Wikipedia
Al-Mishraq
Al-Mishraq is a state run sulfur plant near Mosul, Iraq. In June 2003, it was the site of the largest human-made release of sulfur dioxide ever recorded when a fire (thought to have been deliberately started) gained control and burned for about three weeks.
At its height, the fire was putting 21,000 tons of sulfur dioxide a day into the atmosphere. The pollution in Mosul, which is about 45 kilometres from Mishraq, reached a catastrophic level. For over 48 hours the white smoke from sulfur dioxide could be seen in the air. Many people were taken into hospitals and most vegetation was killed.