It doesnt go away until you wash in any water a few seconds. It disappears on client side after you enter a different level. But reappears when you relog. They added that probably because last year there was a bug that caused the green cloud to NOT dosappear after washing in water.
It's like the easter bunny came up with a master plan to bomb everyone while they were offline. Glad it's not just me - no matter how many baths I take or how long I swim around looting, it comes back when I log in again.