Japan is 5,000 miles away and experts said they are confident that if radioactive isotopes were to reach the U.S., the amount of radiation will be well within safe limits.
There are radiation monitors throughout the Southland. Fire departments have portable units and there are more elaborate models to measure radiation in near real-time. That means if levels go up, you will know about it.
"The good news is that these instruments will pick up even very low levels," said Phillip Fine from the Air Quality Management District.
The U.S. Environmental Protection Agency and the state have been monitoring radiation for 60 years. A machine that pumps in what you breathe every day is the latest generation. Not only are the particles analyzed, the monitor automatically transmits data to the EPA every hour.
"Right now the levels are the same as the last four or five years we have been running this monitor," said Fine. "There has been no increase yet."
Health officials are skeptical of computer models that try to predict plume movement. They said radiation does not have a front like a cloud and disperses faster.
State Public Health Director Dr. Howard Backer said to expect radiation amounts that are barely detectable.
"The winds in Japan have been shifting onshore and offshore," said Backer. "Some of the radiation will be blowing west, but almost all of that will get washed out of the atmosphere by the storms that are there and dissipate over the distance of 5,000 miles."
Chuck Pickering, the radiation safety monitor at City of Hope Medical Center, measured a tripod that just spent days in Tokyo. He said it would take around 3,000 millisieverts to pose a hazard. The level in the lab even with the exposed tripod is 2 to 3 millisieverts, which is typical of what we breathe every day.
"We expect this cloud might expose people to about the same amount of background," said Pickering. "It will be in the order of single digit millisieverts at worst."
For doubters who still seek anti-radiation drugs, he said to take a lesson from the past.
"We didn't experience any health effects at all during the Chernobyl incident with clouds passing over our area," said Pickering. "We don't think this will be any worse than that."
State officials said even in a worst case scenario, there is nothing to indicate that there will be a radioactive cloud that will arrive Friday or anytime soon.