Easy, the meltdown if we care about the next generations ;)
The analysis of the health impact of radioactive land contamination by the accident at the Fukushima Daiichi nuclear power plant, made by Professor Chris Busby (the European Committee of Radiation Risk) based on official Japanese Ministry of Education, Culture, Sports, Science and Technology data, has shown that over the next 50 years it would be possible to have around 400,000 additional cancer patients within a 200-kilometer radius of the plant.
And that it is without taken in consideration the thousands of fish (including tuna) already detected to be contaminated by the current leakage which they cannot stop.

