Within days of the start of the Japanese nuclear emergency, the NRC made statements that no unsafe levels of radiation would impact the U.S. Other federal agencies also concluded the radiation reaching the U.S. from the damaged Japanese reactors would not be at levels of public health concern.
What does that actually mean? Radiation released from Japan had to travel a very far distance to arrive in the U.S.—while all along the way being diluted by wind, rain, and radioactive decay. Even the two closest states – Hawaii and Alaska – are still a distance away from the source of radiation.
We expected to detect trace amounts of radiation from the Japanese reactors in the U.S.—modern radiation detection equipment is very sensitive and able to detect very small amounts of radioactivity. However, just because something is detected doesn’t mean it’s hazardous.
Scientists estimate that we receive a dose of about 620 millirem each year from natural sources – like radon – and human sources – such as x-rays. There are NO known health impacts from this typical annual dose. To put this into context, even people living in places where the background radiation is much higher – such as Denver, Colo., where the rate of background radiation is above 1,000 mrem a year – don’t experience adverse health effects.
The U.S. EPA and Department of Energy concluded from their environmental monitoring of the Japanese radioactivity in the U.S. that peak concentrations of particles and gas detected in California or Washington State were 100,000 times less than the dose rate from background sources.
Radiation experts make the conservative assumption, as part of an overall radiation protection philosophy, that any amount of radiation may increase the risk for cancer and damage to DNA, and that the risk increases as the radiation exposure increases. And we do know that high doses of radiation may cause cancer. But there are no studies that clearly show cancer being caused by exposure to low doses of radiation – considered to be below about 10,000 mrem.
The bottom line? The radiation coming from the Japanese emergency can be detected by sensitive instruments, but that does not mean it’s a public health concern. The levels of radiation detected in the U.S. are well below radiation standards and only a small fraction of the average background of radiation we are exposed to in everyday life.
For additional information on radiation protection and health effects visit the NRC website at http://www.nrc.gov/about-nrc/radiation.html.
Sara Mroz Emergency Preparedness Specialist
U.S. NRC Blog 