From NEI’s Japan Earthquake launch page:
UPDATE AS OF 2:30 P.M. EDT, MARCH 22:
According to the South Coast Air Quality Management District, which manages three radiation measurement areas for the U.S. Environmental Protection Agency, radiation levels in the United States have not exceeded natural background levels since before the earthquake and tsunami in Japan. These levels are thousands of times below any level that would result in public health impacts, the agency said.
Fukushima Daiichi Update
Power cables have been attached to all reactors at Japan's Fukushima Daiichi nuclear plant, but the power distribution network at reactors 1 and 2 must be repaired before off-site electricity can be restored.