Japanese and American authorities are being reassuring about the risk of radiation from the two or three or four reactors facing multiple meltdowns following the Sendai earthquake and tsunami. Few details are available, but in at least one case, the use of salt water to cool a core suggests they have run out of options, as this permanently damages a reactor.

Authorities being reassuring but providing little information is a classic symptom of a situation that is not in control. For Japan, this may well be the case and we can only hope for the best, but elsewhere it might be prudent to explore what a worst-case scenario could look like and to ask if we are ready for it. I’ve tried to do this for Hawaii.

Let’s say there is a massive release of radioactive material from the reactors. There are three things that would concern us here in Hawaii: how much?, how soon would it get here?, and what it is?

How much? We don’t know, so let’s assume it would be enough to be a threat to health.

How soon? Honolulu is at 21° N, Sendai is at 38° N. The Hawaiian Islands are about 3800 miles from Sendai as the albatross flies. If the plume of radioactive material rises high enough, it could hitch a ride on the jet stream, at 100-400 mph, and cover 3,800 miles in as little as 9.5 hours or as much as 38 hours. If it got here by jet stream, we’d be radioactive toast, as we would have no time to respond. The good news is that the jet stream doesn’t usually get as far south as us, it tends to stay at 30° – 45 North. The plume might however pass over the Pacific Northwest, which is not good news for them.

If the plume stayed low, the winds are slower, so a very rough estimate is that it might take a minimum 10 days to two weeks to get here, with the winds pushing it east at 11-16 miles an hour. This is enough time to take action, if we have actions planned.

What is it: The main worry will be 131 I or radioactive iodine. Good news and bad news. Bad news: 131 I causes thyroid cancer, often decades later, in young people. Anyone over 40 is at much less risk. American children eventually got thyroid cancer from drinking milk contaminated from fallout during nuclear tests in the 1950’s. Japanese survivors of the atom bombs also experienced significant thyroid effects, with worse effects at increased exposure. The International Atomic Energy Agency reported “the main consequence of the Chernobyl accident is thyroid cancer in children”.

The good news is that 131 I has a half life of a little over eight days: half of it disappears in that time, and in another eight days it is 25 percent as radioactive as when it started. If the plume takes 10 days to get here, it will be half as radioactive as when it left Japan. The better news is that potassium iodide (KI) can be used as a diet supplement to saturate the body with iodine, so that it doesn’t pick up radioactive iodine from the environment. Poland used potassium iodide to protect its citizens during the Chernobyl accident in 1986 and had almost no thyroid cancer while in unprotected parts of Russia, thyroid cancer is expected to remain a continuing health issue as new cancers develop.

Thyroid cancer is treatable and no one should die of it in a developed country, but the costs of treating it are high. In this case, facing a known threat, prevention is much cheaper and would help avoid future suffering.

If the reactors in Japan go, Hawaii has to be ready to protect everyone under 40, but most especially those under 10, with potassium iodide pills. We will have at least 10 days to get ready. Are we?

Here are some questions that need to be asked:

Is there a stockpile of potassium iodide in Hawaii? States with nuclear power plants were given stocks of potassium iodide by the federal government. We don’t have nuclear power, so did we still get a stock?

Is the stock sufficient to sustain the entire population under 40 years of age for say 40 days? It takes 80 days for radioactive iodine to essentially burn itself out. Let’s be liberal and use only half that time period.

If we don’t have a stockpile, how fast can we get it here? This should be easy, unless the radioactive cloud is really big and bad and other states want to keep their stockpiles.

Do we have a plan in place to distribute it? This could be the weak point. We didn’t do well with flu vaccines. Could we distribute through schools, colleges and universities to protect those under 20? But what about the critically sensitive preschoolers? And for the rest of the population under 40? And if supplies are limited, people over 40 won’t get the pills, but they may not like this. How do we keep a blackmarket in check?

We don’t know the risk of one of the Japanese reactors melting down and discharging radioactive material into the atmosphere. It may never happen or it may have happened by the time you read this. We do know that in Hawaii, the resulting threat is limited to fallout from radioactive iodine. There is no need to invoke Chicken Little, even if the skies do fall. We just need to know the state has a plan.

About the author: David Duffy runs the Pacific Cooperative Studies Unit and is a professor in the Botany Department at the University of Hawaii Manoa. He has worked on the ecology of diseases including Lyme Disease, avian flu, and avian malaria in such places as Peru, Alaska, southern Africa, eastern Long Island, southern Africa and here in Hawaii. He received his Ph.D. in population biology from Princeton University.