I have been receiving many phone calls this week from patients asking if they can have prescriptions for potassium iodide pills. They want to protect their thyroids in case the sea winds blow the radiation from Japan to the U.S. , and then across from California to New York, where I live. 

These radiation fears are irrational, and they are reminiscent of the nervous calls I received for Cipro during the anthrax scare of 2001 and for Tamiflu during the bird flu scare of 2005.

But I also understand where these worries come from; people are afraid of the unknown, afraid of death, and we all personalize the risk. Since the best antidote for fear is facts, I've decided to do my best to put these fears into perspective. 

1. Even if the three affected reactors in Japan experience a complete meltdown and begin spewing radiation, there is no telling how much radiation will escape. 

I believe workers inside the facilities may already be at risk for radiation sickness, and several have reportedly been hospitalized. But consider that real acute radiation sickness (symptoms include hair loss, scorched skin, nausea, vomiting, diarrhea, and headache) would generally only result from exposure to more than 50-100 REMS of radiation. (by comparison, this is 5,000 to 10,000 times the amount of radiation you receive from a routine chest x-ray). 

Cases of radiation sickness at Chernobyl, which experienced a full meltdown, were only 200. 

So it appears extremely unlikely that the Japanese reactors -- even in a worst case scenario -- would sicken large sections of the population.

2. Concerns about long term risks of exposure to the radiation present in these reactors -- if it ever gets out -- are more rational if still inconclusive and frequently laced with hysteria. 

Following the Chernobyl nuclear reactor explosion in 1986, there were 6,000 cases of thyroid cancer linked to radioactive iodine exposure (mostly from drinking contaminated milk), though very few cases in the almost 10 million Polish children and 7 million Polish adults who received potassium iodide. This prophylactic treatment protects the thyroid against radioactive iodine-131. It is a reasonable precaution for those residing near the reactors to take these pills, as is evacuating the area around the site, even if both measures provoke fear.

3. There are other major carcinogens found in the radiation, including cesium, strontium-90, and plutonium-239. Cesium has been associated with solid tumors, strontium with leukemia, and plutonium with lung cancer

Whereas radioactive iodine only remains in its most dangerous form for a week, plutonium stays around for 24,000 years. But though there was a lot of concern about cancer following the Chernobyl disaster, several rigorous studies have shown no link beyond the thyroid cancer, and substantial birth defects. The risk to DNA from this exposure requires further study.

Though the radiation remains a legitimate concern to Japan if not the U.S. in terms of long term health risks, this risk is dwarfed by the current risks to life and limb of a society which still has to bury thousands of drowning victims and care for thousands of injured, has seen massive destruction of property, and faces the loss of power and clean drinking water. 

Infection and injury will sicken and kill far more in post-earthquake post-tsunami Japan than radiation ever will.

Marc Siegel M.D. is an associate professor of medicine and medical director of Doctor Radio at NYU Langone Medical Center. He is a Fox News medical contributor and the author of "False Alarm: the Truth About the Epidemic of Fear."

Dr. Marc Siegel, a practicing internist, joined FOX News Channel (FNC) as a contributor in 2008..