March 16, 2011 -- Despite U.S. consumers' growing awareness of iodide pills, Geiger counters and emergency kits in the wake of Japan's nuclear scare, most people here have little to worry about, experts say.
Radiation, they say, is all around us, even inside of us, and it's perfectly safe for the most part.
To illustrate the point, ABC News took a Geiger counter around New York City to test different objects and locations. Even in the middle of Central Park, there is always a background level of radiation.
At a food stand in the park, a banana makes the Geiger counter rise a little bit. Bananas contain potassium, which people need to live, but is also radioactive.
At Grand Central Station, the meter on the Geiger counter moved a lot. Grand Central was built with granite and marble, which are both radioactive.
Eric Hall, a nuclear researcher at Columbia University in New York City, said that the thousands of people who walk through Grand Central every day are not at risk of getting sick because of the radioactivity around them.
"The doses are very, very small," Hall said.
Another activity that exposes people to radiation is air travel.
ABC News' Abbie Boudreau flew from Los Angeles to Denver to test the radiation levels during a flight.
"We're just about to take off on our flight and I turned the device on and it's going back and forth between .01 and .02," Boudreau said of the dose in millisieverts.
An hour and a half into the flight, at 40,000 feet, the meter showed a reading of 0.34, which is because the plane was closer to the radiation of outer space.
Every year, just walking around the planet, each individual is exposed to about 3.5 millisieverts of radiation. That's about 67 chest X-rays, or 134 cross- country plane trips.
Here is a comparison of the radiation levels of everyday items and activities:
Banana: .0007 mSv
Pistachio: .001 mSv
Smoke Detector: .0029 mSv
Abdominal CT Scan: 10 mSv
In the course of a year, a flight crew flying between Tokyo and New York is exposed to 14 mSv of radiation.
What Would a Full Meltdown Mean for the United States?
Even a full meltdown in Japan would be no reason for alarm in the United States, experts say.
"If any radiation were to make it here, it would be merely background levels and nothing for people on the West Coast or people in the United States to be concerned about," said Jere Jenkins, the director of Radiation Laboratories at Purdue University in West Lafayette, Ind.
In order to get radiation sickness, a person would need to be exposed to at least 1,000 millisieverts of radiation at once. For most people, a fatal dose is about five times that amount; a range of 3,500 to 5,000 mSv of radiation at once is deadly, which would be 10 hours at the Fukushima Daiichi reactor.
To put that in perspective, the radiation levels at the scene of the fire at the nuclear plant in Japan have reached about 400 millisieverts per hour, meaning a person would have to be right there at the fire for two and a half hours to get sick.
Radiation workers have a limit of 50 mSv per year. Workers who're reaching that limit are being pulled out now.
Another comparison: Three Mile Island came to a 1mSv reading in 1979, while Fukushima Daiichi rated at 400 mSv Monday. Chernobyl, on the other hand, was 16,000 mSv in 1986.
"Not all radiation is dangerous," ABC News health and medical editor Dr. Richard Besser said, "but the levels of radiation we're hearing about in the plant really are."