California Coastal Commission, STATE OF CALIFORNIA—NATURAL RESOURCES AGENCY(pdf), Apr. 30, 2014: Attached for your information is a report investigating the release of radioactivity materials during the disaster and the implications for residents of California. […]

Airborne Contamination in California

• Several massive pulses of radionuclides were released to the atmosphere from Fukushima between March 12 and 18, 2011 […] 134Cs and 137Cs persisted at trace levels […] in on-going air monitoring at Berkeley through the end of 2012.

Rainwater Contamination in California

• March 2011 was an unusually wet month in California (~200% of normal monthly precipitation in the Bay Area) due to several large storms which resulted in discrete wet deposition events on March 18-20 and 22-26. […] 134Cs and 137Cs were present, at low levels, after 70 days. However, it is worth noting that low levels of radioactive cesium were still detectable in rainwater during subsequent wet seasons in 2012 and 2013, reflecting the continued presence of Fukushima-derived cesium in the atmosphere. […]

Food Chain Contamination in California

• Fukushima-derived radionuclides transferred from the atmosphere to the land through rainout or dry deposition have the potential to contaminate soil and water supplies, and to enter the food chain. […] Sampling of soil and sediments from several California locations detected a clear pulse of 131I, 134Cs and 137Cs between April – June 2011, with only 137Cs remaining above the pre-accident background thereafter (through Nov 2012). Plant and food samples collected in the Bay Area in April and May 2011 contained detectable concentrations of Fukushima-derived 131I, 134Cs, and 137Cs, indicating that low-level contamination of the water and soil had worked its way into local ecosystems.

Public Health Impacts

• Fukushima disaster presented (and continues to present) a low risk to public health relative to other concerns. However, it is worth reiterating that the health implications of exposure to low levels of radiation remain incompletely understood, and that the incremental impacts of the radiation released at Fukushima may be very difficult to separate from those of other radiation sources and the many other causes of disease.

See also: Fukushima fallout in N. America at 400,000,000,000,000 Bq of Cesium-137 — Study: Hazardous on a ‘continental scale’ — CBS: Inaccurate internet reports stoked fear radiation had somehow come California’s way (VIDEO)