In the weeks and months after the Fukushima Disaster we were repeatedly told not to worry about possible radiation being carried over the Pacific and around the world. The first arguments were that containment was never breached. Next it was there wasn't enough leakage to worry about. Then it was the type of radiation that we could be exposed to would be long degraded by the time it reached us.
Radioactive isotopes I-131, Cs-134, or Cs-137, products of uranium fission, were measured at approximately 20 percent of 167 sampled National Atmospheric Deposition Program monitoring sites in North America (primarily in the contiguous United States and Alaska) after the Fukushima Dai-Ichi Nuclear Power Plant incident on March 12, 2011. Samples from the National Atmospheric Deposition Program were analyzed for the period of March 8–April 5, 2011. Calculated 1- or 2-week radionuclide deposition fluxes at 35 sites from Alaska to Vermont ranged from 0.47 to 5,100 Becquerels per square meter during the sampling period of March 15–April 5, 2011. No fission-product isotopes were measured in National Atmospheric Deposition Program samples obtained during March 8–15, 2011, prior to the arrival of contaminated air in North America.Read the full PDF here.
Looking at the maps starting on page 19 of the PDF shows Portland, Oregon received large quantities of radioactive pollution from the Fukushima Disaster.
Filtered particulate samples were analyzed prior to analysis of the water samples. No fission products were detected on individual filters or on composited filters. Therefore, the transported fission products were either on particles smaller than the 0.45-μm pore size of the filter, or they were associated with soluble aerosol salts present in the collected samples.What could be the result of this pollution?
I-131 was quantified and adjusted for decay to the time of sample collection for five whole-water wet-deposition samples from California, Colorado, and Washington. The activities of the quantified I-131 ranged from 29.6 to 1,090 pCi/L, and calculated deposition values ranged from 211 to 5,100 Bq/m2. Several weeks transpired between sample collection and analysis of the I-131 in the water samples, which were prioritized for analysis from west (high priority) to east (low priority). Therefore, I-131 activities likely decayed in most of the samples before they could be measured.
Cs-134 activities were quantified for 23 samples from Alaska, California, Colorado, Illinois, Minnesota, Missouri, New York, South Dakota, Tennessee, Vermont, Washington, and Wyoming. The Cs-134 ranged from 0.40 to 55 pCi/L, and deposition values ranged from 0.47 to 180 Bq/m2. Cs-134 values reported for all but one site (CO90 near Nederland, Colo.) have substantial error because they were manually estimated from the gamma-ray spectra. Cs-137 activities were quantified for 33 samples from Alaska, California, Colorado, Illinois, Maryland, Michigan, Minnessota, Missouri, Montana, New York, Oregon, South Dakota, Tennessee, Virginia, Vermont, Washington, Wisconsin, and Wyoming. These samples ranged from 0.70 pCi/L to 39 pCi/L, and calculated deposition values ranged from 0.78 to 240 Bq/m2. Cs-134 and Cs-137 activities were not adjusted for decay to date of sample collection because radioactive decay during the 2-month period between collection and analysis was negligible for these isotopes.