They are dusting off Down Under after millions of tonnes of grimy grit from the desert Outback blew into town.Australia’s worst dust storm in seven decades smothered Sydney, meaning a massive clean-up operation is needed for normal life to resume. But the long-term effects will not be easily washed away. The deluge severely disrupted air travel and closed several construction sites. The estimated cost in lost productivity runs to tens of millions of dollars. The city was shrouded in a red glow by the storm,. “Doomsday” proclaimed a newspaper. It felt like “Armageddon”, according to a Sydney resident. Amid one of Australia’s worst ever droughts, the storm spread to Queensland after dumping dust over New South Wales.