toxic sludge& one question.. today i red an article about the ecological catastrophe in Hungary--toxic sludge came from an aluminum plant...what a tragedy it is..it'll take a long long time to recover..what can people do ?? i feel so sorry for them..i hope the spill can be held as soon as possible...stop wipping out our home our beautiful world .. then there's my question..i know several words meaning almost the same meaning..disaster tragedy catastrophe ..so ,how can i use them in the right position?? how to distinguish ?? thanks....