect baseline levels of radioactive materials.
Some of the data may be withheld for national security purposes.
Similarly, the Department of Homeland Security and National Nuclear Security Administration sent low-flying helicopters over the San Francisco Bay Area in 2012 to test for radiation . But they have not released the results.
Indeed, residents of Seattle breathed in 5 hot particles each day in April of 2011 … a full 50% of what Tokyo residents were breathing at the time:
(the video is from June 2011.)
After all, the reactors at Fukushima literally exploded … and ejected cladding from the reactors and fuel particles . And see this .
Gundersen says that geiger counters don’t measure hot particles. Unless the government or nuclear scientists measure and share their data, we are in the dark as to what’s really going on.