Japan's nuclear-safety agency decided Tuesday morning to increase the crisis level at the country's troubled Fukushima Daiichi plant from 5 to 7, the highest disaster ranking recognized internationally. The scary 7 has only been used once in history—in 1986, during the Chernobyl disaster in the Soviet Union. Officials said they would increase Fukushima's ranking because it is releasing a massive amount of radioactive material that continues to be a threat to humans and wildlife across a wide area. A week after the earthquake that started the plant's woes, it was given a 5 rating, the same rating given to the Three Mile Island plant in Pennsylvania that suffered a partial meltdown in 1979. Despite the jump, Japanese officials stressed that the cumulative damage from Fukushima is still not nearly as bad as the Chernobyl meltdown, despite the two having the same disaster ratings.