According to media news of a Nuclear disaster in Japan and a tsunami which hit NZ today, I am expecting radiation levels could rise depending on a lot of things like windspeed etc (a lot of it up to nature of course.) I doubt there would be a significant risk to a human here at this time, however, I would highly recommend getting some Iodine or Potassium Iodide for oral consumption before too long. My understanding of events such as the nuclear plant is that the rainfall will probably be more acidic and plantlife may become contaminated etc. A human can prevent a lot of damage by ingesting the aforementioned prior to any contamination entering the area by 24 to 48 hours. When a similar disaster occured many years ago in a location about as far as where I am now from the event, I recall that the rainfall was very acidic and crops etc did not do so well even though it was very far from the event. If you was exposed without taking the Iodine, it is not very good really. You may be OK, who knows.
Another thing, use powdered milk until the cattle has been properly checked.