That town had negligible amounts of radiation, but this was a clear case of better safe than sorry and calling an evacuation was clearly a good idea. However, after a few weeks the area was at normal background levels, so keeping a large exclusion zone is perhaps overly cautious.
One sievert carries with it a ~5.5% chance of eventually developing cancer. These places are dealing with ~0.000001 Sv per hour level which is .008sievert after 10 years which when multiplied by say 100,000 people may suggest reasonable cancer risks. However, there is a fair amount of evidence that suggests ultra low levels of radiation are significantly less harmful than that. But, it's really hard to measure small effects on large populations as there are lot's of cancer risks.