Radiation fallout risk for pets?

This isn't an infectious disease topic but I've had a few questions about it nonetheless, so I thought it would be worth making some comments here.

With nuclear meltdown concerns in Japan, some pet owners (particularly on the west coast of the US) are flocking to veterinarians looking for potassium iodide pills for their pets. Potassium iodide is given to people (and I guess it could be given to pets) who have been exposed to radiation or who are at high risk of exposure, as a way to reduce the risk of thyroid cancer. 

For pets in North America, and other regions far away from Japan, the risk of radiation exposure from the damaged nuclear power plants appears to be basically non-existent. There's no evidence that, even with a major meltdown, clinically relevant levels of radiation would reach populated areas in North America or beyond.

  • Even if something unexpected happened, there are intensive monitoring efforts underway downwind (i.e. east) of Japan to detect any spike in radiation levels. There's no need to take potassium iodide weeks in advance - at-risk individuals only need it at the time of exposure.
  • Also consider that if potassium iodide treatment is indicated in pets, it's also needed in people in the same area. Given the available supplies, it'd be hard to justify treating pets if there's not a full supply for all the people who might need it.
  • Potassium iodide isn't a benign drug. Overdosing can cause adverse effects, and we don't have good information about appropriate doses for pets. If it was clearly needed, it would be reasonable to make an educated guess from human doses, but with no indication of need, it makes no sense to take the chance.
  • Compared to humans, pets are probably at much lower risk of adverse effects from radiation exposure, because pets have much shorter lifespans, but the effects of radiation exposure tend to cause disease over very long periods of time.

What about pets in Japan? That's a different story, since there is greater potential for risk of exposure now and perhaps through food and water in the future. Still, broad use of potassium iodide isn't being recommended in Japan in humans and there's no reason to treat pets any differently. If there are regions where treatment of people is recommended and where there are adequate supplies, treatment of pets may be a good idea.