Do understand that's because the situation is not yet fully understood or controlled. These BWR reactors (Units 1-3) and their safety systems, especially the passive ones, are getting their first true test (unlike airplanes, we can't afford to test them to destruction, and Three Mile Island and Chernobyl were both of different design, PWR and the criminal (at least, illegal in the US) RBMK).

The situation is not good ... but I'm sure the environmentalists are sure the casualties in Japan from coal electrical plants in Japan and the PRC are much greater (and they're likely right).